Two-photon polymerization-generated and micromolding-replicated 3D scaffolds for peripheral neural tissue engineering applications.

In this study, we explore the production of well-defined macroscopic scaffolds with two-photon polymerization (2PP) and their use as neural tissue engineering scaffolds. We also demonstrate that these 3D scaffolds can be replicated via soft lithography, which increases production efficiency. Photopolymerizable polylactic acid (PLA) was used to produce scaffolds by 2PP and soft lithography. We assessed the biocompatibility of these scaffolds using an SH-SY5Y human neuronal cell line and primary cultured rat Schwann cells (of direct relevance to the repair of nerve injuries). A Comet assay with SH-SY5Y human neuronal cells revealed minimal DNA damage after washing the photocured material for 7 days in ethanol. Additionally, thin films and 3D scaffolds of the photocured PLA sustained a high degree of Schwann cell purity (99%), enabled proliferation over 7 days and provided a suitable substrate for supporting Schwann cell adhesion such that bi-polar and tri-polar morphologies were observed. Evidence of orthogonally aligned and organized actin thin filaments and the formation of focal contacts were observed for the majority of Schwann cells. In summary, this work supports the use of PLA as a suitable material for supporting Schwann cell growth and in turn use of 3D soft lithography for the synthesis of neural scaffolds in nerve repair.

Laser ablation imparts controlled micro-scale pores in electrospun scaffolds for tissue engineering applications.

Electrospun scaffolds have been used extensively for tissue engineering applications due to the simple processing scheme and versatility. However, many additional benefits can be imparted to these materials via post-processing techniques. Specifically the addition of structured pores on the micro-scale can offer a method to enable patterned cell adhesion, enhanced diffusional properties, and/or guide vascular infiltration upon implantation in vivo. In this study, we laser ablated electrospun poly(L: -lactic acid) (PLA) scaffolds and assessed the ablation process and cellular interaction by examining human adipose-derived stem cell (hASC) viability and proliferation on laser micro-machined scaffolds. Laser ablated pores of 150, 300, and 600 µm diameter were micro-machined through electrospun PLA scaffolds. Laser ablation parameters were varied and it was determined that the aperture and z-travel direction of the laser linearly correlated with the ablated pore diameter. To assess cytocompatibility of the micro-machined scaffolds, hASCs were seeded on each scaffold and cell viability was assessed on day 7. Human ASCs were able to adhere around the micro-machined features. DNA content was quantified on all scaffolds and it was determined that hASCs were able to proliferate on all scaffolds. The process of laser ablation could impart many beneficial features to electrospun scaffolds by increasing mass transport and mimicking micro-scale features and assisting in patterning of cells around micro-machined features.

Pulsed laser deposition of antimicrobial silver coating on Ormocer microneedles.

One promising option for transdermal delivery of protein- and nucleic acid-based pharmacologic agents involves the use of microneedles. However, microneedle-generated pores may allow microorganisms to penetrate the stratum corneum layer of the epidermis and cause local or systemic infection. In this study, microneedles with antimicrobial functionality were fabricated using two-photon polymerization-micromolding and pulsed laser deposition.The antibacterial activity of the silver-coated organically modified ceramic (Ormocer)microneedles was demonstrated using an agar diffusion assay. Human epidermal keratinocyte viability on the Ormocer surfaces coated with silver was similar to that on uncoated Ormocer surfaces. This study indicates that coating microneedles with silver thin films using pulsed laser deposition is a useful and novel approach for creating microneedles with antimicrobial functionality.