Covalent immobilization of chitosan/heparin complex with a photosensitive hetero-bifunctional crosslinking reagent on PLA surface

Thoroughly Hydrophilized Electrospun Poly(L-Lactide)/ Poly(ε-Caprolactone) Sponges for Tissue Engineering Application

Biodegradable electrospun sponges are of interest for various applications including tissue engineering, drug release, dental therapy, plant protection, and plant fertilization. Biodegradable electrospun poly(l-lactide)/poly(ε-caprolactone) (PLLA/PCL) blend fiber-based sponge with hierarchical pore structure is inherently hydrophobic, which is disadvantageous for application in tissue engineering, fertilization, and drug delivery. Contact angles and model studies for staining with a hydrophilic dye for untreated, plasma-treated, and surfactant-treated PLLA/PCL sponges are reported. Thorough hydrophilization of PLLA/PCL sponges is found only with surfactant-treated sponges. The MTT assay on the leachates from the sponges does not indicate any cell incompatibility. Furthermore, the cell proliferation and penetration of the hydrophilized sponges are verified by in vitro cell culture studies using MG63 and human fibroblast cells.

Crosslinked Layered Surfaces of Heparin and Poly(L-Lysine) Enhance Mesenchymal Stromal Cell Behavior in the Presence of Soluble Interferon Gamma

Human mesenchymal stromal cells (hMSCs) are multipotent cells that have been proposed for the treatment of immune-mediated diseases. Culturing hMSCs on tissue culture plastic reduces their therapeutic potential in part due to the lack of extracellular matrix components. The aim of this study is to evaluate multilayers of heparin and poly(L-lysine) (HEP/PLL) as a bioactive surface for hMSCs stimulated with soluble interferon gamma (IFN-γ). Multilayers were formed, via layer-by-layer assembly, with HEP as the final layer and supplemented with IFN-γ in the culture medium. Multilayer construction and chemistry were confirmed using Azure A staining, quartz crystal microbalance, and X-ray photoelectron spectroscopy. hMSCs adhesion, viability, and differentiation, were assessed. Results showed that (HEP/PLL) multilayer coatings were poorly adhesive for hMSCs. However, performing chemical crosslinking using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide significantly enhanced hMSCs adhesion and viability. The immunosuppressive properties of hMSCs cultured on crosslinked (HEP/PLL) multilayers were confirmed by measuring indoleamine 2,3-dioxygenase activity. Lastly, hMSCs cultured on crosslinked (HEP/PLL) multilayers in the presence of soluble IFN- γ successfully differentiated towards the osteogenic and adipogenic lineages as confirmed by Alizarin red, and oil-red O staining, as well as alkaline phosphatase activity. This study suggests that crosslinked (HEP/PLL) films can modulate hMSCs response to soluble factors, which may improve hMSCs-based therapies aimed at treating several immune diseases.

Immunomodulatory functions of human mesenchymal stromal cells are enhanced when cultured on HEP/COL multilayers supplemented with interferon-gamma

Human mesenchymal stromal cells (hMSCs) are multipotent cells that have been proposed for cell therapies due to their immunosuppressive capacity that can be enhanced in the presence of interferon-gamma (IFN-γ). In this study, multilayers of heparin (HEP) and collagen (COL) (HEP/COL) were used as a bioactive surface to enhance the immunomodulatory activity of hMSCs using soluble IFN-γ. Multilayers were formed, via layer-by-layer assembly, varying the final layer between COL and HEP and supplemented with IFN-γ in the culture medium. We evaluated the viability, adhesion, real-time growth, differentiation, and immunomodulatory activity of hMSCs on (HEP/COL) multilayers. HMSCs viability, adhesion, and growth were superior when cultured on (HEP/COL) multilayers compared to tissue culture plastic. We also confirmed that hMSCs osteogenic and adipogenic differentiation remained unaffected when cultured in (HEP/COL) multilayers in the presence of IFN-γ. We measured the immunomodulatory activity of hMSCs by measuring the level of indoleamine 2,3-dioxygenase (IDO) expression. IDO expression was higher on (HEP/COL) multilayers treated with IFN-γ. Lastly, we evaluated the suppression of peripheral blood mononuclear cell (PBMC) proliferation when co-cultured with hMSCs on (HEP/COL) multilayers with IFN-γ. hMSCs cultured in (HEP/COL) multilayers in the presence of soluble IFN-γ have a greater capacity to suppress PBMC proliferation. Altogether, (HEP/COL) multilayers with IFN-γ in culture medium provides a potent means of enhancing and sustaining immunomodulatory activity to control hMSCs immunomodulation.

Co-delivery of norfloxacin and tenoxicam in Ag-TiO2/poly(lactic acid) nanohybrid

A nanohybrid formulation of silver‑titanium dioxide nanoparticles/poly(lactic acid) (Ag-TiO₂/PLA) was designed for Norfloxacin/Tenoxicam (NOR/TENO) targeted delivery to maximize the bioavailability and minimize the side effects of the drugs. Ag-TiO₂ nanoparticles were prepared via Stober method. NOR, TENO and a mixture of NOR/TENO (NT) were loaded onto Ag-TiO₂ nanoparticles and coated by PLA via solution casting. The physical interaction between the drugs and carrier was confirmed by Fourier-transform infrared (FTIR) analysis. X-ray diffraction (XRD) demonstrated that Ag-TiO₂ consists of a cubic phase of Ag with two phases of TiO₂ (anatase and brookite). Ag nanoparticle fine spots coated with TiO₂ were collected to form spheres averaging at 100 nm in size. In-vitro release behavior of drugs was studied at different pH (5.4, 7.4) and the release of drug from NT/Ag-TiO₂/PLA was faster at pH 7.4. Gram-positive and Gram-negative bacteria were used to investigate antibacterial properties of the nanohybrid. Cytotoxicity of the nanohybrid using an MTT assay was studied against different tumor and normal cell lines. It was found that NT/Ag-TiO₂/PLA has an excellent cytotoxic effect against various bacterial cells and tumor cell lines. In addition, antioxidant properties of the nanohybrids were tested using ABTS method and the nanohybrid showed moderate antioxidant activity.

Effects of reinforcement of sodium alginate functionalized halloysite clay nanotubes on thermo-mechanical properties and biocompatibility of poly (vinyl alcohol) nanocomposites

In the present work sodium alginate functionalized halloysite nanotubes (HNTs) reinforced poly (vinyl alcohol) nanocomposite films were prepared by solution casting technique. Sodium alginate surface functionalizing on the HNTs through hydrogen bonding was confirmed by spectroscopic and morphological analysis. The functionalized HNTs were successfully incorporated into the PVA matrix. Further, the films were characterized by using FTIR, TGA, XRD, SEM, AFM, UTM, WCA and swelling ratio analysis. The obtained results indicated improved physico-thermal properties, and uniform distribution of nanotubes in the matrix and roughness of the surface compared with the pristine PVA films. After inclusion of functionalized nanotubes causes enhancement of tensile strength as well as young's modulus of the nanocomposite films. Water contact angle measurement was carried out to know the hydrophilic or hydrophobic nature of the films and results were correlated with swelling ratio analysis. Furthermore, the films were analyzed for in-vitro biocompatibility studies. In -vitro enzymatic degradation was carried out in PBS media and cellular behaviour studies were analyzed using NIH3T3 cell lines. The results showed enhancement in the enzymatic degradation, proliferation, adhesion activity compared to that of pristine PVA films. In extension, nanocomposite films were subjected to hemocompatibility studies using human erythrocyte. The results revealed that nanocomposite films were biocompatible and hemocompatible. The fabricated films can be used in biomedical application.

Correlation between Surface Properties of Polystyrene and Polylactide Materials and Fibroblast and Osteoblast Cell Line Behavior: A Critical Overview of the Literature

Bone reconstruction remains an important challenge today in several clinical situations, notably regarding the control of the competition occurring during proliferation of osteoblasts and fibroblasts. Polystyrene and polylactide are reference materials in the biomedical field. Therefore, it could be expected from the literature that clear correlations have been already established between the behavior of fibroblasts or osteoblasts and the surface characteristics of these materials. After an extensive analysis of the literature, although general trends could be established, our critical review has highlighted the need to develop a more in-depth analysis of the surface properties of these materials. Moreover, the large variation noticed in the experimental conditions used for in vitro animal cell studies impairs comparison between studies. From our comprehensive review on this topic, we have suggested several parameters that would be valuable to standardize to integrate the data from the literature and improve our knowledge on the cell-material interactions.

Atmospheric pressure cold plasma versus wet-chemical surface treatments for carboxyl functionalization of polylactic acid: A first step toward covalent immobilization of bioactive molecules

The use of polylactic acid (PLA) has attracted growing interest, particularly in recent years, for biomedical applications because of its mechanical properties, biocompatibility, and biodegradability. Despite this, features such as surface hydrophobicity and the absence of suitable functional groups for covalent immobilization of bioactive molecules, make it challenging to endow PLA-based medical devices with additional features and thus broaden their range of applicability. In the present study, we demonstrate the suitability of atmospheric pressure dielectric barrier discharges operating in the Townsend regime as a promising alternative to other surface treatments, such as diazonium and alkali hydrolytic treatments, for carboxyl functionalization of PLA. Chemical changes in PLA surfaces are evaluated by contact angle measurements and by X-ray photoelectron spectroscopy while physical changes are investigated by scanning electron microscopy and atomic force microscopy. The amount of carboxyl groups generated on PLA surfaces is assessed by toluidine blue O assay and substantiated by grafting, through carboxyl groups, a fluorescent probe containing amino functionalities. All of the surface treatments have proven to be very effective in generating carboxylic groups on the PLA surface. Nevertheless, plasma treatment is shown to not degrade the PLA surface, in sharp contrast with diazonium and alkali hydrolytic treatments.

Progress in electrospun composite nanofibers: composition, performance and applications for tissue engineering

The discovery of novel methods to fabricate optimal scaffolds that mimic both mechanical and functional properties of the extracellular matrix (ECM) has always been the "holy grail" in tissue engineering. In recent years, electrospinning has emerged as an attractive material fabrication method and has been widely applied in tissue engineering due to its capability of producing non-woven and nanoscale fibers. However, from the perspective of biomimicry, it is difficult for single-component electrospun fiber membranes to achieve the biomimetic purposes of the multi-component extracellular matrix. Based on electrospinning, various functional components can be efficiently and expediently introduced into the membranes, and through the complementation and correlation of the properties of each component, composite materials with comprehensive and superior properties are obtained while maintaining the primitive merits of each component. In this review, we will provide an overview of the attempts made to fabricate electrospinning-based composite tissue engineering materials in the past few decades, which have been divided into organic additives, inorganic additives and organic-inorganic additives.

Fabrication of electrospun poly(lactic acid) nanoporous membrane loaded with niobium pentoxide nanoparticles as a potential scaffold for biomaterial applications

Tissue engineering aims to regenerate and restore damaged human organs and tissues using scaffolds that can mimic the native tissues. The requirement for modern and efficient biomaterials that are capable of accelerating the healing process has been considerably increased. In this work, a novel electrospun poly(lactic acid) (PLA) nanoporous membrane incorporated with niobium pentoxide nanoparticles (Nb₂ O₅ ) for biomaterial applications was developed. Nb₂ O₅ nanoparticles were obtained by microwave-assisted hydrothermal synthesis, and different concentrations (0, 1, 3, and 5% wt/wt) were tested. Chemical, morphological, mechanical, and biological properties of membranes were evaluated. Cell viability results demonstrated that the membranes presented nontoxic effects. The incorporation of Nb₂ O₅ improved cell proliferation without impairing the wettability, porosity, and mechanical properties of membranes. Membranes containing Nb₂ O₅ nanoparticles presented biocompatible properties with suitable porosity, which facilitated cell attachment and proliferation while allowing diffusion of oxygen and nutrients. This study has demonstrated that Nb₂ O₅ nanoparticle-loaded electrospun PLA nanoporous membranes are potential candidates for drug delivery and wound dressing applications.

Surface Modification of 3D Printed PLA Objects by Fused Deposition Modeling: A Review

Polylactic acid (PLA) filaments are very popular as a thermoplastic source used in the 3D printing field by the “Fused Deposition Modeling” method in the last decade. The PLA market is expected to reach 5.2 billion US dollars in 2020 for all of its industrial uses. On the other hand, 3D printing is an expanding technology that has a large economic potential in many industries where PLA is one of the main choices as the source polymer due to its ease of printing, environmentally friendly nature, glossiness and multicolor appearance properties. In this review, we first reported the chemical structure, production methods, general properties, and present market of the PLA. Then, the chemical modification possibilities of PLA and its use in 3D printers, present drawbacks, and the surface modification methods of PLA polymers in many different fields were discussed. Specifically, the 3D printing method where the PLA filaments are used in the extrusion-based 3D printing technologies is reviewed in this article. Many methods have been proposed for the permanent surface modifications of the PLA where covalent attachments were formed such as alkaline surface hydrolysis, atom transfer polymerization, photografting by UV light, plasma treatment, and chemical reactions after plasma treatment. Some of these methods can be applied for surface modifications of PLA objects obtained by 3D printing for better performance in biomedical uses and other fields. Some recent publications reporting the surface modification of 3D printed PLA objects were also discussed.

Tailored functionalization of poly(L-lactic acid) substrates at the nanoscale to enhance cell response

Poly(L-lactic) acid (PLLA) has been widely employed in tissue engineering due to its mechanical properties, biodegradability and biocompatibility. The layer-by-layer (LbL) technique was here proposed as a simple method to impart bioactivity to the surface of PLLA substrates. Aminolysis treatment was applied to introduce amino groups on the surface of PLLA solvent cast films. Then, PLLA films were coated with heparin (HE)/chitosan (CH) multilayer by the LbL technique. Each functionalization step was characterized through physico-chemical and morphological analyses. Aminolysis treatment increased film surface wettability (64.8° ± 2.4° against 74.6° ± 1.3° for untreated PLLA) due to the formation of surface amino groups, which were quantified by acid orange colorimetric assay (0.05 nmol/mm²). After the deposition of 9 layers, the static contact angle varied between values close to 40° C (HE-based layer) and 60 °C (CH-based layer), showing the typical alternate trend of LbL coating. The successful HE/CH deposition was confirmed by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analyses. Particularly, XPS spectra of coated samples showed the presence of nitrogen (indicative of HE and CH deposition), and sulfur (indicative of HE deposition). The amount of deposited HE was quantified by Taylor's Blue colorimetric method: after the deposition of 19 and 20 layers the HE concentration was around 33 µg/cm². Finally, in vitro studies performed using HaCaT immortalized human skin keratinocytes, C2C12 immortalized mouse myoblasts and human fibroblasts demonstrated that HE/CH multilayer-coated PLLA is a promising substrate for soft tissue engineering, as cell response may be modulated by changing the surface chemical properties.

Functionalization of PLLA with Polymer Brushes to Trigger the Assembly of Fibronectin into Nanonetworks

Poly-l-lactic acid (PLLA) has been used as a biodegradable polymer for many years; the key characteristics of this polymer make it a versatile and useful resource for regenerative medicine. However, it is not inherently bioactive. Thus, here, a novel process is presented to functionalize PLLA surfaces with poly(ethyl acrylate) (PEA) brushes to provide biological functionality through PEA's ability to induce spontaneous organization of the extracellular matrix component fibronectin (FN) into physiological-like nanofibrils. This process allows control of surface biofunctionality while maintaining PLLA bulk properties (i.e., degradation profile, mechanical strength). The new approach is based on surface-initiated atomic transfer radical polymerization, which achieves a molecularly thin coating of PEA on top of the underlying PLLA. Beside surface characterization via atomic force microscopy, X-ray photoelectron spectroscopy and water contact angle to measure PEA grafting, the biological activity of this surface modification is investigated. PEA brushes trigger FN organization into nanofibrils, which retain their ability to enhance adhesion and differentiation of C2C12 cells. The results demonstrate the potential of this technology to engineer controlled microenvironments to tune cell fate via biologically active surface modification of an otherwise bioinert biodegradable polymer, gaining wide use in tissue engineering applications.

Preparation of Chitosan-Coated Poly(L-Lactic Acid) Fibers for Suture Threads

Poly(L-lactic acid) (PLA) is a biodegradable fiber, and a promising material for use in biomedical applications. However, its hydrophobicity, low hydrolyzability, and poor cell adhesion can be problematic in some cases; consequently, the development of improved PLA-based materials is required. In this study, chitosan-coated (CS-coated) PLA was prepared by plasma treatment and the layer-by-layer (LBL) method. Plasma treatment prior to CS coating effectively hydrophilized and activated the PLA surface. The LBL method was used to increase the number of CS and sodium alginate (SA) coating layers by electrostatically superposing alternating anionic and cationic polymers. The prepared fibers were characterized by tensile testing, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), nitrogen analysis and degradation testing, which revealed that the 100 W plasma treatment for 60 s was optimum, and that plasma treatment and the LBL method effectively coated CS onto the PLA fibers. The existence or not of a coating on the PLA fiber did not appear to influence the degradation of the fiber, which is ascribable to the extremely thin coating, as evidenced by nitrogen analysis and SEM. The CS-coated PLA fibers were prepared without damaging the PLA surface and can be used in biomaterial applications such as suture threads.

Cardiovascular stents: overview, evolution, and next generation

Compared to bare-metal stents (BMSs), drug-eluting stents (DESs) have been regarded as a revolutionary change in coronary artery diseases (CADs). Releasing pharmaceutical agents from the stent surface was a promising progress in the realm of cardiovascular stents. Despite supreme advantages over BMSs, in-stent restenosis (ISR) and long-term safety of DESs are still deemed ongoing concerns over clinically application of DESs. The failure of DESs for long-term clinical use is associated with following factors including permanent polymeric coating materials, metallic stent platforms, non-optimal drug releasing condition, and factors that have recently been supposed as contributory factors such as degradation products of polymers, metal ions due to erosion and degradation of metals and their alloys utilizing in some stents as metal frameworks. Discovering the direct relation between stent materials and associating adverse effects is a complicated process, and yet it has not been resolved. For clinical success it is of significant importance to optimize DES design and explore novel strategies to overcome all problems including inflammatory response, delay endothelialization, and sub-acute stent thrombosis (ST) simultaneously. In this work, scientific reports are reviewed particularly focusing on recent advancements in DES design which covers both potential improvements of existing and recently novel prototype stent fabrications. Covering a wide range of information from the BMSs to recent advancement, this study mostly sheds light on DES's concepts, namely stent composition, drug release mechanism, and coating techniques. This review further reports different forms of DES including fully biodegradable DESs, shape-memory ones, and polymer-free DESs.

A Sandwich-Structured Piezoresistive Sensor with Electrospun Nanofiber Mats as Supporting, Sensing, and Packaging Layers

Electrospun nanofiber mats have been used as sensing elements to construct piezoresistive devices due to their large surface area and high porosity. However, they have not been utilized as skin-contact supporting layers to package conductive nanofiber networks for the fabrication of piezoresistive sensors. In this work, we developed a sandwich-structured pressure sensor, which can sensitively monitor human motions and vital signs, with electrospun nanofiber mats as supporting, sensing, and packaging layers. The nanofiber mats were prepared by electrospinning with biocompatible poly (l-lactide) (PLA), silk fibroin (SF), and collagen (COL) as raw materials. The synthesized PLA–SF–COL mat possesses a non-woven structure with a fiber diameter of 122 ± 28 nm and a film thickness of 37 ± 5.3 μm. Polypyrrole (PPy) nanoparticles were grown in-situ on the mat to form a conductive layer. After stacking the pristine and conductive mats to form a PLA–SF–COL mat/(PPy-coated mat)₂ structure, another layer was electrospun to pack the multilayers for the construction of a sandwich-structured piezoresistive sensor. The as-prepared device can sensitively detect external pressures caused by coin loading and finger tapping/pressing. It can also tolerate more than 600 times of pressing without affecting its sensing capability. The human body-attached experiments further demonstrate that the sensor could real-time monitor finger/arm bending, arterial pulse, respiration rate, and speaking-caused throat vibration. The electrospinning-based fabrication may be used as a facile and low-cost strategy to produce flexible piezoresistive sensors with excellent skin-compatibility and great pressure sensing capability.

Study on the morphological and biocompatible properties of chitosan grafted silk fibre reinforced PVA films for tissue engineering applications

The current study delineates the preparation of novel chitosan grafted silk fibre reinforced Poly (vinyl alcohol) (PVA) composite films with desirable properties. Although silk fibroin has been extensively used for various biomedical applications, its properties could be further re-tailored for its suitability in the field of regenerative medicine. Chitosan was successfully grafted over silk, via acylation with succinic anhydride and thereby the fibres were incised and used for the preparation of the films. The grafted silk fibre reinforced PVA films were subjected to FTIR studies, microscopic analysis by atomic force microscopy (AFM) and optical microscopy techniques, X-ray diffraction (XRD) analysis and further evaluated for in vitro biocompatibility studies. The composite films demonstrated improved surface roughness with increasing concentration of the fibre and its dispersion in the polymer matrix was observed. Furthermore, in vitro biocompatibility and cellular behaviour such as adhesion and proliferation of mouse fibroblasts as well as astrocyte cells was studied and the results showed improved proliferative activity, when compared to the pristine PVA films. These results were further supported by the results confirmed by MTT assay demonstrating the films to be non-toxic. The efficiency and feasibility of the films to be used for tissue engineering, was further evaluated by haemocompatibility studies using human erythrocytes, thus making them a potential material to be used for biomedical applications.

Biodegradation and Biocompatibility of Poly L-lactic Acid Implantable Mesh

Purpose

The purpose of this study was to evaluate the biodegradation and biocompatibility of poly L-lactic acid (PLLA) implantable mesh under in vitro and in vivo conditions.

Methods

PLLA mesh was examined for changes in weight and tensile strength. The histology of the tissue around the PLLA implant was also evaluated.

Results

The weight and tensile strength of the PLLA prosthesis was stable for 180 days. In addition, the surface of the PLLA mesh was not digested under in vitro or in vivo conditions as determined by scanning electron microscope. Histologically, there were no significant changes in the diameters of implanted PLLA mesh and subtype fibers over the course of 180 days. Likewise, there were no significant changes in the number of inflammatory and mast cells after 180 days, nor was there an increase in the percentage of collagen surrounding the PLLA mesh.

Conclusions

The results indicate that PLLA prostheses have good rigidity and biocompatibility in vivo and in vitro.

Impact of Collagen/Heparin Multilayers for Regulating Bone Cellular Functions

Bone cell interaction with extracellular matrix (ECM) microenvironment is of critical importance when engineering surface interfaces for bone regeneration. In this work layer-by-layer films of type I collagen (coll), the major constituent of bone ECM, and heparin (hep), a glycosaminoglycan, were assembled on poly(l-lactic acid) (PLLA) substrates to evaluate the impact of the biomacromolecular coating on cell activity. The surface modification of PLLA demonstrated that the hep/coll multilayer is stable after 10 bilayers (confirmed by contact angle, infrared spectroscopy, and morphological analysis). This simple approach provided novel information on the effect of heparin on type I collagen hierarchical organization and subsequent cell response of osteoblast-like (MC3T3-E1) and human bone marrow-derived mesenchymal stem cells (hMSCs). Interestingly, the number of deposited heparin layers (1 or 10) appeared to play an important role in the self-assembly of collagen into fibrils, stabilizing the fibrous collagen layer, and potentially impacting hMSCs activity.

Biocompatibility, degradability, bioactivity and osteogenesis of mesoporous/macroporous scaffolds of mesoporous diopside/poly(L-lactide) composite

Bioactive mesoporous diopside (m-DP) and poly(L-lactide) (PLLA) composite scaffolds with mesoporous/macroporous structure were prepared by the solution-casting and particulate-leaching method. The results demonstrated that the degradability and bioactivity of the mesoporous/macroporous scaffolds were significantly improved by incorporating m-DP into PLLA, and that the improvement was m-DP content-dependent. In addition, the scaffolds containing m-DP showed the ability to neutralize acidic degradation products and prevent the pH from dropping in the solution during the soaking period. Moreover, the scaffolds containing m-DP enhanced attachment, proliferation and alkaline phosphatase activity of MC3T3-E1 cells, which were also m-DP content-dependent. Furthermore, the histological and immunohistochemical analysis results showed that the scaffolds with m-DP significantly promoted new bone formation and improved the materials degraded in vivo, indicating good biocompatibility. The results suggested that the mesoporous/macroporous scaffolds of the m-DP/PLLA composite with osteogenesis had a potential for bone regeneration.

Immunogenicity of Renal Microvascular Endothelial Cells From Genetically Modified Pigs

BACKGROUND

Disrupting the porcine GGTA1 and CMAH genes [double knockout (DKO)] that produce the gal-α(1,3)-gal and N-glycolylneuraminic acid xenoantigens reduces human antibody binding to porcine peripheral blood mononuclear cells. It is important to examine rejection pathways at an organ-specific level. The object of this study is to evaluate the human preformed antibody reactivity against DKO renal microvascular endothelial cells (RMEC) in vitro.

METHODS

Characteristics of DKO RMEC were analyzed using flow cytometry. Human IgG/M binding to primary RMEC, immortalized RMEC (iRMEC), and iRMEC-deficient in B4GALNT2 genes were examined using flow cytometric crossmatch assay.

RESULTS

Porcine RMEC expressed gal-α(1,3)-gal, N-glycolylneuraminic acid, and Dolichos biflorus agglutinin glycans recognized by human preexisting antibodies in humans. Antigenicity of DKO RMEC was lower than GGTA1 KO RMEC. The disruption of B4GALNT2 gene in DKO iRMEC further reduced human IgG/IgM binding.

CONCLUSIONS

Silencing the porcine GGTA1, CMAH, and B4GALNT2 genes is an effective strategy to reduce human preformed antibody binding to RMEC. Porcine RMEC will be a useful reagent for the further study of xenoimmunology.

Nitrogen-doped graphene-chitosan matrix based efficient chemiluminescent immunosensor for detection of chicken interleukin-4

Chicken interleukin-4 (ChIL-4), which is released by activated type 2 helper (Th2) cells following their stimulation in vitro, is an important indicator for the study of cell-mediated immunity in chickens after infection or vaccination. In this work, the first ChIL-4 chemiluminescent (CL) immunosensor was developed via the immobilization of monoclonal ChIL-4 antibodies on a nitrogen-doped graphene (NG)-chitosan nanocomposite matrix. NG nanosheets were used for the first time in the CL immunoassay to provide a biocompatible microenvironment for the immobilized capture antibody. The ChIL-4 immunosensor was characterized systematically. The proposed immunosensor displayed a wide linear range from 0.05 to 70ngmL^-1 and a low detection limit of 0.02ngmL^-1 at a signal-to-noise ratio of 3. Compared to traditional assay methods, this system was more flexible, simple, rapid, and sensitive. Moreover, this CL immunoassay system had an excellent detection and fabrication reproducibility, a high specificity, an acceptable accuracy, and a high stability. This work enables the specific detection of ChIL-4 and the further study of its role in the immune responses of poultry.

Powering tyrosol antioxidant capacity and osteogenic activity by biocatalytic polymerization

Oxidative polymerization of tyrosol afforded a mixture of oligomers (OligoTyr) which proved to be more active than tyrosol as antioxidant and as stimulator of alkaline phosphatase (ALP) activity when loaded into polylactic acid (PLA) scaffolds.

Multifunctional coating based on EPC-specific peptide and phospholipid polymers for potential applications in cardiovascular implants fate

Surface biofunctional modification of cardiovascular implants via the conjugation of biomolecules to prevent thrombosis and restenosis formation and to accelerate endothelialization has attracted considerable research interest.

Recent progress in designing shell cross-linked polymer capsules for drug delivery

This tutorial review highlights the progress made during recent years in the development of the shell cross-linked (SCL) polymer nanocapsules and the impact of the most important scientific ideas on this field of knowledge.

Preparation and Characterization of Films Extruded of Polyethylene/Chitosan Modified with Poly(lactic acid)

The use of mixtures of synthetic and natural polymers is a potential option to reduce the pollution by plastic waste. In this work, the method for the chemical modification of chitosan with poly(lactic acid) was developed; then, the preparation of films of blends of polyethylene and chitosan-poly(lactic acid) produced by an extrusion method using polyethylene-graft maleic anhydride as a compatibilizer. It was possible to obtain films with a maximum content of 20 wt% and 30 wt%, chitosan, with and without compatibilizer, respectively. Scanning electron microscope (SEM) analysis showed a homogeneous surface on all films. The addition of the compatibilizer had a significant effect on the mechanical properties of the films, such as an increase in Young’s modulus and a decrease in the elongation at break; additionally, the compatibilizer promotes thermal degradation in a single step and gives the film a slight increase in thermal resistance. These results are attributed to an improved interaction in the interface of polyethylene and chitosan-poly(lactic acid), promoted by the compatibilizer.

Poly(lactic acid)/chitosan hybrid nanoparticles for controlled release of anticancer drug

Poly(lactic acid) (PLA) is a kind of non-toxic biological materials with excellent absorbability, biocompatibility and biodegradability, which can be used for drug release, tissue engineering and surgical treatment applications. In this study, we prepared chitosan modified PLA nanoparticles as carriers for encapsulation of docetaxel by anti-solvent precipitation method. The morphology, particle size, zeta potential and composition of the PLA/chitosan were characterized by SEM, DLS, FTIR and XPS. As-prepared PLA/chitosan particles exhibited average size of 250 nm and showed very narrow distribution with polydispersity index of 0.098. Their large surface charge-ability was confirmed by zeta potential value of 53.9 mV. Docetaxel was released from PLA/chitosan nanoparticles with 40% initial burst release in 5 h and 70% cumulative release within 24 h, while from PLA nanoparticles 65% of docetaxel was released in 5h. In vitro drug release study demonstrated that PLA/chitosan nanoparticles prolonged drug release and decreased the burst release over the unmodified PLA nanoparticles. These results illustrated high potential of chitosan modified PLA nanoparticles for usage as anticancer drug carriers.

The mechanics of PLGA nanofiber scaffolds with biomimetic gradients in mineral for tendon-to-bone repair

Attachment of dissimilar materials is prone to failure due to stress concentrations that can arise their interface. A compositionally or structurally graded transition can dissipate these stress concentrations and thereby toughen an attachment. The interface between compliant tendon and stiff bone utilizes a monotonic change in hydroxylapatite mineral ("mineral") content to produce a gradient in mechanical properties and mitigate stress concentrations. Previous efforts to mimic the natural tendon-to-bone attachment have included electrospun nanofibrous polymer scaffolds with gradients in mineral. Mineralization of the nanofiber scaffolds has typically been achieved using simulated body fluid (SBF). Depending on the specific formulation of SBF, mineral morphologies ranged from densely packed small crystals to platelike crystal florets. Although this mineralization of scaffolds produced increases in modulus, the peak modulus achieved remained significantly below that of bone. Missing from these prior empirical approaches was insight into the effect of mineral morphology on scaffold mechanics and on the potential for the approach to ultimately achieve moduli approaching that of bone. Here, we applied two mineralization methods to generate scaffolds with spatial gradations in mineral content, and developed methods to quantify the stiffening effects and evaluate them in the context of theoretical bounds. We asked whether either of the mineralization methods we developed holds potential to achieve adequate stiffening of the scaffold, and tested the hypothesis that the smoother, denser mineral coating could attain more potent stiffening effects. Testing this hypothesis required development of and comparison to homogenization bounds, and development of techniques to estimate mineral volume fractions and spatial gradations in modulus. For both mineralization strategies, energy dispersive X-ray analysis demonstrated the formation of linear gradients in mineral concentration along the length of the scaffolds, and Raman spectroscopic analysis revealed that the mineral produced was hydroxylapatite. Mechanical testing showed that the stiffness gradient using the new method was significantly steeper. By analyzing the scaffolds using micromechanical modeling techniques and extrapolating from our experimental results, we present evidence that the new mineralization protocol has the potential to achieve levels of stiffness adequate to contribute to enhanced repair of tendon-to-bone attachments.