The electrospinning of polymer melts can offer an advantage over solution electrospinning, in the development of layered tissue constructs for tissue engineering. Melt electrospinning does not require a solvent, of which many are cytotoxic in nature, and the use of nonwater soluble polymers allows the collection of fibers on water or onto cells. In this article, melt electrospinning of a blend of PEO-block-PCL with PCL was performed with in vitro cultured fibroblasts as the collection target. The significant parameters governing electrospinning polymer melts were determined before electrospinning directly onto fibroblasts. In general, a high electric field resulted in the most homogeneous and smallest fibers, although it is important that an optimal pump rate to the spinneret needs to be determined for different configurations. Many parameters governing melt electrospinning differ to those reported for solution electrospinning: the pump rate was a magnitude lower and the viscosity a magnitude higher than successful parameters for solution electrospinning. Cell vitality was maintained throughout the electrospinning process. Six days after electrospinning, fibroblasts adhered to the electrospun fibers and appeared to detach from the underlying flat substrate. The morphology of the fibroblasts changed from spread and flat, to long and spindle-shaped as adherence onto the fiber progressed. Therefore, an important step for producing layer-on-layer tissue constructs of cells and polymers in view of scaffold construction for tissue engineering was successfully demonstrated. The process of using cultured cells as the collection target was termed "direct in vitro electrospinning".

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This article reviews surface grafting of star-shaped PEO. The use of star-shaped polymers is compared to linear PEO chains regarding the layer preparation and the ability of the resulting surfaces to resist protein adsorption. We then focus on the use of end-functionalized, star-shaped, PEO-based prepolymers that are able to form covalent crosslinks and functional polymer networks on the substrate. Examples are given for specific protein adsorption as well as for cell adhesion on such layers by covalent embedding of biofunctional molecules. The possibility of coating biomedically relevant polymer substrates in three-dimensional geometries is discussed and examples are shown for poly(ethylene terephthalate) monofilament constructs.

Based on high quality surgery and scientific data, scientists and surgeons are committed to protecting patients as well as healthcare staff and hereby provide this Guidance to address the special issues circumstances related to the exponential spread of the Coronavirus disease 2019 (COVID-19) during this pandemic. As a basis, the authors used the British Intercollegiate General Surgery Guidance as well as recommendations from the USA, Asia, and Italy. The aim is to take responsibility and to provide guidance for surgery during the COVID-19 crisis in a simplified way addressing the practice of surgery, healthcare staff and patient safety and care. It is the responsibility of scientists and the surgical team to specify what is needed for the protection of patients and the affiliated healthcare team. During crises, such as the COVID-19 pandemic, the responsibility and duty to provide the necessary resources such as filters, Personal Protective Equipment (PPE) consisting of gloves, fluid resistant (Type IIR) surgical face masks (FRSM), filtering face pieces, class 3 (FFP3 masks), face shields and gowns (plastic ponchos), is typically left up to the hospital administration and government. Various scientists and clinicians from disparate specialties provided a Pandemic Surgery Guidance for surgical procedures by distinct surgical disciplines such as numerous cancer surgery disciplines, cardiothoracic surgery, ENT, eye, dermatology, emergency, endocrine surgery, general surgery, gynecology, neurosurgery, orthopedics, pediatric surgery, reconstructive and plastic surgery, surgical critical care, transplantation surgery, trauma surgery and urology, performing different surgeries, as well as laparoscopy, thoracoscopy and endoscopy. Any suggestions and corrections from colleagues will be very welcome as we are all involved and locked in a rapidly evolving process on increasing COVID-19 knowledge.

Mechanical stress is a decisive factor for the differentiation, proliferation, and general behavior of cells. However, the specific signaling of mechanotransduction is not fully understood. One basic problem is the clear distinction between the different extracellular matrix (ECM) constituents that participate in cellular adhesion and their corresponding signaling pathways. Here, a system is proposed that enables mechanical stimulation of human-skin-derived keratinocytes and human dermal fibroblasts that specifically interact with peptide sequences immobilized on a non-interacting but deformable substrate. The peptide sequences mimic fibronectin, laminin, and collagen type IV, three major components of the ECM. To achieve this, PDMS is activated using ammonia plasma and coated with star-shaped isocyanate-terminated poly(ethylene glycol)-based prepolymers, which results in a functional coating that prevents unspecific cell adhesion. Specific cell adhesion is achieved by functionalization of the layers with the peptide sequences in different combinations. Moreover, a method that enables the decoration of deformable substrates with cell-adhesion peptides in extremely defined nanostructures is presented. The distance and clustering of cell adhesion molecules below 100 nm has been demonstrated to be of utmost importance for cell adhesion. Thus we present a new toolbox that allows for the detailed analysis of the adhesion of human-skin-derived cells on structurally and biochemically decorated deformable substrates.

Electrospun fibers that are protein resistant and functionalized with bioactive signals were produced by solution electrospinning amphiphilic block copolymers. Poly (ethylene glycol)-block-poly(D,L-lactide) (PEG-b-PDLLA) was synthesized in two steps, with a PEG segment of 10 kDa, while the PDLLA block ranged from 20 to 60 kDa. Depending on the PEG and PDLLA segment ratio, as well as solvent selection, the hydrophilicity and protein adsorption could be altered on the electrospun mesh. Furthermore, an alpha-acetal PEG-b-PDLLA was synthesized that allowed the conjugation of active molecules, resulting in surface functionalization of the electrospun fiber. Electrospun material with varying morphologies and diameter were electrospun from 10, 20, and 30 wt.% solutions. Sessile drop measurements showed a reduction in the contact angle from 120 degrees for pure poly(D,L-lactide) with increasing PEG/PDLLA ratio. All electrospun block PEG-b-PDLLA fibers had hydrophilic properties, with contact angles below 45 degrees . The fibers were collected onto six-arm star-poly(ethylene glycol) (star-PEG) coated silicon wafers and incubated with fluorescently labeled proteins. All PEG-b-PDLLA fibers showed no detectable adsorption of bovine serum albumin (BSA) independent of their composition while a dependence between hydrophobic block length was observed for streptavidin adsorption. Fibers of block copolymers with PDLLA blocks smaller than 39 kDa showed no adsorption of BSA or streptavidin, indicating good non-fouling properties. Fibers were surface functionalized with N(epsilon)-(+)-biotinyl-L-lysine (biocytin) or RGD peptide by attaching the molecule to the PEG block during synthesis. Protein adsorption measurements, and the controlled interaction of biocytin with fluorescently labeled streptavidin, showed that the electrospun fibers were both resistant to protein adsorption and are functionalized. Fibroblast adhesion was contrasting between the unfunctionalized and RGD-coupled electrospun fabrics, confirming that the surface of the fibers was functionalized. The PEG-b-PDLLA surface functionalized electrospun fibers are promising substrates for controlling cell-material interactions, particularly for tissue-engineering applications.