In vitro biocompatibility assessment of poly($epsiv;-caprolactone) films using L929 mouse fibroblasts

Elastomeric Polyesters in Cardiovascular Tissue Engineering and Organs-on-a-Chip

Cardiovascular tissue constructs provide unique design requirements due to their functional responses to substrate mechanical properties and cyclic stretching behavior of cardiac tissue that requires the use of durable elastic materials. Given the diversity of polyester synthesis approaches, an opportunity exists to develop a new class of biocompatible, elastic, and immunomodulatory cardiovascular polymers. Furthermore, elastomeric polyester materials have the capability to provide tailored biomechanical synergy with native tissue and hence reduce inflammatory response in vivo and better support tissue maturation in vitro. In this review, we highlight underlying chemistry and design strategies of polyester elastomers optimized for cardiac tissue scaffolds. The major advantages of these materials such as their tunable elasticity, desirable biodegradation, and potential for incorporation of bioactive compounds are further expanded. Unique fabrication methods using polyester materials such as micromolding, 3D stamping, electrospinning, laser ablation, and 3D printing are discussed. Moreover, applications of these biomaterials in cardiovascular organ-on-a-chip devices and patches are analyzed. Finally, we outline unaddressed challenges in the field that need further study to enable the impactful translation of soft polyesters to clinical applications.

Response of preosteoblasts on micromachined Ti-6Al-4V surface to microstructure dimension

The cell incubation depends on the cultured surface, but various machining methods produce different surface topographies, but it has not been clear how it is related to the topographic feature until now. Hence, the machined Ti-6Al-4V surface is characterized for preosteoblasts incubation via different mechanical fabrication. The relationship between surface topography created by various machining methods and cell incubation behaviour was explored. The objective is to control the surface preosteoblasts growth in machining of biological titanium alloy. According to the cell growth kinetic, the cell incubation behaviour was first proposed and modelled in relation to microstructural dimension and culture duration. Then, the topological cultured microstructure surface was fabricated via mechanical fabrication. Finally, the cell initial adhesion and incubation behaviour on microstructured surface was investigated. It is shown that the surface undulation on machined microstructure is conducive to controlling the direction and distribution of cell incubation from cell growth kinetic model. The cell culture can be controlled on the peak with a small undulation, while it is concentred on the sidewall with a high aspect ratio. Increasing the aspect ratio extends cell growth, while low aspect ratio promotes initial cell adhesion and growth rate. Within the optimal cultured duration, the microstructured surface is more favourable for cell survival, and the cell growth keep positive beyond critical aspect ratio. As a result, the cell adhesion ability is topologically controlled to 5.4 times higher and the growth rate can be improved by 101.7% on milled microgrooved surface. It may be applied to the rapid production of biomedical Ti-6Al-4V implant.

Effect of In Vitro Culture Length on the Bone-Forming Capacity of Osteoblast-Derived Decellularized Extracellular Matrix Melt Electrowritten Scaffolds

Recent advancements in decellularization have seen the development of extracellular matrix (ECM)-decorated scaffolds for bone regeneration; however, little is understood of the impact of in vitro culture prior to decellularization on the performances of these constructs. Therefore, this study investigated the effect of in vitro culture on ECM-decorated melt electrowritten polycaprolactone scaffold bioactivity. The scaffolds were seeded with osteoblasts and cultured for 1, 2, or 4 weeks to facilitate bone-specific ECM deposition and subsequently decellularized to form an acellular ECM-decorated scaffold. The utilization of mild chemicals and DNase was highly efficient in removing DNA while preserving ECM structure and composition. ECM decoration of the melt electrowritten fibers was observed within the first week of culture, with increased ECM at 2 and 4 week culture periods. Infiltration of re-seeded cells as well as overall bone regeneration in a rodent calvarial model was impeded by a longer culture period. Thus, it was demonstrated that the length of culture has a key influence on the osteogenic properties of decellularized ECM-decorated scaffolds, with long-term culture (2+ weeks) causing pore obstruction and creating a physical barrier which interfered with bone formation. These findings have important implications for the development of effective ECM-decorated scaffolds for bone regeneration.

Chemical Recycling of PET Using Catalysts from Layered Double Hydroxides: Effect of Synthesis Method and Mg-Fe Biocompatible Metals

The chemical recycling of poly(ethylene terephthalate) (PET) residues was performed via glycolysis with ethylene glycol (EG) over Mg-Fe and Mg-Al oxide catalysts derived from layered double hydroxides. Catalysts prepared using the high supersaturation method (h.s.c.) presented a higher surface area and larger particles, but this represented less PET conversion than those prepared by the low supersaturation method (l.s.c.). This difference was attributed to the smaller mass transfer limitations inside the (l.s.c.) catalysts. An artificial neural network model well fitted the PET conversion and bis(2-hydroxyethyl) terephthalate (BHET) yield. The influence of Fe in place of Al resulted in a higher PET conversion of the Mg-Fe-h.s.c. catalyst (~95.8%) than of Mg-Al-h.s.c. (~63%). Mg-Fe catalysts could be reused four to five times with final conversions of up to 97% with reaction conditions of EG: PET = 5:1 and catalyst: PET = 0.5%. These results confirm the Mg-Fe oxides as a biocompatible novel catalyst for the chemical recycling of PET residues to obtain non-toxic BHET for further polymerization, and use in food and beverage packaging.

Computational Mechanics of Form-Fitting 3D-Printed Lattice-Based Wrist-Hand Orthosis for Motor Neuron Disease

Motor neuron disease (MND) patients often experience hand-wrist muscle atrophy resulting in severe social consequences and hampering their daily activities. Although hand-wrist orthosis is commonly used to assist weakened muscles, its effectiveness is limited due to the rapid progression of the disease and the need for customization to suit individual patient requirements. To address these challenges, this study investigates the application of three-dimensional (3D) printing technology to design and fabricate two lattice structures inspired by silkworm cocoons, using poly-ε-caprolactone as feedstock material. Finite element method (FEM) analysis is employed to study the mechanical behavior, enabling control over the geometric configuration incorporated into the hand-wrist orthosis. Through tensile displacement and three-point bending simulations, the stress distribution is examined for both lattice geometries. Geometry-1 demonstrates anisotropic behavior, while geometry-2 exhibits no strict directional dependence due to its symmetry and uniform node positioning. Moreover, the biocompatibility of lattices with human skin fibroblasts is investigated, confirming excellent biocompatibility. Lastly, the study involves semi-structured interviews with MND patients to gather feedback and develop prototypes of form-fitting 3D-printed lattice-based hand-wrist orthosis. By utilizing 3D printing technology, this study aims to provide customized orthosis that can effectively support weakened muscles and reposition the hand for individuals with MND.

Biodegradable Poly(ester) Urethane Acrylate Resins for Digital Light Processing: From Polymer Synthesis to 3D Printed Tissue Engineering Constructs

Digital light processing (DLP) is an accurate and fast additive manufacturing technique to produce a variety of products, from patient-customized biomedical implants to consumer goods. However, DLP's use in tissue engineering has been hampered due to a lack of biodegradable resin development. Herein, a library of biodegradable poly(esters) capped with urethane acrylate (with variations in molecular weight) is investigated as the basis for DLP printable resins for tissue engineering. The synthesized oligomers show good printability and are capable of creating complex structures with mechanical moduli close to those of medium-soft tissues (1-3 MPa). While fabricated films from different molecular weight resins show few differences in surface topology, wettability, and protein adsorption, the adhesion and metabolic activity of NCTC clone 929 (L929) cells and human dermal fibroblasts (HDFs) are significantly different. Resins from higher molecular weight oligomers provide greater cell adhesion and metabolic activity. Furthermore, these materials show compatibility in a subcutaneous in vivo pig model. These customizable, biodegradable, and biocompatible resins show the importance of molecular tuning and open up new possibilities for the creation of biocompatible constructs for tissue engineering.

Fluidic integrated 3D bioprinting system to sustain cell viability towards larynx fabrication

Herein, we report the first study to create a three-dimensional (3D) bioprinted artificial larynx for whole-laryngeal replacement. Our 3D bio-printed larynx was generated using extrusion-based 3D bioprinter with rabbit's chondrocyte-laden gelatin methacryloyl (GelMA)/glycidyl-methacrylated hyaluronic acid (GMHA) hybrid bioink. We used a polycaprolactone (PCL) outer framework incorporated with pores to achieve the structural strength of printed constructs, as well as to provide a suitable microenvironment to support printed cells. Notably, we established a novel fluidics supply (FS) system that simultaneously supplies basal medium together with a 3D bioprinting process, thereby improving cell survival during the printing process. Our results showed that the FS system enhanced post-printing cell viability, which enabled the generation of a large-scale cell-laden artificial laryngeal framework. Additionally, the incorporation of the PCL outer framework with pores and inner hydrogel provides structural stability and sufficient nutrient/oxygen transport. An animal study confirmed that the transplanted 3D bio-larynx successfully maintained the airway. With further development, our new strategy holds great potential for fabricating human-scale larynxes with in vivo-like biological functions for laryngectomy patients.

Inhibition of WNT signaling by conjugated microRNA nano-carriers: A new therapeutic approach for treating triple-negative breast cancer a perspective review

Triple-Negative Breast Cancer is the most aggressive form and accounts the 15%-25% of all breast cancer. Receptors are absent in triple-negative breast cancer, which makes them unresponsive to the current hormonal therapies. The patients with TNBC are left with the option of cytotoxic chemotherapy. The Wnt pathways are connected to cancer, and when activated, they result in mammary hyperplasia and tumors. The tumor suppressor microRNAs can block tumor cell proliferation, invasion, and migration, lead to cancer cell death, and are also known to down-regulate the WNT signaling. Nanoparticles with microRNA have been seen to be more effective when compared with their single release. In this review, we have tried to understand how Wnt signaling plays a crucial role in TNBC, EMT, metastasis, anti-drug resistance, and regulation of Wnt by microRNA. The role of nano-carriers in delivering micro-RNA. The clinical biomarkers, including the present state-of-the-art, involve novel pathways of Wnt.

Development of 3D-printed subcutaneous implants using concentrated polymer/drug solutions

Implantable drug-eluting devices that provide therapeutic cover over an extended period of time following a single administration have potential to improve the treatment of chronic conditions. These devices eliminate the requirement for regular and frequent drug administration, thus reducing the pill burden experienced by patients. Furthermore, the use of modern technologies, such as 3D printing, during implant development and manufacture renders this approach well-suited for the production of highly tuneable devices that can deliver treatment regimens which are personalised for the individual. The objective of this work was to formulate subcutaneous implants loaded with a model hydrophobic compound, olanzapine (OLZ) using robocasting - a 3D-printing technique. The formulated cylindrical implants were prepared from blends composed of OLZ mixed with either poly(caprolactone) (PCL) or a combination of PCL and poly(ethylene)glycol (PEG). Implants were characterised using scanning electron microscopy (SEM), thermal analysis, infrared spectroscopy, and X-ray diffraction and the crystallinity of OLZ in the formulated devices was confirmed. In vitro release studies demonstrated that all the formulations were capable of maintaining sustained drug release over a period of 200 days, with the maximum percentage drug release observed to be c.a. 60 % in the same period.

Tuning the Properties of Ester-Based Degradable Polymers by Inserting Epoxides into Poly(ϵ-caprolactone)

A series of ester-ether copolymers were obtained via the reaction between α,ω-dihydroxyl poly(ϵ-caprolactone) (PCL) and ethylene oxide (EO) or monosubstituted epoxides catalyzed by strong phosphazene bases. The two types of monomeric units were distributed in highly random manners due to the concurrence of epoxide ring-opening and fast transesterification reactions. The substituent of epoxide showed an interesting bidirectional effect on the enzymatic degradability of the copolymer. Compared with PCL, copolymers derived from EO exhibited enhanced hydrophilicity and decreased crystallinity which then resulted in higher degradability. For the copolymers derived from propylene oxide and 1,2-butylene oxide, the hydrophobic alkyl pendant groups also allowed lower crystallinity of the copolymers thus higher degradation rates. However, further enlarging the pendant groups by using styrene oxide or 2-ethylhexyl glycidyl ether caused a decrease in the degradation rate, which might be ascribed to the higher bulkiness hindering the contact of ester groups with lipase.

Engineering Smooth Muscle to Understand Extracellular Matrix Remodeling and Vascular Disease

The vascular smooth muscle is vital for regulating blood pressure and maintaining cardiovascular health, and the resident smooth muscle cells (SMCs) in blood vessel walls rely on specific mechanical and biochemical signals to carry out these functions. Any slight change in their surrounding environment causes swift changes in their phenotype and secretory profile, leading to changes in the structure and functionality of vessel walls that cause pathological conditions. To adequately treat vascular diseases, it is essential to understand how SMCs crosstalk with their surrounding extracellular matrix (ECM). Here, we summarize in vivo and traditional in vitro studies of pathological vessel wall remodeling due to the SMC phenotype and, conversely, the SMC behavior in response to key ECM properties. We then analyze how three-dimensional tissue engineering approaches provide opportunities to model SMCs’ response to specific stimuli in the human body. Additionally, we review how applying biomechanical forces and biochemical stimulation, such as pulsatile fluid flow and secreted factors from other cell types, allows us to study disease mechanisms. Overall, we propose that in vitro tissue engineering of human vascular smooth muscle can facilitate a better understanding of relevant cardiovascular diseases using high throughput experiments, thus potentially leading to therapeutics or treatments to be tested in the future.

Biodegradable polymeric materials for flexible and degradable electronics

Biodegradable electronics have great potential to reduce the environmental footprint of electronic devices and to avoid secondary removal of implantable health monitors and therapeutic electronics. Benefiting from the intensive innovation on biodegradable nanomaterials, current transient electronics can realize full components’ degradability. However, design of materials with tissue-comparable flexibility, desired dielectric properties, suitable biocompatibility and programmable biodegradability will always be a challenge to explore the subtle trade-offs between these parameters. In this review, we firstly discuss the general chemical structure and degradation behavior of polymeric biodegradable materials that have been widely studied for various applications. Then, specific properties of different degradable polymer materials such as biocompatibility, biodegradability, and flexibility were compared and evaluated for real-life applications. Complex biodegradable electronics and related strategies with enhanced functionality aimed for different components including substrates, insulators, conductors and semiconductors in complex biodegradable electronics are further researched and discussed. Finally, typical applications of biodegradable electronics in sensing, therapeutic drug delivery, energy storage and integrated electronic systems are highlighted. This paper critically reviews the significant progress made in the field and highlights the future prospects.

Synthesis and Characterization of New Polycarbonate-Based Poly(thiourethane-urethane)s

The new segmented poly(thiourethane-urethane)s (PTURs) based on 1,1′-methanediylbis(4-isocyanatocyclohexane) (HMDI, Desmodur W^®), polycarbonate diol (PCD, Desmophen C2200) and (methanediyldibenzene-4,1-diyl)dimethanethiol were synthesized by one-step melt polyaddition method. The obtained PTURs, with a content of 30–60 wt% of the hard segments (HS), were tested in which the influence of changes in the HS content on their properties was determined. The polymers were characterized by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), thermal analysis (DSC, TGA) and thermomechanical analysis (DMTA). Additionally, tensile strength, optical (refractive index, UV-VIS and color) and surface properties of the obtained polymers (contact angle and surface free energy) and adhesion to copper were examined. FTIR analysis verified the supposed structure of the polymers obtained and showed a complete conversion of the isocyanate groups. TGA analysis confirmed the relatively good thermal stability of the polymers. On the other hand, after performing the DSC analysis, it was possible to state that the obtained materials were partially or completely amorphous, and the microphase separation decreased with increasing HS content in the polymer. Similar observations were made from the DMTA data. In addition, the hardness, tensile strength, modulus of elasticity, storage modulus, adhesion to copper, refractive index and total free surface energy increased with increasing HS content in the polymer.

Effect of Nanobubble Presence on Murine Fibroblasts and Human Leukemia Cell Cultures

Nanobubbles can enhance both the proliferation and metabolic activity of microorganisms (mainly bacteria) and the growth of the whole higher organisms such as mice, fish, or plants. The critical fact is that nanobubbles of different gases can affect given cells differently. As animal cell cultures are used in industry and research studies, investigations of their interactions with nanobubbles should be carried out. This study aims to uncover whether the presence of nanobubbles improves the proliferation rate and metabolic activity of L929 fibroblasts and HL60 leukemia cells as exemplary animal cell lines of adherent and non-adherent cells, respectively. The long-term (8-day) cultures of both L929 and HL-60 cells with nanobubble addition to the appropriate medium were carried out. The medium was not exchanged for the whole duration of the culture. Nanobubbles of two gases - oxygen and nitrogen - were dispersed in the appropriate media and then used to culture cells. The density and viability of cells were assessed microscopically while their metabolic activity was determined using PrestoBlue or XTT assays. Additionally, we have performed the analysis of substrate consumption rate during the growth and activity of lactate dehydrogenase. We have shown that nanodispersion of both gases enhances the proliferation rate and metabolic activity of L929. For HL-60 cultures, reference cultures exhibited better viability, cell density, and metabolic activity than those with either oxygen or nitrogen nanobubbles. Obtained results clearly show that nanobubble dispersions of both oxygen and nitrogen positively affect the cultures of L929 while inhibiting the growth of HL-60 cells. We suspect that a similar positive effect would be visible for other adherent cells, similar to L929. Such results are promising for intensifying the growth of animal or human cells in routine cell cultures.

New Segmented Poly(Thiourethane-Urethane)s Based on Poly(ε-Caprolactone)Diol Soft Segment: Synthesis and Characterization

New segmented poly(thiourethane-urethane)s (SPTURs) were synthesized by the reaction of 1,1′-methanediylbis (4-isocyanatocyclohexane) (Desmodur W^®, HMDI) and poly(ε-caprolactone)diol (PCL) and (methanediyldibenzene-4,1-diyl)dimethanethiol as nonconventional polymer chain extender. FTIR spectroscopy was used for the structural analysis of obtained polymers. The molecular weight distribution was examined by GPC chromatography. Based on the measured contact angles, free surface energy parameters were calculated. Thermal properties of polymers were examined by DSC and TGA, while viscoelastic properties were measured by DMTA. The tensile, adhesive and optical properties were also investigated for the obtained polymers. It was shown that SPTURs were transparent or partially transparent solids with high molar masses up to 84,300 Da. These polymers showed a good resistance to hydrolysis during incubation in Optylite^® physiological saline over 8 weeks. Obtained polymers possessed a tensile strength of up to 43.26 MPa, hardness of up to 96.25/59.00 Sh A/D and adhesion to copper of 14.66 MPa. The surface properties of the obtained polymers show that all obtained SPTURs were hydrophilic (CAs for water between 64.07° and 73.12°) with calculated SFE up to 46.69 mN/m.

Novel biohybrid spongy scaffolds for fabrication of suturable intraoral graft substitutes

Despite the fact that classic autograft is the gold standard material for periodontal plastic surgery, it has some drawbacks, including the need for a second surgical site and the scarcity of palatal donor tissue. However, only a few research works on the manufacturing of bioengineered intraoral connective tissue grafts have been conducted. In this work, porous bovine serum albumin methacryloyl/gelatin methacryloyl (BG) biohybrid scaffolds were developed for super-elasticity, shape recovery, suturability for persistent stability, sufficient scaffolding function, and convenient manipulating characteristics to fabricate an intraoral graft substitute with superb stability to resist frequent dynamic forces caused by functional movement (speaking, masticating, and swallowing). Furthermore, in a 3D cell culture assay, BG scaffolds demonstrated excellent cell adhesion and proliferation of L929 cells. In addition, the BG scaffolds were able to release Ibuprofen in a controlled manner for postoperative recovery. The use of a low-cost, optimized cryogelation technique for functional biomacromolecules offers up new possibilities to develop promising scaffolds for dental clinical settings.

3D-printed implantable devices with biodegradable rate-controlling membrane for sustained delivery of hydrophobic drugs

Implantable drug delivery systems offer an alternative for the treatments of long-term conditions (i.e. schizophrenia, HIV, or Parkinson’s disease among many others). The objective of the present work was to formulate implantable devices loaded with the model hydrophobic drug olanzapine (OLZ) using robocasting 3D-printing combined with a pre-formed rate controlling membrane. OLZ was selected as a model molecule due to its hydrophobic nature and because is a good example of a molecule used to treat a chronic condition schizophrenia. The resulting implants consisted of a poly(ethylene oxide) (PEO) implant coated with a poly(caprolactone) (PCL)-based membrane. The implants were loaded with 50 and 80% (w/w) of OLZ. They were prepared using an extrusion-based 3D-printer from aqueous pastes containing 36–38% (w/w) of water. The printing process was carried out at room temperature. The resulting implants were characterized by using infrared spectroscopy, scanning electron microscopy, thermal analysis, and X-ray diffraction. Crystals of OLZ were present in the implant after the printing process. In vitro release studies showed that implants containing 50% and 80% (w/w) of OLZ were capable of providing drug release for up to 190 days. On the other hand, implants containing 80% (w/w) of OLZ presented a slower release kinetics. After 190 days, total drug release was ca. 77% and ca. 64% for implants containing 50% and 80% (w/w) of OLZ, respectively. The higher PEO content within implants containing 50% (w/w) of OLZ allows a faster release as this polymer acts as a co-solvent of the drug.

Biocompatible poly(ethylene succinate) polyester with molecular weight dependent drug release properties

In the present study, we demonstrate that well-known molecular weight-dependent solubility properties of a polymer can also be used in the field of controlled drug delivery. To prove this, poly(ethylene succinate) (PES) polyesters with polycondensation time regulated molecular weights were synthesized via catalyst-free direct polymerization in an equimolar ratio of ethylene glycol and succinic acid monomers at 185 °C. DSC and contact angle measurements revealed that increasing the molecular weight (M_w, 4.3-5.05 kDa) through the polymerization time (40-80 min) increased the thermal stability (T_m= ∼61-80 °C) and slightly the hydrophobicity (Θ_w= ∼27-41°) of the obtained aliphatic polyester. Next, this biodegradable polymer was used for the encapsulation of Ca²⁺ channel blocker Nimodipine (NIMO) to overcome the poor water solubility and enhance the bioavailability of the drug. The drug/ polymer compatibility was proved by the means of solubility (δ) and Flory-Huggins interaction (miscibility) parameters (χ). The nanoprecipitation encapsulation of NIMO into PES with increasing M_w resulted in the formation of spherical 270 ± 103 nm NIMO-loaded PES nanoparticles (NPs). Furthermore, based on the XRD measurements, the encapsulated form of NIMO-loaded PES NPs showed lower drug crystallinity, which enhanced not only the water solubility but even the water stability of the NIMO in an aqueous medium. The in-vitro drug release experiments demonstrated that the release of NIMO drug could be accelerated or even prolonged by the molecular weights of PES as well. Due to the low crystallinity of PES polyester and low particle size of the encapsulated NIMO drug led to enhance solubility and releasing process of NIMO from PES with lower M_w (4.3 kDa and 4.5 kDa) compared to pure crystalline NIMO. However, further increasing the molecular weight (5.05 kDa) was already reduced the amount of drug release that provides the prolonged therapeutic effect and enhances the bioavailability of the NIMO drug.

Fabrication of Polymer/Graphene Biocomposites for Tissue Engineering

Graphene-based materials (GBM) are considered one of the 21st century’s most promising materials, as they are incredibly light, strong, thin and have remarkable electrical and thermal properties. As a result, over the past decade, their combination with a diverse range of synthetic polymers has been explored in tissue engineering (TE) and regenerative medicine (RM). In addition, a wide range of methods for fabricating polymer/GBM scaffolds have been reported. This review provides an overview of the most recent advances in polymer/GBM composite development and fabrication, focusing on methods such as electrospinning and additive manufacturing (AM). As a future outlook, this work stresses the need for more in vivo studies to validate polymer/GBM composite scaffolds for TE applications, and gives insight on their fabrication by state-of-the-art processing technologies.

Silver nanowire loaded poly(ε-caprolactone) nanocomposite fibers as electroactive scaffolds for skeletal muscle regeneration

Volumetric muscle loss (VML) due to trauma and tumor removal operations affects millions of people every year. Although skeletal muscle has a natural repair mechanism, it cannot provide self-healing above a critical level of VML. In this study, nanocomposite aligned fiber scaffolds as support materials were developed for volumetric skeletal muscle regeneration. For this purpose, silver nanowire (Ag NW) loaded poly(ε-caprolactone) (PCL) nanocomposite fiber scaffolds (PCL-Ag NW) were prepared to mimic the aligned electroactive structure of skeletal muscle and provide topographic and conductive environment to modulate cellular behavior and orientation. A computer-aided rotational wet spinning (RWS) system was designed to produce high-yield fiber scaffolds. Nanocomposite fiber bundles with lengths of 50 cm were fabricated via this computer-aided RWS system. The morphological, chemical, thermal properties and biodegradation profiles of PCL and PCL-Ag NW nanocomposite fibers were characterized in detail. The proliferation behavior and morphology of C2C12 mouse myoblasts were investigated on PCL and PCL-Ag NW nanocomposite fibrous scaffolds with and without electrical stimulation. Significantly enhanced cell proliferation was observed on PCL-Ag NW nanocomposite fibers compared to neat PCL fibers with electrical stimulations of 1.5 V, 3 V and without electrical stimulation.

Effects of Electrospinning Parameter Adjustment on the Mechanical Behavior of Poly-ε-caprolactone Vascular Scaffolds

Electrospinning is a perspective method widely suggested for use in bioengineering applications, but the variability in currently available data and equipment necessitates additional research to ascertain the desirable methodology. In this study, we aimed to describe the effects of electrospinning technique alterations on the structural and mechanical properties of (1,7)-polyoxepan-2-one (poly-ε-caprolactone, PCL) scaffolds, such as circumferential and longitudinal stress/strain curves, in comparison with corresponding properties of fresh rat aorta samples. Scaffolds manufactured under different electrospinning modes were analyzed and evaluated using scanning electronic microscopy as well as uniaxial longitudinal and circumferential tensile tests. Fiber diameter was shown to be the most crucial characteristic of the scaffold, correlating with its mechanical properties.

Liquid metal polymer composite: Flexible, conductive, biocompatible, and antimicrobial scaffold

Gallium and its alloys, such as eutectic gallium indium alloy (EGaIn), a form of liquid metal, have recently attracted the attention of researchers due to their low toxicity and electrical and thermal conductivity for biomedical application. However, further research is required to harness EGaIn-composites advantages and address their application as a biomedical scaffold. In this research, EGaIn-polylactic acid/polycaprolactone composites with and without a second conductive filler, MXene, were prepared and characterized. The addition of MXene, into the EGaIn-composite, can improve the composite's electrochemical properties by connecting the liquid metal droplets resulting in electrically conductive continuous pathways within the polymeric matrix. The results showed that the composite with 50% EGaIn and 4% MXene, displayed optimal electrochemical properties and enhanced mechanical and radiopacity properties. Furthermore, the composite showed good biocompatibility, examined through interactions with fibroblast cells, and antibacterial properties against methicillin-resistant Staphylococcus aureus. Therefore, the liquid metal (EGaIn) polymer composite with MXene provides a first proof-of-concept engineering scaffold strategy with low toxicity, functional electrochemical properties, and promising antimicrobial properties.

Evaluation of the In Vitro Biocompatibility of PEDOT:Nafion Coatings

Poly(3,4-ethylenedioxythiophene)-Nafion (PEDOT:Nafion) is emerging as a promising alternative to PEDOT-polystyrene sulfonate (PEDOT:PSS) in organic bioelectronics. However, the biocompatibility of PEDOT:Nafion has not been investigated to date, limiting its deployment toward in vivo applications such as neural recording and stimulation. In the present study, the in vitro cytotoxicity of PEDOT:Nafion coatings, obtained by a water-based PEDOT:Nafion formulation, was evaluated using a primary cell culture of rat fibroblasts. The surface of PEDOT:Nafion coating was characterized by Atomic Force Microscopy (AFM) and water contact angle measurements. Fibroblasts adhesion and morphology was investigated by scanning electron microscopy (SEM) and AFM measurements. Cell proliferation was assessed by fluorescence microscopy, while cell viability was quantified by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT), lactate dehydrogenase (LDH) and neutral red assays. The results showed that PEDOT:Nafion coatings obtained by the water dispersion were not cytotoxic, making the latter a reliable alternative to PEDOT:PSS dispersion, especially in terms of chronic in vivo applications.

In vitro biocompatibility and wound healing properties of latex proteins dressing

The chronification of ulcers or sores may result in a dramatic outcome such as amputation. Currently, the search for plant based treatments of various diseases/disorders, including complicated ones, is getting the attention of researchers worldwide. The soluble latex protein fraction (CpLP) obtained from Calotropis procera (Apocynaceae) was previously demonstrated to accelerate wound healing by topical application or when incorporated in a polyvinyl alcohol biomembrane (BioMemCpLP). Here, in vitro assays were performed to investigate and characterize the biocompatibility and bioactivity of latex proteins dressing. Macrophages (RAW 264.7), fibroblasts (L929) and keratinocytes (HaCaT) cell lines were used to evaluate the effect of CpLP. These cell lines were exposed to concentrations of CpLP comparable to those found in BioMemCpLP during 24-72 h. The cytotoxicity, proliferation, release of wound healing mediators (TGF-β, VEGF, IL-10, IL-6, IL-1β, TNF-α and NO) and migration of cells (E-cadherin and β-catenin) incubated with CpLP was assessed and the cell adhesion to BioMemCpLP as well. The results showed that CpLP has no cytotoxic effects. It induced a suitable balance between pro- and anti-inflammatory mediators, enhanced proliferation and re-epithelialization in all cell lines, but the intensity of each effect was different at various doses in all cell strains. The BioMemCpLP stimulated cell adhesion to PVA substrate. The CpLP-PVA based biomembrane can be a good option for healing of different wounds.

Characterization of a Water-Dispersed Biodegradable Polyurethane-Silk Composite Sponge Using 13C Solid-State Nuclear Magnetic Resonance as Coating Material for Silk Vascular Grafts with Small Diameters

Recently, Bombyx mori silk fibroin (SF) has been shown to be a suitable material for vascular prostheses for small arteries. In this study, we developed a softer SF graft by coating water-dispersed biodegradable polyurethane (PU) based on polycaprolactone and an SF composite sponge on the knitted SF vascular graft. Three kinds of 13C solid-state nuclear magnetic resonance (NMR), namely carbon-13 (13C) cross-polarization/magic angle spinning (MAS), 13C dipolar decoupled MAS, and 13C refocused insensitive nuclei enhanced by polarization transfer (r-INEPT) NMR, were used to characterize the PU-SF coating sponge. Especially the 13C r-INEPT NMR spectrum of water-dispersed biodegradable PU showed that both main components of the non-crystalline domain of PU and amorphous domain of SF were highly mobile in the hydrated state. Then, the small-diameter SF artificial vascular grafts coated with this sponge were evaluated through implantation experiments with rats. The implanted PU-SF-coated SF grafts showed a high patency rate. It was confirmed that the inside of the SF grafts was covered with vascular endothelial cells 4 weeks after implantation. These results showed that the water-dispersed biodegradable PU-SF-coated SF graft created in this study could be a strong candidate for small-diameter artificial vascular graft.

3D-bioprinted gradient-structured scaffold generates anisotropic cartilage with vascularization by pore-size-dependent activation of HIF1α/FAK signaling axis

Articular cartilage injury is one of the most common diseases in orthopedics, which seriously affects patients' life quality, the development of a biomimetic scaffold that mimics the multi-layered gradient structure of native cartilage is a new cartilage repair strategy. It has been shown that scaffold topography affects cell attachment, proliferation, and differentiation; the underlying molecular mechanism of cell-scaffold interaction is still unclear. In the present study, we construct an anisotropic gradient-structured cartilage scaffold by three-dimensional (3D) bioprinting, in which bone marrow stromal cell (BMSC)-laden anisotropic hydrogels micropatterns were used for heterogeneous chondrogenic differentiation and physically gradient synthetic poly (ε-caprolactone) (PCL) to impart mechanical strength. In vitro and in vivo, we demonstrated that gradient-structured cartilage scaffold displayed better cartilage repair effect. The heterogeneous cartilage tissue maturation and blood vessel ingrowth were mediated by a pore-size-dependent mechanism and HIF1α/FAK axis activation. In summary, our results provided a theoretical basis for employing 3D bioprinting gradient-structured constructs for anisotropic cartilage regeneration and revealed HIF1α/FAK axis as a crucial regulator for cell-material interactions, so as to provide a new perspective for cartilage regeneration and repair.

Enhanced Osteogenic Differentiation of Periodontal Ligament Stem Cells Using a Graphene Oxide-Coated Poly(ε-caprolactone) Scaffold

Periodontal diseases occur through bacterial infection in the oral cavity, which can cause alveolar bone loss. Several efforts have been made to reconstruct alveolar bone, such as grafting bone substitutes and 3D-printed scaffolds. Poly(ε-caprolactone) (PCL) is biocompatible and biodegradable, thus demonstrating its potential as a biomaterial substitute; however, it is difficult for cells to adhere to PCL because of its strong hydrophobicity. Therefore, its use as a biomaterial has limitations. In this study, we used graphene oxide (GO) as a coating material to promote the osteogenic differentiation ability of PCL scaffolds. First, 3D-printed PCL scaffolds were fabricated, and the oxygen plasma treatment and coating conditions were established according to the concentration of GO. The physical and chemical properties of the prepared scaffolds were evaluated through water contact angle analysis, Raman spectroscopy, and image analysis. In addition, the adhesion and proliferation of periodontal ligament stem cells (PDLSCs) on the GO scaffolds were assessed via the water-soluble tetrazolium salt-1 (WST-1) assay, and the osteogenic differentiation ability was evaluated through alizarin red S staining. The results confirmed that the cell proliferation and osteogenic differentiation of the PDLSCs were enhanced in the scaffolds coated with oxygen plasma and GO. In conclusion, the plasma-treated GO-coating method that we developed can be used to promote the cell proliferation and osteogenic differentiation of the scaffolds.

Capsaicin-loaded solid lipid nanoparticles: design, biodistribution, in silico modeling and in vitro cytotoxicity evaluation

Lower doses of capsaicin (8-methyl-N-vanillyl-6-nonenamide) have the potential to serve as an anticancer drug, however, due to its pungency, irritant effect, poor water solubility and high distribution volume often linked to various off-target effects, its therapeutic use is limited. This study aimed to determine the biodistribution and anticancer efficacy of capsaicin loaded solid lipid nanoparticles (SLNs) in human hepatocellular carcinoma in vitro. In this study, SLNs of stearic acid loaded with capsaicin was formulated by the solvent evaporation-emulsification technique and were instantly characterized for their encapsulation efficiency, morphology, loading capacity, stability, particle size, charge and in vitro drug release profile. Synthesized SLNs were predominantly spherical, 80 nm diameter particles that proved to be biocompatible with good stability in aqueous conditions. In vivo biodistribution studies of the formulated SLNs showed that 48 h after injection in the lateral tail vein, up to 15% of the cells in the liver, 1.04% of the cells in the spleen, 3.05% of the cells in the kidneys, 3.76% of the cells in the heart, 1.31% of the cells in the lungs and 0% of the cells in the brain of rats were determined. Molecular docking studies against the identified targets in HepG2 cells showed that the capsaicin is able to bind Abelson tyrosine-protein kinase, c-Src kinase, p38 MAP kinase and VEGF-receptor. Molecular dynamic simulation showed that capsaicin-VEGF receptor complex is highly stable at 50 nano seconds. The IC₅₀ of capsaicin loaded SLNs in HepG2 cells in vitro was 21.36 μg × ml^-1. These findings suggest that capsaicin loaded SLNs are stable in circulation for a period up to 3 d, providing a controlled release of loaded capsaicin and enhanced anticancer activity.

High-Resolution Novel Indirect Bioprinting of Low-Viscosity Cell-Laden Hydrogels via Model-Support Bioink Interaction

Bioprinting of unmodified soft extracellular matrix into complex 3D structures has remained challenging to fabricate. Herein, we established a novel process for the printing of low-viscosity hydrogel by using a unique support technique to retain the structural integrity of the support structure. We demonstrated that this process of printing could be used for different types of hydrogel, ranging from fast crosslinking gelatin methacrylate to slow crosslinking collagen type I. In addition, we evaluated the biocompatibility of the process by observing the effects of the cytotoxicity of L929 and the functionality of the human umbilical vein endothelium primary cells after printing. The results show that the bioprinted construct provided excellent biocompatibility as well as supported cell growth and differentiation. Thus, this is a novel technique that can be potentially used to enhance the resolution of the extrusion-based bioprinter.

Biodegradable Materials for Sustainable Health Monitoring Devices

The recent advent of biodegradable materials has offered huge opportunity to transform healthcare technologies by enabling sensors that degrade naturally after use. The implantable electronic systems made from such materials eliminate the need for extraction or reoperation, minimize chronic inflammatory responses, and hence offer attractive propositions for future biomedical technology. The eco-friendly sensor systems developed from degradable materials could also help mitigate some of the major environmental issues by reducing the volume of electronic or medical waste produced and, in turn, the carbon footprint. With this background, herein we present a comprehensive overview of the structural and functional biodegradable materials that have been used for various biodegradable or bioresorbable electronic devices. The discussion focuses on the dissolution rates and degradation mechanisms of materials such as natural and synthetic polymers, organic or inorganic semiconductors, and hydrolyzable metals. The recent trend and examples of biodegradable or bioresorbable materials-based sensors for body monitoring, diagnostic, and medical therapeutic applications are also presented. Lastly, key technological challenges are discussed for clinical application of biodegradable sensors, particularly for implantable devices with wireless data and power transfer. Promising perspectives for the advancement of future generation of biodegradable sensor systems are also presented.

Multifunctional Sutures with Temperature Sensing and Infection Control

The next-generation sutures should provide in situ monitoring of wound condition such as temperature while reducing surgical site infection during wound closure. In this study, functionalized nanodiamond (FND) and reduced graphene oxide (rGO) into biodegradable polycaprolactone (PCL) are incorporated to develop a new multifunctional suture with such capabilities. Incorporation of FND and rGO into PCL enhances its tensile strength by about 43% and toughness by 35%. The sutures show temperature sensing capability in the range of 25-40 °C based on the shift in zero-splitting frequency of the nitrogen-vacancy (NV^- ) centers in FND via optically detected magnetic resonance, paving the way for potential detection of infection or excessive inflammation in healing wounds. The suture surface readily coats with antibiotics to reduce bacterial infection risk to the wounds. The new suture thus is promising in monitoring and supporting wound closure.

Designed and fabrication of triple-layered vascular scaffold with microchannels

Currently, one of the best preparation strategies for the triple-layered vascular scaffold is to imitate the three-layer structure of natural blood vessels to achieve the biofunctional characteristics of vascular transplantation. Here, we developed a combinatorial method to fabricate triple-layered vascular scaffold (TVS) by using electrospinning and coaxial 3 D printing. First, Polycaprolactone-collagen (PCL-Col) was applied to prepared the inner layer of TVS by electrospinning. Second, egg white/sodium alginate (EW/SA) blend hydrogel was extruded to form hollow filaments by coaxial 3 D printing and crosslinking mechanism, which enwound around the surface of the inner layer in a circumferential direction as the intermediate layer of TVS. Finally, electrospun PCL-Col nanofibers were wrapped on the surface of hydrogel layer as the outer layer of TVS. The morphological characterization and mechanical strength of the fabricated TVS were measured. Compared with natural blood vessels, results shown that ultimate tensile stress (UTS), strain to failure (STF), the estimated burst strength and the suture retention strength (SRS) of TVS were superior. Also, the fabricated TVS exhibits good hydrophilicity and excellent flexibility. Moreover, the biocompatibility of TVS was investigated through human umbilical vein endothelial cells (HUVECs), the results demonstrated that cells can successfully attach the surface of graft and maintain high viability. In summary, all of results demonstrated that this method could fabricate a novel triple-layered vascular scaffold, possessing appropriate mechanical properties and good biological properties, which has the potential to be used in tissue engineered vascular grafts applications.

Antimicrobial and Biocompatible Polycaprolactone and Copper Oxide Nanoparticle Wound Dressings against Methicillin-Resistant Staphylococcus aureus

One of the major health problems linked to methicillin-resistant Staphylococcus aureus (MRSA) is severe diabetic foot ulcers (DFU), which are associated with hospital-acquired infections, lower limb amputations and emerging resistance to the current antibiotics. As an alternative, this work aims to develop a biodegradable and biocompatible material with antimicrobial capacity to prevent DFU. This was achieved by producing active polymeric films with metallic nanoparticles dispersed through a polycaprolactone (PCL) dressing. First, the antimicrobial activity of copper oxide nanoparticles (CuONPs) was tested by the microdilution method, selecting the lowest concentration that has an inhibitory effect on MRSA. Then, active PCL films were prepared and characterized in terms of their physicochemical properties, antimicrobial performance, cytotoxicity, genotoxicity and hemocompatibility. Active films had chemical and thermal properties like the ones without the antimicrobial agents, which was confirmed through FTIR, Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) analysis. In relation to antimicrobial activity, active PCL films inhibited MRSA growth when treated with CuONPs at a concentration of 0.07% (w/w). After exposure to the active film extracts, human foreskin fibroblast cells (ATCC^® SCRC1041™) (HFF-1) exhibited a cell viability average above 80% for all treatments and no DNA damage was found. Finally, PCL films with 0.07% (w/w) CuONPs proved to be hemocompatible, and none of the films evaluated had red blood cell breakage greater than 5%, being within the acceptable limits established by the International Organization for Standardization ISO 10993-4:2002.

Mg-Based Metallic Glass-Polymer Composites: Investigation of Structure, Thermal Properties, and Biocompatibility

In this work, the biomedical applicability and physical properties of magnesium-based metallic glass/polycaprolactone (PCL) composites are explored. The composites were fabricated via mechanical alloying and subsequent coextrusion. The coextrusion process was carried out at a temperature near to the supercooled liquid region of the metallic glass and the viscous region of the polymer. The structures, as well as thermal and mechanical properties of the obtained samples were characterized, and in vivo investigations were undertaken. The composite samples possess acceptable thermal and mechanical properties. Tensile tests indicate the ability of the composites to withstand more than 100% deformation. In vivo studies reveal that the composites are biologically compatible and could be promising for biomedical applications.

Synthesis and property of polyurethane elastomer for biomedical applications based on nonaromatic isocyanates, polyesters, and ethylene glycol

Polyurethane (PU) elastomers were synthesized by the reaction of HDI or IPDI diisocyanates and poly(ε-caprolactone) (PCL or poly(ethylene adipate) (PA) diols and ethylene glycol as a polymer chain extender. IR, 1H, and 13C NMR spectroscopy and X-ray analysis were used for the structural analysis of the formed films. The molecular weight distribution was examined by GPC chromatography. Based on the measured contact angles, free surface energy parameters were calculated. The obtained results were analyzed for the possible use of these polyurethanes as biomaterials. The most promising in this respect was PU-3, which was synthesized from IPDI and PCL. This was due to its high molecular weight of approximately 90,000, the presence of a crystalline phase, and the relatively high hydrophobicity, with a SEP value below 25 mJ/m2. These films showed a good resistance to hydrolysis during incubation in Baxter physiological saline during 6 weeks. Both Gram-positive (Bacillus sp.) and Gram-negative (Pseudomonas sp.) types of bacterial strains were used to test the biodegradation property. Synthesized PUs are biodegradable and showed moderate or even mild cytotoxicity against human normal fibroblasts (BJ) and immortalized keratinocytes (HaCaT), estimated with direct contact assay. The most biocompatible was PU-3 film, which revealed rather mild reactivity against both cell lines, and the least was PU-2 film, synthesized from HDI and PA (severe toxicity for HaCaTs).

Heparin-hyaluronic acid nanofibers for growth factor sequestration in spinal cord repair

Growth factor (GF) delivery is a common strategy for spinal cord injury repair, however, GF degradation can impede long-term therapies. GF sequestration via heparin is known to protect bioactivity after delivery. We tested two heparin modifications, methacrylated heparin and thiolated heparin, and electrospun these with methacrylated hyaluronic acid (MeHA) to form HepMAHA and HepSHHA nanofibers. For loaded conditions, MeHA, HepMAHA, and HepSHHA fibers were incubated with soluble basic fibroblast growth factor (bFGF) or nerve growth factor (NGF) and rinsed with PBS. Control groups were hydrated in PBS. L929 fibroblast proliferation was analyzed after 24 hr of culture in either growth media or bFGF-supplemented media. Dissociated chick dorsal root ganglia neurites were measured after 3 days of cell culture in serum free media (SFM) or NGF-supplemented SFM (SFM + NGF). In growth media, fibroblast proliferation was significantly increased in loaded HepMAHA (α < .05) compared to other groups. In SFM, loaded HepMAHA had the longest average neurite length compared to all other groups. In SFM + NGF, HepMAHA and HepSHHA had increased neurite lengths compared to MeHA, regardless of loading (α < .01), suggesting active sequestration of soluble NGF. HepMAHA is a promising biomaterial for sequestering released GFs in a spinal cord injury environment and will be combined with GF filled microspheres for future studies.

Development of a heat labile antibiotic eluting 3D printed scaffold for the treatment of osteomyelitis

In general, osteomyelitis is treated with antibiotics, and in severe cases, the inflammatory bone tissue is removed and substituted with poly (methyl methacrylate) (PMMA) beads containing antibiotics. However, this treatment necessitates re-surgery to remove the inserted PMMA beads. Moreover, rifampicin, a primary heat-sensitive antibiotic used for osteomyelitis, is deemed unsuitable in this strategy. Three-dimensional (3D) printing technology has gained popularity, as it facilitates the production of a patient-customized implantable structure using various biodegradable biomaterials as well as controlling printing temperature. Therefore, in this study, we developed a rifampicin-loaded 3D scaffold for the treatment of osteomyelitis using 3D printing and polycaprolactone (PCL), a biodegradable polymer that can be printed at low temperatures. We successfully fabricated rifampicin-loaded PCL 3D scaffolds connected with all pores using computer-aided design and manufacturing (CAD/CAM) and printed them at a temperature of 60 °C to prevent the loss of the antibacterial activity of rifampicin. The growth inhibitory activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), the representative causative organisms of osteomyelitis, was confirmed. In addition, we optimized the rifampicin-loading capacity that causes no damage to the normal bone tissues in 3D scaffold with toxicity evaluation using human osteoblasts. The rifampicin-releasing 3D scaffold developed herein opens new possibilities of the patient-customized treatment of osteomyelitis.

Bioresorbable Materials on the Rise: From Electronic Components and Physical Sensors to In Vivo Monitoring Systems

Over the last decade, scientists have dreamed about the development of a bioresorbable technology that exploits a new class of electrical, optical, and sensing components able to operate in physiological conditions for a prescribed time and then disappear, being made of materials that fully dissolve in vivo with biologically benign byproducts upon external stimulation. The final goal is to engineer these components into transient implantable systems that directly interact with organs, tissues, and biofluids in real-time, retrieve clinical parameters, and provide therapeutic actions tailored to the disease and patient clinical evolution, and then biodegrade without the need for device-retrieving surgery that may cause tissue lesion or infection. Here, the major results achieved in bioresorbable technology are critically reviewed, with a bottom-up approach that starts from a rational analysis of dissolution chemistry and kinetics, and biocompatibility of bioresorbable materials, then moves to in vivo performance and stability of electrical and optical bioresorbable components, and eventually focuses on the integration of such components into bioresorbable systems for clinically relevant applications. Finally, the technology readiness levels (TRLs) achieved for the different bioresorbable devices and systems are assessed, hence the open challenges are analyzed and future directions for advancing the technology are envisaged.

MicroRNA delivery through nanoparticles

MicroRNAs (miRNAs) are attracting a growing interest in the scientific community due to their central role in the etiology of major diseases. On the other hand, nanoparticle carriers offer unprecedented opportunities for cell specific controlled delivery of miRNAs for therapeutic purposes. This review critically discusses the use of nanoparticles for the delivery of miRNA-based therapeutics in the treatment of cancer and neurodegenerative disorders and for tissue regeneration. A fresh perspective is presented on the design and characterization of nanocarriers to accelerate translation from basic research to clinical application of miRNA-nanoparticles. Main challenges in the engineering of miRNA-loaded nanoparticles are discussed, and key application examples are highlighted to underline their therapeutic potential for effective and personalized medicine.

Endothelialization of cardiovascular devices

Blood-contacting surfaces of cardiovascular devices are not biocompatible for creating an endothelial layer on them. Numerous research studies have mainly sought to modify these surfaces through physical, chemical and biological means to ease early endothelial cell (EC) adhesion, migration and proliferation, and eventually to build an endothelial layer on the surfaces. The first priority for surface modification is inhibition of protein adsorption that leads to inhibition of platelet adhesion to the device surfaces, which may favor EC adhesion. Surface modification through surface texturing, if applicable, can bring some hopeful outcomes in this regard. Surface modifications through chemical and/or biological means may play a significant role in easy endothelialization of cardiovascular devices and inhibit smooth muscle cell proliferation. Cellular engineering of cells relevant to endothelialization can boost the positive outcomes obtained through surface engineering. This review briefly summarizes recent developments and research in early endothelialization of cardiovascular devices. STATEMENT OF SIGNIFICANCE: Endothelialization of cardiovascular implants, including heart valves, vascular stents and vascular grafts is crucial to solve many problems in our health care system. Numerous research efforts have been made to improve endothelialization on the surfaces of cardiovascular implants, mainly through surface modifications in three ways - physically, chemically and biologically. This review is intended to highlight comprehensive research studies to date on surface modifications aiming for early endothelialization on the blood-contacting surfaces of cardiovascular implants. It also discusses future perspectives to help guide endothelialization strategies and inspire further innovations.

3D-bioprinting a genetically inspired cartilage scaffold with GDF5-conjugated BMSC-laden hydrogel and polymer for cartilage repair

Rationale: Articular cartilage injury is extremely common in congenital joint dysplasia patients. Genetic studies have identified Growth differentiation factor 5 (GDF5) as a shared gene in joint dysplasia and OA progression across different populations. However, few studies have employed GDF5 in biological regeneration for articular cartilage repair. Methods & Results: In the present study, we report identified genetic association between GDF5 loci and hip joint dysplasia with genome-wide association study (GWAS). GWAS and replication studies in separate populations achieved significant signals for GDF5 loci. GDF5 expression was dysregulated with allelic differences in hip cartilage of DDH and upregulated in the repaired cartilage in a rabbit cartilage defect model. GDF5 in vitro enhanced chondrogenesis and migration of bone marrow stem cells (BMSCs), GDF5 was tested in ectopic cartilage generation with BMSCs by GDF5 in nude mice in vivo. Genetically inspired, we further generated functional knee articular cartilage construct for cartilage repair by 3d-bioprinting a GDF5-conjugated BMSC-laden scaffold. GDF5-conjugated scaffold showed better cartilage repairing effects compared to control. Meanwhile, transplantation of the 3D-bioprinted GDF5-conjugated BMSC-laden scaffold in rabbit knees conferred long-term chondroprotection. Conclusions: In conclusion, we report identified genetic association between GDF5 and DDH with combined GWAS and replications, which further inspired us to generate a ready-to-implant GDF5-conjugated BMSC-laden scaffold with one-step 3d-bioprinting for cartilage repair.