Infection is the major cause of implant failure after breast reconstruction surgery . Medical-grade polycaprolactone (mPCL) scaffolds designed and rooted in evidence-based research offer a promising alternative to overcome the limitations of clinically routinely used silicone implants for breast reconstruction [2-3]. Nevertheless, as with any implant, biodegradable scaffolds are susceptible to bacterial infection, too. Especially as bacteria from the skin can rapidly colonize the mPCL surface during scaffold implantation and form subsequently biofilms. Biofilm-related infections are clinically challenging to treat and can lead to chronic infection and persisting inflammation of the implant host interface . We hypothesize that scaffold guided breast reconstruction combined with an antibacterial implant coating allows to prevent bacterial infection while promoting, at the same time, implant integration and subsequently tissue regeneration.
Macroporous scaffolds of a mPCL composite containing 45%(w/w) of sucrose particles with crystals size ranging from 20 to 50 µm, were additively manufactured using a BioScaffolder 3.1 (GeSiM mbH, Germany). The printed scaffolds were immersed in ultrapurified water (AriumR pro UF Ultrapure Water System, Germany) for 15 days in order to leach out the sucrose particles and create microporosity on the surface and within the scaffold struts. Fabricated scaffolds were sterilized by exposure to 70%v/v ethanol followed by evaporation. Scaffolds were then incubated in 1% and 5% human serum albumin (HSA) solutions overnight, at room temperature and under agitation. Resulting coatings of HSA were subsequently stabilized/crosslinked by incubating with 10% or 1%TA. Microporosity of scaffolds, as well its influence on the mechanical properties of clinically relevant large scaffolds was characterized by scanning electron microscopy, microcomputed tomography and uniaxial compression testing. Moreover, 3D in vitro assays were used in order to investigate the stability of the newly developed antibacterial coating and its efficacy against two of the most commonly found bacteria in breast implant-infections, S. aureus and P. aeruginosa.
The physical immobilization of 1% and 5%HSA onto the surface of 3D printed macro- and microporous mPCL scaffolds, resulted in a reduction of S. aureus colonization by 71.7± 13.6% and 54.3± 12.8%, respectively. Notably, when treatment of scaffolds with HSA was followed by tannic acid (TA) crosslinking/stabilization, uniform and stable coatings with improved antibacterial activity were obtained. The HSA/TA-coated scaffolds were shown stable when incubated at physiological conditions in cell culture media for 7 days. Moreover, they were capable of inhibiting the growth of S. aureus and P. aeruginosa, two of the most commonly found bacteria in breast implant infections. Most importantly, 1%HSA/10%TA- and 5%HSA/1%TA-coated scaffolds were able to reduce S. aureus colonization on the mPCL surface, by 99.8± 0.1% and 98.8± 0.6%, respectively, in comparison to the non-coated control specimens.
This study presents the first set of results for a new biomaterial strategy designed for the prevention of biofilm-related infections on implant surfaces to be used in scaffold-guided breast reconstruction.
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