Impact of changes in collagen construction and molecular state on integrin - binding properties.

The interaction between the integrin and collagen is important in cell adhesion and signaling. Collagen, as the main component of extracellular matrix, is a base material for tissue engineering constructs. In tissue engineering, the collagen structure and molecule state may be altered to varying degrees in the process of processing and utilizing, thereby affecting its biological properties. In this work, the impact of changes in collagen structure and molecular state on the binding properties of collagen to integrin α2ß1 and integrin specific cell adhesion were explored. The results showed that the molecular structure of collagen is destroyed under the influence of heating, freeze-grinding and irradiation, the triple helix integrity is reduced and molecular breaking degree is increased. The binding ability of collagen to integrin α2ß1 is increased with the increase of triple helix integrity and decays exponentially with the increase of molecular breaking degree. The collagen molecular state can also influences the binding ability of collagen to cellular receptor. The collagen fibrils binding to integrin α2ß1 and HT1080 cells is stronger than to collagen monomolecule. Meanwhile, the hybrid fibril exhibits a different cellular receptor binding performance from corresponding single species collagen fibril. These findings provide ideas for the design and development of new collagen-based biomaterials and tissue engineering research.

Electrospun Nanofibrous Conduit Filled with a Collagen-Based Matrix (ColM) for Nerve Regeneration.

Traumatic nerve defects result in dysfunctions of sensory and motor nerves and are usually accompanied by pain. Nerve guidance conduits (NGCs) are widely applied to bridge large-gap nerve defects. However, few NGCs can truly replace autologous nerve grafts to achieve comprehensive neural regeneration and function recovery. Herein, a three-dimensional (3D) sponge-filled nanofibrous NGC (sf@NGC) resembling the structure of native peripheral nerves was developed. The conduit was fabricated by electrospinning a poly(L-lactide-co-glycolide) (PLGA) membrane, whereas the intraluminal filler was obtained by freeze-drying a collagen-based matrix (ColM) resembling the extracellular matrix. The effects of the electrospinning process and of the composition of ColM on the physicochemical performance of sf@NGC were investigated in detail. Furthermore, the biocompatibility of the PLGA sheath and ColM were evaluated. The continuous and homogeneous PLGA nanofiber membrane had high porosity and tensile strength. ColM was shown to exhibit an ECM-like architecture characterized by a multistage pore structure and a high porosity level of over 70%. The PLGA sheath and ColM were shown to possess stagewise degradability and good biocompatibility. In conclusion, sf@NGC may have a favorable potential for the treatment of nerve reconstruction.

Fabrication, characterization and potential application of biodegradable polydopamine-modified scaffolds based on natural macromolecules.

Sodium alginate (SA)-based implantable scaffolds with slow-release drugs have become increasingly important in the fields of biomedical and tissue engineering. However, high-molecular-weight SA is difficult to remove from the body due to the lack of SA-degrading enzymes. The very slow degradation properties of SA-based scaffolds limit their applications. Herein, we designed a series of biodegradable oxidized SA (OSA)-based scaffolds through amide bonds, imine bonds and hydrogen bridges between OSA and silk fibroin (SF). SF/OSA-0.4 with a blend ratio of 4/1 was chosen for further polydopamine (PDA) surface modification studies through the optimization of those parameters such as different OSA oxidation degrees, and blend ratios. PDA modified SF/OSA-0.4 (Dopa/SF/OSA-0.4) showed the excellent stability, better stretchable properties, a uniform interconnective porous structure, high thermal stability, a low hemolysis ratio and cytotoxicity. In vitro degradation experiments showed that the degradation rate of SF/OSA was significantly higher than that of SF/SA, but the degradation slowed again after PDA modification. Interestingly, the degradation of Dopa/SF/OSA-0.4 in vivo was significantly faster than that in vitro. Dopa/SF/OSA-0.4 was also more conducive to new tissue growth and collagen bundle formation. Moreover, Dopa/SF/OSA-0.4 improved the absorbability of RhB (model drug) and reduced the sudden release of RhB during the sustained release.

A Biomimetic Composite Bilayer Dressing Composed of Alginate and Fibroin for Enhancing Full-Thickness Wound Healing.

Full-thickness skin wound dressings are critically important for acute cutaneous wound healing. In this study, a bilayer sheet originating from biological macromolecules, mimicking skin hierarchy structure is developed. This sheet is composed of a steady silk fibroin (SF)/sodium alginate (SA) composite scaffold as the bottom regenerative layer and a SA film as the protective top layer. Scanning electron microscope analysis revealed the thickness of the top layer is ≈25 µm and is tightly adhered to the composite scaffold layer with interconnected pores (≈150 µm). The bilayer sheets are displayed suitable water uptake capacity and high stability in water. The mass retention percentage of the bilayer sheets is ≈50% during three weeks of PBS degradation in vitro. The tensile strength of the bilayer sheets is significantly increased from 13.41 ± 3.75 kPa (single scaffold) to 59.81 ± 5.98 kPa. The composite scaffolds are more conducive to the growth and proliferation of human dermal microvascular endothelial cells. The experiment results in vivo are demonstrated superior and faster epithelialization and dermal regeneration in the wound treated with bilayer sheets because the sheets are accelerated wound closure, reduced the inflammatory response, and promoted protein synthesis in the extracellular matrix and blood vessel ingrowth.

Repairing Transected Peripheral Nerve Using a Biomimetic Nerve Guidance Conduit Containing Intraluminal Sponge Fillers.

Nerve guide conduits (NGCs) with geometric design have shown significant advantages in guidance of nerve reinnervation across the defect of injured peripheral nerves. It is realized that intraluminal fillers with distinctive structure can effectively provide an inner guidance for sprouting of axons and improve the permeability of NGC. In this work, a poly(lactic-co-glycolic acid) (PLGA) NGC is prepared containing intraluminal sponge fillers (labeled as ISF-NGC) and used for reconstruction of a rat sciatic nerve with a 10 mm gap. For comparison, the same procedure is applied to a single hollow PLGA NGC (labeled as H-NGC) and an autologous nerve. As evidenced by significantly improved nerve morphology and function, the ISF-NGC achieves a superior nerve repair effect over H-NGC, which is comparable to autologous nerve grafting. It is likely that the H-NGC only provides a protected tunnel for nerve fiber regrowth and axonal extension, while ISF-NGC offers an extracellular matrix-mimetic architecture as autograft to provide contact guidance for nerve reinnervation. This newly developed ISF-NGC is a promising candidate to aid nerve reinnervation across longer gaps commonly encountered in clinical cases.

Large-scale and fast synthesis of nano-hydroxyapatite powder by a microwave-hydrothermal method.

A microwave-hydrothermal (M-H) method assisted with ultrasonic atomization precipitation was developed for large-scale and fast synthesis of nano-hydroxyapatite (nano-HAP) powder. This technology combines the uniform mixing effect of ultrasonic atomization precipitation at high concentration with the rapid and uniform heating effect of the M-H method, aiming to obtain a high quality product with low agglomeration, homogeneous size distribution, accurate stoichiometry, and high purity while improving the yield. The influences of reaction temperature, reaction time and reactant concentration on the formation of nano-HAP were investigated. The results show that the crystallinity increases significantly and the diameter of nano-HAP increases to some extent, but the length does not change obviously while the reaction temperature increase from 60 °C to 160 °C and the reaction time increases from 1 minute to 40 minutes respectively. The crystallinity, dispersion and crystal size of nano-HAP do not change obviously while the concentration of Na2HPO4·12H2O increases from 0.06 mol L-1 to 0.4 mol L-1. When the reaction temperature is 160 °C, the reaction time is 40 min, and the concentration of Na2HPO4·12H2O is 0.4 mol L-1, the yield of nano-HAP powder achieved a maximum yield (0.033 kg L-1). The obtained nano-HAP powder exhibits a uniform size and good dispersibility, with a size of 87.62 ± 22.44 nm and crystallinity of 0.92, respectively. This study indicates that the M-H method assisted with ultrasonic atomization precipitation is a facile one-pot method for the rapid and large-scale synthesis of highly crystalline, dispersible nano-HAP particles.

Correction: Large-scale and fast synthesis of nano-hydroxyapatite powder by a microwave-hydrothermal method.

[This corrects the article DOI: 10.1039/C9RA00091G.].

Development and biocompatibility evaluation of biodegradable bacterial cellulose as a novel peripheral nerve scaffold.

Peripheral nerve injury is a serious medical problem and severely affects normal life of patient. Bacterial cellulose (BC) is considered as a novel promising biomaterial for tissue engineering, but the poor biodegradability limits its application. In this study, biodegradable bacterial cellulose scaffolds were prepared with different oxidation degrees (O.Ds.) using sodium periodate, evaluating their potential application in peripheral nerve repair. The chemical structure and surface morphology of the oxidized bacterial cellulose (OBC) scaffolds were characterized using Fourier transform infrared spectroscopy, Wide angle X-ray diffraction, and Scanning electron microscope. The porosity, mechanical properties, and degradation behavior of the OBC series scaffolds were extensively examined. Cellular viability and blood compatibility of OBC scaffolds were studied by MTT assay and hemolytic test using Schwann cells (SCs) and red blood cells (RBCs), respectively. The results demonstrated that the biodegradability of OBC scaffolds was improved significantly. OBC scaffolds with lower O.Ds. displayed high porosity with interconnected pores, suitable mechanical property, and biodegradability for peripheral nerve repair. In vitro cytotoxicity and hemolysis test analysis indicated that OBC0.05/3 scaffold is cellular and blood compatible, demonstrating its potential application as a good candidate for peripheral nerve repair. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1288-1298, 2018.

Development of a novel morphological paclitaxel-loaded PLGA microspheres for effective cancer therapy: in vitro and in vivo evaluations.

Sustained release of therapeutic agents into tumor cells is a potential approach to improve therapeutic efficacy, decrease side effects, and the drug administration frequency. Herein, we used the modified double-emulsion solvent evaporation (DSE) method to prepare a novel morphological paclitaxel (PTX) loaded poly(lactide-co-glycolide) (PLGA) microspheres (MS). The prepared rough PTX-PLGA-MS possessed microporous surface and highly porous internal structures, which significantly influenced the drug entrapment and release behaviors. The rough MS with an average particle size of 53.47 ± 2.87 µm achieved high drug loading (15.63%) and encapsulation efficiency (92.82%), and provided a favorable sustained drug release. The in vitro antitumor tests of flow cytometry and fluoroimmunoassay revealed that the rough PTX-PLGA-MS displayed effective anti-gliomas activity and enhanced the cellular PTX uptake through adsorptive endocytosis. Both in vitro and in vivo antitumor results demonstrated that the sustained-release PTX could induce the microtubules assembly and the over-expression of Bax and Cyclin B1 proteins, resulting in the microtubule dynamics disruption, G2/M phase arrest, and cell apoptosis accordingly. Furthermore, as the rough PTX-PLGA-MS could disperse and adhere throughout the tumor sites and cause extensive tumor cell apoptosis with one therapeutic course (12 days), they could reduce the system toxicity and drug administration frequency, thus achieving significant tumor inhibitory effects with rapid sustained drug release. In conclusion, our results verified that the rough PTX-PLGA-MS drug release system could serve as a promising treatment to malignant glioma.

Paclitaxel-loaded PLGA microspheres with a novel morphology to facilitate drug delivery and antitumor efficiency.

The aim of this study was to develop a novel morphological paclitaxel (PTX) loaded poly(lactide-co-glycolide) (PLGA) microspheres (MS) delivery system to enhance drug delivery and antitumor efficiency as well as reduce drug administration frequency. Therefore, different morphological types of PTX-PLGA-MS were prepared using a modified solvent evaporation technique. Morphology analysis confirmed the successful preparation of the smooth PTX-PLGA-MS with internal sporadic porosity, and the novel rough PTX-PLGA-MS with microporous surface and porous internal structures. The PTX drugs were distributed in the readily bioavailable state (amorphous) in PTX-loaded MS, which allowed fast drug release from MS following intratumoral administration. The drug entrapment and release behaviors indicated that the rough MS could provide enough hydrophobic space for PTX-loading and deep surface folds for fast matrices degradation, thus achieving a higher drug-loading efficiency (17.8%) and a rapid sustained drug release effect. Furthermore, the rough MS showed strengthened in vitro anti-hepatoma efficiency than that of free PTX and smooth MS. The in vivo studies indicated remarkable antitumor activity of rough MS (tumor inhibition rate = 58.33%) for at least 13 days after a single injection, which was because the rapid sustained-release drugs could induce the pro-apoptosis gene and protein expressions, cause extensive tumor cell apoptosis, and reduce the toxicity to normal tissues. In conclusion, the rough PTX-PLGA-MS drug delivery system with outstanding tumor growth inhibition effect could serve as a promising treatment for liver tumor.

A Biomimetic Silk Fibroin/Sodium Alginate Composite Scaffold for Soft Tissue Engineering.

A cytocompatible porous scaffold mimicking the properties of extracellular matrices (ECMs) has great potential in promoting cellular attachment and proliferation for tissue regeneration. A biomimetic scaffold was prepared using silk fibroin (SF)/sodium alginate (SA) in which regular and uniform pore morphology can be formed through a facile freeze-dried method. The scanning electron microscopy (SEM) studies showed the presence of interconnected pores, mostly spread over the entire scaffold with pore diameter around 54~532 µm and porosity 66~94%. With significantly better water stability and high swelling ratios, the blend scaffolds crosslinked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) provided sufficient time for the formation of neo-tissue and ECMs during tissue regeneration. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) results confirmed random coil structure and silk I conformation were maintained in the blend scaffolds. What's more, FI-TR spectra demonstrated crosslinking reactions occurred actually among EDC, SF and SA macromolecules, which kept integrity of the scaffolds under physiological environment. The suitable pore structure and improved equilibrium swelling capacity of this scaffold could imitate biochemical cues of natural skin ECMs for guiding spatial organization and proliferation of cells in vitro, indicating its potential candidate material for soft tissue engineering.

Influence of hydroxyl-terminated polydimethylsiloxane on high-strength biocompatible polycarbonate urethane films.

The present study describes a series of novel polycarbonate urethane films that were fabricated via the solution-casting method from 4,4'-methylenebis(cyclohexyl isocyanate) (H12MDI) and 1,4-butanediol (BDO) chain extender as hard segments, poly(1,6-hexanediol)carbonate diols (PCDL) and hydroxyl-terminated polydimethylsiloxane (PDMS) as soft segments, with dibutyltin dilaurate as the catalyst. Varied molar ratios of PDMS (less than 30%) were utilized to enhance the mechanical properties and biocompatibilities. The microstructure and degrees of phase separation were characterized using atomic force microscopy. The chemical structure and surface morphology of the materials were further confirmed by attenuated total reflectance Fourier transform infrared spectroscopy, 1H NMR and 13C NMR, water droplet contact angle and scanning electron microscopy. Thermal properties were measured by differential scanning calorimetry. MTT assay and hemolytic tests were studied for evaluating cellular viability and hemocompatibility of fabricated films using L929 fibroblast cells and adult rabbit blood. The results demonstrated polyurethane films with soft segments partially replaced by PDMS could remarkably improve the biocompatibility while maintaining relatively stable mechanical behavior, making them exciting potential candidates for artificial vessels or other tissue engineering applications.

Water proof and strength retention properties of thermoplastic starch based biocomposites modified with glutaraldehyde.

Water proof and strength retention properties of thermoplastic starch (TPS) resins were successfully improved by reacting glutaraldehyde (GA) with starch molecules during their gelatinization processes. Tensile strength (σf) values of initial and aged TPS100BC0.02GAx and (TPS100BC0.02GAx)75PLA25 specimens improved significantly to a maximal value as GA contents approached an optimal value, while their moisture content and elongation at break values reduced to a minimal value, respectively, as GA contents approached the optimal value. The σf retention values of (TPS100BC0.02GA0.5)75PLA25 specimen aged for 56 days are more than 50 times higher than those of corresponding aged TPS and TPS100BC0.02 specimens, respectively. New melting endotherms and diffraction peaks of VH-type starch crystals were found on DSC thermograms and WAXD patterns of aged TPS or TPS100BC0.02 specimens, respectively, while negligible retrogradation effect was found for most aged TPS100BC0.02GAx and/or (TPS100BC0.02GAx)75PLA25 specimens.