title: About the Sterilization of Chitosan Hydrogel Nanoparticles.
abstract: In the last years, nanostructured biomaterials have raised a great interest as platforms for delivery of drugs, genes, imaging agents and for tissue engineering applications. In particular, hydrogel nanoparticles (HNP) associate the distinctive features of hydrogels (high water uptake capacity, biocompatibility) with the advantages of being possible to tailor its physicochemical properties at nano-scale to increase solubility, immunocompatibility and cellular uptake. In order to be safe, HNP for biomedical applications, such as injectable or ophthalmic formulations, must be sterile. Literature is very scarce with respect to sterilization effects on nanostructured systems, and even more in what concerns HNP. This work aims to evaluate the effect and effectiveness of different sterilization methods on chitosan (CS) hydrogel nanoparticles. In addition to conventional methods (steam autoclave and gamma irradiation), a recent ozone-based method of sterilization was also tested. A model chitosan-tripolyphosphate (TPP) hydrogel nanoparticles (CS-HNP), with a broad spectrum of possible applications was produced and sterilized in the absence and in the presence of protective sugars (glucose and mannitol). Properties like size, zeta potential, absorbance, morphology, chemical structure and cytotoxicity were evaluated. It was found that the CS-HNP degrade by autoclaving and that sugars have no protective effect. Concerning gamma irradiation, the formation of agglomerates was observed, compromising the suspension stability. However, the nanoparticles resistance increases considerably in the presence of the sugars. Ozone sterilization did not lead to significant physical adverse effects, however, slight toxicity signs were observed, contrarily to gamma irradiation where no detectable changes on cells were found. Ozonation in the presence of sugars avoided cytotoxicity. Nevertheless, some chemical alterations were observed in the nanoparticles.
authors.affiliation: Departamento de Farmácia, Faculdade de Ciências Farmacêuticas-Universidade de São Paulo, Butantã, São Paulo, Brazil.|Centro de Química Estrutural, Instituto Superior Técnico-Universidade de Lisboa, Lisboa, Portugal.
authors.forename: Raquel
authors.initials: R
authors.lastname: Galante
authors.affiliation: Departamento de Farmácia, Faculdade de Ciências Farmacêuticas-Universidade de São Paulo, Butantã, São Paulo, Brazil.|Agência Nacional de Vigilância Sanitária, Brasília, Brazil.
authors.forename: Carolina F
authors.initials: CF
authors.lastname: Rediguieri
authors.affiliation: Departamento de Farmácia, Faculdade de Ciências Farmacêuticas-Universidade de São Paulo, Butantã, São Paulo, Brazil.
authors.forename: Irene Satiko
authors.initials: IS
authors.lastname: Kikuchi
authors.affiliation: Centro de Tecnologia das Radiações-Instituto de Pesquisas Energéticas e Nucleares, Butantã, São Paulo, Brazil.
authors.forename: Pablo A S
authors.initials: PA
authors.lastname: Vasquez
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico-Universidade de Lisboa, Lisboa, Portugal.|Departamento de Engenharia Mecânica and IDMEC-Instituto Superior Técnico-Universidade de Lisboa, Lisboa, Portugal.
authors.forename: Rogério
authors.initials: R
authors.lastname: Colaço
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico-Universidade de Lisboa, Lisboa, Portugal.|Centro de Investigação Interdisciplinar Egas Moniz, Instituto Superior de Ciências da Saúde Egas Moniz, Monte de Caparica, Caparica, Portugal.
authors.forename: Ana Paula
authors.identifier: http://orcid.org/0000-0002-6179-9296
authors.initials: AP
authors.lastname: Serro
authors.affiliation: Departamento de Farmácia, Faculdade de Ciências Farmacêuticas-Universidade de São Paulo, Butantã, São Paulo, Brazil.
authors.forename: Terezinha J A
authors.initials: TJ
authors.lastname: Pinto
mesh_terms: D000818:Animals; D002241:Carbohydrates / Q000737:chemistry; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D048271:Chitosan / Q000737:chemistry*; D004553:Electric Conductivity; D005720:Gamma Rays; D006358:Hot Temperature; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D051379:Mice; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry* / Q000633:toxicity; D010126:Ozone / Q000737:chemistry; D010316:Particle Size; D020011:Protective Agents / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013242:Sterilization / Q000379:methods*
chemical_list: D002241:Carbohydrates; D020011:Protective Agents; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D010126:Ozone; D048271:Chitosan