Engineering and development of a tissue model for the evaluation of microneedle penetration ability, drug diffusion, photothermal activity, and ultrasound imaging: a promising surrogate to ex vivo and in vivo tissues

Driven by regulatory authorities and the ever-growing demands from industry, various artificial tissue models have been developed. Nevertheless, there is no model to date that is capable of mimicking the biomechanical properties of the skin whilst exhibiting the hydrophilicity/hydrophobicity properties of the skin layers. As a proof-of-concept study, Makvandi and colleagues fabricated tissue surrogates based on gel and silicone for evaluation of microneedle penetration, drug diffusion, photothermal activity, and ultrasound bioimaging. The silicone layer aims to imitate the stratum corneum while the gel layer aims to mimic water-rich viable epidermis and dermis present in vivo tissues. We assessed the diffusion of drugs across the tissue model, and the results revealed that our proposed tissue model showed similar behavior to a cancerous kidney. In place of typical in vitro aqueous solutions, this model can also be employed for evaluating the photoactivity of a photothermal agent (e.g., polydopamine) since the tissue model showed a similar heating profile to mice skin when irradiated with near-infrared (NIR) laser. In addition, the designed tissue model exhibited promising results for biomedical applications in optical coherence tomography and ultrasound imaging. Such a tissue model paves the way to reduce the use of animals testing in research whilst obviating ethical concerns.