A microvalve cell printing technique using riboflavin photosensitizer for selective cell patterning onto a retinal chip

Delivery of cells onto subretinal chips for stimulation possess a significant technical challenge. Often, such capabilities are confined by sophisticated laboratory-based commercial instrumentation, which are inherently expensive and equipped with a limited capacity. As a result, exploring new delivery techniques requires an ad hoc approach to suit the requirements of the target deposition method, material(s) and cells under investigation. For the first time, a customised 3D printer, equipped with a microvalve, developed at a low cost, and capable of high resolution placement on a retinal chip is proposed. This allowed the investigation of a pneumatically-driven and microvalve printing technique to deliver cells on a subretinal chip, thus suiting the required resolution and localization of cells. The bioink is coupled with a light-induced collagen photo-crosslinking mechanism. The collagen, mixed with the riboflavin, can be crosslinked after exposure to blue light. The cells printed on the chip remained in the collagen patterns and demonstrated good viability and growth. This technique provided a useful means of delivering cells where high precision, throughput and accuracy is required, such as onto sub-retinal chips.