The organ-on-a-chip (OoC) is an intriguing scientific and technological development in which biology is coupled with microtechnology 1,2 to mimic key aspects of human physiology. The chip takes the form of a microfluidic device containing networks of hair-fine microchannels for guiding and manipulating minute volumes (picolitres up to millilitres) of solution [3][4][5] . The organ is a more relatable term that refers to the miniature tissues grown and residing in the microfluidic chips, which can recapitulate one or more tissue-specific functions. Although they are much simpler than native tissues and organs, scientists have discovered that these systems can often serve as effective mimics of human physiology and disease. OoCs comprise advanced in vitro technology that enables experimentation with biological cells and tissues outside the body. This is achieved by containing them inside vessels conditioned to sustain a reasonable semblance of the in vivo environment, from a biochemical and physical point of view. Working on the microscale lends a unique opportunity to attain a higher level of control over the microenvironment that ensures tissue life support, as well as a means to directly observe cell and tissue behaviour.The OoC is a relatively recent addition to the toolbox of model biological systems available to life science researchers to probe aspects of human pathophysiology and disease. These systems cover a spectrum of physiological relevance, with 2D cell cultures the least relevant, followed in increasing order by 3D cell cultures, organoids and OoCs. Unsurprisingly, the use of model organisms such as mice and Drosophila physiologically exceeds engineered tissue approaches 6,7 . While biological complexity increases with physiological relevance in model organisms, this unfortunately leads to increased experimental difficulty. In vivo physiological processes are, in many ways, the least accessible to direct investigation in mice, humans and other mammals, despite significant advances in in vivo imaging. However, 2D and 3D cell cultures, such as spheroids and stem cell-derived organoids, sacrifice some aspects of in vivo relevance to facilitate experimentation. The OoC may be regarded as a bridging technology, offering the ability to work with complex cell cultures, while providing better engineered microenvironments to maximize the model.Following on from early concepts, including animal-on-a-chip 8 , body-on-a-chip 9 and breathing lung-on-a-chip 10 , research in the OoC and microphysiological systems fields has grown exponentially; evidenced by numerous excellent reviews published recently 1,2,11 . Recognition of OoC technology now extends far beyond university laboratories, driven by a need to better understand the human physiology underlying health and disease, and to find new approaches to improve the human condition. The World Economic Forum, for instance, selected the OoC as one of the top ten emerging technologies in 2016 (ref. 12

Different strategies to design antimicrobial contact lenses and contact lens cases.

Electrospun fibers have emerged as promising materials in the field of biomedicine, due to their superior physical and cell supportive properties. In particular, electrospun mats are being developed for advanced wound dressing applications. Such applications require the firers to possess excellent antimicrobial properties in order to inhibit potential microbial colonization from resident and non-resident bacteria. In this study, we have developed Poly-ε-Caprolactone /gelatin hybrid composite mats loaded with natural herbal extract (Gymnema sylvestre) to prevent bacterial colonization. As-spun scaffolds exhibited good wettability and desirable mechanical properties retaining their fibrous structure after immersing them in phosphate buffered saline (pH 7.2) for up to 30 days. The initial burst release of Gymnema sylvestre prevented the colonization of bacteria as confirmed by the radial disc diffusion assay. Furthermore, the electrospun mats promoted cellular attachment, spreading and proliferation of human primary dermal fibroblasts and cultured keratinocytes, which are crucial parenchymal cell-types involved in the skin recovery process. Overall these results demonstrated the utility of Gymnema sylvestre impregnated electrospun PCL/Gelatin nanofibrous mats as an effective antimicrobial wound dressing.

Burn wounds are susceptible to microbial invasion from both resident and exogenous bacteria, which becomes a critical public health issue and causes substantial economic burden. There is a perceived demand to produce new antimicrobial wound dressings that hinder bacterial colonization while accelerating the healing process and hence would provide an improved standard of care for patients. Since ancient times, herbal extracts from medicinally important plants have extensively been used for treating burn injuries. This work reports the utility of electrospun nanofibers containing plant extracts and antibiotics combination as a multifunctional scaffold for treating second-degree burns. First, we determined the various components of plant extracts from Gymnema sylvestre by two different processing methods and their synergism with minocycline antibiotics. Then, we prepared core− shell nanofibrous dressings with poly-ε-caprolactone/gelatin laden with minocycline hydrochloride as a shell and gelatin infused with G. sylvestre extracts (ultrasound-assisted extracts and cold macerated extracts) as the core using coaxial electrospinning. The electrospun nanofibers displayed a smooth, continuous, and bead-free morphology with adequate wettability. The presence of extract components in the core−shell nanofibers resulted in enhanced mechanical properties when compared to pristine mats. The core− shell structures resulted in sustained release of the bioactive components when compared to nanofiber blends. Core−shell nanofiber mats containing plant extracts and antibiotic combinations displayed potent antimicrobial and antibiofilm properties while promoting the spread and proliferation of skin cells when compared to pristine mats. In a porcine model of cutaneous second-degree burns, we showed that wounds treated with the antimicrobial dressing improved re-epithelialization and collagen organization in comparison to untreated wounds.

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