a04f64c5b2d81577c76bb73ae57f1aaf pharmaceutics-17-01211.pdf a618a95444882bf4ec32f32dddb1cec740126283 pharmaceutics-17-01211.pdf fb5ba90ce1a3e1602553c7a90dbc72f8686fe1e5bde350914c1e81c2d6917f0f pharmaceutics-17-01211.pdf Title: Amino Compound-Synthesized Gold Nanoparticles for SARS-CoV-2 Antigen Delivery Subject: Background: Gold nanoparticles (AuNPs) are a promising platform for vaccine antigen delivery due to their ability to stimulate both innate and adaptive immune responses. These effects depend strongly on physicochemical properties such as size, polydispersity, morphology, and surface charge, which are in turn determined by the synthesis method. While amino acids are often used as capping agents for AuNPs, their direct use as both reducing and stabilizing agents has been rarely investigated. Objectives: This study aimed to establish an ultrasound-assisted method for synthesizing AuNPs using amino compounds as both reducing and stabilizing agents, and assess their physicochemical characteristics, antigen-binding capacity, and immunogenicity. Methods: AuNPs were synthesized using L-cysteine, L-arginine, and cysteamine as dual reducing/stabilizing agents under ultrasonic conditions. The nanoparticles were combined with a recombinant receptor-binding domain (RBD) of SARS-CoV-2 and evaluated in mice for their ability to induce antibody responses. Results: The synthesized AuNPs exhibited hydrodynamic diameters ranging from 6.3 to 12.4 nm and zeta potentials from -40.5 to +36.5 mV, depending on the amino compound used. All formulations elicited robust anti-RBD IgG responses, but virus neutralization activity varied significantly. Notably, AuNP–arginine induced the strongest neutralizing response despite lower adsorption capacity and stability, suggesting that epitope preservation and antigen presentation quality were more decisive than antigen density. Conclusions: These findings underscore the importance of nanoparticle design in optimizing antigen presentation and highlight the potential of amino compound-synthesized AuNPs as effective antigen delivery vehicles for future vaccine development. Keywords: gold nanoparticles; amino compounds; nanomedicine; vaccines; SARS-CoV-2 Author: Layane Souza Rego, Marianna Teixeira Pinho Favaro, Monica Josiane Rodrigues-Jesus, Robert Andreata-Santos, Luiz Mário Ramos Janini, Marcelo Martins Seckler, Luis Carlos de Souza Ferreira and Adriano Rodrigues Azzoni Creator: LaTeX with hyperref Producer: pdfTeX-1.40.25; modified using OpenPDF 1.4.2 CreationDate: Wed Sep 17 12:53:27 2025 CEST ModDate: Thu Sep 18 08:45:36 2025 CEST Custom Metadata: yes Metadata Stream: no Tagged: no UserProperties: no Suspects: no Form: none JavaScript: no Pages: 15 Encrypted: no Page size: 595.276 x 841.89 pts (A4) Page rot: 0 File size: 1287406 bytes Optimized: no PDF version: 1.5 name type encoding emb sub uni object ID ------------------------------------ ----------------- ---------------- --- --- --- --------- ZWJHOT+URWPalladioL-Roma Type 1 Custom yes yes yes 97 0 PRMCDS+URWPalladioL-Ital Type 1 Custom yes yes yes 98 0 YZONLH+VnURWPalladioL Type 1 Custom yes yes yes 99 0 OJYQXC+CMSY10 Type 1 Builtin yes yes yes 100 0 XKDCGO+URWPalladioL-Bold Type 1 Custom yes yes yes 101 0 ZXDKIP+EURM10 Type 1 Builtin yes yes yes 181 0 EBUKYJ+EURB10 Type 1 Builtin yes yes yes 221 0 NLNIDN+PalatinoLinotype TrueType WinAnsi yes yes no 213 0 NLNIDL+PalatinoLinotype,Bold TrueType WinAnsi yes yes no 214 0 NLNIDN+PalatinoLinotype TrueType WinAnsi yes yes no 242 0 NLNIDN+PalatinoLinotype TrueType WinAnsi yes yes no 301 0 FVSNZU+SFRM0900 Type 1 Custom yes yes yes 393 0 Jhove (Rel. 1.28.0, 2023-05-18) Date: 2026-02-14 03:08:41 CET RepresentationInformation: pharmaceutics-17-01211.pdf ReportingModule: PDF-hul, Rel. 1.12.4 (2023-03-16) LastModified: 2026-02-13 19:58:55 CET Size: 1287406 Format: PDF Version: 1.5 Status: Well-Formed and valid SignatureMatches: PDF-hul MIMEtype: application/pdf PDFMetadata: Objects: 465 FreeObjects: 1 IncrementalUpdates: 0 DocumentCatalog: ViewerPreferences: HideToolbar: false HideMenubar: false HideWindowUI: false FitWindow: true CenterWindow: false DisplayDocTitle: false NonFullScreenPageMode: UseNone Direction: L2R ViewArea: CropBox ViewClip: CropBox PrintArea: CropBox PageClip: CropBox PageLayout: SinglePage PageMode: UseNone Outlines: Item: Title: Introduction Item: Title: Materials and Methods Children: Item: Title: Synthesis of AuNPs Reduced and Capped with Amino Compounds Item: Title: Analysis of the Size Distribution and Zeta Potential of the AuNPs Item: Title: Conjugation of AuNPs and RBD Protein Item: Title: Mice Immunization Item: Title: IgG Antibody Levels, Subclass, and Affinity Item: Title: SARS-CoV-2-Neutralizing Effects of Anti-RBD Antibodies Item: Title: Statistical Analysis Item: Title: Results and Discussion Item: Title: Conclusions Item: Title: References Info: Title: Amino Compound-Synthesized Gold Nanoparticles for SARS-CoV-2 Antigen Delivery Author: Layane Souza Rego, Marianna Teixeira Pinho Favaro, Monica Josiane Rodrigues-Jesus, Robert Andreata-Santos, Luiz Mário Ramos Janini, Marcelo Martins Seckler, Luis Carlos de Souza Ferreira and Adriano Rodrigues Azzoni Subject: Background: Gold nanoparticles (AuNPs) are a promising platform for vaccine antigen delivery due to their ability to stimulate both innate and adaptive immune responses. These effects depend strongly on physicochemical properties such as size, polydispersity, morphology, and surface charge, which are in turn determined by the synthesis method. While amino acids are often used as capping agents for AuNPs, their direct use as both reducing and stabilizing agents has been rarely investigated. Objectives: This study aimed to establish an ultrasound-assisted method for synthesizing AuNPs using amino compounds as both reducing and stabilizing agents, and assess their physicochemical characteristics, antigen-binding capacity, and immunogenicity. Methods: AuNPs were synthesized using L-cysteine, L-arginine, and cysteamine as dual reducing/stabilizing agents under ultrasonic conditions. The nanoparticles were combined with a recombinant receptor-binding domain (RBD) of SARS-CoV-2 and evaluated in mice for their ability to induce antibody responses. Results: The synthesized AuNPs exhibited hydrodynamic diameters ranging from 6.3 to 12.4 nm and zeta potentials from -40.5 to +36.5 mV, depending on the amino compound used. All formulations elicited robust anti-RBD IgG responses, but virus neutralization activity varied significantly. Notably, AuNP–arginine induced the strongest neutralizing response despite lower adsorption capacity and stability, suggesting that epitope preservation and antigen presentation quality were more decisive than antigen density. Conclusions: These findings underscore the importance of nanoparticle design in optimizing antigen presentation and highlight the potential of amino compound-synthesized AuNPs as effective antigen delivery vehicles for future vaccine development. 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