Microchimica Acta (2023) 190:125 https://doi.org/10.1007/s00604-023-05692-4 ORIGINAL PAPER Efficient controlled release of cannabinoids loaded in γ‑CD‑MOFs and DPPC liposomes as novel delivery systems in oral health Jorge Rodríguez‑Martínez1 · María‑Jesús Sánchez‑Martín1 · Manuel Valiente1 Received: 7 December 2022 / Accepted: 14 February 2023 © The Author(s) 2023 Abstract Olivetol (OLV), as a cannabidiol (CBD) analog, was incorporated in γ-cyclodextrin metal-organic frameworks (γ-CD-MOFs) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes as potential analgesic drug delivery systems (DDS) for dental hypersensitivity (DH) treatment. These DDS have been scarcely employed in oral health, being the first time in case of MOFs loaded with cannabinoids. In vitro experiments using bovine teeth were performed to verify if the drug is able to reach the dentin, where it can flow to the pulp tissues and exert its analgesic effect; enamel and dentin regions were analyzed by synchrotron radiation-based FTIR microspectroscopy. Principal component analysis (PCA) was used to process the spectroscopic data as a powerful chemometric tool, and it revealed a similar behavior in both regions. The studied DDS have been characterized by different techniques, and is was demonstrated that DDS is an efficient way to carry the drug through dental tissues without compromising their structure. Keywords γ-Cyclodextrin-MOFs (γ-CD-MOFs) · Cannabidiol (CBD) · DPPC liposomes (1,2-dipalmitoyl-sn-glycero-3- phosphocholine) · Oral health · Synchrotron FTIR microspectroscopy Introduction frameworks (MOFs) are well-known drug delivery systems and used in pharmaceutical formulations. Liposomes are Dental hypersensitivity (DH) could be defined as a short spherical vesicles consisting of one or more phospholipid and sharp pain derived from exposed dentin in response to bilayers surrounding a water space that present the ability to different stimuli [1]. Current strategies to avoid this sharp encapsulate different substances; while lipophilic agents are pain are not totally effective, and it is necessary to develop entrapped in the bilayer, hydrophilic agents are enclosed in new treatments [2]. Cannabidiol (CBD) is the main nonpsy- the aqueous core [7]. MOFs are porous crystalline materials chotropic component of Cannabis sativa, and it emerges as consisting of metal ions or clusters linked to organic ligands a promising candidate to avoid this pain since it can modu- by coordination bonds [8]. Due to all these characteristics, late receptors involved in the response caused by DH [3]. both systems have a wide range of application fields, such However, CBD shows low chemical stability and poor aque- as gas storage, catalysis, or drug delivery [9–11]. In the case ous solubility [4]; the use of drug delivery systems (DDS) of medical applications, it is necessary to consider that the for its encapsulation or adsorption could overcome these structures should be non-toxic for biological tissues. For disadvantages [5]. There are plenty of DDS; some of them liposomes, a quite studied phospholipid is 1,2-dipalmitoyl- applied in oral health [6]. Liposomes and metal-organic sn-glycero-3-phosphocholine (DPPC), used as a model sys- tem to mimic the cell membrane [12]. Regarding MOFs, γ-cyclodextrin-MOFs (γ-CD-MOFs) have been reported as Jorge Rodríguez-Martínez and María-Jesús Sánchez-Martín shared suitable materials in biomedicine due to its high biocompat- co-first authorship. ibility since they are composed of γ-CD as organic ligand * María‑Jesús Sánchez‑Martín and usually potassium ions as metal linker [13]. Therefore, mariajesus.sanchez@uab.cat both systems present unique advantages for applications 1 in encapsulation and release of cannabinoids. MOFs have GTS Research Group, Department of Chemistry, Faculty of Science, Universitat Autònoma de Barcelona, been scarce studied as carriers of CBD, but some researchers 08193 Bellaterra, Spain have developed some liposomal formulations with CBD for 13 Vol.:(0123456789) 125 Page 2 of 10 Microchim Acta (2023) 190:125 biological and medical applications such as cancer treatment be possible to trace the penetration of the drug in the tooth [14]. However, there are no specific reports about the use of structure using this technique coupling it to the synchrotron CD-MOFs and DPPC liposomes loaded with CBD for oral radiation source and using PCA for data processing. Fur- health application, either other material used as CBD carri- thermore, the penetration patterns according to the delivery ers for oral health; thus, our approach involves a novelty in system were evaluated and how the γ-CD-MOFs and DPPC this topic. CD-MOFs are biocompatible MOFs and they do liposomes help in the release process. Besides, the effect of not induce any toxicity up to 2000 μg/mL of concentration. the different treatments over the tooth was assessed based And DPPC liposomes are well-known as DDS, and they on the changes in the HAP band. have been already applied successfully in dentistry for other applications such as tooth whitening [15]. Besides, another important aspect for both systems is to verify whether scal- Materials and methods ing up the production of the formulation from the laboratory level to the industrial level is technically and economically Reagents possible. In these two cases, the authors have developed methodologies that can be scaled up. The following reagents were used: chloroform, potassium Dental structure has been studied using different character- nitrate, potassium chloride, sodium azide, 2-[4-(2-hydroxye- ization techniques. Fourier Transform Infrared Spectroscopy thyl)piperazin-1-yl]ethanesulfonic acid (HEPES), 1,2-dipal- (FTIR Analysis) is a very useful technique in dental research mitoyl-sn-glycero-3-phosphocholine (DPPC), cannabidiol, since it is able to study the tooth structure and its chemis- methanol, ethanol, polyethylene glycol 20000, olivetol, try, organic and inorganic material, and their interactions, γ-cyclodextrin (98%), and MilliQ water. More details about and it has been used to diagnose tooth structure alterations these reagents can be found in the Electronic Supporting and pathologies [16]. Nevertheless, conventional vibrational Material (ESM). spectroscopic methods are not always enough accurately to assess modifications in dental composition. Thus, the addi- tion of a synchrotron radiation light source to FTIR tech- Drug delivery system synthesis nique (synchrotron radiation-based FTIR microspectros- copy, SR-μFTIR) provides the high intensity, spectral purity, A fast method using microwave irradiation was performed and spatial and energy resolution necessary to study dental for γ-CD-MOF synthesis, and a cocrystallization method structure at micro- and nanolevels [17]. However, analysis was used to load olivetol into these MOFs. This method- of spectral data obtained is quite challenging due to the high ology has been described in a previous work [21]. DPPC number of spectra, the fact that many of the spectral bands are liposomes were obtained by hydration and mechanical dis- overlapping and small changes could not be appreciated using persion following a modified method previously described visual comparison. To solve these problems, chemometrics [15]. The complete description of these syntheses can be have been used, being principal component analysis (PCA) found in the ESM. one of the most common applied in combination with FTIR spectroscopy since it can resolve small differences in the spec- Characterization techniques tra and establish subgroups in the data [18]. Several researchers have already explored the large capa- Morphology and crystallinity of MOF samples were evalu- bilities of the combination of synchrotron source infrared ated by Scanning Electron Microscopy (SEM) and X-ray spectroscopy with chemometrics in dental field [19]. In this powder diffraction (XRPD), respectively. Liposome dis- study, γ-CD-MOFs and DPPC liposomes containing olive- persions were characterized by cryo-transmission electron tol (OLV) were synthesized and characterized as potential microscopy (Cryo-TEM) and dynamic light scattering analgesic delivery systems for DH treatment. OLV was (DLS). All the details concerning the instruments and the employed as an affordable CBD analog, since it is a pre- measurements can be found in the ESM. cursor in cannabidiol biosynthesis, and they share part of the chemical structure [20]. To verify if the drug is able to Drug release and quantification cross the enamel and get into dentinal tubules, where it can flow to the pulp tissues and exert its analgesic effect, in vitro The quantification of the OLV content into the MOFs was experiments using bovine teeth were developed. The pri- performed following a methodology previously stablished mary component in the tooth is hydroxyapatite (HAP) that [21]. For liposomes, the encapsulation of the drug was has well-defined bands in the infrared spectra (1600–700 determined adapting a method previously described [7]. The ­cm−1), and the spectrum of CBD and olivetol has several drug encapsulation for each carrier was calculated following absorption bands in the infrared region. Therefore, it would equation 1: 13 Microchim Acta (2023) 190:125 Page 3 of 10 125 Drug encapsulation(%) = Encapsulation OLV into the carrer (mg) ⋅ 100 The big mapping per sample was limited to two smaller Total weight of OLV − loaded carrier (mg) mappings, one in the inner enamel and another in the inner (1) dentin. The wavenumber range was also limited from 1600 All determinations were performed by triplicate. to 700 c­ m−1 where the main bands of HAP are located. The complete description of this experimental part can Before PCA, mean centering preprocessing was applied to be found in the ESM. all the spectra. Besides, in each region of the tooth, enamel and dentin, liposomes, and MOF treatments were analyzed Tooth sample preparation separately. All the details of the PCA can be found in the ESM. Bovine incisors were embedded in self-curing acrylic resin (Paladur, Germany) leaving the frontal enamel free of resin. Specimens were cut in half, and its lateral surface was polished Results and discussion down to 1 µm particle size. Then, teeth were treated with 0.1 mL of each treatment 3 times per day for 5 days (Table 1, Fig. S2.A). Drug delivery systems characterization and olivetol Since MOFs’ treatments are the only ones which are in pow- quantification der, 1 mg of each MOF formulation was mixed with 15 µL of HEPES buffer and, then, was applied over the teeth. The com- In order to evaluate the morphology and the crystal structure plete description of this tooth sample preparation can be found of the γ-CD-MOFs loaded with the drug, SEM and PXRD in the ESM. analysis were performed. The diffraction patterns of both γ-CD-MOFs KCl and γ-CD-MOFs ­KNO3 presented their Synchrotron radiation‑based FTIR peaks at the same 2θ angles (Fig. 1.1): 5.3°, 7.4°, 10.5°, microspectroscopy (SR‑µFTIR) measurements 11.5°, 12.1°, 14.2°, 14.9°, 15.8°, and 16.7°. Peaks were quite narrow for both potassium salts, indicating high crystallin- Specular reflectance spectra were acquired using FTIR ity, especially when ­KNO3 was employed since their peaks microscope in the reflection mode at MIRAS beamline of were sharper and more intense. These PXRD patterns have ALBA synchrotron (Cerdanyola del Vallès, Spain). Hype- been already compared previously to the simulated refer- rion 3000 microscope coupled to a Vertex 70 spectrometer ences from the Crystalography Open Database (COD), (Bruker, Germany) and an HgCdTe (MCT) detector was including the JCPD card of the conventional CD-MOFs used. A mapping of 300×1000 µm (wide x length) was with the body-centered cubic space group I432 [21]. This made per each sample in the lateral surface from the outside recent publication showed the space group of these diffrac- of the enamel to the dentin. In each mapping, 250 spectra tion patterns matched with trigonal spaces groups when the were measured having 5 spectra wide and 50 spectra length metal linker was not delivered by potassium hydroxide [22]. (Fig. S2.B). OPUS 7.5 (Bruker, Germany) was used to col- This PXRD analysis agreed with SEM evaluation. The prism lect the spectra. All the details concerning the instruments morphology of the crystals was the same for both potas- and the measurements can be found in the ESM. sium salts (Fig. 1.2). The size of these structures was quite heterogeneous, but most of them was around 2 to 50 µm. Principal component analysis (PCA) It could be explained due to the long incubation time to trigger the precipitation of the crystals that was 24 hours, PCA was applied to process the SR-µFTIR data using PLS since it is a key parameter in the kinetics that are involved in toolbox 8.2.1 (20559) for use with MATLAB 9.1 (R2016b). crystal growth [23]. Consequently, SEM and PXRD analysis showed crystalline CD-MOFs with prism shape, regardless of the potassium salt. Table 1  List with the different treatments applied over the dental Regarding the liposomes’ characterization, the size dis- samples tribution is a key aspect to consider, even more when the Treatments’ list final application is as drug delivery systems. In order to Control (HEPES buffer) get information about the size of DPPC liposomes and the Cannabidiol (10 mg/mL) physical stability of these systems after the encapsulation Olivetol (10 mg/mL) of olivetol, DLS and cryo-TEM analysis were performed. DPPC liposomes DPPC formulations loaded with the drug showed more poly- DPPC liposomes loaded with olivetol dispersity than empty DPPC liposomes with wider and more γ-CD-MOFs KCl loaded with olivetol asymmetric peaks in DLS results (Fig. 2A). These results γ-CD-MOFs ­KNO3 loaded with olivetol were in agreement with cryo-TEM analysis where bigger 13 125 Page 4 of 10 Microchim Acta (2023) 190:125 Fig. 1  X-ray powder diffraction patterns (1) using Cu Kα anode (l = 1.5406 Å), tube voltage of 45 kV, tube current of 40 mA in a step size scan mode (0.03° ­min−1) and scanning electron microscopy images (2) with the Secondary Electron Detector at low voltage of 2 kV, 2000x of magnification and a working distance of 4.3 mm of OLV loaded γ-CD-MOF formulations using ­KNO3 (A) and KCl (B) as potassium sources liposomes and with several concentric lipidic bilayers could if the amount of drug applied over the teeth in liposomes be observed in the samples with OLV (Fig. 2B). The mean and MOF formulations was comparable, the OLV amount diameter of the liposomes was below 200 nm: 125 ± 52 nm per application was calculated based on the sample prepara- for DPPC liposomes and 159 ± 67 nm for DPPC liposomes tion process (Tooth sample preparation). This amount was of loaded with OLV. Mean diameter and standard deviation the same order for the three carriers (Table 2). Besides, the were similar in both liposomes’ formulations. However, the amount of drug applied without carrier as positive control size distribution observed in the liposomes without drug was was extremely high to study the efficiency when the carrier closer to a normal distribution than the formulations with was used. In any case, the drug could be quantified in all the OLV, and the polydispersity index values were lower in the formulations, making them suitable as carriers for olivetol empty liposomes (0.3) than in the loaded ones (0.9). This and for their application over the tooth structure. fact means that the samples with low polydispersity index had homogeneous distribution of the vesicles of similar Peaks assignment of enamel and dentin diameters without aggregates. It could be explained since olivetol is an organic compound and it is encapsulated in Enamel and dentin are the main tissues that comprise the the bilayer increasing the rigidity of liposomes, such as the teeth. Enamel is composed of 96% of mineral content, effect of cholesterol addition [24]. Cryo-TEM analysis cor- while in the dentin it is reduced to approximately 70%. roborated these results. Anyway, the synthesis method was Regarding the organic matter, the enamel presents only found to be useful for producing stable DPPC liposomes 2% and, in the dentin, it increases to 20%. The inorganic with and without olivetol of relatively controllable particle mineral that mainly composes both tissues is the carbon- size. ated calcium-deficient hydroxyapatite (HAP), which is The UV-Vis spectrophotometry analysis confirmed the a crystalline calcium phosphate [­ Ca10(PO4)6(OH)2] and presence of olivetol in all the carriers (Table 2). For MOF carbonates impurities [­ CO32−] [26]. Bovine enamel and formulations, OLV encapsulation percentages were in the dentin reflection spectra are shown in Fig. 3 between 1600 order of the values reported in previous studies using CD- and 700 c­ m−1 where the bands of carbonate and phosphate MOFs for the encapsulation of different compounds [25]. groups of HAP could be observed. Due to the high degree For liposome formulation, OLV encapsulation percentage of crystallinity of the enamel, the bands that correspond was higher than the values for both MOFs. These percent- to this mineral matrix are more intense than in the dentin ages could not be compared between MOFs and liposomes, tissue which has a low crystallinity [27]. Antisymmet- since the values are expressed in terms of mass and the ric stretching vibration of phosphates groups ­(v3 ­PO43−) weight of each carrier is different [22, 25]. In order to verify appears as a wide band in the 1200–900 c­ m−1 region, in 13 Microchim Acta (2023) 190:125 Page 5 of 10 125 Fig. 2  Size distribution by intensity (A) using a laser with λ0 = 632.8 nm, 175° angle, 1.0031 cP, and 1.330 of R.I. for the viscosity of water and cryo- TEM images (B) using 5000x of magnification of OLV loaded DPPC liposomes and DPPC liposomes in HEPES buffer solution Table 2  Olivetol encapsulation OLV encapsulation OLV/CBD amount percentage for each formulation (%) per application (µg) with their standard deviations and drug amount per application DPPC loaded with olivetol MLV (molar ratio 2:1) 9.1 ± 0.1 36.8 ± 0.5 γ-CD-MOFs KCl loaded with olivetol 2.4 ± 0.3 24 ± 3 γ-CD-MOFs ­KNO3 loaded with olivetol 1.6 ± 0.2 16 ± 2 CBD or OLV (10 mg/mL) – 1000 both enamel and dentin tissues with a maximum at 1045 98.44% of the variance, respectively (Fig. 4). The two car- and 1028 ­cm−1, respectively. These broad bands are attrib- riers’ analysis had a similar distribution in the enamel, and uted to triply degenerated v­ 3 ­PO43− [28]. The shoulder at only two groups could be distinguished along PC1 according 956 ­cm−1 corresponds to the symmetric stretching vibra- to drug presence (Fig. 4A). The group with drug included tion of the same group (­ v1 ­PO43−) in both tissues [29]. The CBD, OLV, and OLV-loaded liposomes or MOFs (depend- peaks at 1403 and 1442 ­cm−1 match with antisymmetric ing on the carrier analysis), and the group without drug com- stretching vibration of carbonate groups (­ v3 ­CO32−) and prised HEPES control for both carriers and also unloaded the one at 867 ­cm−1 with symmetric angular deformation liposomes for liposome analysis. Therefore, it revealed that ­(v2 ­CO32−) in both tissues. Besides, organic matter (amide both OLV-loaded carriers may transport the drug, since II) is detected at 1540 c­ m−1 in the dentin, since its percent- these treatments were in the same group as CBD and OLV age in this tissue is higher than that in the enamel. control treatments. Nevertheless, the separation between the groups that contained or not drug was not perfectly clear. Study of the treatments’ effect over the enamel This fact could be explained due to the large inorganic material content and high crystallinity of the enamel [30]. In the present study, the enamel FTIR spectra of the differ- Because of these enamel properties, the signal of carbonate ent samples were analyzed by PCA, where the weights of and phosphate groups of HAP was too high overlapping the the main components were concentrated in the components possible vibrations peaks of organic material that can be 1 and 2 (PC1 and PC2) for both carriers. Liposomes and present in the enamel, as the drugs and carriers employed in MOF analysis had a PC1 of 95.20% and 96.01% versus PC2 the different treatments [31]. For this same reason, no more of 3.39% and 2.43% accounting for a total of 98.59% and differences related with the treatments could be observed 13 125 Page 6 of 10 Microchim Acta (2023) 190:125 reflective properties, and its infrared signal is higher [33]. Besides, shifts were not detected in the average of the spec- tra of the samples with and without drug for both carriers, so the treatments did not compromise carbonate and phos- phate groups of HAP [34]. These results agreed with the distribution in scores graphs along PC1 (Fig. 4A), where the group with drug is in the negative part of the component (less intense signal) and the group without drug in the posi- tive part (more intense signal). PC2 loading profiles revealed in the positive part of the graphs, v­ 3 ­CO32− and ­v2 ­CO32− peaks of carbonate groups from 1475 to 1380 ­cm−1 and 867 ­cm−1, respectively (Fig. 4C). A secondary phase vibration of ­v3 ­PO43− at 1113 ­cm−1 was observed. This vibration contributes to the shoulder at 1103 ­cm−1 of the peak assignment, and it is related with the bandwidth [63]. Meanwhile, the maximum peak of ­v3 ­PO43− was in the negative part. This profile was in agreement with the distribution of the scores according to the depth in the enamel structure (Fig. 4B). Enamel tissue presents het- erogeneous distribution of the inorganic material, since its carbonate content increases from the outer to inner enamel and the phosphates decrease showing more crystallinity and more packing in the outer part [35]. Therefore, the fact that the scores in the positive part of the graph correspond to the inner parts of the enamel and the ones in the negative part to the outer region matched with the PC2 loading profiles for both carriers. This information is in accordance with the Fig. 3  Average of the specular reflectance FTIR spectra of control typical mineral gradient of the enamel, verifying that PC2 enamel and dentin of bovine tooth and band assignment numbers distributes the samples following the depth in this tissue. (n=30). The spectra were acquired in the reflection mode and for each one, 64 scans were carried out from 4000 ­cm−1 to 600 ­cm−1 with 4 ­cm−1 spectral resolution at room temperature, using 10×10 μm2 of Study of the treatments’ effect over the dentin aperture size. A gold mirror was used as background reference The analysis of the dentin was also performed using PCA between groups, since spectra were distributed according for the different treatments. As in the enamel results, the to the depth in the enamel structure along PC2 (Fig. 4B). weights of the main components were in the components Regarding the loading graphs (Fig. 4C), PC1 comprised 1 and 2 (PC1 and PC2) for both carriers. Liposomes and all the bands of carbonates and phosphates groups of HAP MOF analysis had a PC1 of 87.68% and 86.30% versus PC2 previously assigned for both liposomes and MOF analysis of 8.43% and 9.39% accounting for a total of 96.11% and in the positive part of the graphs. Taking into account the 95.69% of the variance, respectively (Fig. 5A). In com- enamel structure properties, no contribution of drugs, lipo- parison to the enamel analysis, the separation between the some, or MOF vibration peaks were expected to be distin- groups in the dentin was much better and more consistent guished, since their signals are not significant in comparison information can be obtained. This better separation of the with the signal of the inorganic material of the enamel [32]. different groups in the dentin may be due to the less mineral Thus, only changes over HAP structure could be noted. The content and less crystal packing in this tissue, having the treatments with drug (CBD, OLV, OLV-loaded liposomes, organic matter of the drug stronger presence improving the and MOFs) produced the decrease of the bands of carbonate sample grouping [27]. Therefore, the signal of carbonate and and phosphate groups of HAP in comparison with the aver- phosphate groups of HAP decreases, and the vibrations of age of the spectra of the samples without drug, especially in the organic material could be distinguished. All the groups in the antisymmetric stretching vibration v­ 3 ­PO43− (Fig. S3.A). both carriers’ analysis had similar distribution in the scores’ This fact could be explained due to the organic matter incre- graphs along PC1 and PC2 (Fig. 5A). Loaded liposome and ment in the samples treated with drug, because the crystal- MOF groups were closer to the samples treated with only linity of the enamel in these samples was worse detected drug (CBD and OLV) than the samples without treatment than in the ones without any drug, since they have better or unloaded carrier. Thus, it means that both carriers led 13 Microchim Acta (2023) 190:125 Page 7 of 10 125 Fig. 4  Principal component analysis of liposomes (1) and MOFs (2) essing technique; score plots grouping according to the drug presence in the inner enamel; a mapping of 30 spectra was analyzed per sample (A); score plots showing the distribution across the enamel depth (B); from 1600 to 700 ­cm−1, and mean centering was applied as preproc- loading profiles of PC1 and PC2 (C) the drug transport until the dentin tissue efficiently increas- in the positive part of the profile (Fig. 5B). As in the enamel ing the diffusion process, despite the drug concentration analysis, drug vibrations did not appear since the contribution per application was much lower than in the CBD and OLV of the inorganic material was much more significant that the control groups (Table 2) [15]. Furthermore, CBD and OLV contribution of the drug. The comparison between the average control groups are completely overlapped in this analysis, of the spectra without drug with the average of the spectra confirming that OLV could be used as CBD analog in this with drug (CBD, OLV, OLV-loaded liposomes, and MOFs) experiment. Dentin analysis also revealed differences related revealed a reduction in the intensity of all the bands, related to the presence of liposomes or MOFs along PC2. Mean- to a higher organic matter content in the dentin tissue that while, the groups without any carrier were in the positive decreased the crystallinity and the signal of the bands (Fig. part of PC2, the groups with carrier were in the negative part S3.B) [36]. The only band that did not decrease is the one at of this component regardless the drug presence. Therefore, 1540 ­cm−1 in case of the liposome analysis, since this vibra- PC1 may group the samples according to the drug presence tion may be related to the N­ H3+ deformation from the DPPC and PC2 according to the carrier presence in the dentin tis- structure avoiding the loss of intensity of this peak despite sue. Moreover, these results from the dentin analysis verified the decrease in crystallinity due to the drug presence [37]. and supported the previous results of the enamel. However, the main vibrations did not shift, so the chemical PC1 loading graphs included all the characteristic vibra- structure of the dentin was not changed. The loading profiles tions previously assigned in the dentin tissue for both carriers of PC1 were in agreement with the scores’ graphs since the 13 125 Page 8 of 10 Microchim Acta (2023) 190:125 Fig. 5  Principal component analysis of liposomes (1) and MOFs (2) cessing technique; scores plots grouping according to the drug pres- in the inner dentin; a mapping of 30 spectra was analyzed per sample ence and carrier presence (A); loadings profiles of PC1 and PC2 (B) from 1600 to 700 cm-1 and mean centering was applied as pre-pro- samples without drug were in the positive part of this com- [39]. Even though there are a great number of possible strate- ponent (more intense signal) and the samples with drug were gies as a treatment of DH, up to date, none of them has yet in less positive values (less intense signal). been found to be efficient [40]. In any case, further insights PC2 profiles comprised the wide band of the antisymmetric could be performed in the development of these materials, stretching vibration ­v3 ­PO43− in the negative part emphasizing such as the optimization of the formulations in terms of drug the shoulder at 1103 c­ m−1 of the peaks’ assignment, while encapsulation to improve its efficacy. Another aspect to con- the rest of the peaks were in the positive half of this compo- sider, it is the stability of the DDS in a suitable marketed nent (Fig. 5B). This negative band gives information about formulation. For example, a liquid or gel formulation based the bandwidth and the groups that were in the more nega- on water would not be appropriate since the degradation will tive part of the scores’ graphs correspond to treatments with be very fast [41]. Other important point is to verify whether liposomes and MOFs that contributed with the increase of the scaling up the production of the formulation from the labora- organic material in the dentin tissue, reducing the crystallinity tory level to the industrial level is technically and economi- and making the mentioned phosphate bandwidth when these cally possible. Thus, this research will lead to the develop- groups were compared to the ones without any carrier [38]. ment of important advances in drug delivery technologies This information agreed with score distribution along PC2 and in oral health, since it is the first time that these carriers where the samples without carrier were in the positive part has been used in combination of CBD against DH [42]. and the samples with carrier in the negative half. The fact that the rest of the bands were in the positive part means that the presence of any carrier did not affect these vibrations. These results have demonstrated that thanks to the devel- Conclusions oped formulation using these two DDS, CBD can reach the dentin in an efficient way where the drug will be able to exert In the present study, olivetol-loaded γ-CD-MOFs and DPPC its analgesic effect. Without the proposed carriers, CBD liposomes have been proposed as potential analgesic delivery could not be able to reach it due to its low chemical stability systems of CBD for DH treatment. PCA showed that the treat- and poor aqueous solubility, unless the drug is applied in a ment could reach the enamel and the dentin as PC1 grouped high concentration, which would not be viable in terms of the samples according to the drug presence in both tissues, toxicity to tissues or in economic terms at the market level meanwhile, PC2 grouped the samples according to the depth 13 Microchim Acta (2023) 190:125 Page 9 of 10 125 in the enamel structure due to the typical mineral gradient of novel approaches to prevent side effects. J Esthet Restor Dent this tissue. Moreover, no differences were observed between 31:431–440 2. Alrusayes AA, Assal NA, Althobity AM, Alfraih YK, Alfraih OLV and CBD validating the hypothesis of OLV application MI (2021) Dentin hypersensitivity: a review of its treatment. Ann as CBD analog in this experimental approach. Int Medical Dent Res 7(3):8–15. https://​doi.​org/​10.​21276/​aimdr.​ On the other hand, OLV loaded liposomes and MOFs tar- 2021.7.​3.​DE3 geted the drug transport in a more efficient way, since these 3. Atalay S, Jarocka-Karpowicz I, Skrzydlewska E (2019) Antioxida- tive and anti-inflammatory properties of cannabidiol. Antioxidants groups were closer to the CBD and OLV control groups 9(21):9:21. https://​doi.​org/​10.​3390/​ANTIO​X9010​021 despite the fact that drug concentration per application was 4. Borges RS, Da Silva ABF (2017) Cannabidiol as an antioxidant. In much lower. Therefore, it was possible to trace the penetra- Handbook of Cannabis and Related Pathologies (pp. e122–e130). tion of the drug in the tooth structure and to know that the Academic Press https://​doi.​org/​10.​1016/​B978-0-​12-​800756-​3.​ 00093-4 carriers helped in the delivery process making it more effi- 5. Millar SA, Maguire RF, Yates AS, O’Sullivan SE (2020) Towards cient. Besides, shifts in the HA bands were not observed better delivery of cannabidiol (CBD). Pharm 13(219):219–13:219. meaning that the treatments did not affect the tooth structure. https://​doi.​org/​10.​3390/​PH130​90219 In conclusion, new potential analgesic delivery systems 6. Swanson WB, Gong T, Zhang Z et al (2020) Controlled release of odontogenic exosomes from a biodegradable vehicle mediates loaded with cannabinoids for oral health were developed, dentinogenesis as a novel biomimetic pulp capping therapy. J Con- leading the drug transport in an efficient way to cross the trol Release 324:679–694. https://​doi.​org/​10.​1016/J.​JCONR​EL.​ tooth structure. Without the developed DDS, CBD will not be 2020.​06.​006 able to reach the dentin due to its low chemical stability and 7. Najlah M, Suliman AS, Tolaymat I et al (2019) Development of injectable PEGylated liposome encapsulating disulfiram for colo- poor aqueous solubility; there are no other materials used as rectal cancer treatment. Pharmaceutics 11:1–16. https://​doi.​org/​ CBD carriers for oral health. However, further insights must 10.​3390/​pharm​aceut​ics11​110610 be explored from the laboratory to the final market in order 8. Zeng Q, Bie B, Guo Q et al (2020) Hyperpolarized Xe NMR to assess the encapsulation capacity and stability. signal advancement by metal-organic framework entrapment in aqueous solution. Proc Natl Acad Sci U S A 117:17558–17563. Supplementary Information The online version contains supplemen- https://d​ oi.o​ rg/1​ 0.1​ 073/P ​ NAS.2​ 00412​ 1117/S ​ UPPL_F ​ ILE/P ​ NAS.​ tary material available at https://d​ oi.o​ rg/1​ 0.1​ 007/s​ 00604-0​ 23-0​ 5692-4. 20041​21117.​SAPP.​PDF 9. Wang MR, Deng L, Liu GC et al (2019) Porous organic polymer- Acknowledgements Jorge Rodríguez-Martínez acknowledges the derived nanopalladium catalysts for chemoselective synthesis of FI-2018 fellowship from Agència de Gestió d'Ajuts Universitaris i de antitumor benzofuro[2,3-b]pyrazine from 2-bromophenol and Recerca (Generalitat de Catalunya). The SR-µFTIR experiment was isonitriles. Org Lett 21:4929–4932. https://​doi.​org/​10.​1021/​ACS.​ performed at MIRAS beamline at ALBA Synchrotron (Cerdanyola del ORGLE​TT.​9B012​30/​SUPPL_​FILE/​OL9B0​1230_​SI_​001.​PDF Vallès, Spain), with the collaboration of ALBA staff. 10. Yang Y, Wang SQ, Wen H et al (2019) Nanoporous gold embed- ded ZIF composite for enhanced electrochemical nitrogen fixation. Funding Open Access Funding provided by Universitat Autonoma de Angew Chemie Int Ed 58:15362–15366. https://​doi.​org/​10.​1002/​ Barcelona. This work has been funded by ALBA Synchrotron through ANIE.​20190​9770 granted proposal (grant reference: 2020024303). 11. Li J, Zhao J, Tan T et al (2020)

Nanoparticle drug delivery system for glioma and its efficacy improvement strategies: a com- prehensive review

. Int J Nanomed 15:2563–2582. https://d​ oi.​ Declarations org/​10.​2147/​IJN.​S2432​23 12. Bulbake U, Doppalapudi S, Kommineni N, Khan W (2017) Lipo- Competing interests The authors declare no competing interests. somal formulations in clinical use: an updated review. Pharma- ceutics 9:12. https://​doi.​org/​10.​3390/​pharm​aceut​ics90​20012 Open Access This article is licensed under a Creative Commons Attri- 13. Liu B, He Y, Han L et al (2017) Microwave-assisted rapid syn- bution 4.0 International License, which permits use, sharing, adapta- thesis of γ-cyclodextrin metal-organic frameworks for size con- tion, distribution and reproduction in any medium or format, as long trol and efficient drug loading. Cryst Growth Des 17:1654–1660. as you give appropriate credit to the original author(s) and the source, https://​doi.​org/​10.​1021/​acs.​cgd.​6b016​58 provide a link to the Creative Commons licence, and indicate if changes 14. Sharma A, Kumar A, Li C et al (2021) A cannabidiol-loaded Mg- were made. The images or other third party material in this article are gallate metal-organic framework-based potential therapeutic for included in the article's Creative Commons licence, unless indicated glioblastomas. J Mater Chem B 9:2505–2514. https://​doi.​org/​10.​ otherwise in a credit line to the material. If material is not included in 1039/​d0tb0​2780d the article's Creative Commons licence and your intended use is not 15. Babot-Marquillas C, Sánchez-Martín MJ, Rodríguez-Martínez J permitted by statutory regulation or exceeds the permitted use, you will et al (2020) Flash tooth whitening: a friendly formulation based on need to obtain permission directly from the copyright holder. To view a a nanoencapsulated reductant. Colloids Surfaces B Biointerfaces copy of this licence, visit http://​creat​iveco​mmons.​org/​licen​ses/​by/4.​0/. 195:111241. https://​doi.​org/​10.​1016/j.​colsu​rfb.​2020.​111241 16. Jegova G, Titorenkova R, Rashkova M, Mihailova B (2013) Raman and IR reflection micro-spectroscopic study of Er:YAG laser treated permanent and deciduous human teeth. J Raman References Spectrosc 44:1483–1490. https://​doi.​org/​10.​1002/​jrs.​4373 17. Seredin P, Goloshchapov D, Ippolitov Y, Vongsvivut J (2020) Development of a new approach to diagnosis of the early fluorosis 1. Rodríguez-Martínez J, Valiente M, Sánchez-Martín MJ forms by means of FTIR and Raman microspectroscopy. Sci Rep (2019) Tooth whitening: from the established treatments to 10:1–12. https://​doi.​org/​10.​1038/​s41598-​020-​78078-8 13 125 Page 10 of 10 Microchim Acta (2023) 190:125 18. Song CL, Kazarian SG (2020) Micro ATR-FTIR spectroscopic 31. Kim IH, Son JS, Min BK et al (2016) (2016) A simple, sensitive imaging of colon biopsies with a large area Ge crystal. Spectro- and non-destructive technique for characterizing bovine dental chim Acta - Part A Mol Biomol Spectrosc 228:117695. https://​ enamel erosion: attenuated total reflection Fourier transform infra- doi.​org/​10.​1016/j.​saa.​2019.​117695 red spectroscopy. Int J Oral Sci 81(8):54–60. https://​doi.​org/​10.​ 19. Diez-García S, Jesús Sánchez-Martín M-J, Amigo JM, Valiente 1038/​ijos.​2015.​58 M (2022) Combination of two synchrotron radiation-based tech- 32. France CAM, Sugiyama N, Aguayo E (2020) Establishing a pres- niques and chemometrics to study an enhanced natural remin- ervation index for bone, dentin, and enamel bioapatite mineral eralization of enamel. Anal Chem. https://​doi.​org/​10.​1021/​ACS.​ using ATR-FTIR. J Archaeol Sci Rep 33:102551. https://​doi.​org/​ ANALC​HEM.​1C054​98 10.​1016/J.​JASREP.​2020.​102551 20. Raharjo TJ, Te Chang W, Choi YH et al (2004) Olivetol as product 33. McGuire JD, Walker MP, Dusevich V et al (2014) Enamel organic of a polyketide synthase in Cannabis sativa L. Plant Sci 166:381– matrix: potential structural role in enamel and relationship to 385. https://​doi.​org/​10.​1016/J.​PLANT​SCI.​2003.​09.​027 residual basement membrane constituents at the dentin enamel 21. Rodríguez-Martínez J, Sánchez-Martín MJ, López-Patarroyo O, junction. Connect Tissue Res 55:33. https://​doi.​org/​10.​3109/​ Valiente M (2023) Novel cannabinoid release system: encapsula- 03008​207.​2014.​923883 tion of a cannabidiol precursor into γ-cyclodextrin metal-organic 34. González-López S, Torres-Rodríguez C, Bolaños-Carmona V et al frameworks. J Drug Deliv Sci Technol 79:104085. https://d​ oi.o​ rg/​ (2016) Effect of 30 % hydrogen peroxide on mineral chemical 10.​1016/J.​JDDST.​2022.​104085 composition and surface morphology of bovine enamel. Odontol- 22. Smaldone RA, Forgan RS, Furukawa H et al (2010) Metalorganic ogy 104:44–52. https://​doi.​org/​10.​1007/​s10266-​014-​0189-7 frameworks from edible natural products. Angew Chemie - Int Ed 35. Shahmoradi M, Bertassoni LE, Elfallah HM, Swain M (2014) 49:8630–8634. https://​doi.​org/​10.​1002/​anie.​20100​2343 Fundamental structure and properties of enamel, dentin and 23. Khan NA, Jhung SH (2015) Synthesis of metal-organic frame- cementum. Adv Calcium Phosphate Biomater 511–547. https://​ works (MOFs) with microwave or ultrasound: rapid reaction, doi.​org/​10.​1007/​978-3-​642-​53980-0_​17 phase-selectivity, and size reduction. Coord Chem Rev 285:11– 36. Carvalho de Lopes CA, Limirio PHJO, Novais VR, Dechichi P 23. https://​doi.​org/​10.​1016/j.​ccr.​2014.​10.​008 (2018) Fourier transform infrared spectroscopy (FTIR) applica- 24. Kaddah S, Khreich N, Kaddah F et al (2018) Cholesterol modu- tion chemical characterization of enamel, dentin and bone. Appl lates the liposome membrane fluidity and permeability for a Spectrosc Rev 53:747–769. https://​doi.​org/​10.​1080/​05704​928.​ hydrophilic molecule. Food Chem Toxicol 113:40–48. https://​ 2018.​14319​23 doi.​org/​10.​1016/J.​FCT.​2018.​01.​017 37. Shurvell HF (2006) Spectra- structure correlations in the mid- and 25. Zhang G, Meng F, Guo Z et al (2018) Enhanced stability of vita- far-infrared. Handbook of Vibrational Spectroscopy. https://​doi.​ min A palmitate microencapsulated by γ-cyclodextrin metal- org/​10.​1002/​04700​27320.​s4101 organic frameworks. J Microencapsul 35:249–258. https://​doi.​ 38. Pleshko N, Boskey A, Mendelsohn R (1991) Novel infrared org/​10.​1080/​02652​048.​2018.​14624​17 spectroscopic method for the determination of crystallinity of 26. Garskaite E, Gross KA, Yang SW et al (2014) Effect of processing hydroxyapatite minerals. Biophys J 60:786–793. https://​doi.​org/​ conditions on the crystallinity and structure of carbonated calcium 10.​1016/​S0006-​3495(91)​82113-0 hydroxyapatite (CHAp). CrystEngComm 16:3950–3959. https://​ 39. Huestis MA, Solimini R, Pichini S et al (2019) Cannabidiol doi.​org/​10.​1039/​c4ce0​0119b adverse effects and toxicity. Curr Neuropharmacol 17:974. https://​ 27. Bachmann L, Diebolder R, Hibst R, Zezell DM (2003) Infrared doi.​org/​10.​2174/​15701​59X17​66619​06031​71901 absorption bands of enamel and dentin tissues from human and 40 Carrouel F, Viennot S, Ottolenghi L et al (2020) Nanoparticles as bovine teeth. Appl Spectrosc Rev 38:1–14. https://​doi.​org/​10.​ anti-microbial, anti-inflammatory, and remineralizing agents in 1081/​ASR-​12001​7479 oral care cosmetics: a review of the current situation. Nanomater 28. Anwar Alebrahim M, Krafft C, Sekhaneh W et al (2014) ATR- 10(1):140. https://​doi.​org/​10.​3390/​NANO1​00101​40 FTIR and Raman spectroscopy of primary and permanent teeth. 41. Singh V, Guo T, Xu H et al (2017) Moisture resistant and biof- Biomed Spectrosc Imaging 3:15–27. https://​doi.​org/​10.​3233/​ riendly CD-MOF nanoparticles obtained via cholesterol shielding. bsi-​130059 Chem Commun 53:9246–9249. https://​doi.​org/​10.​1039/​C7CC0​ 29. Taube F, Marczewski M, Norén JG (2015) Deviations of inorganic 3471 and organic carbon content in hypomineralised enamel. J Dent 42. David C, Elizalde-Hernández A, Barboza AS et al (2022) Can- 43:269–278. https://​doi.​org/​10.​1016/j.​jdent.​2014.​09.​003 nabidiol in Dentistry: A Scoping Review. Dent J 10:193. https://​ 30. Fattibene P, Carosi A, De Coste V et al (2005) A comparative doi.​org/​10.​3390/​DJ101​00193 EPR, infrared and Raman study of natural and deproteinated tooth enamel and dentin. Phys Med Biol 50:1095–1108. https://d​ oi.o​ rg/​ Publisher's note Springer Nature remains neutral with regard to 10.​1088/​0031-​9155/​50/6/​004 jurisdictional claims in published maps and institutional affiliations. 13