Optimal structural and physical properties of aerogels for promoting robust neurite extension in vitro

Influence of aerogel mechanical properties on collagen micromorphology and its architecture

Previously, we demonstrated the promise of aerogels for the repair of nerve injuries as neural cells extend longer processes (neurites) when grown on aerogels compared to a control surface. We also reported that the aerogel surface topography influenced neurite length. Neurite extension may be boosted by depositing collagen on the aerogel prior to plating the cells. Indeed, collagen has many applications in biomaterials for nerve repair because it profoundly influences cellular properties such as shape and motility. Using collagen to enhance neurite extension requires knowing the effect of collagen deposition on the aerogel surface profile as well as how the aerogel's surface topography influences collagen organization into fibers or films. Herein, we have examined by SEM and profilometry the reciprocal relationship between collagen micromorphology and aerogel surface features including pore diameters, surface roughness, and Young's modulus (Y). Using 5 types of aerogels differing from each other by these parameters, we show that increasing the collagen surface concentration from 4 to 20 μg cm-2 leads to a gradual transition in collagen architecture from discrete fibers to films where individual fibers were not discernible. The collagen surface concentration at which deposited collagen changes from filaments to films (transition point, T.P.) was strongly dependent on aerogel physical properties as it increased with increasing pore diameter and surface roughness, while Y had little effect. These results provide a practical framework to customize the organization of collagen fibers on scaffolds for biomedical applications.

A printability study of multichannel nerve guidance conduits using projection-based three-dimensional printing

Multichannel nerve guidance conduits (NGCs) replicating the native architecture of peripheral nerves have emerged as promising alternatives to autologous nerve grafts. However, manufacturing multichannel NGCs is challenging in terms of desired structural stability and resolution. In this study, we systematically investigated the effects of photopolymer properties, inner diameter dimensions, printing parameters, and different conditions on multichannel NGCs printability using projection-based three-dimensional printing. Low viscosity and rapid photocuring properties were essential requirements. A standard model was generated to evaluate multichannel NGC printed quality. The results showed that printing deviations decreased with increased mechanical strength and inner diameter. Subsequently, gelatin methacrylate (GelMA) NGCs was selected as a representative. It was found that printing conditions, including printing temperature, peeling, and shrinkage affected final NGC accuracy and quality. PC-12 cells cultured with the GelMA NGCs displayed non-toxic and promoted cell migration. Our research provides an effective, time-saving, and high-resolution technology for manufacturing multichannel NGCs with high fidelity, which may be used as reference templates for biomedical applications.