Facilitated and Controlled Strontium Ranelate Delivery Using GCS-HA Nanocarriers Embedded into PEGDA Coupled with Decortication Driven Spinal Regeneration.

BACKGROUND AND PURPOSE: Strontium ranelate (SrR) is an oral pharmaceutical agent for osteoporosis. In recent years, numerous unwanted side effects of oral SrR have been revealed. Therefore, its clinical administration and applications are limited. Hereby, this study aims to develop, formulate, and characterize an effective SrR carrier system for spinal bone regeneration. METHODS: Herein, glycol chitosan with hyaluronic acid (HA)-based nanoformulation was used to encapsulate SrR nanoparticles (SrRNPs) through electrostatic interaction. Afterward, the poly(ethylene glycol) diacrylate (PEGDA)-based hydrogels were used to encapsulate pre-synthesized SrRNPs (SrRNPs-H). The scanning electron microscope (SEM), TEM, rheometer, Fourier-transform infrared spectroscopy (FTIR), and dynamic light scattering (DLS) were used to characterize prepared formulations. The rabbit osteoblast and a rat spinal decortication models were used to evaluate and assess the developed formulation biocompatibility and therapeutic efficacy. RESULTS: In vitro and in vivo studies for cytotoxicity and bone regeneration were conducted. The cell viability test showed that SrRNPs exerted no cytotoxic effects in osteoblast in vitro. Furthermore, in vivo analysis for new bone regeneration mechanism was carried out on rat decortication models. Radiographical and histological analysis suggested a higher level of bone regeneration in the SrRNPs-H-implanted groups than in the other experimental groups. CONCLUSION: Local administration of the newly developed formulated SrR could be a promising alternative therapy to enhance bone regeneration in bone-defect sites in future clinical applications.

New Insight into Natural Extracellular Matrix: Genipin Cross-Linked Adipose-Derived Stem Cell Extracellular Matrix Gel for Tissue Engineering.

The cell-derived extracellular matrix (ECM) is associated with a lower risk of pathogen transfer, and it possesses an ideal niche with growth factors and complex fibrillar proteins for cell attachment and growth. However, the cell-derived ECM is found to have poor biomechanical properties, and processing of cell-derived ECM into gels is scarcely studied. The gel provides platforms for three-dimensional cell culture, as well as injectable biomaterials, which could be delivered via a minimally invasive procedure. Thus, in this study, an adipose-derived stem cell (ADSC)-derived ECM gel was developed and cross-linked by genipin to address the aforementioned issue. The genipin cross-linked ADSC ECM gel was fabricated via several steps, including rabbit ADSC culture, cell sheets, decellularization, freeze-thawing, enzymatic digestion, neutralization of pH, and cross-linking. The physicochemical characteristics and cytocompatibility of the gel were evaluated. The results demonstrated that the genipin cross-linking could significantly enhance the mechanical properties of the ADSC ECM gel. Furthermore, the ADSC ECM was found to contain collagen, fibronectin, biglycan, and transforming growth factor (TGF)-ß1, which could substantially maintain ADSC, skin, and ligament fibroblast cell proliferation. This cell-derived natural material could be suitable for future regenerative medicine and tissue engineering application.

Microplasma Cross-Linked Graphene Oxide-Gelatin Hydrogel for Cartilage Reconstructive Surgery.

Herein, we report the cartilage tissue engineering application of nanographene oxide (NGO)-reinforced gelatin hydrogel fabricated by utilizing a microplasma-assisted cross-linking method. NGO sheets with surface functionalities were introduced to enhance the mechanical and biomedical properties of gelatin-based hydrogels. Highly energetic reactive radicals were generated from the nonthermal plasma (NTP), which is used to facilitate the cross-linking and polymerization during the polymeric hydrogel fabrication. The NTP treatment substantially reinforced a small amount (1 wt %) of NGO into the gelatin hydrogel. Systematic material characterization thus shows that the fabricated hydrogel possessed unique properties such as moderate surface roughness and adhesiveness, suitable pores sizes, temperature-dependent viscoelasticity, and controllable degradability. In vitro studies demonstrated that the as-fabricated hydrogel exhibited excellent cell-material interactions with SW 1353 cells, bone marrow-derived mesenchymal stem cells, and a rat chondrocyte cell line, thereby exhibiting appropriate cytocompatibility for cartilage tissue engineering applications. Furthermore, an in vivo study indicated that the formation of a healthy hyaline cartilage after the microfracture was enhanced by the fabricated hydrogel implant, offering a potential biocompatible platform for microfracture-based cartilage reconstructive surgery.

A bioinspired hyperthermic macrophage-based polypyrrole-polyethylenimine (Ppy-PEI) nanocomplex carrier to prevent and disrupt thrombotic fibrin clots.

Fibrinolytic treatments for venous or arterial thrombotic syndromes using systemic administration of thrombolytics, such as streptokinase, can induce life-threatening bleeding complications. In this study, we offer the first proof of concept for a targeted photothermal fibrin clot prevention and reduction technology using macrophages loaded with polypyrrole-polyethylenimine nanocomplexes (Ppy-PEI NCs) and subjected to near-infrared radiation (NIR). We first show that the developed Ppy-PEI NCs could be taken up by defensive macrophages in vitro through endocytosis. The Ppy-PEI NCs generated local hyperthermia upon NIR treatment, which appeared to produce reactive oxygen species in Ppy-PEI NC-loaded macrophages. Preliminary evidence of efficacy as an antithrombotic tool is provided, in vitro, using fibrinogen-converted fibrin clots, and in vivo, in a rat femoral vascular thrombosis model generated by exposure to ferric chloride substance. The in vivo biocompatibility, photothermal behavior, biodistribution, and histological observation of cellular interactions with the Ppy-PEI NCs in the rat model provide rationale in support of further preclinical studies. This Ppy-PEI NC/NIR-based method, which uses a unique macrophage-guided targeting approach to prevent and lyse fibrin clots, may potentially overcome some of the disadvantages of current thrombolytic treatments. STATEMENT OF SIGNIFICANCE: Fibrinolytic treatments for venous or arterial thrombotic syndromes using systemic administration of thrombolytics, such as streptokinase, can induce life-threatening bleeding complications. In this study, we offer the first proof of concept for a targeted photothermal fibrin clot reduction technology using macrophages loaded with polypyrrole-polyethylenimine nanocomplexes (Ppy-PEI NCs) and subjected to near-infrared radiation (NIR). We first show that the developed Ppy-PEI NCs can be taken up by defensive macrophages in vitro through endocytosis. The Ppy-PEI NCs generated local hyperthermia upon NIR treatment, which appeared to produce reactive oxygen species in Ppy-PEI NC-loaded macrophages. Preliminary evidence of efficacy as an antithrombotic tool is provided, in vitro, using fibrinogen-converted fibrin clots, and in vivo, in a rat femoral vascular thrombosis model generated by exposure to ferric chloride substance. The in vivo biocompatibility, photothermal behavior, biodistribution, and histological observation of cellular interactions with the Ppy-PEI NCs in the rat model provide rationale in support of further preclinical studies. This Ppy-PEI NC/NIR-based method, which uses a unique macrophage-guided targeting approach to disintegrate fibrin clots, may potentially overcome some of the disadvantages of current thrombolytic treatments.

A Gelatin Hydrogel-Containing Nano-Organic PEI⁻Ppy with a Photothermal Responsive Effect for Tissue Engineering Applications.

The introduction and designing of functional thermoresponsive hydrogels have been recommended as recent potential therapeutic approaches for biomedical applications. The development of bioactive materials such as thermosensitive gelatin-incorporated nano-organic materials with a porous structure and photothermally triggerable and cell adhesion properties may potentially achieve this goal. This novel class of photothermal hydrogels can provide an advantage of hyperthermia together with a reversibly transformable hydrogel for tissue engineering. Polypyrrole (Ppy) is a bioorganic conducting polymeric substance and has long been used in biomedical applications owing to its brilliant stability, electrically conductive features, and excellent absorbance around the near-infrared (NIR) region. In this study, a cationic photothermal triggerable/guidable gelatin hydrogel containing a polyethylenimine (PEI)⁻Ppy nanocomplex with a porous microstructure was established, and its physicochemical characteristics were studied through dynamic light scattering, scanning electronic microscopy, transmission electron microscopy, an FTIR; and cellular interaction behaviors towards fibroblasts incubated with a test sample were examined via MTT assay and fluorescence microscopy. Photothermal performance was evaluated. Furthermore, the in vivo study was performed on male Wistar rat full thickness excisions model for checking the safety and efficacy of the designed gelatin⁻PEI⁻Ppy nanohydrogel system in wound healing and for other biomedical uses in future. This photothermally sensitive hydrogel system has an NIR-triggerable property that provides local hyperthermic temperature by PEI⁻Ppy nanoparticles for tissue engineering applications. Features of the designed hydrogel may fill other niches, such as being an antibacterial agent, generation of free radicals to further improve wound healing, and remodeling of the promising photothermal therapy for future tissue engineering applications.

Genipin-crosslinked adipose stem cell derived extracellular matrix-nano graphene oxide composite sponge for skin tissue engineering.

Autologous skin grafts, which can cause donor site morbidity, are currently used to treat deep wounds. To improve the regeneration of poorly healing wounds, cell-derived extracellular matrix (ECM) scaffolds are garnering great research interest due to their associated lower risks of pathogen transfer and immune rejection. However, the mechanical properties of cell-derived ECM scaffolds are inferior when compared to those of tissue-derived ECM scaffolds. To overcome this drawback, different amounts (10, 20, 50, and 100 µg mL-1) of graphene oxide (GO) and genipin (1% w/v) were applied to adipose stem cell (ASC)-derived ECM sponges. There are still only a few studies employing cell-derived extracellular matrices as biomimetic scaffolds for biomedical applications. The aim of our study was to develop biocompatible, biodegradable, low immunogenic, and genipin-crosslinked ASC-derived ECM sponges containing a suitable amount of GO for skin-tissue engineering. Sponges were fabricated using cultures of ASCs, cell sheets, and decellularization of an ASC cell sheet, freeze-thawing, and crosslinking in a sequential manner. Scanning electron microscopic analyses of the sponges demonstrated a highly porous microstructure with a pore size of 71.22 ± 19.52 µm. The in vitro degradation rate was found to be significantly higher in the non-crosslinked ECM sponges and pure ECM sponges than in the genipin-crosslinked ECM sponges. During an in vivo study, we investigated the material feasibilities and degradability of the constructed ECM sponges as a suitable skin tissue-engineering scaffold in a xenogenic animal (rat) model for 4 weeks. After subcutaneous implantation, the ECM sponges containing a medium amount of GO showed appropriate biodegradation with a lower inflammatory reaction. Hence, the fabricated ECM sponges might be a suitable xenogenous skin substitute for full-thickness skin defects and in other future soft-tissue engineering applications, such as healing partial tears of the anterior cruciate ligament.