Surface plasma modification and tropoelastin coating of a polyurethane co-polymer for enhanced cell attachment and reduced thrombogenicity

Robust, Sprayable, and Multifunctional Hydrogel Coating through a Polycation Reinforced (PCR) Surface Bridging Strategy

The sprayable hydrogel coatings that can establish robust adhesion onto diverse materials and devices hold enormous potential; however, a significant challenge persists due to monomer hydration, which impedes even coverage during spraying and induces inadequate adhesion post-gelation. Herein, a polycation-reinforced (PCR) surface bridging strategy is presented to achieve tough and sprayable hydrogel coatings onto diverse materials. The polycations offer superior wettability and instant electrostatic interactions with plasma-treated substrates, facilitating an effective spraying application. This PCR-based hydrogel coatings demonstrate tough adhesion performance to inert PTFE and silicone, including remarkable shear strength (161 ± 49 kPa for PTFE), interfacial toughness (198 ± 27 J m-2 for PTFE), and notable tolerance to cyclic tension (10 000 cycles, 200% strain, silicone). Meanwhile, this method can be applied to various hydrogel formulations, offering diverse functionalities, including underwater adhesion, lubrication, and drug delivery. Furthermore, the PCR concept enables the conformal construction of durable hydrogel coatings onto sophisticated medical devices like cardiovascular stents. Given its simplicity and adaptability, this approach paves an avenue for incorporating hydrogels onto solid surfaces and potentially promotes untapped applications.

Biomaterials containing extracellular matrix molecules as biomimetic next-generation vascular grafts

The performance of synthetic biomaterial vascular grafts for the bypass of stenotic and dysfunctional blood vessels remains an intractable challenge in small-diameter applications. The functionalization of biomaterials with extracellular matrix (ECM) molecules is a promising approach because these molecules can regulate multiple biological processes in vascular tissues. In this review, we critically examine emerging approaches to ECM-containing vascular graft biomaterials and explore opportunities for future research and development toward clinical use.

In Vitro and In Silico Studies of Functionalized Polyurethane Surfaces toward Understanding Biologically Relevant Interactions

The solid-aqueous boundary formed upon biomaterial implantation provides a playground for most biochemical reactions and physiological processes involved in implant-host interactions. Therefore, for biomaterial development, optimization, and application, it is essential to understand the biomaterial-water interface in depth. In this study, oxygen plasma-functionalized polyurethane surfaces that can be successfully utilized in contact with the tissue of the respiratory system were prepared and investigated. Through experiments, the influence of plasma treatment on the physicochemical properties of polyurethane was investigated by atomic force microscopy, attenuated total reflection infrared spectroscopy, differential thermal analysis, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and contact angle measurements, supplemented with biological tests using the A549 cell line and two bacteria strains (Staphylococcus aureus and Pseudomonas aeruginosa). The molecular interpretation of the experimental findings was achieved by molecular dynamics simulations employing newly developed, fully atomistic models of unmodified and plasma-functionalized polyurethane materials to characterize the polyurethane-water interfaces at the nanoscale in detail. The experimentally obtained polar and dispersive surface free energies were consistent with the calculated free energies, verifying the adequacy of the developed models. A 20% substitution of the polymeric chain termini by their oxidized variants was observed in the experimentally obtained plasma-modified polyurethane surface, indicating the surface saturation with oxygen-containing functional groups.

Pediatric pulmonary valve replacements: Clinical challenges and emerging technologies

Congenital heart diseases (CHDs) frequently impact the right ventricular outflow tract, resulting in a significant incidence of pulmonary valve replacement in the pediatric population. While contemporary pediatric pulmonary valve replacements (PPVRs) allow satisfactory patient survival, their biocompatibility and durability remain suboptimal and repeat operations are commonplace, especially for very young patients. This places enormous physical, financial, and psychological burdens on patients and their parents, highlighting an urgent clinical need for better PPVRs. An important reason for the clinical failure of PPVRs is biofouling, which instigates various adverse biological responses such as thrombosis and infection, promoting research into various antifouling chemistries that may find utility in PPVR materials. Another significant contributor is the inevitability of somatic growth in pediatric patients, causing structural discrepancies between the patient and PPVR, stimulating the development of various growth-accommodating heart valve prototypes. This review offers an interdisciplinary perspective on these challenges by exploring clinical experiences, physiological understandings, and bioengineering technologies that may contribute to device development. It thus aims to provide an insight into the design requirements of next-generation PPVRs to advance clinical outcomes and promote patient quality of life.

Non-invasive detection of bladder cancer via microfluidic immunoassay of the protein biomarker NMP22

Bladder cancer (BC) is a malignant tumor that occurs in the bladder mucosa and has a high morbidity and mortality rate. Early diagnosis means that cystoscopy-aided imaging is invasive and pricey. Microfluidic immunoassay enables noninvasive detection of early BC. However, its clinical applications are limited due to the poor internal design and hydrophobic surface of polydimethylsiloxane (PDMS) chip. This study aims to design a PDMS chip with right-moon capture arrays and prepare a hydrophilic surface by APTES with different concentrations (PDMS-three-step: O₂ plasma-5-98% APTES), which facilitates early detection of BC with enhanced sensitivity. Simulations showed that the right-moon arrays in the capture chamber reduced the flow velocity and shear stress of the target molecule NMP22, improving the capture performance of the chip. PDMS-three-step surface was measured by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), contact angle, and antibody immobilization. The results displayed that the contact angle of PDMS-three-step remained in the range of 40° to 50° even after 30 days of exposure to air, leading to a more stable hydrophilic surface. The effectiveness of the PDMS chip was assessed via the quantitative immunoassay of the protein marker NMP22 and its sensitivity analysis to urine. After the assessment, the LOD of NMP22 was 2.57 ng mL^-1, and the sensitivity was 86.67%, which proved that the PDMS chip was effective. Thus, this study provided a novel design and modification method of the microfluidic chip for the early detection of BC.

Development of tropoelastin-functionalized anisotropic PCL scaffolds for musculoskeletal tissue engineering

The highly organized extracellular matrix (ECM) of musculoskeletal tissues, encompassing tendons, ligaments and muscles, is structurally anisotropic, hierarchical and multi-compartmental. These features collectively contribute to their unique function. Previous studies have investigated the effect of tissue-engineered scaffold anisotropy on cell morphology and organization for musculoskeletal tissue repair and regeneration, but the hierarchical arrangement of ECM and compartmentalization are not typically replicated. Here, we present a method for multi-compartmental scaffold design that allows for physical mimicry of the spatial architecture of musculoskeletal tissue in regenerative medicine. This design is based on an ECM-inspired macromolecule scaffold. Polycaprolactone (PCL) scaffolds were fabricated with aligned fibers by electrospinning and mechanical stretching, and then surface-functionalized with the cell-supporting ECM protein molecule, tropoelastin (TE). TE was attached using two alternative methods that allowed for either physisorption or covalent attachment, where the latter was achieved by plasma ion immersion implantation (PIII). Aligned fibers stimulated cell elongation and improved cell alignment, in contrast to randomly oriented fibers. TE coatings bound by physisorption or covalently following 200 s PIII treatment promoted fibroblast proliferation. This represents the first cytocompatibility assessment of novel PIII-treated TE-coated PCL scaffolds. To demonstrate their versatility, these 2D anisotropic PCL scaffolds were assembled into 3D hierarchical constructs with an internally compartmentalized structure to mimic the structure of musculoskeletal tissue.

Novel electrospun conduit based on polyurethane/collagen enhanced by nanobioglass for peripheral nerve tissue engineering

Peripheral nerve injury can significantly affect the daily life of individuals with impaired nerve function and permanent nerve deformity. One of the most common treatments is autograft transplantation. Tissue engineering is one of the efficient methods to regenerate injured nerves using scaffolds, cells, and growth factors. Conduits, which are produced by a variety of techniques, could be used as an alternative treatment for patients with damaged nerves. The electrospinning technique is one of the most important and widely used methods for generating nanofiber conduits from biocompatible polymers. In this study, using the electrospinning method, three different conduits, including polyurethane (PU), polyurethane/collagen (PU/C), and a new conduit based on polyurethane + collagen + nanobioglass (PU/C/NBG), were prepared. The characteristics of these three types of conduits were evaluated by SEM, XRD, and various experiments, including porosity, degradation, contact angle, DMTA, FTIR, MTT, and DAPI staining. The results of MTT and DAPI assays revealed the safety of conduits and proper cell attachment. Overall, the results obtained from various experiments showed that the novel PU/C/NBG conduit has better mechanical properties in terms of porosity, hydrophilicity, and biocompatibility in comparison with PU and PU/C conduits and could be a suitable candidate for peripheral nerve regeneration and axonal growth due to its repair potential.

Tropoelastin improves adhesion and migration of intra-articular injected infrapatellar fat pad MSCs and reduces osteoarthritis progression

Intra-articular injection of mesenchymal stem cells (MSCs) is a promising strategy for osteoarthritis (OA) treatment. However, more and more studies reveal that the injected MSCs have poor adhesion, migration, and survival in the joint cavity. A recent study shows that tropoelastin (TE) regulates adhesion, proliferation and phenotypic maintenance of MSCs as a soluble additive, indicating that TE could promote MSCs-homing in regenerative medicine. In this study, we used TE as injection medium, and compared it with classic media in MSCs intra-articular injection such as normal saline (NS), hyaluronic acid (HA), and platelet-rich plasma (PRP). We found that TE could effectively improve adhesion, migration, chondrogenic differentiation of infrapatellar fat pad MSCs (IPFP-MSCs) and enhance matrix synthesis of osteoarthritic chondrocytes (OACs) in indirect-coculture system. Moreover, TE could significantly enhance IPFP-MSCs adhesion via activation of integrin β1, ERK1/2 and vinculin (VCL) in vitro. In addition, intra-articular injection of TE-IPFP MSCs suspension resulted in a short-term increase in survival rate of IPFP-MSCs and better histology scores of rat joint tissues. Inhibition of integrin β1 or ERK1/2 attenuated the protective effect of TE-IPFP MSCs suspension in vivo. In conclusion, TE promotes performance of IPFP-MSCs and protects knee cartilage from damage in OA through enhancement of cell adhesion and activation of integrin β1/ERK/VCL pathway. Our findings may provide new insights in MSCs intra-articular injection for OA treatment.

Bioabsorbable poly(4-hydroxybutyrate) (P4HB) fibrous membranes as a potential dermal substitute

Dermal substitutes are indispensable for repairing large full-thickness skin defects. Only a few biomaterials for dermal substitution have been put into clinical practice. Therefore, novel artificial dermal substitutes that can meet clinical requirements are in urgent need. Biodegradable poly(4-hydroxybutyrate) (P4HB), which has been approved by the U.S. FDA, can be considered as a possible alternative biomaterial to construct dermal substitutes. In this work, three-dimensional P4HB fibrous membranes were constructed by an electrospinning technique. These P4HB fibrous membranes showed excellent air-permeability, and better water uptake capacity compared to P4HB strip and polycaprolactone (PCL) fibrous membrane controls. The in vitro hemocompatibility and cytotoxicity of P4HB fibrous membranes were investigated. In vivo Sprague-Dawley (SD) rat model studies revealed that P4HB fibrous membranes can be used as artificial dermis to improve wound healing for full-thickness skin defects.

Manipulating Chemical Processes by Pseudosolid Spatial Limitation

It is always preferred to perform chemical processes in liquid or gas phases because of the merits of operation convenience, reaction efficiency, and component homogeneity. However, tremendous efforts have to be made to purify the final product and minimize procedure losses unless a well-defined chemical mechanism is found. Herein, an unconventional chemical functioning system accommodating molecule-in-pseudosolid manipulation is reported. It entails the properties of enhanced molecular effective collision and directional guidance for delicate chemical reaction spatial controls. This design achieves facilitated rates on multicomponent chemical reactions with pros of unique simultaneous final product separation through intrapseudosolid spatial limitation. Localized homogeneous component mixing, pronounced molecular collision, and pure product separation happening in this action surmount the obstacles of conventional chemical operation with a straightforward sketch. A path toward fine chemistry is therefore paved, where traditional thoughts on beneficial reaction environments may be reconsidered.

Tubular Fibrous Scaffolds Functionalized with Tropoelastin as a Small-Diameter Vascular Graft

Cardiovascular disorders are a healthcare problem in today's society. The clinically available synthetic vascular grafts are thrombogenic and could induce intimal hyperplasia. Rapid endothelialization and matched mechanical properties are two major requirements to be considered when designing functional vascular grafts. Herein, an electrospun tubular fibrous (eTF) scaffold was biofunctionalized with tropoelastin at the luminal surface. The luminal surface functionalization was confirmed by an increase of the zeta potential and by the insertion of NH₂ groups. Tropoelastin was immobilized via its -NH₂ or -COOH groups at the activated or aminolysed eTF scaffolds, respectively, to study the effect of exposed functional groups on human endothelial cells (ECs) behavior. Tensile properties demonstrated that functionalized eTF scaffolds presented strength and stiffness within the range of those of native blood vessels. Tropoelastin immobilized on activated eTF scaffolds promoted higher metabolic activity and proliferation of ECs, whereas when immobilized on aminolysed eTF scaffolds, significantly higher protein synthesis was observed. These biofunctional eTF scaffolds are a promising small-diameter vascular graft that promote rapid endothelialization and have compatible mechanical properties.

Dry Surface Treatments of Silk Biomaterials and Their Utility in Biomedical Applications

Silk-based materials are widely used in biomaterial and tissue engineering applications due to their cytocompatibility and tunable mechanical and biodegradation properties. Aqueous-based processing techniques have enabled the fabrication of silk into a broad range of material formats, making it a highly versatile material platform across multiple industries. Utilizing the full potential of silk in biomedical applications frequently requires modification of silk's surface properties. Dry surface modification techniques, including irradiation and plasma treatment, offer an alternative to the conventional wet chemistry strategies to modify the physical and chemical properties of silk materials without compromising their bulk properties. While dry surface modification techniques are more prevalent in textiles and sterilization applications, the range of modifications available and resultant changes to silk materials all point to the utility of dry surface modification for the development of new, functional silk biomaterials. Dry surface treatment affects the surface chemistry, secondary structure, molecular weight, topography, surface energy, and mechanical properties of silk materials. This Review describes and critically evaluates the effect of physical dry surface modification techniques, including irradiation and plasma processes, on silk materials and discusses their utility in biomedical applications, including recent examples of modulation of cell/protein interactions on silk biomaterials, in vivo performance of implanted biomaterials, and applications in material biofunctionalization and lithographic surface patterning approaches.

PLLA/POSS Nanofibers Loaded with Multitargeted pANG Composite Nanoparticles for Promotion of Vascularization in Shear Flow

In vitro prevascularization is particularly important for the clinical application of tissue engineering scaffolds that require vascularization. The principal challenge is simulating the dynamic in vivo environment to promote the continuous growth of blood vessels. In this study, two targeting polypeptides are linked to the two ends of an amphiphilic block copolymer, polyethyleneimine-b-poly(lactide-co-3(S)-methyl-morpholine-2,5-dione)-b-polyethyleneimine (PEI-PLMD-PEI), and self-assembled to form positively charged nanoparticles (NPs), which can bind to negatively charged pANG through electrostatic interactions; the polypeptides are finally loaded into PLLA/polyhedral oligomeric silsesquioxane (POSS) porous fibers to prepare untargeted nanofibers (unTFs), targeted porous nanofibers (TFBs), and targeted nanofiber bundles. The effects of the porous nanofibers on human umbilical vein endothelial cell (HUVEC) transfection, spreading, proliferation, morphology, and expression of related factors are investigated under the action of shear flow force. The results show that the PLLA/POSS nanofibers can maintain stable release of multitargeted NPs for nearly 45 days. Both the dual-targeted porous NPs and shear flow improve the pANG transfection efficiency and promote cell proliferation, and they have a good synergistic effect. These results provide a potential strategy for designing HUVEC-specific gene carriers and using shear flow to enhance endothelialization.

Enhanced biocompatibility of polyurethane-type shape memory polymers modified by plasma immersion ion implantation treatment and collagen coating: An in vivo study

As one of the promising smart materials, polyurethane-type shape memory polymers (SMPU) have been extensively investigated as potential biomedical implant materials. However, the hydrophobicity and bio-inertness of SMPU are major problems for biomedical applications. We applied plasma immersion ion implantation (PIII) to increase surface wettability and enable one-step covalent, functionalisation of SMPU with biological molecules to create a tuneable, biocompatible surface. The changes of surface properties due to PIII treatment in nitrogen plasma were determined by measurements of morphology, contact angle, surface energy, and nanoindentation. Collagen attachment on SMPU with and without PIII treatment was measured by Attenuated total reflectance-Fourier transform infrared (ATR-FTIR). To investigate in vivo biocompatibility, SMPU with/without PIII and with/without collagen were subcutaneously implanted in mice. SMPU implants with surrounding tissue were collected at days 1, 3, 7, 14 and 28 to study acute/subacute inflammatory responses at histopathological and immunohistochemical levels. The results show that PIII treatment improves wettability and releases residual stress in the SMPU surfaces substantially. Covalent attachment of collagen on PIII treated SMPU in a single step incubation was demonstrated by its resistance to removal by rigorous Sodium Dodecyl Sulfonate (SDS) washing. The in-vivo results showed significantly lower acute/subacute inflammation in response to SMPU with PIII treatment + collagen coating compared to untreated SMPU, collagen coated untreated SMPU, and PIII treated SMPU, characterised by lower total cell numbers, macrophages, neovascularisation, cellular proliferation, cytokine production, and matrix metalloproteinase production. This comprehensive in vivo study of PIII treatment with protein coating demonstrates that the combination of PIII treatment and collagen coating is a promising approach to enhance the biocompatibility of SMPU, facilitating its application as an implantable biomaterial.

Plasma processing of PDMS based spinal implants for covalent protein immobilization, cell attachment and spreading

PDMS is widely used for prosthetic device manufacture. Conventional ion implantation is not a suitable treatment to enhance the biocompatibility of poly dimethyl siloxane (PDMS) due to its propensity to generate a brittle silicon oxide surface layer which cracks and delaminates. To overcome this limitation, we have developed new plasma based processes to balance the etching of carbon with implantation of carbon from the plasma source. When this carbon was implanted from the plasma phase it resulted in a surface that was structurally similar and intermixed with the underlying PDMS material and not susceptible to delamination. The enrichment in surface carbon allowed the formation of carbon based radicals that are not present in conventional plasma ion immersion implantation (PIII) treated PDMS. This imparts the PDMS surfaces with covalent protein binding capacity that is not observed on PIII treated PDMS. The change in surface energy preserved the function of bound biomolecules and enhanced the attachment of MG63 osteosarcoma cells compared to the native surface. The attached cells, an osteoblast interaction model, showed increased spreading on the treated over untreated surfaces. The carbon-dependency for these beneficial covalent protein and cell linkage properties was tested by incorporating carbon from a different source. To this end, a second surface was produced where carbon etching was balanced against implantation from a thin carbon-based polymer coating. This had similar protein and cell-binding properties to the surfaces generated with carbon inclusion in the plasma phase, thus highlighting the importance of balancing carbon etching and deposition. Additionally, the two effects of protein linkage and bioactivity could be combined where the cell response was further enhanced by covalently tethering a biomolecule coating, as exemplified here with the cell adhesive protein tropoelastin. Providing a balanced carbon source in the plasma phase is applicable to prosthetic device fabrication as illustrated using a 3-dimensional PDMS balloon prosthesis for spinal implant applications. Consequently, this study lays the groundwork for effective treatments of PDMS to selectively recruit cells to implantable PDMS fabricated biodevices.

Effect of chemical structure on properties of polyurethanes: Temperature responsiveness and biocompatibility

Polyurethanes are known as one of the most biocompatible and inherently blood-compatible materials and have a wide range of applications in the medical field due to their controllable structure and properties. Durability, elasticity, elastomeric structure, fatigue resistance, versatility, and easy acceptance by the biological media after the application makes these polymers preferable in medical area. In this study, polyurethane films were prepared using poly(propylene-ethylene glycol) and either toluene-2,4-diisocyanate or 4,4′-methylenediphenyl diisocyanate without adding any other ingredients such as solvent, catalyst, or chain extender to prevent negative effects of leachable molecules. Mechanical tests were performed at room temperature while swelling tests were conducted in water and phosphate-buffered saline at 4°C, 25°C, and 37°C. Temperature responsiveness was observed for the samples synthesized using toluene-2,4-diisocyanate and poly(propylene-ethylene glycol). These samples had more than 100% swelling at 4°C and about 4% swelling at 25°C and 37°C. Cytocompatibility tests were performed by culturing the samples and their extracts with mouse fibroblast cells (L929). Viability of human umbilical vein endothelial cells was studied to examine the compatibility of the films for blood contacting devices. Both toluene-2,4-diisocyanate and 4,4-methylenediphenyl diisocyanate–based polyurethane films showed no cytotoxic effect and good biocompatibility. Oxygen plasma treatment enhanced hydrophilicity of the films. After plasma treatment, human umbilical vein endothelial cell attachment on toluene-2,4-diisocyanate–based polyurethane films improved and 4,4-methylenediphenyl diisocyanate–based polyurethane films maintained their high cell affinity. Polyurethanes presenting temperature responsiveness, high biocompatibility, and high affinity for human umbilical vein endothelial cells were synthesized in medical purity and in a reaction media involving only diisocyanate and diol components without addition of any solvent, chain extender, or catalyst. Polyurethanes with these properties and as produced in this study are reported for the first time in the literature.

Strategies for directing cells into building functional hearts and parts

This review presents the current state-of-the-art, emerging directions and future trends to direct cells for building functional heart parts.

Surface changes of nanotopography by carbon ion implantation to enhance the biocompatibility of silicone rubber: an in vitro study of the optimum ion fluence and adsorbed protein

Lower cellular adhesion and dense fibrous capsule formation around silicone breast implants caused by lower biocompatibility is a serious clinical problem. Preliminary work has shown that ion implantation enhances cell adhesion. Whether the biocompatibility is further enhanced by higher doses of carbon ion implantation and the mechanism by which ion implantation enhances biocompatibility remain unclear. In this study, five doses of carbon ions, which gradually increase, were implanted on the surface of silicone rubber and then the surface characteristics were surveyed. Then, cell adhesion, proliferation and migration were investigated. Furthermore, the vitronectin (VN) protein was used as a model protein to investigate whether the ion implantation affected the adsorbed protein on the surface. The obtained results indicate that enhanced cytocompatibility is dose dependent when the doses of ion implantation are less than 1 × 10¹⁶ ions/cm². However, when the doses of ion implantation are more than 1 × 10¹⁶ ions/cm², enhanced cytocompatibility is not significant. In addition, surface physicochemical changes by ion implantation induced a conformational change of the adsorbed vitronectin protein that enhanced cytocompatibility. Together, these results suggest that the optimum value of carbon ion implantation in silicone rubber to enhance biocompatibility is 1 × 10¹⁶ ions/cm², and ion implantation regulates conformational changes of adsorbed ECM proteins, such as VN, and mediates the expression of intracellular signals that enhance the biocompatibility of silicone rubber. The results herein provide new insights into the surface modification of implant polymer materials to enhance biocompatibility. It has potentially broad applications in the biomedical field.

Blended Polyurethane and Tropoelastin as a Novel Class of Biologically Interactive Elastomer

Polyurethanes are versatile elastomers but suffer from biological limitations such as poor control over cell attachment and the associated disadvantages of increased fibrosis. We address this problem by presenting a novel strategy that retains elasticity while modulating biological performance. We describe a new biomaterial that comprises a blend of synthetic and natural elastomers: the biostable polyurethane Elast-Eon and the recombinant human tropoelastin protein. We demonstrate that the hybrid constructs yield a class of coblended elastomers with unique physical properties. Hybrid constructs displayed higher elasticity and linear stress-strain responses over more than threefold strain. The hybrid materials showed increased overall porosity and swelling in comparison to polyurethane alone, facilitating enhanced cellular interactions. In vitro, human dermal fibroblasts showed enhanced proliferation, while in vivo, following subcutaneous implantation in mice, hybrid scaffolds displayed a reduced fibrotic response and tunable degradation rate. To our knowledge, this is the first example of a blend of synthetic and natural elastomers and is a promising approach for generating tailored bioactive scaffolds for tissue repair.

Understanding Polymer-Cell Attachment

The development of polymeric materials with cell adhesion abilities requires an understanding of cell-surface interactions which vary with cell type. To investigate the correlation between cell attachment and the nature of the polymer, a series of random and block copolymers composed of 2-(dimethylamino)ethyl acrylate and ethyl acrylate are synthesized through single electron transfer living radical polymerization. The polymers are synthesized with highly defined and controlled monomer compositions and exhibited narrow polydispersity indices. These polymers are examined for their performance in the attachment and growth of HeLa and HEK cells, with attachment successfully modeled on monomer composition and polymer chain length, with both cell lines found to preferentially attach to moderately hydrophobic functional materials. The understanding of the biological-material interactions assessed in this study will underpin further investigations of engineered polymer scaffolds with predictable cell binding performance.

The effect of polyurethane scaffold surface treatments on the adhesion of chondrocytes subjected to interstitial perfusion culture

The purpose of this study was to measure chondrocytes detachment from cellularized constructs cultured in a perfusion bioreactor, and to evaluate the effect of different scaffold coatings on cell adhesion under a fixed flow rate. The scaffolds were polyurethane foams, treated to promote cell attachment and seeded with human chondrocytes. In a preliminary static culture experiment, the scaffolds were imbibed with fetal bovine serum (FBS) and then cultured for 4 weeks. To quantify cell detachment, the number of detached cells from the scaffold treated with FBS was estimated under different interstitial perfusion flow rates and shear stress levels (0.005 mL/min equivalent to 0.05 mPa, 0.023 mL/min equivalent to 0.23 mPa, and 0.045 mL/min equivalent to 0.45 mPa). Finally, groups of scaffolds differently treated (FBS, plasma plus FBS, plasma plus collagen type I) were cultured under a fixed perfusion rate of 0.009 mL/min, equivalent to a shear stress of 0.09 mPa, and the detached cells were counted. Static cultivation showed that cell proliferation increased with time and matrix biosynthesis decreased after the first week of culture. Perfused culture showed that the number of detached cells increased with the perfusion rate on FBS-treated constructs. The plasma-treated/collagen-coated scaffolds showed the highest resistance to cell detachment. To minimize cell detachment, the perfusion rate must be maintained in the order of 0.02 mL/min, giving a shear stress of 0.2 mPa. Our set-up allowed estimating the resistance to cell detachment under interstitial perfusion in a repeatable manner, to test other scaffold coatings and cell types.

Collagen and Elastin Biomaterials for the Fabrication of Engineered Living Tissues

Collagen and elastin represent the two most predominant proteins in the body and are responsible for modulating important biological and mechanical properties. Thus, the focus of this review is the use of collagen and elastin as biomaterials for the fabrication of living tissues. Considering the importance of both biomaterials, we first propose the notion that many tissues in the human body represent a reinforced composite of collagen and elastin. In the rest of the review, collagen and elastin biosynthesis and biophysics, as well as molecular sources and biomaterial fabrication methodologies, including casting, fiber spinning, and bioprinting, are discussed. Finally, we summarize the current attempts to fabricate a subset of living tissues and, based on biochemical and biomechanical considerations, suggest that future tissue-engineering efforts consider direct incorporation of collagen and elastin biomaterials.

Adding Functions to Biomaterial Surfaces through Protein Incorporation

The concept of biomaterials has evolved from one of inert mechanical supports with a long-term, biologically inactive role in the body into complex matrices that exhibit selective cell binding, promote proliferation and matrix production, and may ultimately become replaced by newly generated tissues in vivo. Functionalization of material surfaces with biomolecules is critical to their ability to evade immunorecognition, interact productively with surrounding tissues and extracellular matrix, and avoid bacterial colonization. Antibody molecules and their derived fragments are commonly immobilized on materials to mediate coating with specific cell types in fields such as stent endothelialization and drug delivery. The incorporation of growth factors into biomaterials has found application in promoting and accelerating bone formation in osteogenerative and related applications. Peptides and extracellular matrix proteins can impart biomolecule- and cell-specificities to materials while antimicrobial peptides have found roles in preventing biofilm formation on devices and implants. In this progress report, we detail developments in the use of diverse proteins and peptides to modify the surfaces of hard biomaterials in vivo and in vitro. Chemical approaches to immobilizing active biomolecules are presented, as well as platform technologies for isolation or generation of natural or synthetic molecules suitable for biomaterial functionalization.

Force fields for simulating the interaction of surfaces with biological molecules

The interaction of biomolecules with solid interfaces is of fundamental importance to several emerging biotechnologies such as medical implants, anti-fouling coatings and novel diagnostic devices. Many of these technologies rely on the binding of peptides to a solid surface, but a full understanding of the mechanism of binding, as well as the effect on the conformation of adsorbed peptides, is beyond the resolution of current experimental techniques. Nanoscale simulations using molecular mechanics offer potential insights into these processes. However, most models at this scale have been developed for aqueous peptide and protein simulation, and there are no proven models for describing biointerfaces. In this review, we detail the current research towards developing a non-polarizable molecular model for peptide-surface interactions, with a particular focus on fitting the model parameters as well as validation by choice of appropriate experimental data.

Structural-mechanical and antibacterial properties of a soft elastic polyurethane surface after plasma immersion N2(+) implantation

The surface of elastic polyurethane treated by plasma immersion N2(+) ion implantation at different fluences has been investigated. A folded surface structure is observed in all cases. Analysis has been performed to study the structural (roughness, steepness and fraction of folds, fractal characteristics), mechanical (stiffness, adhesion force between the AFM probe and the material) and wetting properties of surfaces. Under uniaxial stretching the cracks orthogonal to the axis of deformation and longitudinal folds are formed on the examined surfaces. After unloading the initial structure of the surface of deformed materials exposed to low fluences becomes smoother and does not recover, i.e. it has plastic properties. By contrast, the structure of the surfaces of materials subjected to high-fluence treatment recovers without visible changes and the cracks are fully closed. The study of Staphylococcus colonies grown on these materials has demonstrated significant reduction (from 3 to 5 times) in the vitality of bacteria on treated surfaces. This result was repeated on samples after 11 months of storage. Such antibacterial properties are primarily related to the structural changes of the surfaces accompanied by the increased hydrophilicity.

Perspectives on the Molecular and Biological Implications of Tropoelastin in Human Tissue Elasticity

The elasticity of a range of vertebrate and particularly human tissues depends on the dynamic and persistent protein elastin. This elasticity is diverse, and comprises skin, blood vessels, and lung, and is essential for tissue viability. Elastin is predominantly made by assembling tropoelastin, which is an asymmetric 20-nm-long protein molecule. This overview considers tropoelastin’s molecular features and biological interactions in the context of its value in tissue repair.

REDV–polyethyleneimine complexes for selectively enhancing gene delivery in endothelial cells

Gene therapy provides a new strategy for promoting endothelialization, and rapid endothelialization has attracted increasing attention for inhibiting thrombosis and restenosis in artificial vascular implants.

Surface Modification of Biodegradable Polymers towards Better Biocompatibility and Lower Thrombogenicity

Purpose

Drug-eluting stents (DES) based on permanent polymeric coating matrices have been introduced to overcome the in stent restenosis associated with bare metal stents (BMS). A further step was the development of DES with biodegradable polymeric coatings to address the risk of thrombosis associated with first-generation DES. In this study we evaluate the biocompatibility of biodegradable polymer materials for their potential use as coating matrices for DES or as materials for fully bioabsorbable vascular stents.

Materials and Methods

Five different polymers, poly(L-lactide) PLLA, poly(D,L-lactide) PDLLA, poly(L-lactide-co-glycolide) P(LLA-co-GA), poly(D,L-lactide-co-glycolide) P(DLLA-co-GA) and poly(L-lactide-co-ε-caprolactone), P(LLA-co-CL) were examined in vitro without and with surface modification. The surface modification of polymers was performed by means of wet-chemical (NaOH and ethylenediamine (EDA)) and plasma-chemical (O₂ and NH₃) processes. The biocompatibility studies were performed on three different cell types: immortalized mouse fibroblasts (cell line L929), human coronary artery endothelial cells (HCAEC) and human umbilical vein endothelial cells (HUVEC). The biocompatibility was examined quantitatively using in vitro cytotoxicity assay. Cells were investigated immunocytochemically for expression of specific markers, and morphology was visualized using confocal laser scanning (CLSM) and scanning electron (SEM) microscopy. Additionally, polymer surfaces were examined for their thrombogenicity using an established hemocompatibility test.

Results

Both endothelial cell types exhibited poor viability and adhesion on all five unmodified polymer surfaces. The biocompatibility of the polymers could be influenced positively by surface modifications. In particular, a reproducible effect was observed for NH₃-plasma treatment, which enhanced the cell viability, adhesion and morphology on all five polymeric surfaces.

Conclusion

Surface modification of polymers can provide a useful approach to enhance their biocompatibility. For clinical application, attempts should be made to stabilize the plasma modification and use it for coupling of biomolecules to accelerate the re-endothelialization of stent surfaces in vivo.

Recombinant Technology in the Development of Materials and Systems for Soft-Tissue Repair

The field of biomedicine is constantly investing significant research efforts in order to gain a more in-depth understanding of the mechanisms that govern the function of body compartments and to develop creative solutions for the repair and regeneration of damaged tissues. The main overall goal is to develop relatively simple systems that are able to mimic naturally occurring constructs and can therefore be used in regenerative medicine. Recombinant technology, which is widely used to obtain new tailored synthetic genes that express polymeric protein-based structures, now offers a broad range of advantages for that purpose by permitting the tuning of biological and mechanical properties depending on the intended application while simultaneously ensuring adequate biocompatibility and biodegradability of the scaffold formed by the polymers. This Progress Report is focused on recombinant protein-based materials that resemble naturally occurring proteins of interest for use in soft tissue repair. An overview of recombinant biomaterials derived from elastin, silk, collagen and resilin is given, along with a description of their characteristics and suggested applications. Current endeavors in this field are continuously providing more-improved materials in comparison with conventional ones. As such, a great effort is being made to put these materials through clinical trials in order to favor their future use.

Tropoelastin incorporation into a dermal regeneration template promotes wound angiogenesis

Severe burn injury results in substantial skin loss and cannot be treated by autografts. The Integra Dermal Regeneration Template (IDRT) is the leading synthetic skin substitute because it allows for wound bed regeneration and wound healing. However, all substitutes suffer from slow blood vessel ingrowth and would benefit considerably from enhanced vascularization to nurture tissue repair. It is shown here that by incorporating the human elastic protein tropoelastin into a dermal regeneration template (TDRT) we can promote angiogenesis in wound healing. In small and large animal models comprising mice and pigs, the hybrid TDRT biomaterial and IDRT show similar contraction to autografts and decrease wound contraction compared to open wounds. In mice, TDRT accelerates early stage angiogenesis by 2 weeks, as evidenced by increased angiogenesis fluorescent radiant efficiency in live animal imaging and the expression of endothelial cell adhesion marker CD146. In the pig, a full thickness wound repair model confirms increased numbers of blood vessels in the regenerating areas of the dermis closest to the hypodermis and immediately below the epidermis at 2 weeks post-surgery. It is concluded that including tropoelastin in a dermal regeneration template has the potential to promote wound repair through enhanced vascularization.

Small interfering RNA delivery by polyethylenimine-functionalised porous silicon nanoparticles

Polyethyleneimine-coated mesoporous silicon nanoparticles efficiently deliver siRNA in glioblastoma cells, subsequently reducing the protein expression of a chemotherapy resistance gene by 70% within 72 hours.

Antimicrobial surfaces grafted random copolymers with REDV peptide beneficial for endothelialization

Multifunctional surfaces have been created by surface modification and click reactions. These surfaces possess excellent hemocompatibility and endothelialization, as well as effective antimicrobial activity.

Microstructure and antibacterial performance of functionalized polyurethane based on polysiloxane tethered cationic biocides

The designed polyurethane containing polysiloxanes tethered quaternary ammonium salt groups exhibited special surface migrations, low surface free energy and excellent antibacterial activity towardsEscherichia coli.

A hierarchical rippled and crumpled PLA microstructure generated through double emulsion: the interesting roles of Pickering nanoparticles

The delicate roles of Pickering nanoparticles for the in situ creation of hierarchical rippled and crumpled textures upon biomedical polymers were uncovered and demonstrated.

Poly(urethane-dimethylsiloxane) copolymers displaying a range of soft segment contents, noncytotoxic chemistry, and nonadherent properties toward endothelial cells

Polyurethane copolymers based on α,ω-dihydroxypropyl poly(dimethylsiloxane) (PDMS) with a range of soft segment contents were prepared by two-stage polymerization, and their microstructures, thermal, thermomechanical, and surface properties, as well as in vitro hemo- and cytocompatibility were evaluated. All utilized characterization methods confirmed the existence of moderately microphase separated structures with the appearance of some microphase mixing between segments as the PDMS (i.e., soft segment) content increased. Copolymers showed higher crystallinity, storage moduli, surface roughness, and surface free energy, but less hydrophobicity with decreasing PDMS content. Biocompatibility of copolymers was evaluated using an endothelial EA.hy926 cell line by direct contact, an extraction method and after pretreatment of copolymers with multicomponent protein mixture, as well as by a competitive protein adsorption assay. Copolymers showed no toxic effect to endothelial cells and all copolymers, except that with the lowest PDMS content, exhibited resistance to endothelial cell adhesion, suggesting their unsuitability for long-term biomedical devices which particularly require re-endothelialization. All copolymers exhibited excellent resistance to fibrinogen adsorption and adsorbed more albumin than fibrinogen in the competitive adsorption assay, suggesting their good hemocompatibility. The noncytotoxic chemistry of these synthesized materials, combined with their nonadherent properties which are inhospitable to cell attachment and growth, underlie the need for further investigations to clarify their potential for use in short-term biomedical devices.