Inorganic-organic polymer hybrid scaffold for tissue engineering--II: partial enzymatic degradation of hydroxyapatite-chitosan hybrid

Chitosan Microspheres Loaded with Curcumin and Gallic Acid: Modified Synthesis, Sustainable Slow Release, and Enhanced Biological Property

Improving the utilization rate of loaded-drugs is of huge importance for generating chitosan-based (CS) micro-carriers. This study aims to fabricate a novel CS microspheres co-delivered curcumin (Cur) and gallic acid (Ga) to assess drug loading and release kinetics, the blood compatibility and anti-osteosarcoma properties. The present study observes the interaction between CS and Cur/Ga molecules and estimates the change in crystallinity and loading and release rate. In addition, blood compatibility and cytotoxicity of such microspheres are also evaluated. Cur-Ga-CS microspheres present high entrapment rate of (55.84 ± 0.34) % for Ga and (42.68 ± 0.11) % for Cur, possibly attributed to surface positive charge (21.76 ± 2.46) mV. Strikingly, Cur-Ga-CS microspheres exhibit slowly sustainable release for almost 7 days in physiological buffer. Importantly, these microspheres possess negligibly toxic to blood and normal BMSC cells, but strong anti-osteosarcoma effect on U2OS cells. Overall, Cur-Ga-CS microspheres are promising to become a novel anti-osteosarcoma agent or sustainable delivery carrier in biomedical applications.

Organic-Inorganic Composite Films Based on Gd3Ga3Al2O12:Ce Scintillator Nanoparticles for X-ray Imaging Applications

Organic-inorganic nanocomposite self-standing films of Gd₃Ga₃Al₂O₁₂ (GGAG) uniformly dispersed in poly(methyl methacrylate) (PMMA) and polystyrene polymer are prepared for radiography application. GGAG:Ce nanoscintillator has been chosen because of its high light output and fast decay time. The nanopowder of GGAG is synthesized by coprecipitation method and dispersed in the polymer matrix by a simple blending technique. The nanocomposite films of thickness in the range of 150-450 μm with a very high inorganic content is achieved by this technique. These films are characterized by their uniformity, optical absorption, photoluminescence, and radioluminescence. These films are further tested for their application in radiography by recording X-ray images using a commercially available charge-coupled device camera. A resolution of 10 lp/mm is obtained using GGAG:PMMA composite film with 50% loading, confirming their application in imaging devices.

In Situ Swelling Behavior of Chitosan-Polygalacturonic Acid/Hydroxyapatite Nanocomposites in Cell Culture Media

The molecular and mechanical characteristics of in situ degradation behavior of chitosan-polygalacturonic acid/hydroxyapatite (Chi-PgA-HAP) nanocomposite films is investigated using Fourier Transform Infrared spectroscopy (FTIR), Atomic Force Microscopy (AFM), and modulus mapping techniques for up to 48 days of soaking in cell culture media. The surface molecular structure of media-soaked samples changes over the course of 48 days of soaking, as indicated by significant changes in phosphate vibrations (1200–900 ) indicating apatite formation. Chitosan-Polygalacturonic acid polyelectrolyte complexes (PECs) govern structural integrity of Chi-PgA-HAP nanocomposites and FTIR spectra indicate that PECs remain intact until 48 days of soaking. In situ AFM experiments on media-soaked samples indicate that soaking results in a change in topography and swelling proceeds differently at the initial soaking periods of about 8 days than for longer soaking. In situ modulus mapping experiments are done on soaked samples by probing 1–3 nm of surface indicating elastic moduli of 4 GPa resulting from proteins adsorbed on Chi-PgA-HAP nanocomposites. The elastic modulus decreases by 2 GPa over a long exposure to cell culture media (48 days). Thus, as water enters the Chi-PgA-HAP sample, surface molecular interactions in Chi-PgA-HAP structure occur that result in swelling, causing small changes in nanoscale mechanical properties.

Preparation and properties of chitosan/calcium phosphate composites for bone repair

Chitosan/calcium phosphate (CaP) composites composed of bioactive calcium phosphate and flexible chitosan were made by a simple mixing-and-heating method. Phase composition, morphology, and mechanical properties--including in-air and in vitro fatigue behavior - were evaluated. Experimental results showed that the chitosan matrix did not affect the crystalline phase of CaP. However, the content of CaP additive affected the three-point bending strength of the composites. A CaP/ chitosan ratio of 5% by mass to volume in the composite achieved the significantly highest bending strength of 45.7 MPa. Stability of chitosan/CaP hybrid composites was apparently affected by in vitro cyclic loading. Nonetheless, when applied a loading stress of 11.4 MPa, the sample containing the optimal 5 mass/vol% CaP lasted 40 minutes in in vitro fatigue test until failure occurred. It was thus concluded that hybrid biocomposites with initial high strength might be a potential implant candidate for bone defect repair.

In vitro evaluation of a poly(lactide-co-glycolide)–collagen composite scaffold for bone regeneration

Numerous materials have been proposed for bone tissue regeneration. However, none has been shown to be entirely satisfactory. In this study we fabricated a hybrid composite scaffold composed of poly(D,L-lactide-co-glycolide) (PLGA) and a naturally derived collagen matrix derived from porcine bladder submucosa matrix (BSM), and evaluated the biological activities and physical properties of the scaffold for use in bone tissue regeneration. The BSM-PLGA composite scaffolds are able to promote cellular interactions and possess uniformly interconnected pores with adequate structural integrity. The composite scaffolds were tested with both human embryonic stem (hES) cells and bovine osteoblasts (bOB). Cells seeded on the composite scaffolds readily attached, infiltrated and proliferated, as confirmed by cell viability and mitochondrial metabolic activity. Use of the composite scaffolding system with cells may enhance the formation of bone tissue for therapeutic regeneration.

Controlled release based on the dissolution of a calcium carbonate layer deposited on hydrogels

It is possible that inorganic materials conjugated to suitable organic materials may induce unique mechanical, optical and other functional properties. Therefore, artificial conjugation of organic and inorganic components is attractive for preparing novel functional materials. Recently, we developed an alternate soaking process for calcium salt formation on/in polymer materials. In this study, a poly(vinyl alcohol) (PVA) hydrogel-calcium carbonate (CaCO(3)) composite was prepared by the aforementioned process as a controlled release support. Brilliant blue FCF (Mw = 794), FITC labeled BSA (Mw = 6.6 x 10(4)), FITC labeled dextran-10 k (Mw = 9.5 x 10(3)) and FITC labeled dextran-40 k (Mw = 4.3 x 10(4)) were loaded into the composite as model drugs. CaCO(3) dissolution and model drug release rates increased with a decrease in buffer pH. In addition, model drug release rates increased with a decrease in model drug molecular weight. These results show that CaCO(3) layers on hydrogels behave as capping layers for model drug release; the release rate of model drugs can be controlled by the dissolution rate of CaCO(3) and the molecular weight of the drug.

Cell-compatible properties of calcium carbonates and hydroxyapatite deposited on ultrathin poly(vinyl alcohol)-coated polyethylene films

Poly(vinyl alcohol) (PVA) was coated onto polyethylene (PE) films by a repetitive adsorption and drying process, and then the PVA-coated PE films were alternately immersed into aqueous solutions of Ca2+ and CO3(2-) ions (alternate soaking cycles), to deposit calcium carbonate (CaCO3) onto the films. The PVA coating was essential for the CaCO3 deposition. The amount of CaCO3 deposited increased with an increasing number of cycles. Scanning electron microscopic observations and attenuated total reflection spectra revealed the presence of both calcite and aragonite as the crystal structures of CaCO3 on the film. L929 fibroblast cells adhered and proliferated on these CaCO3-deposited PE films, as well as the hydroxyapatite-coated PE films previously prepared. It was found that the PVA coating and the subsequent deposition of calcium salts on certain films facilitated cell compatibility.

Bioinspired organic‐inorganic composite materials prepared by an alternate soaking process as a tissue reconstitution matrix

Poly(acrylic acid) (PAAc) grafted poly(ethylene) (PE) (PAAc-g-PE) film-apatite or calcium carbonate (CaCO3) composite materials were prepared by an alternate soaking process, which simply forms apatite or CaCO3 on the polymer materials by alternate soaking in Ca(2+)- and PO(3-)4- or CO(3)2- -containing solutions. X-ray diffraction analysis of the composite films indicated the presence of hydroxyapatite or CaCO3 on the film. Scanning electron microscopic observation revealed that the whole surface of the film was covered by the apatite or CaCO3. Cell compatibility tests of the apatite- or CaCO3-coated film suggested that the greater number of cells adhered on the films and that the cell proliferation properties were extremely greater on the films.