Chitosan/collagen composite scaffolds encapsulating allantoin and lidocaine hydrochloride were formulated in various ratios and characterized in vitro for their applications in wound healing. After fabrication, scaffolds were characterized in terms of topographical properties, surface roughness, and swelling behavior, and then their stabilities were monitored by hydrolytic and enzymatic degradation studies. Following compatibility studies among the active ingredients, drugs were encapsulated within scaffolds, and encapsulation efficiency and drug release studies were carried. Finally, in vitro cell viability and scratch wound healing assays were carried to assess scaffolds as wound dressings. Results suggest that blending of polymers with drugs changed topographical properties and surface roughness prominently. It is found that the formulation with chitosan/collagen ratio of 70/30 is more resistant to both hydrolytic and enzymatic degradation routes due to having favored properties of both collagen and chitosan. In vitro drug release studies indicated rapid release of drugs, hence the scaffolds could be advantageous for patients that need an immediate anesthetic effect in wound healing therapy. The cell culture studies demonstrated that the chitosan/collagen composite scaffolds showed no toxicity, and cell migrations were increased depending on the collagen ratio in scaffolds. These results suggest that chitosan/collagen scaffolds combined with allantoin and lidocaine hydrochloride could be a promising candidate for wound healing applications.

Responsive co-polymers based on polyethyleneglycol methacrylate (PEGMA) monomers have been grown by aqueous phase ATRP from a model protein, trypsin, to generate hybrid polymer-protein block conjugates. The conjugates (Hybrids I and II) both contained the same segment of grafted responsive co-polymer to afford a phase transition at 37 °C, Hybrid II however differed from Hybrid I by having a second block of hydrophilic pPEGMA monomer grown from the end of the responsive block. The resultant ‘diblock’ and ‘triblock’ hybrids were characterised in terms of their temperature-dependent behaviour in solution by dynamic light scattering, small-angle neutron scattering and pulsed-gradient spin-echo NMR, and their structures at surfaces examined by aqueous phase atomic force microscopy and cryo transmission electron microscopy. These data showed that Hybrids I and II differed in their solution behaviour with temperature, dependent on the arrangement of their grafted polymer blocks. Hybrid I self-assembled into higher-order structures above 37 °C before precipitating reversibly, whereas Hybrid II remained essentially constant in size across a similar temperature range even when its attached intermediate polymer block underwent a phase transition. The differences in polymer-protein hybrid behaviour were also manifest in enzyme activity assays with temperature-dependent hydrolysis of both peptide and protein substrates varying with hybrid architecture. Overall the data show that it is possible to grow responsive polymer-protein block co-polymers of varied structures, architectures and solution behaviour and that these can be used to control bioconjugate activity.

The skin is the largest and most exposed organ in the human body. Not only it is involved in numerous biological processes essential for life but also it represents a significant endpoint for the application of pharmaceuticals. The area of in vitro skin tissue engineering has been progressing extensively in recent years. Advanced in vitro human skin models strongly impact the discovery of new drugs thanks to the enhanced screening efficiency and reliability. Nowadays, animal models are largely employed at the preclinical stage of new pharmaceutical compounds development for both risk assessment evaluation and pharmacokinetic studies. On the other hand, animal models often insufficiently foresee the human reaction due to the variations in skin immunity and physiology. Skin-on-chips devices offer innovative and state-of-the-art platforms essential to overcome these limitations. In the present review, we focus on the contribution of skin-on-chip platforms in fundamental research and applied medical research. In addition, we also highlighted the technical and practical difficulties that must be overcome to enhance skin-on-chip platforms, e.g. embedding electrical measurements, for improved modeling of human diseases as well as of new drug discovery and development.