Effect of culture condition on cell viability and gel contraction in a skin chip

Microfluidic-based skin-on-chip systems for safety assessment of nanomaterials

The skin is the body's largest organ, continuously exposed to and affected by natural and anthropogenic nanomaterials (materials with external and internal dimensions in the nanoscale range). This broad spectrum of insults gives rise to irreversible health effects (from skin corrosion to cancer). Organ-on-chip systems can recapitulate skin physiology with high fidelity and potentially revolutionize the safety assessment of nanomaterials. Here, we review current advances in skin-on-chip models and their potential to elucidate biological mechanisms. Further, strategies are discussed to recapitulate skin physiology on-chip, improving control over nanomaterials exposure and transport across cells. Finally, we highlight future opportunities and challenges from design and fabrication to acceptance by regulatory bodies and industry.

Design and evaluation of a skin-on-a-chip pumpless microfluidic device

The development of microfluidic culture technology facilitates the progress of study of cell and tissue biology. This technology expands the understanding of pathological and physiological changes. A skin chip, as in vitro model, consisting of normal skin tissue with epidermis and dermis layer (full thickness) was developed. Polydimethylsiloxane microchannels with a fed-batched controlled perfusion feeding system were used to create a full-thick ex-vivo human skin on-chip model. The design of a novel skin-on-a-chip model was reported, in which the microchannel structures mimic the architecture of the realistic vascular network as nutrients transporter to the skin layers. Viabilities of full-thick skin samples cultured on the microbioreactor and traditional tissue culture plate revealed that a precise controlled condition provided by the microfluidic enhanced tissue viability at least for seven days. Several advantages in skin sample features under micro-scale-controlled conditions were found such as skin mechanical strength, water adsorption, skin morphology, gene expression, and biopsy longevity. This model can provide an in vitro environment for localizing drug delivery and transdermal drug diffusion studies. The skin on the chip can be a valuable in vitro model for representing the interaction between drugs and skin tissue and a realistic platform for evaluating skin reaction to pharmaceutical materials and cosmetic products.

Modeling an Optimal 3D Skin-on-Chip within Microfluidic Devices for Pharmacological Studies

Preclinical research remains hampered by an inadequate representation of human tissue environments which results in inaccurate predictions of a drug candidate’s effects and target’s suitability. While human 2D and 3D cell cultures and organoids have been extensively improved to mimic the precise structure and function of human tissues, major challenges persist since only few of these models adequately represent the complexity of human tissues. The development of skin-on-chip technology has allowed the transition from static 3D cultures to dynamic 3D cultures resembling human physiology. The integration of vasculature, immune system, or the resident microbiome in the next generation of SoC, with continuous detection of changes in metabolism, would potentially overcome the current limitations, providing reliable and robust results and mimicking the complex human skin. This review aims to provide an overview of the biological skin constituents and mechanical requirements that should be incorporated in a human skin-on-chip, permitting pharmacological, toxicological, and cosmetic tests closer to reality.

Coenzyme Q10 Efficacy Test for Human Skin Equivalents Using a Pumpless Skin-On-A-Chip System

A human skin equivalent (HSE) composed of the epidermis and dermis is cultured using a pumpless skin-on-a-chip system to supply cultures the desired flow rate using gravity flow without a pump or an external tube connection. Coenzyme Q10 efficacy is tested by adjusting its concentration, as it is known to have anti-aging and antioxidant effects in culture solutions. The relationship between the contraction rate of a full-thickness human skin equivalent and secreted transforming growth factor (TGF) β-1 is analyzed via enzyme-linked immunosorbent assay (ELISA). Following hematoxylin and eosin (H&E) staining, an image of the skin equivalent is analyzed to measure the epidermal layer’s thickness. The cell density and differentiation of the dermis layer are investigated. Gene and protein expression in the dermal and epidermal layers are quantitatively analyzed using quantitative real time polymerase chain reaction (qPCR) and immunohistochemical staining. As the coenzyme Q10 treatment concentration increased, the number of cells per unit area and the thickness of the epidermal layer increased, the expression level of filaggrin increased, and the contraction rate of full-thickness HSE was proportional to the amount of TGF β-1 secreted.

Novel Strategies in Artificial Organ Development: What Is the Future of Medicine?

The technology of tissue engineering is a rapidly evolving interdisciplinary field of science that elevates cell-based research from 2D cultures through organoids to whole bionic organs. 3D bioprinting and organ-on-a-chip approaches through generation of three-dimensional cultures at different scales, applied separately or combined, are widely used in basic studies, drug screening and regenerative medicine. They enable analyses of tissue-like conditions that yield much more reliable results than monolayer cell cultures. Annually, millions of animals worldwide are used for preclinical research. Therefore, the rapid assessment of drug efficacy and toxicity in the early stages of preclinical testing can significantly reduce the number of animals, bringing great ethical and financial benefits. In this review, we describe 3D bioprinting techniques and first examples of printed bionic organs. We also present the possibilities of microfluidic systems, based on the latest reports. We demonstrate the pros and cons of both technologies and indicate their use in the future of medicine.