Hyaluronan Receptor LYVE-1-Expressing Macrophages Maintain Arterial Tone through Hyaluronan-Mediated Regulation of Smooth Muscle Cell Collagen.

The maintenance of appropriate arterial tone is critically important for normal physiological arterial function. However, the cellular and molecular mechanisms remain poorly defined. Here, we have shown that in the mouse aorta, resident macrophages prevented arterial stiffness and collagen deposition in the steady state. Using phenotyping, transcriptional profiling, and targeted deletion of Csf1r, we have demonstrated that these macrophages-which are a feature of blood vessels invested with smooth muscle cells (SMCs) in both mouse and human tissues-expressed the hyaluronan (HA) receptor LYVE-l. Furthermore, we have shown they possessed the unique ability to modulate collagen expression in SMCs by matrix metalloproteinase MMP-9-dependent proteolysis through engagement of LYVE-1 with the HA pericellular matrix of SMCs. Our study has unveiled a hitherto unknown homeostatic contribution of arterial LYVE-1+ macrophages through the control of collagen production by SMCs and has identified a function of LYVE-1 in leukocytes.

Interpenetrating Network of Alginate-Human Adipose Extracellular Matrix Hydrogel for Islet Cells Encapsulation.

Transplantation of microencapsulated islet cells holds great potential for the treatment of type 1 diabetes mellitus. However, its clinical translation is hampered by the peri-transplantation loss of islet viability and functionality in the microcapsules. In this work, a novel islet cells biomimetic microencapsulant material that is based on the interpenetrating networks of alginate and extracellular matrix (ECM) hydrogel composite (AEC) is presented. The ECM component is derived from human lipoaspirate. In situ encapsulation of pancreatic ß islet cells (MIN6 ß-cells) can be achieved via ionotropic gelation of the alginate matrix and thermal-induced gelation of the pepsin-solubilized ECM pre-gel. Due to the enhanced cell-matrix interaction, islets encapsulated within the AEC microcapsules (≈640 µm) display sevenfold increase in cell growth over 1 week of culture and characteristic glucose-stimulated insulin response in vitro. The results show that the AEC microcapsule is a potent platform to bioaugment the performance of islet cells.

Surface modification of PVDF using non-mammalian sources of collagen for enhancement of endothelial cell functionality.

Although polyvinylidene fluoride (PVDF) is non-toxic and stable in vivo, its hydrophobic surface has limited its bio-applications due to poor cell-material interaction and thrombus formation when used in blood contacting devices. In this study, surface modification of PVDF using naturally derived non-mammalian collagen was accomplished via direct surface-initiated atom transfer radical polymerisation (SI-ATRP) to enhance its cytocompatibility and hemocompatibility. Results showed that Type I collagen was successfully extracted from fish scales and bullfrog skin. The covalent immobilisation of fish scale-derived collagen (FSCOL) and bullfrog skin-derived collagen (BFCOL) onto the PVDF surface improves the attachment and proliferation of human umbilical vein endothelial cells (HUVECs). Furthermore, both FSCOL and BFCOL had comparable anti-thrombogenic profiles to that of commercially available bovine collagen (BVCOL). Also, cell surface expression of the leukocyte adhesion molecule was lower on HUVECs cultured on non-mammalian collagen surfaces than on BVCOL, which is an indication of lower pro-inflammatory response. Overall, results from this study demonstrated that non-mammalian sources of collagen could be used to confer bioactivity to PVDF, with comparable cell-material interactions and hemocompatibility to BVCOL. Additionally, higher expression levels of Type IV collagen in HUVECs cultured on FSCOL and BFCOL were observed as compared to BVCOL, which is an indication that the non-mammalian sources of collagen led to a better pro-angiogenic properties, thus making them suitable for blood contacting applications.

Physical and mechanical characterisation of 3D-printed porous titanium for biomedical applications.

The elastic modulus of metallic orthopaedic implants is typically 6-12 times greater than cortical bone, causing stress shielding: over time, bone atrophies through decreased mechanical strain, which can lead to fracture at the implantation site. Introducing pores into an implant will lower the modulus significantly. Three dimensional printing (3DP) is capable of producing parts with dual porosity features: micropores by process (residual pores from binder burnout) and macropores by design via a computer aided design model. Titanium was chosen due to its excellent biocompatibility, superior corrosion resistance, durability, osteointegration capability, relatively low elastic modulus, and high strength to weight ratio. The mechanical and physical properties of 3DP titanium were studied and compared to the properties of bone. The mechanical and physical properties were tailored by varying the binder (polyvinyl alcohol) content and the sintering temperature of the titanium samples. The fabricated titanium samples had a porosity of 32.2-53.4% and a compressive modulus of 0.86-2.48 GPa, within the range of cancellous bone modulus. Other physical and mechanical properties were investigated including fracture strength, density, fracture toughness, hardness and surface roughness. The correlation between the porous 3DP titanium-bulk modulus ratio and porosity was also quantified.

Attenuating Epithelial-to-Mesenchymal Transition in Cancer through Angiopoietin-Like 4 Inhibition in a 3D Tumor Microenvironment Model.

Epithelial-to-mesenchymal transition (EMT) plays a crucial role in metastatic cancer progression, and current research, which relies heavily on 2D monolayer cultures, falls short in recapitulating the complexity of a 3D tumor microenvironment. To address this limitation, a transcriptomic meta-analysis is conducted on diverse cancer types undergoing EMT in 2D and 3D cultures. It is found that mechanotransduction is elevated in 3D cultures and is further intensified during EMT, but not during 2D EMT. This analysis reveals a distinct 3D EMT gene signature, characterized by extracellular matrix remodeling coordinated by angiopoietin-like 4 (Angptl4) along with other canonical EMT regulators. Utilizing hydrogel-based 3D matrices with adjustable mechanical forces, 3D cancer cultures are established at varying physiological stiffness levels. A YAP:EGR-1 mediated up-regulation of Angptl4 expression is observed, accompanied by an upregulation of mesenchymal markers, at higher stiffness during cancer EMT. Suppression of Angptl4 using antisense oligonucleotides or anti-cAngptl4 antibodies leads to a dose-dependent abolishment of EMT-mediated chemoresistance and tumor self-organization in 3D, ultimately resulting in diminished metastatic potential and stunted growth of tumor xenografts. This unique programmable 3D cancer cultures simulate stiffness levels in the tumor microenvironment and unveil Angptl4 as a promising therapeutic target to inhibit EMT and impede cancer progression.

Squid Suckerin-Spider Silk Fusion Protein Hydrogel for Delivery of Mesenchymal Stem Cell Secretome to Chronic Wounds.

Chronic wounds are non-healing wounds characterized by a prolonged inflammation phase. Excessive inflammation leads to elevated protease levels and consequently to a decrease in growth factors at wound sites. Stem cell secretome therapy has been identified as a treatment strategy to modulate the microenvironment of chronic wounds via supplementation with anti-inflammatory/growth factors. However, there is a need to develop better secretome delivery systems that are able to encapsulate the secretome without denaturation, in a sustained manner, and that are fully biocompatible. To address this gap, a recombinant squid suckerin-spider silk fusion protein is developed with cell-adhesion motifs capable of thermal gelation at physiological temperatures to form hydrogels for encapsulation and subsequent release of the stem cell secretome. Freeze-thaw treatment of the protein hydrogel results in a modified porous cryogel that maintains slow degradation and sustained secretome release. Chronic wounds of diabetic mice treated with the secretome-laden cryogel display increased wound closure, presence of endothelial cells, granulation wound tissue thickness, and reduced inflammation with no fibrotic scar formation. Overall, these in vivo indicators of wound healing demonstrate that the fusion protein hydrogel displays remarkable potential as a delivery system for secretome-assisted chronic wound healing.

A 3D physio-mimetic interpenetrating network-based platform to decode the pro and anti-tumorigenic properties of cancer-associated fibroblasts.

Three-dimensional (3D) biomaterials with physiologically relevant and experimentally tractable biomechanical features are important platforms to advance our understanding of the influence of tissue mechanics in disease progression. Herein, an interpenetrating network (IPN) of collagen and alginate 3D culture system with tunable extracellular microstructure and mechanics is exploited as a tumor stroma proxy to study phenotypic plasticity of colorectal cancer-associated fibroblasts (CAF). In combination with Next Generation Sequencing (NGS) data analysis, we demonstrated that tuning the storage modulus of the IPN hydrogel between 49 and 419 Pa can trigger a reversible switch between an inflammatory (i-state, α-SMAlowIL-6high) and myofibroblastic (m-state, α-SMAhighIL-6low) state in CAF that is dependent on the polymer network confinement effect and ROS-HIF1-α mechanotransduction signaling axis. Secretome from m-state CAF upregulated several epithelial-mesenchymal-transition (EMT) transcripts and induced robust scattering in DLD-1, HCT116, and SW480 human colorectal adenocarcinoma, while the EMT-inducing capacity is muted in i-state CAF, suggestive of an anti-tumorigenic role. Our findings were further validated through Gene Expression Profiling Interactive Analysis (GEPIA), which showed that cytokines secreted at higher levels by i-state CAF are correlated (p < 0.05) with good overall colorectal cancer patient survival. Therefore, 3D network density and spatial cellular confinement are critical biophysical determinants that can profoundly influence CAF states, paracrine signaling, and EMT-inducing potential. STATEMENT OF SIGNIFICANCE: The communication between cancer cells and cancer-associated fibroblasts (CAF) contributes to tumor metastasis. CAF represent a diverse population of cellular subsets that can either promote or restrain tumor progression. However, the origin and cause of CAF heterogeneity remain elusive, limiting CAF-directed therapies for clinical use. We studied the dynamic phenotypes of CAF using a 3D physio-mimetic culture platform consisting of an interpenetrating collagen-alginate network. Combined with transcriptomic stratification and correlative analysis using cancer patient dataset, we showed phenotypic interconversion between inflammatory and myofibroblastic states, with anti- and pro-tumorigenic functions, in human colorectal CAF. This multidisciplinary study reveals the functional diversity of colorectal CAF caused by biophysical cues. The finding will influence the development of new CAF biomarkers and cancer therapies.

Sustainable aquaculture side-streams derived hybrid biocomposite for bone tissue engineering.

Despite being a rich source of bioactive compounds, the current exploitation of aquatic biomass is insufficient. Majority of the aquaculture industry side-streams are currently used for low-value purposes such as animal feed or composting material, with low economical returns. To maximize resource reuse and minimize waste generation, valorization efforts should be augmented with the aim to produce high-value products. Herein, we present a novel aquaculture wastes-derived multi-scale osteoconductive hybrid biocomposite that is composed of chemically crosslinked American bullfrog (Rana catesbeiana) skin-derived type I tropocollagen nanofibrils (~22.3 nm) network and functionalized with micronized (~1.6 µm) single-phase hydroxyapatite (HA) from discarded snakehead (Channa micropeltes) fish scales. The bioengineered construct is biocompatible, highly porous (>90%), and exhibits excellent osteoconductive properties, as indicated by robust adhesion and proliferation of human fetal osteoblastic 1.19 cell line (hFOB 1.19). Furthermore, increased expression level of osteo-related ALPL and BGLAP mRNA transcripts, as well as enhanced osteocalcin immunoreactivity and increasing Alizarin red S staining coverage on the hybrid biocomposite was observed over 21 days of culture. Collectively, the devised "waste-to-resource" platform represents a sustainable waste valorization strategy that is amendable for advanced bone repair and regeneration applications.

Bioinspired short peptide hydrogel for versatile encapsulation and controlled release of growth factor therapeutics.

A short bioinspired octapeptide, GV8, can self-assemble under mild conditions into biodegradable supramolecular physical hydrogels with high storage modulus and good biocompatibility. GV8 hydrogels can encapsulate both single or multiple macromolecular protein-based therapeutics in a simple one-pot formulation manner, making it a promising candidate to address challenges faced by existing synthetic polymer or peptide hydrogels with complex gelation and drug-encapsulation processes. Alongside its versatility, the hydrogel exhibits concentration-dependent storage modulus and controlled drug-release action. We demonstrate that GV8 hydrogels loaded with adipose-derived mesenchymal stem cells (ADMSC) secretome remain mechanically robust, and exhibit promising potential for wound healing applications by preserving secretome activity while maintaining a constant supply of ADMSC secretome to promote epithelial cell migration. Overall, our work highlights the potential of GV8 peptide hydrogel as a versatile and safe carrier for encapsulation and delivery of macromolecular therapeutics. STATEMENT OF SIGNIFICANCE: Supramolecular peptide hydrogels are a popular choice for protein-based macromolecular therapeutics delivery; however, despite the development of abundant hydrogel systems, several challenges limit their adaptability and practical applications. GV8 short peptide hydrogel circumvents these drawbacks and demonstrates the ability to function as a versatile growth factor (GF) encapsulant. It can encapsulate precise concentrations of complex adipose-derived mesenchymal stem cells secretome mixtures with a one-pot formulation approach and perform controlled release of GFs with preserved activity without compromising the self-assembly and mechanical properties of the hydrogel's supramolecular network. The significance of GV8 hydrogel lies in its gelation simplicity and versatility to encapsulate and deliver macromolecular therapeutics, thus representing a promising biomaterial for regenerative medicine applications.

Flexible conducting polymer-based cellulose substrates for on-skin applications.

Flexible electroactive cellulose-based substrates were successfully fabricated via electropolymerization of either polypyrrole (PPy) or poly(3,4-ethylenedioxythiophene) (PEDOT) in the presence of sodium dodecyl sulphate (SDS) onto platinum-coated cellulose substrates. Results showed that the conductive polymers were evenly deposited onto the platinum-coated cellulose substrates, respectively without compromising the submicro roughness topography of the substrate. In fact, nanoroughness feature was formed by the deposition of conductive polymers on the individual fibres of the cellulose paper, both of which are highly important in regulating cell adhesion, proliferation and migration. The various electroactive cellulose-based papers exhibited good mechanical and structural properties as well as good cytocompatibility by supporting the attachment and proliferation of immortalized human keratinocytes (HaCaT cells). In addition, copper (Cu2+) and the zinc (Zn2+) ions were proved to be successfully doped into these PPy- and PEDOT-cellulose substrates. The PEDOT resulted in the higher doping of Cu2+ and Zn2+ ions, which was confirmed by the ions release studies. Furthermore, the PEDOT-cellulose substrates exhibited significantly higher mechanical properties, better initial cell attachment and higher electrochemical capacitance as compared to PPy-cellulose substrates. Overall, the results suggested that the PEDOT-cellulose substrates could potentially be a better choice of smart skin dressings, integration interface between skin and artificial devices or implantable electronic materials.

Photocurable platelet rich plasma bioadhesives.

Closure of wounds with tissue adhesives has many advantages over sutures, but existing synthetic adhesives are toxic and have poor workability. Blood-derived adhesives display complete resorption but have adhesion too weak for reliable wound dressings. We propose a semi-synthetic design that combines the positive attributes of synthetic and blood-derived tissue adhesives. PAMAM-g-diazirine (PDz) is a rapidly gelling bioadhesive miscible in both aqueous and organic solvents. PDz blended with platelet-rich plasma (PRP) forms PDz/PRP composite, a semi-synthetic formulation that combines PDz's wet tissue adhesion with PRP's potent wound healing properties. Light-activated PDz/PRP bioadhesive composite has similar elasticity to soft tissues and behaves as an induced hemostat-an unmet clinical need for rapid wound dressings. PDz/PRP composite applied to in-vivo full-thickness wounds observed a 25% reduction in inflammation, as assessed by the host-cell response.

Fish scale-derived collagen patch promotes growth of blood and lymphatic vessels in vivo.

In this study, Type I collagen was extracted from fish scales asa potential alternative source of collagen for tissue engineering applications. Since unmodified collagen typically has poor mechanical and degradation stability both in vitro and in vivo, additional methylation modification and 1,4-butanediol diglycidyl ether (BDE) crosslinking steps were used to improve the physicochemical properties of fish scale-derived collagen. Subsequently, in vivo studies using a murine model demonstrated the biocompatibility of the different fish scale-derived collagen patches. In general, favorable integration of the collagen patches to the surrounding tissues, with good infiltration of cells, blood vessels (BVs) and lymphatic vessels (LVs) were observed under growth factor-free conditions. Interestingly, significantly higher (p<0.05) number of LVs was found to be more abundant around collagen patches with methylation modification and BDE crosslinking. Overall, we have demonstrated the potential application of fish scale-derived collagen as a promising scaffolding material for various biomedical applications. STATEMENT OF SIGNIFICANCE: Currently the most common sources of collagen are of bovine and porcine origins, although the industrial use of collagen obtained from non-mammalian species is growing in importance, particularly since they have a lower risk of disease transmission and are not subjected to any cultural or religious constraints. However, unmodified collagen typically has poor mechanical and degradation stability both in vitro and in vivo. Hence, in this study, Type I collagen was successfully extracted from fish scales and chemically modified and crosslinked. In vitro studies showed overall improvement in the physicochemical properties of the material, whilst in vivo implantation studies showed improvements in the growth of blood and lymphatic host vessels in the vicinity of the implants.

Supercritical carbon dioxide extracted extracellular matrix material from adipose tissue.

Adipose tissue is a rich source of extracellular matrix (ECM) material that can be isolated by delipidating and decellularizing the tissue. However, the current delipidation and decellularization methods either involve tedious and lengthy processes or require toxic chemicals, which may result in the elimination of vital proteins and growth factors found in the ECM. Hence, an alternative delipidation and decellularization method for adipose tissue was developed using supercritical carbon dioxide (SC-CO2) that eliminates the need of any harsh chemicals and also reduces the amount of processing time required. The resultant SC-CO2-treated ECM material showed an absence of nuclear content but the preservation of key proteins such as collagen Type I, collagen Type III, collagen Type IV, elastin, fibronectin and laminin. In addition, other biological factors such as glycosaminoglycans (GAGs) and growth factors such as basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) were also retained. Subsequently, the resulting SC-CO2-treated ECM material was used as a bioactive coating on tissue culture plastic (TCP). Four different cell types including adipose tissue-derived mesenchymal stem cells (ASCs), human umbilical vein endothelial cells (HUVECs), immortalized human keratinocyte (HaCaT) cells and human monocytic leukemia cells (THP-1) were used in this study to show that the SC-CO2-treated ECM coating can be potentially used for various biomedical applications. The SC-CO2-treated ECM material showed improved cell-material interactions for all cell types tested. In addition, in vitro scratch wound assay using HaCaT cells showed that the presence of SC-CO2-treated ECM material enhanced keratinocyte migration whilst the in vitro cellular studies using THP-1-derived macrophages showed that the SC-CO2-treated ECM material did not evoke pro-inflammatory responses from the THP-1-derived macrophages. Overall, this study shows the efficacy of SC-CO2 method for delipidation and decellularization of adipose tissue whilst retaining its ECM and its subsequent utilization as a bioactive surface coating material for soft tissue engineering, angiogenesis and wound healing applications.

A Periosteum-Inspired 3D Hydrogel-Bioceramic Composite for Enhanced Bone Regeneration .

A 3D injectable hydrogel-bioceramic composite consisting of gelatin-3-(4-hydroxyphenyl) propionic acid (Gtn-HPA) and carboxymethyl cellulose-tyramine (CMC-Tyr), incorporated with fish scale-derived calcium phosphate (CaP), is developed for bone applications. The hydrogel-bioceramic composite has significantly improved the elastic modulus compared to the non-filled hydrogel, of which the addition of 10 w/v% CaP showed zero order fluorescein isothiocyanate (FITC)-dextran release profile and a significantly higher proliferation rate of encapsulated cells. All the samples promote the nucleation and growth of CaP minerals when exposed to 1× SBF. Overall, the hydrogel-bioceramic composite with 10 w/v% CaP can potentially be used as a periosteum-mimicking membrane to facilitate bone regeneration.

Development of a miniaturized stimulation device for electrical stimulation of cells.

BACKGROUND: Directing cell behaviour using controllable, on-demand non-biochemical methods, such as electrical stimulation is an attractive area of research. While there exists much potential in exploring different modes of electrical stimulation and investigating a wider range of cellular phenomena that can arise from electrical stimulation, progress in this field has been slow. The reasons for this are that the stimulation techniques and customized setups utilized in past studies have not been standardized, and that current approaches to study such phenomena rely on low throughput platforms with restricted variability of waveform outputs. RESULTS: Here, we first demonstrated how a variety of cellular responses can be elicited using different modes of DC and square waveform stimulation. Intracellular calcium levels were found to be elevated in the neuroblast cell line SH-SY5Y during stimulation with 5 V square waves and, stimulation with 150 mV/mm DC fields and 1.5 mA DC current resulted in polarization of protein kinase Akt in keratinocytes and elongation of endothelial cells, respectively. Next, a miniaturized stimulation device was developed with an integrated cell chamber array to output multiple discrete stimulation channels. A frequency dividing circuit implemented on the device provides a robust system to systematically study the effects of multiple output frequencies from a single input channel. CONCLUSION: We have shown the feasibility of directing cellular responses using various stimulation waveforms, and developed a modular stimulation device that allows for the investigation of multiple stimulation parameters, which previously had to be conducted with different discrete equipment or output channels. Such a device can potentially spur the development of other high throughput platforms for thorough investigation of electrical stimulation parameters on cellular responses.

Imparting electroactivity to polycaprolactone fibers with heparin-doped polypyrrole: Modulation of hemocompatibility and inflammatory responses.

Hemocompatibility, anti-inflammation and anti-thrombogenicity of acellular synthetic vascular grafts remains a challenge in biomaterials design. Using electrospun polycaprolactone (PCL) fibers as a template, a coating of polypyrrole (PPy) was successfully polymerized onto the fiber surface. The fibers coated with heparin-doped PPy (PPy-HEP) demonstrated better electroactivity, lower surface resistivity (9-10-fold) and better anti-coagulation response (non-observable plasma recalcification after 30min vs. recalcification at 8-9min) as compared to fibers coated with pristine PPy. Red blood cell compatibility, measured by% hemolysis, was greatly improved on PPy-HEP-coated PCL in comparison to uncoated PCL (3.9±2.1% vs. 22.1±4.1%). PPy-HEP-coated PCL fibers also exhibited higher stiffness values (6.8±0.9MPa vs. 4.2±0.8MPa) as compared to PCL fibers, but similar tensile strengths. It was also observed that the application of a low alternating current led to a 4-fold reduction of platelet activation (as quantitated by CD62p expression) for the PPy-HEP-coated fibers as compared to non-stimulated conditions. In parallel, a reduction in the leukocyte adhesion to both pristine PPy-coated and PPy-HEP-coated fibers was observable with AC stimulation. Overall, a new strategy involving the use of hemocompatible conducting polymers and electrical stimulation to control thrombogenicity and inflammatory responses for synthetic vascular graft designs was demonstrated.

Polymer-Enriched 3D Graphene Foams for Biomedical Applications.

Graphene foams (GFs) are versatile nanoplatforms for biomedical applications because of their excellent physical, chemical, and mechanical properties. However, the brittleness and inflexibility of pristine GF (pGF) are some of the important factors restricting their widespread application. Here, a chemical-vapor-deposition-assisted method was used to synthesize 3D GFs, which were subsequently spin-coated with polymer to produce polymer-enriched 3D GFs with high conductivity and flexibility. Compared to pGF, both poly(vinylidene fluoride)-enriched GF (PVDF/GF) and polycaprolactone-enriched GF (PCL/GF) scaffolds showed improved flexibility and handleability. Despite the presence of the polymers, the polymer-enriched 3D GF scaffolds retained high levels of electrical conductivity because of the presence of microcracks that allowed for the flow of electrons through the material. In addition, polymer enrichment of GF led to an enhancement in the formation of calcium phosphate (Ca-P) compounds when the scaffolds were exposed to simulated body fluid. Between the two polymers tested, PCL enrichment of GF resulted in a higher in vitro mineralization nucleation rate because the oxygen-containing functional group of PCL had a higher affinity for Ca-P deposition and formation compared to the polar carbon-fluorine (C-F) bond in PVDF. Taken together, our current findings are a stepping stone toward future applications of polymer-enriched 3D GFs in the treatment of bone defects as well as other biomedical applications.

Endothelial cell thrombogenicity is reduced by ATRP-mediated grafting of gelatin onto PCL surfaces.

Reducing the thrombogenicity of a tissue-engineered vascular graft prior to implantation is important for improving graft patency. As functionalization of synthetic materials with cell-adhesive proteins is routinely utilized as a means to promote endothelial cell (EC) growth, we conducted detailed investigation on the proliferation and thrombogenicity of ECs on such functionalized surfaces. We observed that polycaprolactone (PCL) surfaces functionalized with poly(glycidyl methacrylate) [(P(GMA)] brushes via atom transfer radical polymerization (ATRP) alone resulted in the enhancement of an activated EC profile characterized by low production of nitric oxide (NO), platelet activation and elevated expression levels of von Willebrand factor (vWF) and matrix metalloproteinase-2 (MMP-2). When gelatin was conjugated onto the PCL-g-P(GMA) surfaces, not only were EC proliferation and endothelial coverage significantly improved, but an anti-thrombogenic profile was also observed. We demonstrated that PCL can be successfully functionalized by a controllable surface-initiated polymerization method and importantly, the thrombogenic profile of the endothelial cells can be influenced by material surface chemistry (e.g. the presence of polymer graft chains). Our findings emphasize the importance of a careful consideration of materials for vascular graft applications, as well as differential endothelial cell physiology on surfaces with different material chemistry.