Impact of Collagen/Heparin Multilayers for Regulating Bone Cellular Functions

Synergistic nanocoating with layer-by-layer functionalized PCL membranes enhanced by manuka honey and essential oils for advanced wound healing

Chronic wounds represent a significant global health concern, statistically impacting 1-2% of the population in developed countries throughout their lifetimes. These wounds cause considerable discomfort for patients and necessitate substantial expenditures of time and resources for treatment. Among the emerging therapeutic approaches, medicated dressings incorporating bioactive molecules, including natural compounds, are particularly promising. Hence, the objective of this study was to develop novel antimicrobial dressings for wound treatment. Specifically, polycaprolactone membranes were manufactured using the electrospinning technique and subsequently coated with natural polyelectrolytes (chitosan as a polycation and a mixture of manuka honey with essential oils nanoemulsions as a polyanion) employing the Layer-by-Layer assembly technique. Physico-chemical and morphological characterization was conducted through QCM-D, FTIR-ATR, XPS, and SEM analyses. The results from SEM and QCM-D demonstrated successful layer deposition and coating formation. Furthermore, FTIR-ATR and XPS analyses distinguished among different coating compositions. The coated membranes were tested in the presence of fibroblast cells, demonstrating biocompatibility and expression of genes coding for VEGF, COL1, and TGF-β1, which are associated with the healing process (assessed through RT-qPCR analysis). Finally, the membranes exhibited excellent antibacterial activity against both Staphylococcus aureus and Pseudomonas aeruginosa, with higher bacterial strain inhibition observed when cinnamon essential oil nanoemulsion was incorporated. Taken together, these results demonstrate the potential application of nanocoated membranes for biomedical applications, such as wound healing.

Protein-based layer-by-layer films for biomedical applications

The surface engineering of biomaterials is crucial for their successful (bio)integration by the body, i.e. the colonization by the tissue-specific cell, and the prevention of fibrosis and/or bacterial colonization. Performed at room temperature in an aqueous medium, the layer-by-layer (LbL) coating method is based on the alternating deposition of macromolecules. Versatile and simple, this method allows the functionalization of surfaces with proteins, which play a crucial role in several biological mechanisms. Possessing intrinsic properties (cell adhesion, antibacterial, degradable, etc.), protein-based LbL films represent a powerful tool to control bacterial and mammalian cell fate. In this article, after a general introduction to the LbL technique, we will focus on protein-based LbL films addressing different biomedical issues/domains, such as bacterial infection, blood contacting surfaces, mammalian cell adhesion, drug and gene delivery, and bone and neural tissue engineering. We do not consider biosensing applications or electrochemical aspects using specific proteins such as enzymes.

Layer-by-Layer Coatings of Collagen-Hyaluronic acid Loaded with an Antibacterial Manuka Honey Bioactive Compound to Fight Metallic Implant Infections

Implant-associated severe infections can result in catastrophic implant failures; thus, advanced antibacterial coatings are needed to combat infections. This study focuses on harnessing nature-inspired self-assembly of extracellular matrix (ECM)-like coatings on Ti alloy with a combination of jellyfish-derived collagen (J-COLL) and hyaluronic acid (HA) using our customized automated hybrid layer-by-layer apparatus. To improve the anti-infection efficacy of coatings, we have incorporated a natural antibacterial agent methylglyoxal (MGO, a Manuka honey compound) in optimized multilayer coatings. The obtainment of MGO-loaded multilayer coatings was successfully assessed by profilometry, contact angle, attenuated total reflectance (ATR)-Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. In vitro degradation confirmed the controlled release activity of MGO with a range of concentrations from 0.90 to 2.38 mM up to 21 days. A bacterial cell culture study using Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis) confirmed that the MGO incorporated within layers 7 and 9 had a favorable effect on preventing bacterial growth and colonization on their surfaces. An in vitro cytocompatibility study confirmed that MGO agents included in the layers did not affect or reduce the cellular functionalities of L929 fibroblasts. In addition, MGO-loaded layers with Immortalized Mesenchymal Stem Cells (Y201 TERT-hMSCs) were found to favor the growth and differentiation of Y201 cells and promote calcium nodule formation. Overall, these surface coatings are promising candidates for delivering antimicrobial activity with bone-inducing functions for future bone tissue engineering applications.

Physical Chemistry Study of Collagen-Based Multilayer Films

The surface properties of a biomaterial play an important role in cell behavior, e.g., recolonization, proliferation, and migration. Collagen is known to favor wound healing. In this study, collagen (COL)-based layer-by-layer (LbL) films were built using different macromolecules as a partner, i.e., tannic acid (TA), a natural polyphenol known to establish hydrogen bonds with protein, heparin (HEP), an anionic polysaccharide, and poly(sodium 4-styrene sulfonate) (PSS), an anionic synthetic polyelectrolyte. To cover the whole surface of the substrate with a minimal number of deposition steps, several parameters of the film buildup were optimized, such as the pH value of the solutions, the dipping time, and the salt (sodium chloride) concentration. The morphology of the films was characterized by atomic force microscopy. Built at an acidic pH, the stability of COL-based LbL films was studied when in contact with a physiological medium as well as the TA release from COL/TA films. In contrast to COL/PSS and COL/HEP LbL films, COL/TA films showed a good proliferation of human fibroblasts. These results validate the choice of TA and COL as components of LbL films for biomedical coatings.

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.

Adhesive Bioinspired Coating for Enhancing Glass-Ceramics Scaffolds Bioactivity

Bioceramic scaffolds, composed of a biphasic composite containing bioactive glass and hydroxyapatite, were prepared in this work to overcome the intrinsic limits of the two components taken separately (in particular, their specific reactivities and dissolution rates, which should be tunable as a function of the given clinical requirements). To mimic the biological environment and tune the different stages of cellular response, a coating with gelatin and chondroitin sulphate via Layer-by-Layer (LbL) assembly was presented and discussed. The resulting functionalized scaffolds were affected by the coating in terms of microstructure and porosity. In addition, the LbL coating significantly enhanced the seeded cell behaviour, with high adhesion, proliferation and osteogenic activity, as revealed by the alkaline phosphatase activity and overexpression of osteopontin and osteocalcin.

Suppressing the Hofmeister Anion Effect by Thermal Annealing of Thin-Film Multilayers Made of Weak Polyelectrolytes

Thin films made of weak polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) have been fabricated on silicon wafers using the layer-by-layer (LbL) method. To study the influence of counteranion type on the growth and properties of PAH/PAA multilayers, the nature of the supporting sodium salt was varied from cosmotropic to chaotropic anions (F^–, Cl^–, and ClO₄^–). Results of ellipsometry and AFM measurements indicate that the film thickness and surface roughness systematically increase on the order F^– < Cl^– < ClO₄^–. Furthermore, we found that the hydrophobicity of the PAH/PAA multilayer also follows the described trend when a polycation is the terminating layer. However, the heating of PAH/PAA multilayers to 60 °C during the LbL assembly suppressed the influence of background anions on the multilayer formation and properties. On the basis of the obtained results, it could be concluded that thermal annealing induces changes at the polymer–air interface in the sense of reorientation and migration of polymer chains.

Heparin/Collagen-REDV Modification of Expanded Polytetrafluoroethylene Improves Regional Anti-thrombosis and Reduces Foreign Body Reactions in Local Tissues

Prosthetic implants of expanded polytetrafluoroethylene (ePTFE) in the cardiovascular system have a high failure rate over the long term because of thrombosis and intimal hyperplasia. Although multiple surface modification methods have been applied to improve the anti-thrombotic and in situ endothelialization abilities of ePTFE, none have delivered outstanding results in vivo. Our previous study combined heparin/collagen multilayers and REDV peptides to modify ePTFE, and the in-vitro results showed that modification ePTFE with heparin/collagen-REDV can promote the cytocompatibility and antiplatelet property. This study illustrated the physical change, selective endothelial cells capture ability, and in vivo performance in further. The physical test demonstrated that this modification improved the hydrophilicity, flexibility and strength of ePTFE. A competition experiment of co-cultured endothelial cells and vascular smooth muscle cells verified that the heparin/collagen-REDV modification had high specificity for endothelial cell capture. A rabbit animal model was constructed to evaluate the in vivo performance of modified ePTFE implanted in the right ventricular outflow tract. The results showed that heparin/collagen-REDV modification was safe, promoted endothelialization, and successfully achieved regional anti-thrombosis without influencing body-wide coagulation function. The pathologic manifestations and mRNA expression pattern in tissues in contact with modified ePTFE indicated that this modification method may reduce M2-type macrophage infiltration and the expression of genes related to immune and inflammatory responses. The heparin/collagen-REDV modification may lower the incidence of complications related to ePTFE implantation and has good prospects for clinical use.

Effects of Hyaluronic Acid/Collagen Resorbable Gel Use in Endoscopic Dacryocystorhinostomy

The purpose of this study was to investigate whether the use of hyaluronic acid/collagen resorbable gel (Regenwel®) has an inhibitory effect on rhinostomy obstruction during endoscopic dacryocystorhinostomy (Endo DCR). A total of 298 patients diagnosed with unilateral primary acquired nasolacrimal duct obstruction from May 2017 to June 2021 who underwent Endo DCR were enrolled. The patients were divided into the Regenwel group (152 patients) and the Control group (146 patients) that did not use Regenwel during surgery, and the medical records were compared and analyzed retrospectively. The mean age of the Regenwel group was 65.8 years, and that of the Control group was 63.2 years. Regarding anatomical success as the primary outcome, the Regenwel group had a higher success rate than the Control group (96.7% vs 86.3%, P = .012), and the functional success result confirmed that the Regenwel group had a higher success rate than the Control group (94.1% vs 84.3%, P = .024). Among secondary outcomes, granulation formation occurred less frequently in the Regenwel group than in the Control group (9.2% vs 32.2%, P < .001), and there was no statistically significant difference in postoperative bleeding between the 2 groups (0% vs 1.4%, P = .478). The Regenwel group had fewer infections after surgery than the Control group (5.3% vs 8.9%, P = .012) and required less frequent revision surgery (2.0% vs 15.8%, P < .001). In conclusion, Regenwel is a resorbable gel containing hyaluronic acid and collagen that is used during Endo DCR and is thought to contribute to the improvement of surgical success rate by preventing complications such as rhinostomy obstruction and bleeding after surgery.

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.

Heparin Enriched-WPI Coating on Ti6Al4V Increases Hydrophilicity and Improves Proliferation and Differentiation of Human Bone Marrow Stromal Cells

Titanium alloy (Ti6Al4V) is one of the most prominent biomaterials for bone contact because of its ability to bear mechanical loading and resist corrosion. The success of Ti6Al4V implants depends on bone formation on the implant surface. Hence, implant coatings which promote adhesion, proliferation and differentiation of bone-forming cells are desirable. One coating strategy is by adsorption of biomacromolecules. In this study, Ti6Al4V substrates produced by additive manufacturing (AM) were coated with whey protein isolate (WPI) fibrils, obtained at pH 2, and heparin or tinzaparin (a low molecular weight heparin LMWH) in order to improve the proliferation and differentiation of bone-forming cells. WPI fibrils proved to be an excellent support for the growth of human bone marrow stromal cells (hBMSC). Indeed, WPI fibrils were resistant to sterilization and were stable during storage. This WPI-heparin-enriched coating, especially the LMWH, enhanced the differentiation of hBMSC by increasing tissue non-specific alkaline phosphatase (TNAP) activity. Finally, the coating increased the hydrophilicity of the material. The results confirmed that WPI fibrils are an excellent biomaterial which can be used for biomedical coatings, as they are easily modifiable and resistant to heat treatments. Indeed, the already known positive effect on osteogenic integration of WPI-only coated substrates has been further enhanced by a simple adsorption procedure.

Programmed BMP-2 release from biphasic calcium phosphates for optimal bone regeneration

This study aimed to fabricate a multi-layered biphasic calcium phosphate (BCP) platform for programmed bone morphogenetic protein-2 (BMP-2) release, which means to block the initial burst release and promote releasing during the differentiation phase of osteogenic cells. And it is to confirm in vivo whether this platform has osteogenic inductivity even when extremely low doses of BMP-2 are loaded compared to the conventional soaking method. Our strategy consisted of preparing a multilayer coating on BCP to minimize the contact between BMP-2 and BCP and allow the loading of BMP-2. The multilayer, which is surface-modified on BCP, is composed of an organosilicate and a natural polymer-based layer-by-layer (LbL) film. We applied (3-Aminopropyl)triethoxysilane (APTES) as an organosilicate was used for amine-functionalized BCP and (collagen/heparin)₅ film was used to delay and sustain BMP-2 release. The coated multilayer not only reduced the initial burst release by more than 50% but also loaded more BMP-2. For in vivo experiment, histomorphometric analysis, it was observed that the BCP platform loaded with extremely low concentration BMP-2 (0.01 mg/ml) induced a significantly larger amount of new bones at 8 weeks compared to the conventional soaking method in the rabbit calvarium onlay graft model.

Methods for the Assembly and Characterization of Polyelectrolyte Multilayers as Microenvironments to Modulate Human Mesenchymal Stromal Cell Response

Thin films are of interest in materials design because they allow for the modification of surface properties of materials while the bulk properties of the material are largely unaffected. In this work, we outline methods for the assembly of thin films using a technique known as layer-by-layer (LbL). Furthermore, their interactions with human mesenchymal stromal cells (hMSCs) are discussed. hMSCs are a subject of growing interest because of their potential to treat or cure diseases, given their immunosuppressive properties, multipotent differentiation capabilities, and tissue regeneration capabilities. Numerous improvements and modifications have been suggested for the harvesting, treatment, and culture of hMSCs prior to their administration in human subjects. Here, we discuss methods to assess the interactions of hMSCs with thin LbL-assembled films of heparin and collagen. Three different methods are discussed. The first details the preparation of heparin/collagen multilayers on different surfaces and the seeding of cells on these multilayers. The second method details the characterization of multilayers, including techniques to assess the thickness, roughness, and surface charge of the multilayers, as well as in situ deposition of multilayers. The third method details the analysis of cell interactions with the multilayers, including techniques to assess proliferation, viability, real-time monitoring of hMSC behavior, analysis of hMSC-adhesive proteins on the multilayers, immunomodulatory factor expression of hMSCs, and cytokine expression on heparin/collagen multilayers. We propose that the methods described in this work will assist in the design and characterization of LbL-assembled thin films and the analysis of hMSCs cultured on these thin films.

Real-time monitoring of human Schwann cells on heparin-collagen coatings reveals enhanced adhesion and growth factor response

In this work, we evaluate the enhancing effect of six bilayers of heparin/collagen (HEP/COL)₆ layer-by-layer coatings on human Schwann cell (hSCs) adhesion and proliferation in the presence or absence of nerve growth factor (NGF). hSCs behavior and in vitro bioactivity were studied during six days of culture using end-point viability and proliferation assays as well as an impedance-based real-time monitoring system. An end-point viability assay revealed that hSCs cultured on the (HEP/COL)₆ coatings increased their growth by more than 230% compared to controls. However, an EdU proliferation assay revealed that the proliferation rate of hSCs in all conditions were similar, with 45% of cells proliferating after 18 hours of incubation. Fluorescence microscopy revealed that hSCs spreading was similar between the tissue culture plastic control and the (HEP/COL)₆. The presence of NGF in solution resulted in cells with a larger spread area. Real-time monitoring of hSCs seeded on (HEP/COL)₆ with and without NGF reveals that initial cell adhesion is improved by the presence of the (HEP/COL)₆ coatings, and it is further improved by the presence of NGF. Our results suggest that (HEP/COL)₆ coatings enhance Schwann cell behavior and response to NGF. This simple modification could be applied to current nerve regeneration strategies to improve the repair of damaged nerve.

Potential of Manuka Honey as a Natural Polyelectrolyte to Develop Biomimetic Nanostructured Meshes With Antimicrobial Properties

The use of antibiotics has been the cornerstone to prevent bacterial infections; however, the emergency of antibiotic-resistant bacteria is still an open challenge. This work aimed to develop a delivery system for treating soft tissue infections for: (1) reducing the released antimicrobial amount, preventing drug-related systemic side effects; (2) rediscovering the beneficial effects of naturally derived agents; and (3) preserving the substrate functional properties. For the first time, Manuka honey (MH) was proposed as polyelectrolyte within the layer-by-layer assembly. Biomimetic electrospun poly(ε-caprolactone) meshes were treated via layer-by-layer assembly to obtain a multilayered nanocoating, consisting of MH as polyanion and poly-(allylamine-hydrochloride) as polycation. Physicochemical characterization demonstrated the successful nanocoating formation. Different cell lines (human immortalized and primary skin fibroblasts, and primary endothelial cells) confirmed positively the membranes cytocompatibility, while bacterial tests using Gram-negative and Gram-positive bacteria demonstrated that the antimicrobial MH activity was dependent on the concentration used and strains tested.

A self-assembly and higher order structure forming triple helical protein as a novel biomaterial for cell proliferation

Collagen plays a critical role in the structural design of the extracellular matrix (ECM) and cell signaling in mammals, which makes it one of the most promising biomaterials with versatile applications. However, there is considerable concern regarding the purity and predictability of the product performance. At present, it is mainly derived as a mixture of collagen (different types) from animal tissues, where the selective enrichment of a particular type of collagen is generally difficult and expensive. Collagen derived from bovine sources poses the risk of transmitting diseases and can cause adverse immunologic and inflammatory responses. Hence, recombinant collagen can be a good alternative. Nevertheless, the necessity of post-translational hydroxyproline (Hyp) modification limits large-scale recombinant collagen production. Here, we recombinantly expressed the collagen-like protein (CLTP) and genetically introduced the Hyp in the CLTP to form a higher order self-assembled fibril structure, similar to human collagen. During the current study, it was observed that the Hyp incorporated CLTP protein (CLTHP) formed a stable triple helical polyproline-II like structure and self-assembled to form fibrils at neutral pH, which had an initial lag phase followed by a growth phase similar to animal collagen. In contrast, the higher order fibrillar assembly was missing in the nonhydroxylated CLTP. This study demonstrated that CLTHP self-association is based on the common underlying lateral interactions between triple helical structured proteins, where the hydroxyproline forms the significantly stable hydration network. Hence, this work will be the first fundamental empirical research for flexible modifications of recombinant collagen for structural analysis and biomedical applications.

Treated dentin matrix particles combined with dental follicle cell sheet stimulate periodontal regeneration

OBJECTIVE

Periodontal tissue engineering is an attractive approach for restoring periodontal-supporting structures and functions. However, complete periodontal regeneration has not been accomplished. Previous studies demonstrated the feasibility of using cell sheets and treated dentin matrix (TDM) to regenerate bio-roots.

METHODS

In this study, we regenerated periodontal tissue using cell sheets combined with TDM particles (TDMPs). Human dental follicle cells (hDFCs) were isolated and characterized. Human dental follicle cells sheets (hDFCSs) and human TDMPs (hTDMP) were fabricated and characterized. The osteogenic effect of hTDMP was evaluated on human bone marrow stromal cells (hBMSCs) in vitro and a rat calvarial bone defect in vivo. Real-time PCR, western blotting, radiograph analysis, and histological analysis were performed to evaluate the periodontal induction capacity of hTDMP. One-wall periodontal intrabony defects were prepared to evaluate the periodontal regeneration capacity of TDMP/DFCSs on beagle dogs.

RESULTS

The results showed that hDFCs were mesenchymal stem cells. hTDMP promoted the proliferation and osteogenic differentiation of hBMSCs. New bone formation was observed in the rat calvarial bone defect zone in both the hTDMP and hydroxyapatite/β-tricalcium phosphate groups. Periodontal-like tissues showed better regeneration in the canine TDMP+DFCS group than in the other groups.

SIGNIFICANCE

These results demonstrate the potential of using TDMP/DFCSs in periodontal regeneration.

Multilayer nanoscale functionalization to treat disorders and enhance regeneration of bone tissue

The coatings application onto medical devices has experienced a continuous growth in the last few years. Medical device coating market is expected to grow at a CAGR of 5.16% to reach USD 10 million by 2023 due to the increasing geriatric population and the growing demand for continuous innovation. Layer-by-Layer (LbL) assembly represents a versatile method to modify the surface properties, in order to control cell interaction and thus enhance biological functions. Furthermore, LbL is environmentally friendly, able to coat all types of surfaces with the creation of homogenous film and to include and control the release of biomolecules/drugs. This feature review provides a critical overview on recent progresses in functionalizing materials by LbL assembly for bone regeneration and disorder treatment. An overview of emerging and visionary opportunities on LbL technologies and further combination with other existing methods used in biomedical field, is also discussed to evidence the new challenges and potential developments in bone regenerative medicine.

Layer-by-layer adsorption: Factors affecting the choice of substrates and polymers

The electrostatic layer-by-layer technique for fabrication of multi-layered structures of various sizes and shapes using flat and colloidal templates coupled with polyelectrolyte layer-forming materials has attracted significant interest among both academic and industrial researchers due to its versatility and relative simplicity of the procedures involved in its execution. Fabrication of the multi-layered structures using the electrostatic layer-by-layer method involves several distinct stages each of which holds great importance when considering the production of a high-quality product. These stages include selection of materials (both template and a pair of construction polyelectrolytes), adsorption of the first polyelectrolyte layer onto the selected templates, formation of the second layer comprised of the oppositely charged polyelectrolyte and guided by the interactions between the two chosen polyelectrolytes, and multi-layering, where a selected number of layers are produced, and which is conditioned by both intrinsic properties of the involved construction materials and external fabrication conditions such as temperature, pH and ionic strength. The current review summarises the most important aspects of each stage mentioned above and gives examples of the materials suitable for utilization of the technique and describes the underlying physics involved.

[Implantation strategy of tissue-engineered liver based on decellularized spleen matrix in rats]

OBJECTIVE

To explore the optimal implantation strategy of tissue-engineered liver (TEL) constructed based on decellularized spleen matrix (DSM) in rats.

METHODS

DSM was prepared by freeze-thawing and perfusion with sodium dodecyl sulfate (SDS) of the spleen of healthy SD rats. Primary rat hepatocytes isolated using modified Seglen 2-step perfusion method were implanted into the DSM to construct the TEL. The advantages and disadvantages were evaluated of 4 transplant strategies of the TEL, namely ectopic vascular anastomosis, liver cross-section suture transplantation, intrahepatic insertion and mesenteric transplantation.

RESULTS

The planting rate of hepatocytes in the DSM was (74.5∓7.7)%. HE staining and scanning electron microscopy showed satisfactory cell status, and immunofluorescence staining confirmed the normal expression of ALB and G6Pc in the cells. For TEL implantation, ectopic vascular anastomosis was difficult and resulted in a mortality rate of 33.3% perioperatively and massive thrombus formation in the matrix within 6 h. Hepatic cross-section suture failed to rapidly establish sufficient blood supply, and no viable graft was observed 3 days after the operation. With intrahepatic insertion method, the hepatocytes in the DSM could survive as long as 14 days. Mesenteric transplantation resulted in a hepatocyte survival rate of (38.3+7.1)% at 14 days after implantation.

CONCLUSION

TEL constructed based on DSM can perform liver-specific functions with a good cytological bioactivity. Mesenteric transplantation of the TEL, which is simple, safe and effective, is currently the optimal transplantation strategy.

Application of Heparin/Collagen-REDV Selective Active Interface on ePTFE Films to Enhance Endothelialization and Anticoagulation

Expanded polytetrafluoroethylene (ePTFE) prosthetic valves have been widely used in clinical applications in Asian countries. However, these valves still have limits with regard to thrombosis, neointimal hyperplasia, restenosis, and valvar vegetation. The achievement of in situ endothelialization on implant materials is a promising way to overcome those limits. Here, heparin/collagen multilayers were fabricated on ePTFE films via a layer-by-layer (LBL) self-assembly technique, and then, the endothelial cell (EC) adhesive peptide sequence Arg-Glu-Asp-Val (REDV) was immobilized on the multilayers. After modification with the heparin/collagen multilayers with or without REDV peptide, less platelet activation and aggregation were observed, the blood coagulation time was increased, and the hemolysis rate was decreased compared to that on pristine ePTFE films. The REDV-functionalized ePTFE films positively impacted early EC adhesion, later cell proliferation and cell activity. The EC barrier was confirmed to be successfully achieved on the functionalized ePTFE film surface in vitro. The successful assembly of the REDV-functionalized heparin/collagen multilayer on ePTFE films improved the blood compatibility, anticoagulant properties, and cell compatibility of the films in vitro, and thus, represents a candidate approach for applications requiring quick in situ endothelialization in vivo.

Guided osteoporotic bone regeneration with composite scaffolds of mineralized ECM/heparin membrane loaded with BMP2-related peptide

Introduction

At present, the treatment of osteoporotic defects poses a great challenge to clinicians, owing to the lower regeneration capacity of the osteoporotic bone as compared with the normal bone. The guided bone regeneration (GBR) technology provides a promising strategy to cure osteoporotic defects using bioactive membranes. The decellularized matrix from the small intestinal submucosa (SIS) has gained popularity for its natural microenvironment, which induces cell response.

Materials and methods

In this study, we developed heparinized mineralized SIS loaded with bone morphogenetic protein 2 (BMP2)-related peptide P28 (mSIS/P28) as a novel GBR membrane for guided osteoporotic bone regeneration. These mSIS/P28 membranes were obtained through the mineralization of SIS (mSIS), followed by P28 loading onto heparinized mSIS. The heparinized mSIS membrane was designed to improve the immobilization efficacy and facilitate controlled release of P28. P28 release from mSIS-heparin-P28 and its effects on the proliferation, viability, and osteogenic differentiation of bone marrow stromal stem cells from ovariectomized rats (rBMSCs-OVX) were investigated in vitro. Furthermore, a critical-sized OVX calvarial defect model was used to assess the bone regeneration capability of mSIS-heparin-P28 in vivo.

Results

In vitro results showed that P28 release from mSIS-heparin-P28 occurred in a controlled manner, with a long-term release time of 40 days. Moreover, mSIS-heparin-P28 promoted cell proliferation and viability, alkaline phosphatase activity, and mRNA expression of osteogenesis-related genes in rBMSCs-OVX without the addition of extra osteogenic components. In vivo experiments revealed that mSIS-heparin-P28 dramatically stimulated osteoporotic bone regeneration.

Conclusion

The heparinized mSIS loaded with P28 may serve as a potential GBR membrane for repairing osteoporotic defects.

Polyelectrolyte multi-layers assembly of SiCHA nanopowders and collagen type I on aminolysed PLA films to enhance cell-material interactions

This paper presents a new approach in assembling bone extracellular matrix components onto PLA films, and investigates the most favourable environment which can be created using the technique for cell-material interactions. Poly (lactic acid) (PLA) films were chemically modified by covalently binding the poly(ethylene imine) (PEI) as to prepare the substrate for immobilization of polyelectrolyte multilayers (PEMs) coating. Negatively charged polyelectrolyte consists of well-dispersed silicon-carbonated hydroxyapatite (SiCHA) nanopowders in hyaluronic acid (Hya) was deposited onto the modified PLA films followed by SiCHA in collagen type I as the positively charged polyelectrolyte. The outermost layer was finally cross-linked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrocholoride and N-hydroxysulfosuccinimide sodium salt (EDC/NHS) solutions. The physicochemical features of the coated PLA films were monitored via X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscope (AFM). The amounts of calcium and collagen deposited on the surface were qualitatively and quantitatively determined. The surface characterizations suggested that 5-BL has the optimum surface roughness and highest amounts of calcium and collagen depositions among tested films. In vitro human mesenchymal stem cells (hMSCs) cultured on the coated PLA films confirmed that the coating materials greatly improved cell attachment and survival compared to unmodified PLA films. The cell viability, cell proliferation and Alkaline Phosphatase (ALP) expression on 5-BL were found to be the most favourable of the tested films. Hence, this newly developed coating materials assembly could contribute to the improvement of the bioactivity of polymeric materials and structures aimed to bone tissue engineering applications.

Inflammation-responsive self-regulated drug release from ultrathin hydrogel coating

Heterotopic ossification(HO) is a potential severe complication after many biomaterial implanting surgeries, and the inflammation environment caused by the implanting-associated infections is considered as the main nosogenesis. Herein, an inflammation-responsive drug release system was designed by chemically conjugating indometacin (via ester group) onto hydrogel coating to realize local self-regulated drug release to prevent HO. In our strategy, poly(3-mercaptopropyl)trimethoxysilane-co-acrylic acrylate and polyvinyl alcohol (providing anchoring sites for drug molecules) were firstly synthesized and functionalized with ene-groups, then a hydrogel layer was formed and covalently attached onto thiol-modified substrate via thiol-ene click chemistry, followed by grafting indometacin. A porous structure of the attached hydrogel layer was observed by scanning electron microscopy, and the presence of drug molecules in the hydrogel layer was confirmed by X-ray photoelectron spectroscopy and UV-vis absorption spectra. The drug release could be triggered under the mimicking inflammation environment, and the release rate was responsive to the inflammation degree. In addition, after attaching the hydrogel coating, the substrate showed low cytotoxicity, and high promotion for cell adhesion and proliferation. The excellent hemocompatibility of the hydrogel coating was also demonstrated by prolonged clotting time and suppressed platelet adhesion. This work suggests that the inflammation-responsive indometacin conjugated hydrogel coating has great potential to be used for prophylaxis HO.

Biosynthetic PCL-graft-Collagen Bulk Material for Tissue Engineering Applications

Biosynthetic materials have emerged as one of the most exciting and productive fields in polymer chemistry due to their widespread adoption and potential applications in tissue engineering (TE) research. In this work, we report the synthesis of a poly(ε-caprolactone)-graft-collagen (PCL-g-Coll) copolymer. We combine its good mechanical and biodegradable PCL properties with the great biological properties of type I collagen as a functional material for TE. PCL, previously dissolved in dimethylformamide/dichloromethane mixture, and reacted with collagen using carbodiimide coupling chemistry. The synthesised material was characterised physically, chemically and biologically, using pure PCL and PCL/Coll blend samples as control. Infrared spectroscopy evidenced the presence of amide I and II peaks for the conjugated material. Similarly, XPS evidenced the presence of C-N and N-C=O bonds (8.96 ± 2.02% and 8.52 ± 0.63%; respectively) for PCL-g-Coll. Static contact angles showed a slight decrease in the conjugated sample. However, good biocompatibility and metabolic activity was obtained on PCL-g-Coll films compared to PCL and blend controls. After 3 days of culture, fibroblasts exhibited a spindle-like morphology, spreading homogeneously along the PCL-g-Coll film surface. We have engineered a functional biosynthetic polymer that can be processed by electrospinning.

Biomimetic Principles to Develop Blood Compatible Surfaces

Functionalized biomaterial surface patterns capable of resisting nonspecific adsorption while retaining their bioactivity are crucial in the advancement of biomedical technologies, but currently available biomaterials intended for use in whole blood frequently suffer from nonspecific adsorption of proteins and cells, leading to a loss of activity over time. In this review, we address two concepts for the design and modification of blood compatible biomaterial surfaces, zwitterionic modification and surface functionalization with glycans – both of which are inspired by the membrane structure of mammalian cells – and discuss their potential for biomedical applications.