Ozone Gas as a Benign Sterilization Treatment for PLGA Nanofiber Scaffolds

Sterilization of Polymeric Implants: Challenges and Opportunities

Degradable and environmentally responsive polymers have been actively developed for drug delivery and regenerative medicine applications, yet inadequate consideration of their compatibility with terminal sterilization presents notable barriers to clinical translation. This Review discusses industry-established terminal sterilization methods and aseptic processing and contrasts them with innovative approaches aimed at preserving the integrity of polymeric implants. Regulatory guidelines, fiscal considerations, and potential pitfalls are discussed to encourage early integration of sterility regulatory considerations in material designs.

Functionalized Electrospun Scaffold-Human-Muscle-Derived Stem Cell Construct Promotes In Vivo Neocartilage Formation

Polycaprolactone (PCL) is a non-cytotoxic, completely biodegradable biomaterial, ideal for cartilage tissue engineering. Despite drawbacks such as low hydrophilicity and lack of functional groups necessary for incorporating growth factors, it provides a proper environment for different cells, including stem cells. In our study, we aimed to improve properties of scaffolds for better cell adherence and cartilage regeneration. Thus, electrospun PCL–scaffolds were functionalized with ozone and loaded with TGF-β3. Together, human-muscle-derived stem cells (hMDSCs) were isolated and assessed for their phenotype and potential to differentiate into specific lineages. Then, hMDSCs were seeded on ozonated (O) and non-ozonated (“naïve” (NO)) scaffolds with or without protein and submitted for in vitro and in vivo experiments. In vitro studies showed that hMDSC and control cells (human chondrocyte) could be tracked for at least 14 days. We observed better proliferation of hMDSCs in O scaffolds compared to NO scaffolds from day 7 to day 28. Protein analysis revealed slightly higher expression of type II collagen (Coll2) on O scaffolds compared to NO on days 21 and 28. We detected more pronounced formation of glycosaminoglycans in the O scaffolds containing TGF-β3 and hMDSC compared to NO and scaffolds without TGF-β3 in in vivo animal experiments. Coll2-positive extracellular matrix was observed within O and NO scaffolds containing TGF-β3 and hMDSC for up to 8 weeks after implantation. These findings suggest that ozone-treated, TGF-β3-loaded scaffold with hMDSC is a promising tool in neocartilage formation.

The Effect of Ozone Treatment on the Physicochemical Properties and Biocompatibility of Electrospun Poly(ε)caprolactone Scaffolds

Ozonation has been proved as a viable surface modification technique providing certain properties to the scaffolds that are essential in tissue engineering. However, the ozone (O3) treatment of PCL scaffolds in aqueous environments has not yet been presented. O3 treatment performed in aqueous environments is more effective compared with traditional, executed in ambient air treatment due to more abundant production of hydroxyl radicals (•OH) within the O3 reaction with water molecules. During interaction with •OH, the scaffold acquires functional groups which improve wettability properties and encapsulate growth factors. In this study, a poly(ε)caprolactone (PCL) scaffold was fabricated using solution electrospinning and was subsequently ozonated in a water reactor. The O3 treatment resulted in the expected occurrence of oxygen-containing functional groups, which improved scaffold wettability by almost 27% and enhanced cell proliferation for up to 14 days. The PCL scaffold was able to withhold 120 min of O3 treatment, maintaining fibrous morphology and mechanical properties.

The Investigation of the Structure and Properties of Ozone-Sterilized Nonwoven Biopolymer Materials for Medical Applications

Nowadays, the development and research of nonwoven medical fibrous materials based on biopolymers is an area of a great practical interest. One of the most promising methods for producing nonwoven materials with a highly developed surface is electrospinning (ES). In this article, the possibility of efficient sterilization of ultrathin fibers based on polyhydroxybutyrate (PHB) by ozone treatment was considered. The purpose of this work was to select the most optimal morphology of nonwoven materials for medical purposes and to establish the correlation between the supramolecular structure and the physical properties of fibrous materials while under the influence of an ozone sterilization process.

Plasmonic Microneedle Arrays for in Situ Sensing with Surface-Enhanced Raman Spectroscopy (SERS)

Surface-enhanced Raman spectroscopy (SERS) is a sensitive, chemically specific, and short-time response probing method with significant potential in biomedical sensing. This paper reports the integration of SERS with microneedle arrays as a minimally invasive platform for chemical sensing, with a particular view toward sensing in interstitial fluid (ISF). Microneedle arrays were fabricated from a commercial polymeric adhesive and coated with plasmonically active gold nanorods that were functionalized with the pH-sensitive molecule 4-mercaptobenzoic acid. This sensor can quantitate pH over a range of 5 to 9 and can detect pH levels in an agar gel skin phantom and in human skin in situ. The sensor array is stable and mechanically robust in that it exhibits no loss in SERS activity after multiple punches through an agar gel skin phantom and human skin or after a month-long incubation in phosphate-buffered saline. This work is the first to integrate SERS-active nanoparticles with polymeric microneedle arrays and to demonstrate in situ sensing with this platform.

The enhanced photocatalytic properties of MnO2/g-C3N4 heterostructure for rapid sterilization under visible light

Herein, a heterostructure based on MnO₂ and g-C₃N₄ was constructed on the surface of metallic Ti implants, in which MnO₂ favored the transfer and separation of free charges to enhance the photoconversion efficiency of g-C₃N₄ by 21.11%. Consequently, the yield of ROS was promoted significantly, which denatured protein and damaged DNA to kill bacteria efficiently. In addition, glutathione (GSH, l-γ-glutamyl-l-cysteinyl-glycine) defending oxidative stress in bacteria, was oxidized by MnO₂ in the hybrid coating once the bacterial membrane was disrupted by ROS. Hence, after visible light irradiation for 20 min, MnO₂/g-C₃N₄ coating exhibited superior disinfection efficacy of 99.96% and 99.26% against S. aureus and E. coli severally. This work provided a practical sterilization strategy about MnO₂/g-C₃N₄ systems through the synergistic effects of enhanced photodynamic antibacterial therapy and oxidization effect of MnO₂ with great biosafety, in which MnO₂ enhanced the photocatalyst property of g-C₃N₄ to generate more ROS and deplete GSH to improve antibacterial efficiency. It will bring more insight into rapid and highly effective disinfection and antibacterial strategy without using traditional high-temperature, ultraviolet ray and antibiotics that cause side-effects.

Sterilization of implantable polymer-based medical devices: A review

This review article is focused on the sterilization techniques used for polymer-based implantable medical devices as well as the regulatory aspects governing sterile medical devices. Polymeric materials are increasingly used in implantable devices due to their biodegradable and biocompatible nature. Patients and medical staff often prefer long-term implantable devices and these can be achieved using high molecular weight polymers. Sterilization of polymer-based implantable devices is critical. Since all implantable devices must be sterile, the effect of the sterilization method on the different device components (such as, the polymer, the drug, the electronics, etc.) has to be considered. A comprehensive summary of the established sterilization methods is provided along with the possible effects on polymers. In addition, novel sterilization methods are also discussed.

Sterilization of silicone-based hydrogels for biomedical application using ozone gas: Comparison with conventional techniques

Sterilization of hydrogels is challenging due to their often reported sensitivity to conventional methods involving heat or radiation. Although aseptic manufacturing is a possibility, terminal sterilization is safer in biological terms, leading to a higher overall efficiency, and thus should be used whenever it is possible. The main goal of this work was to study the applicability of an innovative ozone gas terminal sterilization method for silicone-based hydrogels and compare its efficacy and effects with those of traditional sterilization methods: steam heat and gamma irradiation. Ozone gas sterilization is a method with potential interest since it is reported as a low cost green method, does not leave toxic residues and can be applied to thermosensitive materials. A hydrogel intended for ophthalmological applications, based on tris(trimethylsiloxy)silyl] propyl methacrylate, was prepared and extensively characterized before and after the sterilization procedures. Alterations regarding transparency, swelling, wettability, ionic permeability, friction coefficient, mechanical properties, topography and morphology and chemical composition were monitored. Efficacy of the ozonation was accessed by performing controlled contaminations and sterility tests. In vitro cytotoxicity testes were also performed. The results show that ozonation may be applied to sterilize the studied material. A treatment with 8 pulses allowed sterilizing the material with bioburdens≤10³CFU/mL, preserving all the studied properties within the required known values for contact lenses materials. However, a higher exposure (10 pulses) led to some degradation of the material and induced mild cytotoxicity. Steam heat sterilization led to an increase of swelling capacity and a decrease of the water contact angle. Regarding gamma irradiation, the increase of irradiation dose led to an increase of the friction coefficient. The higher dose (25kGy) originated surface degradation and affected the mechanical properties of the hydrogel by inducing a significant increase of the Young's modulus. Overall, the results show that ozonation may be considered as a valid and promising alternative for the sterilization of silicon-based hydrogels for biomedical applications.

About the Sterilization of Chitosan Hydrogel Nanoparticles

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.

Polylactides in additive biomanufacturing

New advanced manufacturing technologies under the alias of additive biomanufacturing allow the design and fabrication of a range of products from pre-operative models, cutting guides and medical devices to scaffolds. The process of printing in 3 dimensions of cells, extracellular matrix (ECM) and biomaterials (bioinks, powders, etc.) to generate in vitro and/or in vivo tissue analogue structures has been termed bioprinting. To further advance in additive biomanufacturing, there are many aspects that we can learn from the wider additive manufacturing (AM) industry, which have progressed tremendously since its introduction into the manufacturing sector. First, this review gives an overview of additive manufacturing and both industry and academia efforts in addressing specific challenges in the AM technologies to drive toward AM-enabled industrial revolution. After which, considerations of poly(lactides) as a biomaterial in additive biomanufacturing are discussed. Challenges in wider additive biomanufacturing field are discussed in terms of (a) biomaterials; (b) computer-aided design, engineering and manufacturing; (c) AM and additive biomanufacturing printers hardware; and (d) system integration. Finally, the outlook for additive biomanufacturing was discussed.