Safety and efficacy of composite collagen–silver nanoparticle hydrogels as tissue engineering scaffolds

Abstract

The increasing number of multidrug resistant bacteria has revitalized interest in seeking alternative sources for controlling bacterial infection. Silver nanoparticles (AgNPs), are amongst the most promising candidates due to their wide microbial spectrum of action. In this work, we report on the safety and efficacy of the incorporation of collagen coated AgNPs into collagen hydrogels for tissue engineering.The resulting hybrid materials at [AgNPs] < 0.4 µM retained the mechanical properties and biocompatibility for primary human skin fibroblasts and keratinocytes of collagen hydrogels; they also displayed remarkable anti-infective properties against S. aureus, S. epidermidis, E. coli and P. aeruginosa at considerably lower concentrations than silver nitrate. Further, subcutaneous implants of materials containing 0.2 µM AgNPs in mice showed a reduction in the levels of IL-6 and other inflammation markers (CCL24, sTNFR-2, and TIMP1). Finally, an analysis of silver contents in implanted mice showed that silver accumulation primarily occurred within the tissue surrounding the implant. IntroductionBiomaterial-associated infections are a significant healthcare problem and have been linked to medical morbidity and death. [2][3][4][5][6] This has motivated the development of materials with anti-infective properties, such as biomaterials loaded with antibiotics. 7 However, with the increasing number of bacteria that are resistant to antibiotics, 8 silver with historically documented anti-microbial activity has re-gained its attractiveness as an alternative to antibiotics. 9 While toxic to bacteria, it unfortunately is also toxic to mammalian cells. 9,10 More recently, therefore, silver nanoparticles (AgNPs) have been evaluated as a safer alternative to ionic silver. 1,[11][12][13][14][15][16][17][18][19][20] The recent work from our team showed that in comparison with silver, biomolecule-coated, photochemically-produced AgNPs can have both bactericidal and bacteriostatic properties with almost negligible cytotoxic effects. 12 We also showed that oxidation of Ag to AgO is most likely the cause of the cytotoxic effects observed with AgNPs. Our overarching goal is to expand the safe use of AgNPs in the development of implantable hybrid-biomaterials with antiinfective properties for future use as scaffolds to enable regeneration of tissue and organs at a risk of bacterial colonization and concomitant biofilm formation like diabetic foot ulcers. Although some collagen-based materials including † Electronic supplementary information (ESI) available: Representative absorption spectra of AgNP@collagen nanoparticles before and after lyophilization. Absorption spectra for the washes obtained from a 1.0 µM AgNP hydrogel over the course of 5 days. Area under the curve (AUC) calculated from the absorption spectra of 500 µm thickness collagen hydrogels prepared using different concentrations of AgNP@collagen. Selected Cryo-SEM images of BDDGE type I collagen-based hydrogels in the absence or presence of 1.0 µM AgNP. An image of a sel...

Biomaterials and Nanotherapeutics for Enhancing Skin Wound Healing

“…In addition, AgNPs have also been shown to be anti-inflammatory in a peritoneal adhesion model (Wong et al, 2009). Recently, the safety and efficacy of collagen-coated AgNPs encapsulated in collagen hydrogels was shown in primary human skin fibroblasts and keratinocytes; while antimicrobial properties were shown against S. aureus, Staphylococcus epidermidis, E. coli , and P. aeruginosa (Alarcon et al, 2015). To gain insight on the health and environmental impact of AgNPs, they were tested on zebrafish models (Asharani et al, 2008) and found that the NPs induce a dose-dependent toxicity in embryos.…”

Development of silver nanoparticle-based hydrogel composites for antimicrobial activity

“…Hydrogels are 3-dimensionally interconnected hydrophilic polymers, which can absorb an extensive amount of water within the structures without being dissolved in water. Since the chemical, electrical, and mechanical properties of polymer hydrogels could be quite analogous with those present in biological tissues, there have been extensive efforts to utilize the hydrogels in biological applications such as drug delivery (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12), wound/burn dressing (13,14), scaffolds for tissue engineering (15)(16)(17), and others (18)(19)(20)(21). In particular, the inclusion of drugs inside polymer hydrogels may represent an innovative drug delivery system because the release rate of the loaded drugs can be regulated by external stimuli (1,2,(4)(5)(6)(7)(8)(9).…”

Collagen-Nanoparticles Composites for Wound Healing and Infection Control

“…It was reported that this hybrid material retained the mechanical properties and biocompatibility for primary human skin fibroblasts and keratinocytes of collagen hydrogels. In addition, it was observed that these materials present remarkable anti-infective properties against S. aureus, E. coli, S. epidermidis and P. aeruginosa at considerably lower concentrations than silver nitrate [57,58].…”

“…The recent development of dressing impregnated with silver has widened its use for many other wound types that are either colonized or infected [56,57]. Several studies were performed to incorporate Ag NPs into collagen hydrogels for tissue engineering applications.…”