Rapid Adhesion Research Articles

Regulation of macrophage polarization and promotion of endothelialization by NO generating and PEG-YIGSR modified vascular graft

As an effective clinic treatment for cardiovascular disease, vascular transplantation gains much acceptance recently. However, due to the acute thrombosis and intimal hyperplasia, long-term failure of synthetic grafts after implanted in small diameter blood vessel decelerates its commercial use. The continued acute inflammation and delayed endothelialization have been considered as fundamental reasons. To enhance the adhesion and organization of endothelial cells (ECs) and improve the vascular remodeling process, we have constructed a vascular graft based on electrospun polycaprolactone (PCL) matrix, on which organoselenium-immobilized polyethyleneimine (SePEI) for in situ nitric oxide (NO) generation and hyaluronic acid (HA) grafted with poly (ethylene glycol) (PEG) modified Tyr-Ile-Gly-Ser-Arg (YIGSR) for antifouling and EC adhesion were deposited through electrostatic layer-by-layer assembly. The in vitro results showed that SePEI deposited on the grafts could catalyze stable generation of NO. After in situ implantation in rats for 4 and 8weeks, the graft promoted the transformation of macrophages into an anti-inflammatory phenotype (M2), which helped endothelium remodeling. YIGSR on the outmost layer facilitated more rapid and organized EC adhesion compared to PCL and non-modified grafts. PEG polymer chain on the outmost layer mitigated nonspecific adsorption of undesirable blood components. In our study, we first demonstrated the regulation of macrophage polarization by an NO-generating vascular graft. The results indicated that the approach of anti-inflammatory macrophage polarization and enhanced endothelialization through NO generation and PEG-modified YIGSR in our study may provide a new perspective for the clinic application of cell-free small-diameter vascular grafts.

Mesenchymal-like stem cells in canine ovary show high differentiation potential.

Recent studies have reported the existence of stem cells in ovarian tissue that show enhanced proliferative and differentiation potential compared to other adult tissues. Based on this evidence, we hypothesized that ovarian tissue contained mesenchymal-like stem cells (MSC) that could be isolated using a novel rapid plastic adhesion technique. We established MSC lines derived from ovarian and adipose tissue based on their ability to rapidly adhere to plastic culture dishes in the first 3hours after plating and studied their potentiality in terms of molecular markers and differentiation capacity. Morphological and kinetic properties of in vitro cultured ovarian MSC were similar to adipose-derived MSC, and both reached senescence after similar passage numbers. Ovarian-derived MSC expressed mesenchymal (CD90 and CD44) but not haematopoietic markers (CD34 and CD45), indicating similarity to adipose-derived MSC. Moreover, ovarian-derived MSC expressed NANOG, TERT, SOX2, OCT4 and showed extensive capacity to differentiate not only into adipogenic, osteogenic and chondrogenic tissue but also towards neurogenic and endodermal lineages and even precursors of primordial germ cells. These results show for the first time the derivation of ovarian cells with the molecular properties of MSC as well as wide differentiation potential. Canine ovarian tissue is accessible, expandable, multipotent and has high plasticity, holding promise for applications in regenerative medicine.

Cardiosphere-Derived Cells Demonstrate Metabolic Flexibility That Is Influenced by Adhesion Status

Adult stem cells demonstrate metabolic flexibility that is regulated by cell adhesion status. The authors demonstrate that adherent cells primarily utilize glycolysis, whereas suspended cells rely on oxidative phosphorylation for their ATP needs. Akt phosphorylation transduces adhesion-mediated regulation of energy metabolism, by regulating translocation of glucose transporters (GLUT1) to the cell membrane and thus, cellular glucose uptake and glycolysis. Cell dissociation, a pre-requisite for cell transplantation, leads to energetic stress, which is mediated by Akt dephosphorylation, downregulation of glucose uptake, and glycolysis. They designed hydrogels that promote rapid cell adhesion of encapsulated cells, Akt phosphorylation, restore glycolysis, and cellular ATP levels.

STATISTICAL OPTIMIZATION OF GELATIN IMMOBILISATION ON MODIFIED SURFACE PCL MICROCARRIER TO IMPROVE PCL MICROCARRIER COMPATIBILITY

Growing cells on microcarriers may have overcome the limitation of conventional cell culture system. However, the main challenge remains at ensuring the surface biocompatibility with cells. Polycaprolactone (PCL), a biodegradable polymer, has received considerable attention because of its excellent mechanical properties and degradation kinetics that suit various applications, but its non-polar hydrocarbon moiety renders it sub-optimal for cell attachment. In this present study, the aim was to improve biocompatibility of PCL microcarrier by introducing oxygen functional group via ultraviolet irradiation and ozone aeration (UV/O3 system) to allow covalent immobilization of gelatin on the PCL microcarrier surface. Respond surface methodology was used as a statistical approach to optimized parameters that effect the immobilization of gelatin. The parameters used to maximized amount of gelatin immobilize were the mol ratio of COOH:EDAC, NHS concentration and gelatin concentration. The optimum conditions for maximum amount of gelatin (1797.33 µg/g) on the surface of PCL were as follows: 1.5 of COOH:EDAC ratio, 10 mM NHS concentration and, 80 mg/ml gelatin. The result shows that gelatin coated PCL microcarrier promote more and rapid cell adhesion with density of as compared to raw PCL microcarrier ( and UV/O3 treated PCL microcarrier ( . Therefore, immobilization of gelatin with optimized parameters onto PCL microcarrier improved biocompatibility of PCL microcarrier.

INHIBITION OF PROTEIN ARGININE DEIMINASES IMPROVES COGNITION AND REDUCES NEUROPATHOLOGICAL CHANGES IN MOUSE MODELS OF ALZHEIMER’S DISEASE

Inflammation has been correlated to Alzheimer's disease (AD) and a better understanding of its mechanisms may help to develop new therapies for AD. We have recently demonstrated that neutrophils infiltrate the brain and produce neutrophil extracellular traps (NETs) in subjects with AD and mice with AD-like disease. Furthermore, inhibition of neutrophil trafficking has therapeutic effect in animal models of AD. Recent studies have shown that protein arginine deiminases (PADs) mediate NET formation and have a role in innate immunity responses. PAD inhibitors have demonstrated remarkable efficacy in numerous inflammatory diseases including rheumatoid arthritis, lupus, ulcerative colitis, multiple sclerosis and atherosclerosis. The aim of our study was to test the potential therapeutic effect of PAD inhibition in AD models. BB-Cl-amidine, a pan-PAD inhibitor, and GSK199, a PAD4 specific inhibitor were used to study the role of PADs in vitro and in vivo. The role of PADs in rapid adhesion in vitro was assessed in adhesion assays on integrin ligands. Epifluorescence intravital microscopy and two-photon microscopy were performed to study the role of PADs in neutrophil adhesion in vivo. 5xFAD mice, which develop amyloid pathology, and 3xTg-AD mice, which develop both amyloid and tau pathology, were used to test the effect of PAD inhibition on disease. Treatment of neutrophils with PAD inhibitors reduced integrin-dependent rapid adhesion triggered by chemoattractants and TNF. PAD inhibition also reduced rolling interactions and drastically inhibited firm adhesion in inflamed brain microcirculation. Moreover, two-photon microscopy performed in the brain of AD mice showed a drastic reduction of adhesion and intravascular crawling of neutrophils treated with BB-Cl-amidine compared to untreated cells, suggesting that PADs control neutrophil trafficking in the AD brain. Notably, treatment with BB-Cl-amidine of 3xTg-AD and 5xFAD mice led to a significant restoration of memory in Y maze and contextual fear conditioning behavioral tests when compared to control animals. Neuropathological studies showed that treatment with BB-Cl-amidine reduced microglial activation and amyloid deposition compared to control animals. PAD inhibition interferes with neutrophil trafficking and ameliorates cognitive impairment and neuropathological changes in animal models of AD, suggesting PADs represent new therapeutic targets in AD.

Mussel-Inspired Polyglycerol Coatings with Controlled Wettability: From Superhydrophilic to Superhydrophobic Surface Coatings.

Facile approaches to substrate-independent surface coatings with special wettability properties, such as superhydrophobicity, superhydrophilicity, and superamphiphobicity, have been limited. To address this problem, we combined two separate biomimetic concepts of mussel-inspired adhesion and highly hierarchical lotuslike surface structures to develop a universal fabrication method for various superwetting systems on any kind of material. In this feature article, we summarize our work on mussel-inspired polyglycerol (MI-dPG) and its application in the area of superwetting interfacial materials. MI-dPG mimics not only the functional groups of mfp-5 but also their molecular weight and molecular structure, which results in strong and rapid adhesion to the substrate. Furthermore, the MI-dPG coating process provides precise roughness control. The construction of highly hierarchical and superhydrophilic structures was achieved either directly by pH-controlled aggregation or in combination with nanoparticles. Subsequent postmodification of these highly hierarchical structures with different fluorinated or nonfluorinated hydrophobic molecules yielded a surface with superhydrophobic and even superamphiphobic properties.

Optimization of electrospun poly(N-isopropyl acrylamide) mats for the rapid reversible adhesion of mammalian cells.

Poly(N-isopropyl acrylamide) (pNIPAM) is a "smart" polymer that responds to changes in altering temperature near physiologically relevant temperatures, changing its relative hydrophobicity. Mammalian cells attach to pNIPAM at 37 °C and detach spontaneously as a confluent sheet when the temperature is shifted below the lower critical solution temperature (∼32 °C). A variety of methods have been used to create pNIPAM films, including plasma polymerization, self-assembled monolayers, and electron beam ionization. However, detachment of confluent cell sheets from these pNIPAM films can take well over an hour to achieve potentially impacting cellular behavior. In this work, pNIPAM mats were prepared via electrospinning (i.e., espNIPAM) by a previously described technique that the authors optimized for cell attachment and rapid cell detachment. Several electrospinning parameters were varied (needle gauge, collection time, and molecular weight of the polymer) to determine the optimum parameters. The espNIPAM mats were then characterized using Fourier-transform infrared, x-ray photoelectron spectroscopy, and scanning electron microscopy. The espNIPAM mats showing the most promise were seeded with mammalian cells from standard cell lines (MC3T3-E1) as well as cancerous tumor (EMT6) cells. Once confluent, the temperature of the cells and mats was changed to ∼25 °C, resulting in the extremely rapid swelling of the mats. The authors find that espNIPAM mats fabricated using small, dense fibers made of high molecular weight pNIPAM are extremely well-suited as a rapid release method for cell sheet harvesting.

Biocompatible nanostructured solid adhesives for biological soft tissues.

The present study indicates a new application of inorganic biomaterials (bioceramics) as a soft tissue adhesive. Organic adhesives such as fibrin glues or cyanoacrylate derivatives have been commonly used clinically. However, their limited biocompatibility and/or low adhesion strength are some drawbacks that impair their clinical application. In this study, we synthesized a novel solid adhesive with biocompatible and biodegradable HAp nanoparticles without the aid of organic molecules, and showed a rapid and strong adhesion of mouse soft tissues compared to conventional fibrin glues. Given the importance of wet adhesion in biomedicine and biotechnology applications, our results will help not only in developing an efficient approach to close incised soft tissues, but also in finding novel ways to integrate soft tissues with synthetic hydrogels (such as drug reservoirs).

Tissue-engineered cartilage constructed by a biotin-conjugated anti-CD44 avidin binding technique for the repairing of cartilage defects in the weight-bearing area of knee joints in pigs.

ObjectivesThe lack of effective treatment for cartilage defects has prompted investigations using tissue engineering techniques for their regeneration and repair. The success of tissue-engineered repair of cartilage may depend on the rapid and efficient adhesion of transplanted cells to a scaffold. Our aim in this study was to repair full-thickness defects in articular cartilage in the weight-bearing area of a porcine model, and to investigate whether the CD44 monoclonal antibody biotin-avidin (CBA) binding technique could provide satisfactory tissue-engineered cartilage.MethodsCartilage defects were created in the load-bearing region of the lateral femoral condyle of mini-type pigs. The defects were repaired with traditional tissue-engineered cartilage, tissue-engineered cartilage constructed with the biotin-avidin (BA) technique, tissue-engineered cartilage constructed with the CBA technique and with autologous cartilage. The biomechanical properties, Western blot assay, histological findings and immunohistochemical staining were explored.ResultsThe CBA group showed similar results to the autologous group in biomechanical properties, Moran’s criteria, histological tests and Wakitani histological scoring.ConclusionsThese results suggest that tissue-engineered cartilage constructed using the CBA technique could be used effectively to repair cartilage defects in the weight-bearing area of joints.Cite this article: H. Lin, J. Zhou, L. Cao, H. R. Wang, J. Dong, Z. R. Chen. Tissue-engineered cartilage constructed by a biotin-conjugated anti-CD44 avidin binding technique for the repairing of cartilage defects in the weight-bearing area of knee joints in pigs. Bone Joint Res 2017;6:–295. DOI: 10.1302/2046-3758.65.BJR-2016-0277.

RhoA promotes epidermal stem cell proliferation via PKN1-cyclin D1 signaling

ObjectiveEpidermal stem cells (ESCs) play a critical role in wound healing, but the mechanism underlying ESC proliferation is not well defined. Here, we explore the effects of RhoA on ESC proliferation and the possible underlying mechanism.MethodsHuman ESCs were enriched by rapid adhesion to collagen IV. RhoA(+/+)(G14V), RhoA(-/-)(T19N) and pGFP control plasmids were transfected into human ESCs. The effect of RhoA on cell proliferation was detected by cell proliferation and DNA synthesis assays. Induction of PKN1 activity by RhoA was determined by immunoblot analysis, and the effects of PKN1 on RhoA in terms of inducing cell proliferation and cyclin D1 expression were detected using specific siRNA targeting PKN1. The effects of U-46619 (a RhoA agonist) and C3 transferase (a RhoA antagonist) on ESC proliferation were observed in vivo.ResultsRhoA had a positive effect on ESC proliferation, and PKN1 activity was up-regulated by the active RhoA mutant (G14V) and suppressed by RhoA T19N. Moreover, the ability of RhoA to promote ESC proliferation and DNA synthesis was interrupted by PKN1 siRNA. Additionally, cyclin D1 protein and mRNA expression levels were up-regulated by RhoA G14V, and these effects were inhibited by siRNA-mediated knock-down of PKN1. RhoA also promoted ESC proliferation via PKN in vivo.ConclusionThis study shows that the effect of RhoA on ESC proliferation is mediated by activation of the PKN1-cyclin D1 pathway in vitro, suggesting that RhoA may serve as a new therapeutic target for wound healing.

Decellularized extracellular matrix of human umbilical vein endothelial cells promotes endothelial differentiation of stem cells from exfoliated deciduous teeth

Dental stem cells can serve as a potential source of functional endothelial cells for tissue engineering applications, but the endothelial-lineage differentiation efficiency is rather low even with growth factors and mechanical stimuli, which greatly limits their clinical applications. This is partly due to the deficiency of standard two-dimensional (2-D) culture systems, which is unable to recapitulate the three-dimensional (3-D) in vivo milieu that is rich in extracellular matrix. Hence, we extracted decellularized extracellular matrix from human umbilical vein endothelial cells (HUVECs-DECM) to provide a bioactive substratum conducive to the endothelial differentiation of dental stem cells. Compared to cells plated on tissue culture polystyrene (TCP), stem cells from exfoliated deciduous teeth (SHED) cultured on the HUVECs-DECM demonstrated more regular arrangement and elongated morphology. HUVECs-DECM significantly enhanced the rapid adhesion and proliferation rates of SHED, as demonstrated by WST-8 assay and immunocytochemistry indicating higher expression levels of vinculin by newly adherent SHED on HUVECs-DECM versus TCP. In addition, there was twofold to fivefold higher mRNA expression levels of endothelial-specific markers CD31 and VEGFR-2 in SHED after seven days of culture on DECM versus TCP. Functional testing with in vitro matrigel angiogenesis assay identified more capillary-like structure formation with significantly higher tubule length in SHED induced by DECM versus TCP. Hence, the results of this study provide a better understanding of the unique characteristics of cell-specific ECM and demonstrated the potential use of HUVECs-DECM as a culture substratum conducive for stimulating the endothelial differentiation of SHED for therapeutic angiogenic applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1083-1093, 2017.

Mobilisation of Joint-resident Mesenchymal Stromal Cells for Articular Cartilage Regeneration

Background and Objectives:Microfracture is a recognized procedure used to treat isolated cartilage injuries or defects, in which bone marrow mesenchymal stromal cells (BM-MSCs) are thought to migrate into the resulting blood clot, leading to subsequent cartilage repair via fibrocartilage formation. The discovery of MSCs in the synovium and synovial fluid (SF) provides a potential mechanism for repairing cartilage from the top down via their migration and homing to the microfracture site, however SF-MSCs low in number and usually lost with joint irrigation. The purpose of this work was threefold; first to test the hypothesis that SF-MSCs can be replaced, and also their numbers further increased by synovial agitation, second that these cells were capable of rapid adhesion to clots and third that the clot composition improve MSC migration.Materials-Methods:Ex-vivo mechanical agitation of human superficial synovium and in vivo intra-operative agitation of synovium in patients undergoing arthroscopy were performed using a Cytology brush and custom designed Synovial brush. Colony-forming unit-fibroblast (CFU-F) assay was performed to quantify released MSCs. Adhesion to clots was studied by comparing Platelet Rich Plasma (PRP), Whole Blood (WB) and Fibrin Glue (FG). Migration studies were performed using passage 2-4 synovial MSCs in trans-well migration assay. MSC migration, over a five hour period, was compared between PRP and pooled human Platelet Lysate (hPL).Results:Ex-vivo mechanical agitating of the synovium with the cytology brush compared to irrigation alone increased MSC number 2.7-fold (n=10, p=0.002). Irrigation during arthroscopy was seen to effectively remove the majority of CFU-Fs for the synovial fluid. Use of a custom designed synovial brush, compared to the cytology brush resulted in a median 65-fold increase in the number of CFU-Fs (n=8, p=0.0148). Trilineage differentiation of released synovial MSCs was at least comparable to donor match synovial fluid MSCs. These MSCs adhered to clots within 30 minutes with no difference seen between clot compositions. Released synovial MSCs demonstrated a trend for a better migration towards hPL compared to PRP.Conclusions:Existing surgical procedures wash away SF-MSCs. Using a novel brushing technique and a custom designed synovial brush, synovial MSCs can be mechanically released in vivo, and these cells were capable of migration and rapid adhesion to clots. Collectively these findings aid in the rapid replenishment of endogenous minimally manipulated MSCs, and provide a one-stage procedure combining synovial brushing with microfracture, as a strategy for cost effective joint repair.

α6 Integrin (α6high)/Transferrin Receptor (CD71)low Keratinocyte Stem Cells Are More Potent for Generating Reconstructed Skin Epidermis Than Rapid Adherent Cells.

The epidermis basal layer is composed of two keratinocyte populations: Keratinocyte Stem cells (KSC) and Transitory Amplifying (TA) cells that arise from KSC division. Unfortunately, no specific marker exists to differ between KSC and TA cells. Here, we aimed at comparing two different methods that pretended to isolate these two populations: (i) the rapid adhesion method on coated substrate and (ii) the flow cytometry method, which is based on the difference in cell surface expressions of the α6 integrin and transferrin receptor (CD71). Then, we compared different parameters that are known to discriminate KSC and TA populations. Interestingly, we showed that both methods allow enrichment in stem cells. However, cell sorting by flow cytometry (α6high/CD71low) phenotype leads to a better enrichment of KSC since the colony forming efficiency is five times increased versus total cell suspension, whereas it is only 1.4 times for the adhesion method. Moreover, α6high/CD71low cells give rise to a thicker pluristratified epithelium with lower seeding density and display a low Ki67 positive cells number, showing that they have reached the balance between proliferation and differentiation. We clearly demonstrated that cells isolated by a rapid adherent method are not the same population as KSC isolated by flow cytometry following α6high/CD71low phenotype.

Simple peptide coacervates adapted for rapid pressure-sensitive wet adhesion.

We report here that a dense liquid formed by spontaneous condensation, also known as simple coacervation, of a single mussel foot protein-3S-mimicking peptide exhibits properties critical for underwater adhesion. A structurally homogeneous coacervate is deposited on underwater surfaces as micrometer-thick layers, and, after compression, displays orders of magnitude higher underwater adhesion at 2 N m-1 than that reported from thin films of the most adhesive mussel-foot-derived peptides or their synthetic mimics. The increase in adhesion efficiency does not require nor rely on post-deposition curing or chemical processing, but rather represents an intrinsic physical property of the single-component coacervate. Its wet adhesive and rheological properties correlate with significant dehydration, tight peptide packing and restriction in peptide mobility. We suggest that such dense coacervate liquids represent an essential adaptation for the initial priming stages of mussel adhesive deposition, and provide a hitherto untapped design principle for synthetic underwater adhesives.

Rapid Fabrication of Soft, Multilayered Electronics for Wearable Biomonitoring

Soft integrated electronics are key components for emerging applications in wearable biomonitoring, soft co‐robotics, and physical human–machine interaction. They are composed of soft and elastically deformable circuits and sensors that are combined with packaged microelectronics for signal processing, power regulation, and communication. While promising, widespread use of soft wearable electronics is currently limited by the lack of robust fabrication techniques to rapidly, efficiently, and precisely assemble soft and rigid components into multilayered systems. Here, an efficient digital fabrication approach is presented to create highly customizable wearable electronics through rapid laser machining and adhesion controlled soft materials assembly. Well aligned, multilayered materials are created from 2D and 3D elements that stretch and bend while seamlessly integrating with rigid components such as microchip integrated circuits, discrete electrical components, and interconnects. These techniques are applied using commercially available materials and components and the fabrication of thin, lightweight, customized sensor skins is demonstrated in under an hour. These fully integrated wireless devices conformably bond to the hand and are successfully used for monitoring hand gesture, pulse rate, and blood oxygenation. These materials and methods enable custom wearable electronics while offering versatility in design and functionality for a variety of applications through material selection and construction.

Fabrication of 3-D Reconstituted Organoid Arrays by DNA-Programmed Assembly of Cells (DPAC).

Tissues are the organizational units of function in metazoan organisms. Tissues comprise an assortment of cellular building blocks, soluble factors, and extracellular matrix (ECM) composed into specific three-dimensional (3-D) structures. The capacity to reconstitute tissues in vitro with the structural complexity observed in vivo is key to understanding processes such as morphogenesis, homeostasis, and disease. In this article, we describe DNA-programmed assembly of cells (DPAC), a method to fabricate viable, functional arrays of organoid-like tissues within 3-D ECM gels. In DPAC, dissociated cells are chemically functionalized with degradable oligonucleotide "Velcro," allowing rapid, specific, and reversible cell adhesion to a two-dimensional (2-D) template patterned with complementary DNA. An iterative assembly process builds up organoids, layer-by-layer, from this initial 2-D template and into the third dimension. Cleavage of the DNA releases the completed array of tissues that are captured and fully embedded in ECM gels for culture and observation. DPAC controls the size, shape, composition, and spatial heterogeneity of organoids and permits positioning of constituent cells with single-cell resolution even within cultures several centimeters long. © 2016 by John Wiley & Sons, Inc.

Label-Free Detection and Discrimination of Bacterial Pathogens Based on Hemin Recognition.

Hemin linked to hexa(ethylene glycol)bishydrazide was patterned by inkjet printing into periodic microarrays, and evaluated for their ability to capture bacterial pathogens expressing various hemin receptors. Bacterial adhesion was imaged under darkfield conditions with Fourier analysis, supporting a label-free method of pathogen detection. Hemin microarrays were screened against a panel of 16 bacteria and found capable of capturing multiple species, some with limits of detection as low as 10(3) cfu/mL. Several Gram-positive strains including Staphylococcus aureus and Bacillus anthracis also exhibited rapid adhesion, enabling pattern recognition within minutes of exposure. This can be attributed to differences in hemin acquisition systems: aggressively adherent bacteria express cell-surface hemin receptors (CSHRs) that enable direct hemin binding and uptake, whereas other types of bacteria including most Gram-negative strains rely on the secretion and recapture of soluble proteins (hemophores) for hemin acquisition, with consequently longer times for ligand binding and detection.

Winner of the Young Investigator Award of the Society for Biomaterials (USA) for 2016, 10th World Biomaterials Congress, May 17-22, 2016, Montreal QC, Canada: Aligned microribbon-like hydrogels for guiding three-dimensional smooth muscle tissue regeneration.

Smooth muscle tissue is characterized by aligned structures, which is critical for its contractile functions. Smooth muscle injury is common and can be caused by various diseases and degenerative processes, and there remains a strong need to develop effective therapies for smooth muscle tissue regeneration with restored structures. To guide cell alignment, previously cells were cultured on 2D nano/microgrooved substrates, but such method is limited to fabricating 2D aligned cell sheets only. Alternatively, aligned electrospun nanofiber has been employed as 3D scaffold for cell alignment, but cells can only be seeded post fabrication, and nanoporosity of electrospun fiber meshes often leads to poor cell distribution. To overcome these limitations, we report aligned gelatin-based microribbons (µRBs) as macroporous hydrogels for guiding smooth muscle alignment in 3D. We developed aligned µRB-like hydrogels using wet spinning, which allows easy fabrication of tissue-scale (cm) macroporous matrices with alignment cues and supports direct cell encapsulation. The macroporosity within µRB-based hydrogels facilitated cell proliferation, new matrix deposition, and nutrient diffusion. In aligned µRB scaffold, smooth muscle cells showed high viability, rapid adhesion, and alignment following µRB direction. Aligned µRB scaffolds supported retention of smooth muscle contractile phenotype, and accelerated uniaxial deposition of new matrix (collagen I/IV) along the µRB. In contrast, cells encapsulated in conventional gelatin hydrogels remained round with matrix deposition limited to pericellular regions only. We envision such aligned µRB scaffold can be broadly applicable in growing other anisotropic tissues including tendon, nerves and blood vessel.

Underwater contact adhesion and microarchitecture in polyelectrolyte complexes actuated by solvent exchange.

Polyelectrolyte complexation is critical to the formation and properties of many biological and polymeric materials, and is typically initiated by aqueous mixing followed by fluid-fluid phase separation, such as coacervation. Yet little to nothing is known about how coacervates evolve into intricate solid microarchitectures. Inspired by the chemical features of the cement proteins of the sandcastle worm, here we report a versatile and strong wet-contact microporous adhesive resulting from polyelectrolyte complexation triggered by solvent exchange. After premixing a catechol-functionalized weak polyanion with a polycation in dimethyl sulphoxide (DMSO), the solution was applied underwater to various substrates whereupon electrostatic complexation, phase inversion, and rapid setting were simultaneously actuated by water-DMSO solvent exchange. Spatial and temporal coordination of complexation, inversion and setting fostered rapid (∼25 s) and robust underwater contact adhesion (Wad ≥ 2 J m(-2)) of complexed catecholic polyelectrolytes to all tested surfaces including plastics, glasses, metals and biologicalmaterials.

Engineered protein coatings to improve the osseointegration of dental and orthopaedic implants

Here we present the design of an engineered, elastin-like protein (ELP) that is chemically modified to enable stable coatings on the surfaces of titanium-based dental and orthopaedic implants by novel photocrosslinking and solution processing steps. The ELP includes an extended RGD sequence to confer bio-signaling and an elastin-like sequence for mechanical stability. ELP thin films were fabricated on cp-Ti and Ti6Al4V surfaces using scalable spin and dip coating processes with photoactive covalent crosslinking through a carbene insertion mechanism. The coatings withstood procedures mimicking dental screw and hip replacement stem implantations, a key metric for clinical translation. They promoted rapid adhesion of MG63 osteoblast-like cells, with over 80% adhesion after 24 h, compared to 38% adhesion on uncoated Ti6Al4V. MG63 cells produced significantly more mineralization on ELP coatings compared to uncoated Ti6Al4V. Human bone marrow mesenchymal stem cells (hMSCs) had an earlier increase in alkaline phosphatase activity, indicating more rapid osteogenic differentiation and mineral deposition on adhesive ELP coatings. Rat tibia and femur in vivo studies demonstrated that cell-adhesive ELP-coated implants increased bone-implant contact area and interfacial strength after one week. These results suggest that ELP coatings withstand surgical implantation and promote rapid osseointegration, enabling earlier implant loading and potentially preventing micromotion that leads to aseptic loosening and premature implant failure.