Peptide-Functionalized Polyurethane Coatings Prepared via Grafting-To Strategy to Selectively Promote Endothelialization

Recent advances of multifunctional zwitterionic polymers for biomedical application

Zwitterionic polymers possess equal total positive and negative charges in the repeating units, making them electrically neutral overall. This unique property results in superhydrophilicity, which makes the zwitterionic polymers highly effective in resisting protein adsorption, thus endowing the drug carriers with long blood circulation time, inhibiting thrombus formation on biomedical devices in contact with blood, and ensuring the good sensitivity of sensors in biomedical application. Moreover, zwitterionic polymers have tumor-targeting ability and pH-responsiveness, rendering them ideal candidates for antitumor drug delivery. Additionally, the high ionic conductivity of zwitterionic polymers makes them an important raw material for ionic skin. Zwitterionic polymers exhibit remarkable resistance to bacterial adsorption and growth, proving their suitability in a wide range of biomedical applications such as ophthalmic applications, and wound dressings. In this paper, we provide an in-depth analysis of the different structures and characteristics of zwitterionic polymers and highlight their unique qualities and suitability for biomedical applications. Furthermore, we discuss the limitations and challenges that must be overcome to realize the full potential of zwitterionic polymers and present an optimistic perspective for zwitterionic polymers in the biomedical fields. STATEMENT OF SIGNIFICANCE: Zwitterionic polymers have a series of excellent properties such as super hydrophilicity, anti-protein adsorption, antibacterial ability and good ionic conductivity. However, biomedical applications of multifunctional zwitterionic polymers are still a major field to be explored. This review focuses on the design and application of zwitterionic polymers-based nanosystems for targeted and responsive delivery of antitumor drugs and cancer diagnostic agents. Moreover, the use of zwitterionic polymers in various biomedical applications such as biomedical devices in contact with blood, biosensors, ionic skin, ophthalmic applications and wound dressings is comprehensively described. We discuss current results and future challenges for a better understanding of multifunctional zwitterionic polymers for biomedical applications.

Nanotexture and crystal phase regulation for synergistic enhancement in re-endothelialization on medical pure titanium surface

Re-endothelialization has been recognized as a promising strategy to address the tissue hyperplasia and subsequent restenosis which are major complications associated with vascular implant/interventional titanium devices. However, the uncontrollable over-proliferation of smooth muscle cells (SMCs) limits the clinical application of numerous modified strategies. Herein, a novel modified strategy involving with a two-step anodic oxidation and annealing treatment was proposed to achieve rapid re-endothelialization function regulated by regular honeycomb nanotexture and specific anatase phase on the titanium surface. Theoretical calculation revealed that the presence of nanotexture reduced the polar component of surface energy, while the generation of anatase significantly enhanced the polar component and total surface energy. Meanwhile, the modified surface with regular nanotexture and anatase phase produced positive effect on the expression of CD31, VE-Cadherin and down-regulated α-SMA proteins expression, indicating excellent capacity of pro-endothelial regeneration and inhibition of SMCs proliferation and migration. One-month in vivo implantation in rabbit carotid arteries further confirmed that modified tube implant surface effectively accelerated confluent endothelial monolayer formation and promoted native-like endothelium tissue regeneration. By contrast, original titanium tube implant induced a disorganized tissue proliferation in the lumen with a high risk of restenosis. Collectively, this study opens us an alternative route to achieve the function that selectively promotes endothelial cells (ECs) growth and suppresses SMCs on the medical titanium surface, which has a great potential in facilitating re-endothelialization on the surface of blood-contacting titanium implant.

One-Pot Microfluidics to Engineer Chitosan Nanoparticles Conjugated with Antimicrobial Peptides Using "Photoclick" Chemistry: Validation Using the Gastric Bacterium Helicobacter pylori

Surface bioconjugation of antimicrobial peptides (AMP) onto nanoparticles (AMP-NP) is a complex, multistep, and time-consuming task. Herein, a microfluidic system for the one-pot production of AMP-NP was developed. Norbornene-modified chitosan was used for NP production (NorChit-NP), and thiolated-AMP was grafted on their surface via thiol-norbornene "photoclick" chemistry over exposure of two parallel UV LEDs. The MSI-78A was the AMP selected due to its high activity against a high priority (level 2) antibiotic-resistant gastric pathogen: Helicobacter pylori (H. pylori). AMP-NP (113 ± 43 nm; zeta potential 14.3 ± 7 mV) were stable in gastric settings without a cross-linker (up to 5 days in pH 1.2) and bactericidal against two highly pathogenic H. pylori strains (1011 NP/mL with 96 μg/mL MSI-78A). Eradication was faster for H. pylori 26695 (30 min) than for H. pylori J99 (24 h), which was explained by the lower minimum bactericidal concentration of soluble MSI-78A for H. pylori 26695 (32 μg/mL) than for H. pylori J99 (128 μg/mL). AMP-NP was bactericidal by inducing H. pylori cell membrane alterations, intracellular reorganization, generation of extracellular vesicles, and leakage of cytoplasmic contents (transmission electron microscopy). Moreover, NP were not cytotoxic against two gastric cell lines (AGS and MKN74, ATCC) at bactericidal concentrations. Overall, the designed microfluidic setup is a greener, simpler, and faster approach than the conventional methods to obtain AMP-NP. This technology can be further explored for the bioconjugation of other thiolated-compounds.

Amphiphilic multi-targeting copolymer micelles efficiently deliver pZNF580 to promote endothelial cell proliferation and migration

Cationic copolymers are widely used in gene delivery as a non-viral gene vector, but their applications are limited by low transfection efficiency and high cytotoxicity. In order to enhance the transfection efficiency of copolymer micelles to endothelial cells (HUVECs) and reduce their cytotoxicity, this study synthesized an amphipathic multi-targeted copolymer micelle delivery system PCLMD-PPEGMA-NLS-TAT-REDV (TCMs). Gel test results showed that TCMs showed good pZNF580 binding ability and could effectively load the pZNF580 plasmid. The CCK-8 results show that when the concentration of TCMs is greater than 60 μg mL-1, it will affect cell viability and have low cytotoxicity. We found that the multi-targeted copolymer micelles can be effectively taken up by HUVECs in vitro. The transfection efficiency of TCMs@pZNF580 (w/wpZNF580 = 3) to HUVECs was comparable to that of the positive control group lip2000@pZNF580, and WB also showed the same trend. In addition, the TCMs@pZNF580 complex also significantly enhanced the proliferation and migration of HUVECs. The experimental results on blood vessel formation showed that TCMs@pZNF580 accelerated the vascularization of HUVECs. This experiment provided a new technology platform for targeted gene therapy, especially for endothelialization and vascularization. The research results have important reference value for the treatment of cardiovascular diseases.

Bioactive mesoporous silica nanoparticle-functionalized titanium implants with controllable antimicrobial peptide release potentiate the regulation of inflammation and osseointegration

Bacterial infection and delayed osseointegration are two major challenges for titanium-based orthopedic implants. In the present study, we developed a functionalized titanium implant Ti-M@A by immobilizing antimicrobial peptide (AMP) HHC36-loaded diselenide-bridged mesoporous silica nanoparticles (MSNs) on the surface, which showed good long-term and mechanical stability. The functionalized implants can realize the sustained release of AMP over 30 days and exhibit over 95.71 % antimicrobial activity against four types of clinical bacteria (S. aureus, E. coli, P. aeruginosa and MRSA), which arose from the capability to destroy the bacterial membranes. Moreover, Ti-M@A can efficiently inhibit the biofilm formation of the bacteria. The functionalized implants can also significantly promote the osteogenic differentiation of mouse bone marrow-derived mesenchymal stem cells (mBMSCs) because of the Se in MSNs. Notably, it can trigger macrophages toward M2 polarization in vitro by scavenging ROS in LPS-activated macrophages. Consequently, in vivo assays with infection and non-infection bone defect models demonstrated that such bioactive implants can not only kill over 98.82 % of S. aureus, but also promote osseointegration. Hence, this study provides a combined strategy to resolve bacterial infection and delayed osseointegration for titanium implants.

Polyphenol-mediated sandwich-like coating promotes endothelialization and vascular healing

Drug-eluting stents have become one of the most effective methods to treat cardiovascular diseases. However, this therapeutic strategy may lead to thrombosis, stent restenosis, and intimal hyperplasia and prevent re-endothelialization. In this study, we selected 3-aminophenylboronic acid-modified hyaluronic acid and carboxylate chitosan as polyelectrolyte layers and embedded an epigallocatechin-3-gallate-tanshinone IIA sulfonic sodium (EGCG-TSS) complex to develop a sandwich-like layer-by-layer coating. The introduction of a functional molecular EGCG-TSS complex improved not only the biocompatibility of the coating but also its stability by enriching the interaction between the polyelectrolyte coatings through electrostatic interactions, hydrogen bonding, π-π stacking, and covalent bonding. We further elucidated the effectiveness of sandwich-like coatings in regulating the inflammatory response, smooth muscle cell growth behavior, stent thrombosis and restenosis suppression, and vessel re-endothelialization acceleration via in vivo and in vitro. Conclusively, we demonstrated that sandwich-like coating assisted by an EGCG-TSS complex may be an effective surface modification strategy for cardiovascular therapeutic applications.

Water-Triggered Segment Orientation of Long-Lasting Anti-Biofouling Polyurethane Coatings on Biomedical Catheters via Solvent Exchange Strategy

The formation of biofilm and thrombus on medical catheters poses a significant life-threatening concern. Hydrophilic anti-biofouling coatings upon catheter surfaces with complex shapes and narrow lumens are demonstrated to have the potential in reducing complications. However, their effectiveness is constrained by poor mechanical stability and weak substrate adhesion. Herein, a novel zwitterionic polyurethane (SUPU) with strong mechanical stability and long-term anti-biofouling is developed by controlling the ratio of sulfobetaine-diol and ureido-pyrimidinone. Once immersed in water, as-synthesized zwitterionic coating (SUPU3 SE) would undergo a water-driven segment reorientation to obtain much higher durability than its direct drying one, even under various extreme treatments, including acidic solution, abrasion, ultrasonication, flushing, and shearing, in PBS at 37 °C for 14 days. Moreover, SUPU3 SE coating could achieve a 97.1% of exceptional reducing protein fouling, complete prevention of cell adhesion, and long-lasting anti-biofilm performance even after 30 days. Finally, the good anti-thrombogenic formations of SUPU3 SE coating with bacterial treatment are validated in blood circulation through an ex vivo rabbit arteriovenous shunt model. This work provides a facile approach to fabricating stable hydrophilic coating through a simple solvent exchange to reduce thrombosis and infection of biomedical catheters.

Challenges and advances in materials and fabrication technologies of small-diameter vascular grafts

The arterial occlusive disease is one of the leading causes of cardiovascular diseases, often requiring revascularization. Lack of suitable small-diameter vascular grafts (SDVGs), infection, thrombosis, and intimal hyperplasia associated with synthetic vascular grafts lead to a low success rate of SDVGs (< 6 mm) transplantation in the clinical treatment of cardiovascular diseases. The development of fabrication technology along with vascular tissue engineering and regenerative medicine technology allows biological tissue-engineered vascular grafts to become living grafts, which can integrate, remodel, and repair the host vessels as well as respond to the surrounding mechanical and biochemical stimuli. Hence, they potentially alleviate the shortage of existing vascular grafts. This paper evaluates the current advanced fabrication technologies for SDVGs, including electrospinning, molding, 3D printing, decellularization, and so on. Various characteristics of synthetic polymers and surface modification methods are also introduced. In addition, it also provides interdisciplinary insights into the future of small-diameter prostheses and discusses vital factors and perspectives for developing such prostheses in clinical applications. We propose that the performance of SDVGs can be improved by integrating various technologies in the near future.

Development of Polyurethane/Peptide-Based Carriers with Self-Healing Properties

In situ-forming gels with self-assembling and self-healing properties are materials of high interest for various biomedical applications, especially for drug delivery systems and tissue regeneration. The main goal of this research was the development of an innovative gel carrier based on dynamic inter- and intramolecular interactions between amphiphilic polyurethane and peptide structures. The polyurethane architecture was adapted to achieve the desired amphiphilicity for self-assembly into an aqueous solution and to facilitate an array of connections with peptides through physical interactions, such as hydrophobic interactions, dipole-dipole, electrostatic, π–π stacking, or hydrogen bonds. The mechanism of the gelation process and the macromolecular conformation in water were evaluated with DLS, ATR-FTIR, and rheological measurements at room and body temperatures. The DLS measurements revealed a bimodal distribution of small (~30–40 nm) and large (~300–400 nm) hydrodynamic diameters of micelles/aggregates at 25 °C for all samples. The increase in the peptide content led to a monomodal distribution of the peaks at 37 °C (~25 nm for the sample with the highest content of peptide). The sol–gel transition occurs very quickly for all samples (within 20–30 s), but the equilibrium state of the gel structure is reached after 1 h in absence of peptide and required more time as the content of peptide increases. Moreover, this system presented self-healing properties, as was revealed by rheological measurements. In the presence of peptide, the structure recovery after each cycle of deformation is a time-dependent process, the recovery is complete after about 300 s. Thus, the addition of the peptide enhanced the polymer chain entanglement through intermolecular interactions, leading to the preparation of a well-defined gel carrier. Undoubtedly, this type of polyurethane/peptide-based carrier, displaying a sol–gel transition at a biologically relevant temperature and enhanced viscoelastic properties, is of great interest in the development of medical devices for minimally invasive procedures or precision medicine.

A Polymeric Strategy Empowering Vascular Cell Selectivity and Potential Application Superior to Extracellular Matrix Peptides

Endothelialization of vascular implants plays a vital role in maintaining the long-term vascular patency. In situ endothelialization and re-endothelialization is generally achieved by selectively promoting endothelial cell (EC) adhesion and, meanwhile, suppressing smooth muscle cell (SMC) adhesion. Currently, such EC versus SMC selectivity is achieved and extensively used in vascular-related biomaterials utilizing extracellular-matrix-derived EC-selective peptides, dominantly REDV and YIGSR. Nevertheless, the application of EC-selective peptides is limited due to their easy proteolysis, time-consuming synthesis, and expensiveness. To address these limitations, a polymeric strategy in designing and finding EC-selective biomaterials using amphiphilic β-peptide polymers by tuning serum protein adsorption is reported. The optimal β-peptide polymer displays EC versus SMC selectivity even superior to EC-selective REDV peptide regarding cell adhesion, proliferation, and migration of ECs versus SMCs. Study of the mechanism indicates that surface adsorption of bovine serum albumin, an abundant and anti-adhesive serum protein, plays a critical role in the ECs versus SMCs selectivity of β-peptide polymer. In addition, surface modification of the optimal β-peptide polymer effectively promotes the endothelialization of vascular implants and inhibits intimal hyperplasia. This study provides an alternative strategy in designing and finding EC-selective biomaterials, implying great potential in the vascular-related biomaterial study and application.

Versatile antibacterial surface with amphiphilic quaternized chitin-based derivatives for catheter associated infection prevention

Microbial colonization of catheter surfaces is responsible for most healthcare-associated infections. Quaternized chitin and chitosan have excellent antimicrobial and biocompatible properties and can be used to provide safe and prolonged protection for biomedical catheters. Herein, we prepared quaternized β-chitin derivative (QC)- and quaternized chitosan derivative (QCS)-based antimicrobial surfaces. The quaternized polysaccharides modified TPU surfaces exhibited hydrophilicity, good biocompatibility. Among these, QCS2-modified TPU exhibited excellent antibacterial properties against Gram-positive and Gram-negative bacteria, and prevented the adherence of bacteria compared with pristine TPU. The antibacterial activity of QCS2-modified surfaces maintained for 8 weeks under the condition of immersion in serum. An in vivo subcutaneous implantation experiment revealed 99.87% reduction of bacteria and reduced expression of inflammation-related factors in the surrounding tissue five days after implantation with QCS2-modified TPU. Therefore, quaternized polysaccharide-modified surfaces have promising potential in preventing medical catheter-associated infections.

Enlargement, Reduction, and Even Reversal of Relative Migration Speeds of Endothelial and Smooth Muscle Cells on Biomaterials Simply by Adjusting RGD Nanospacing

Although many tissue regeneration processes after biomaterial implantation are related to migrations of multiple cell types on material surfaces, available tools to adjust relative migration speeds are very limited. Herein, we put forward a nanomaterial strategy to employ surface modification with arginine-glycine-aspartate (RGD) nanoarrays to tune in vitro cell migration using endothelial cells (ECs) and smooth muscle cells (SMCs) as demonstrated cell types. We found that migrations of both cell types exhibited a nonmonotonic trend with the increase of RGD nanospacing, yet with different peaks-74 nm for SMCs but 95 nm for ECs. The varied sensitivities afford a facile way to regulate the relative migration speeds. Although ECs migrated at a speed similar to SMCs on a non-nano surface, the migration of ECs could be controlled to be significantly faster or slower than SMCs simply by adjusting the RGD nanospacing. This study suggests a potential application of surface modification of biomaterials on a nanoscale level.

Dual mechanism β-amino acid polymers promoting cell adhesion

Cell adhesion has tremendous impact on the function of culture platforms and implants. Cell-adhesive proteins and peptides have been extensively used for decades to promote cell adhesion, however, their application suffers from their easy enzymatic degradation, difficulty in large-scale preparation and expensiveness. To develop the next-generation cell-adhesive materials, we mimic the cell adhesion functions and mechanisms of RGD and KRSR peptides and design cell-adhesive cationic-hydrophobic amphiphilic β-amino acid polymers that are stable upon proteolysis and easily prepared in large scale at low cost. The optimal polymer strongly promotes cell adhesion, using preosteoblast cell as a model, by following dual mechanisms that are independent of sequence and chirality of the statistic copolymer. Our strategy opens avenues in designing the next-generation cell-adhesive materials and may guide future studies and applications.

Synthetic peptide hydrogels as 3D scaffolds for tissue engineering

The regeneration of tissues and organs poses an immense challenge due to the extreme complexity in the research work involved. Despite the tissue engineering approach being considered as a promising strategy for more than two decades, a key issue impeding its progress is the lack of ideal scaffold materials. Nature-inspired synthetic peptide hydrogels are inherently biocompatible, and its high resemblance to extracellular matrix makes peptide hydrogels suitable 3D scaffold materials. This review covers the important aspects of peptide hydrogels as 3D scaffolds, including mechanical properties, biodegradability and bioactivity, and the current approaches in creating matrices with optimized features. Many of these scaffolds contain peptide sequences that are widely reported for tissue repair and regeneration and these peptide sequences will also be discussed. Furthermore, 3D biofabrication strategies of synthetic peptide hydrogels and the recent advances of peptide hydrogels in tissue engineering will also be described to reflect the current trend in the field. In the final section, we will present the future outlook in the design and development of peptide-based hydrogels for translational tissue engineering applications.

A zwitterionic hydrogel coated titanium surface with high-efficiency endothelial cell selectivity for rapid re-endothelialization

Coronary stent implantation is an effective procedure for percutaneous coronary intervention treatment. However, its long-term safety and efficacy are still hindered by the in-stent restenosis and late thrombus formation. Herein, an anti-biofouling and endothelial cell selective zwitterionic hydrogel coating was developed to simultaneously enhance the nonspecific resistance and rapid re-endothelialization of the titanium surface. An endothelial cell selective peptide, REDV, could be simply conjugated on the zwitterionic carboxybetaine (CB) hydrogel to prepare the REDV/CB coating. It was found that the REDV/CB hydrogel layer maintained antifouling properties, which could inhibit the protein adsorption, bacterial adhesion, platelet activation and aggregation, and smooth muscle cell proliferation. More importantly, the co-culture study confirmed that the conjugated REVD peptide could specifically capture endothelial cells and promote their migration and proliferation, and simultaneously decrease the adhesion and proliferation of smooth muscle cells. Therefore, the antifouling and endothelial cell selective coating proposed in this work provides a promising strategy to develop an intravascular stent for promoted re-endothelialization and inhibited neointimal hyperplasia in clinical applications.

Surface Engineering of Cardiovascular Devices for Improved Hemocompatibility and Rapid Endothelialization

Cardiovascular devices have been widely applied in the clinical treatment of cardiovascular diseases. However, poor hemocompatibility and slow endothelialization on their surface still exist. Numerous surface engineering strategies have mainly sought to modify the device surface through physical, chemical, and biological approaches to improve surface hemocompatibility and endothelialization. The alteration of physical characteristics and pattern topographies brings some hopeful outcomes and plays a notable role in this respect. The chemical and biological approaches can provide potential signs of success in the endothelialization of vascular device surfaces. They usually involve therapeutic drugs, specific peptides, adhesive proteins, antibodies, growth factors and nitric oxide (NO) donors. The gene engineering can enhance the proliferation, growth, and migration of vascular cells, thus boosting the endothelialization. In this review, the surface engineering strategies are highlighted and summarized to improve hemocompatibility and rapid endothelialization on the cardiovascular devices. The potential outlook is also briefly discussed to help guide endothelialization strategies and inspire further innovations. It is hoped that this review can assist with the surface engineering of cardiovascular devices and promote future advancements in this emerging research field.

Functional characterization of an enzymatically degradable multi-bioactive elastin-like recombinamer

One of the main goals in both tissue engineering and regenerative medicine is to design innovative synthetic scaffolds that can simulate and control the communication pathways between cells and the extracellular matrix (ECM). In this context, we describe herein the characterization of protein polymer, a recombinant elastin-like recombinamer (ELR) designed for developing tissue-engineered devices for use in vascular regeneration. This ELR is composed of an elastin-like backbone that contains a fibronectin domain, which provides specific, endothelial cell adhesion, and a protease target domain directed towards specific proteases involved in ECM remodeling. We also compare the specific response of endothelial and fibroblast cells to ELR scaffolds and show that cell adhesion and spreading on this ELR is significantly higher for endothelial cells than for fibroblasts. The reactivity of this polymer and its hydrogels to specific enzymatic degradation is demonstrated in vitro. As with natural elastin, enzymatic hydrolysis of the ELR produces elastin-derived peptides, or "matrikines", which, in turn, are potentially able to regulate important cell activities.

Wavy small-diameter vascular graft made of eggshell membrane and thermoplastic polyurethane

In this study, a small-diameter, double-layered eggshell membrane/thermoplastic polyurethane (ESM/TPU) vascular graft with a wavy structure was developed. The avian eggshell membrane, a fibrous structure similar to the extracellular matrix (ECM), has the potential to yield rapid endothelialization in vitro. The dopamine and heparin modification of the ESM surface not only promoted human umbilical vein endothelial cell (HUVEC) proliferation via cytocompatibility assessment, but also improved its anticoagulation properties as verified in platelet adhesion tests. The biomimetic mechanical properties of the vascular graft were provided by the elastic TPU fibers via electrospinning using a wavy cross-section rotating collector. The advantage of combining these two materials is to make use of the bioactivity of ESM as the internal membrane and the tunable mechanical properties of TPU as the external layer. The circumferentially wavy structure of the vascular graft produced a toe region in the non-linear section of the stress-strain curve similar to that of natural blood vessels. The ESM/TPU graft's circumferential ultimate strength was 2.57 MPa, its strain was 339% mm/mm, and its toe region was found to be around 20% mm/mm. Cyclical tension tests showed that the vascular graft could maintain good mechanical properties and showed no structural damage under repeated extension tests.

Pre-mounted dry TAVI valve with improved endothelialization potential using REDV-loaded PEGMA hydrogel hybrid pericardium

Schematic diagram for the preparation of hydrogel hybrid dry valve.

Optimization of a Novel Preferential Covered Stent through Bench Experiments and in Vitro Platelet Activation Studies

Bare metal stenting (BMS) does not adequately address the atheroembolic characteristic of carotid artery stenosis. While simple covered stents (CS) may prevent dislodged fragments of the atherosclerotic plaque from entering the blood stream, they also block blood flow into the major branches of the artery alongside the lesion, which is not desirable. Preferential covered stents (PCS) behave as a covered stent in a tubular part of a vessel but maintain side-branch flow over the bifurcation region by means of slits in the membrane. Stent design, membrane material, and slits configuration are the three main components contributing to stent performance. Optimization of PCS designs was conducted and tested.

METHODS

A newly designed BMS was developed and compared to a commercially available peripheral stent. Two materials (expanded poly(tetrafluoroethylene)) and silicone polyurethane co-polymers (Elast-eon E2A) were used as stent coverings with slits applied using various cutting methods to form the PCS. These PCS samples were tested for physical resilience, flexibility, ability to preserve side-branch flow, slit edge roughness, and platelet activation.

RESULTS

Fabrication of E2A-coated stents required pretreatment of the stent with poly(ethylene glycol) to achieve firm attachment. The newly designed BMS with nine crowns design and larger cell size showed higher flexibility than commercially available stents. A combination of a larger stent cell size, E2A membrane coating, and three slits per stent cell unit configuration resulted in preserved side-branch flow similar to physiological conditions in the flow experiment. Slit edge roughness changed with different cutting methods and laser machine cutting parameters. In vitro studies showed platelet activation was minimal with lower slit edge roughness samples.

CONCLUSION

An optimized PCS prototype was developed consisting of a newly designed stent, E2A membrane, and a three-slit pattern created by specific femtosecond laser cutting.

Aspartic and Glutamic Acid Templated Peptides Conjugation on Plasma Modified Nanofibers for Osteogenic Differentiation of Human Mesenchymal Stem Cells: A Comparative Study

Optimization of nanofiber (NF) surface properties is critical to achieve an adequate cellular response. Here, the impact of conjugation of biomimetic aspartic acid (ASP) and glutamic acid (GLU) templated peptides with poly(lactic-co-glycolic acid) (PLGA) electrospun NF on osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hMSCs) was evaluated. Cold atmospheric plasma (CAP) was used to functionalize the NF surface and thus to mediate the conjugation. The influence of the CAP treatment following with peptide conjugation to the NF surface was assessed using water contact angle measurements, Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS). The effect of CAP treatment on morphology of NF was also checked using Scanning Electron Microscopy (SEM). Both the hydrophilicity of NF and the number of the carboxyl (-COOH) groups on the surface increased with respect to CAP treatment. Results demonstrated that CAP treatment significantly enhanced peptide conjugation on the surface of NF. Osteogenic differentiation results indicated that conjugating of biomimetic ASP templated peptides sharply increased alkaline phosphatase (ALP) activity, calcium content, and expression of key osteogenic markers of collagen type I (Col-I), osteocalcin (OC), and osteopontin (OP) compared to GLU conjugated (GLU-pNF) and CAP treated NF (pNF). It was further depicted that ASP sequences are the major fragments that influence the mineralization and osteogenic differentiation in non-collagenous proteins of bone extracellular matrix.

Enhancing anti-thrombogenicity of biodegradable polyurethanes through drug molecule incorporation

Sufficient and sustained anti-thrombogenicity is essential for blood-contacting materials, because blood coagulation and thrombosis caused by platelet adhesion and activation on material surfaces may lead to functional failure and even fatal outcomes. Covalently conjugating antithrombogenic moieties into polymer, instead of surface modifying or blending, can maintain the anti-thrombogenicity of polymer at a high level over a time range. In this study, series of randomly crosslinked, elastic, biodegradable polyurethanes (PU-DPA) were synthesized through a one-pot and one-step method from polycaprolactone (PCL) diol, hexamethylene diisocyanate (HDI) and anti-thrombogenic drug, dipyridamole (DPA). The mechanical properties, hydrophilicity, in vitro degradation, and anti-thrombogenicity of the resultant PU-DPA polymers can be tuned by altering the incorporated DPA amount. The surface and bulk hydrophilicity of the polyurethanes decreased with increasing hydrophobic DPA amount. All PU-DPA polymers exhibited strong mechanical properties and good elasticity. The degradation rates of the PU-DPAs decreased with increasing DPA content in both PBS and lipase/PBS solutions. Covalently incorporating DPA into the polyurethane significantly reduced the platelet adhesion and activation compared to the polyurethane without DPA, and also can achieve sustained anti-thrombogenicity. The PU-DPA films also supported the growth of human umbilical vein endothelial cells. The attractive mechanical properties, blood compatibility, and cell compatibility of this anti-thrombogenic biodegradable polyurethane indicate that it has a great potential to be utilized for blood-contacting devices, and cardiovascular tissue repair and regeneration.