Relative survivability of human osteoblasts is enhanced by 39 °C and ascorbic acid after exposure to photopolymerization ingredients

Photopolymerizable hydrogels offer great potential in cartilage tissue engineering due to their ability to conform to irregular defect shapes and be applied in a potentially minimally invasive manner. An important process requirement in the use of photopolymerizable hydrogels is the ability of the suspended cells to withstand low intensity ultraviolet light (UV) exposure (4–5 mW/cm²) and photoinitiator concentrations. For cartilage integration with underlying subchondral bone tissue, robust localized osteoblast activity is necessary. Yet, while it is known that osteoblasts do not respond well to UV light, limited work has been conducted to improve their survivability. In this study, we evaluated the cellular cytotoxicity of five different human cell sources at different UV exposure times, with and without a commercially used photoinitiator. We were able to confirm that human osteoblasts were the least tolerant to varying UV exposure times in comparison to bone marrow stem cell, periodontal ligament cell, smooth muscle and endothelial cell lineages. Moreover osteoblasts cultured at 39 °C did not deteriorate in terms of alkaline phosphatase expression or calcium deposition within the extracellular matrix (ECM), but did reduce cell proliferation. We believe however that the lower proliferation diminished osteoblast sensitivity to UV and the photoinitiator. In fact, the relative survivability of osteoblasts was found to be augmented by the combination of a biochemical factor and an elevated incubation temperature; specifically, the use of 50 mg/l of the anti-oxidant, ascorbic acid significantly (P < 0.05) increased the survivability of osteoblasts when cultured at 39 °C. We conclude that ascorbic acid at an incubation temperature of 39 °C can be included in in vitro protocols used to assess cartilage integration with bone ECM. Such inclusion will enhance conditions of the engineered tissue model system in recapitulating in vivo osteoblast activity.     

Strong green fluorescent hydrogels with Ba2MgSi2O7:Eu2+ phosphor embedded in cellulose

Non‐cytotoxic and green‐emitting fluorescent hydrogels were constructed from a cellulose solution containing Ba₂MgSi₂O₇:Eu²⁺ green phosphor in a NaOH/urea aqueous system. The structure, optical properties and cytotoxicity of these hydrogels were studied. The Ba₂MgSi₂O₇:Eu²⁺ phosphor particles were dispersed evenly in the cellulose hydrogel matrix. Good luminescent properties of Ba₂MgSi₂O₇:Eu²⁺ phosphor were maintained in the hydrogels, leading to strong green emission under ultraviolet excitation. Fluorescent hydrogels have no obvious cytotoxicity in a 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) proliferation test, and have potential use in in vivo applications like optical imaging and drug delivery.     

基于天然水凝胶的生物材料在骨组织工程中的应用*

天然水凝胶是指原材料来自于天然生物材料的水凝胶。由于这种天然的聚合物含有构成生物体的天然成分,与天然组织具有生物学和化学相似性,而受到特别关注。天然水凝胶由于其与细胞外基质高度的相似性被认为是骨组织工程中优良的仿生基质材料。而针对天然水凝胶机械性能差、成骨诱导性能弱等缺陷,通常需要对天然水凝胶进行改性、引入其他材料或生物活性因子,以此来获得更适用于骨组织工程支架材料。对近年来基于天然水凝胶的生物材料在骨组织工程的应用,与其不同的应用形式(可注射水凝胶、多孔水凝胶支架、3D生物打印水凝胶支架等)进行了概述,以期对这类基于天然水凝胶的生物材料在未来骨组织工程中的应用提供参考。     

Micro 3D cell culture systems for cellular behavior studies: Culture matrices,devices, substrates,and in‐situ sensing methods

Microfabricated systems equipped with 3D cell culture devices and in‐situ cellular biosensing tools can be a powerful bionanotechnology platform to investigate a variety of biomedical applications. Various construction substrates such as plastics, glass, and paper are used for microstructures. When selecting a construction substrate, a key consideration is a porous microenvironment that allows for spheroid growth and mimics the extracellular matrix (ECM) of cell aggregates. Various bio‐functionalized hydrogels are ideal candidates that mimic the natural ECM for 3D cell culture. When selecting an optimal and appropriate microfabrication method, both the intended use of the system and the characteristics and restrictions of the target cells should be carefully considered. For highly sensitive and near‐cell surface detection of excreted cellular compounds, SERS‐based microsystems capable of dual modal imaging have the potential to be powerful tools; however, the development of optical reporters and nanoprobes remains a key challenge. We expect that the microsystems capable of both 3D cell culture and cellular response monitoring would serve as excellent tools to provide fundamental cellular behavior information for various biomedical applications such as metastasis, wound healing, high throughput screening, tissue engineering, regenerative medicine, and drug discovery and development.     

Evaluation of CO2-based cold sterilization of a model hydrogel

The purpose of the present work is to evaluate a novel CO(2)-based cold sterilization process in terms of both its killing efficiency and its effects on the physical properties of a model hydrogel, poly(acrylic acid-co-acrylamide) potassium salt. Suspensions of Staphylococcus aureus and Escherichia coli were prepared for hydration and inoculation of the gel. The hydrogels were treated with supercritical CO(2) (40 degrees C, 27.6 MPa). The amount of bacteria was quantified before and after treatment. With pure CO(2), complete killing of S. aureus and E. coli was achieved for treatment times as low as 60 min. After treatment with CO(2) plus trace amounts of H(2)O(2) at the same experimental conditions, complete bacteria kill was also achieved. For times less than 30 min, incomplete kill was noted. Several physical properties of the gel were evaluated before and after SC-CO(2) treatment. These were largely unaffected by the CO(2) process. Drying curves showed no significant change between treated (pure CO(2) and CO(2) plus 30% H(2)O(2)) and untreated samples. The average equilibrium swelling ratios were also very similar. No changes in the dry hydrogel particle structure were evident from SEM micrographs.     

Application of a dense gas technique for sterilizing soft biomaterials

Sterilization of soft biomaterials such as hydrogels is challenging because existing methods such as gamma irradiation, steam sterilization, or ethylene oxide sterilization, while effective at achieving high sterility assurance levels (SAL), may compromise their physicochemical properties and biocompatibility. New methods that effectively sterilize soft biomaterials without compromising their properties are therefore required. In this report, a dense-carbon dioxide (CO(2) )-based technique was used to sterilize soft polyethylene glycol (PEG)-based hydrogels while retaining their structure and physicochemical properties. Conventional sterilization methods such as gamma irradiation and steam sterilization severely compromised the structure of the hydrogels. PEG hydrogels with high water content and low elastic shear modulus (a measure of stiffness) were deliberately inoculated with bacteria and spores and then subjected to dense CO(2) . The dense CO(2) -based methods effectively sterilized the hydrogels achieving a SAL of 10(-7) without compromising the viscoelastic properties, pH, water-content, and structure of the gels. Furthermore, dense CO(2) -treated gels were biocompatible and non-toxic when implanted subcutaneously in ferrets. The application of novel dense CO(2) -based methods to sterilize soft biomaterials has implications in developing safe sterilization methods for soft biomedical implants such as dermal fillers and viscosupplements.     

Release studies from smart hydrogels as carriers for piroxicam and copper(II)-oxicam complexes as anti-inflammatory and anti-cancer drugs. X-ray structures of new copper(II)-piroxicam and -isoxicam complex molecules

Piroxicam H₂PIR (H₂PIR, 4-hydroxy-2-methyl-N-pyridin-2-yl-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide), [Cu(HPIR)₂(H₂O)₂] previously prepared and tested from this laboratory and at National Institute of Health, National Cancer Institute, Developmental Therapeutic Program, NIH-NCI-DTP, USA [R. Cini, G. Tamasi, S. Defazio, M.B. Hursthouse, J. Inorg. Biochem. 101 (2007) 1140-1152, and references cited therein], [Cu(HMEL)₂(DMF)] (H₂MEL, 4-hydroxy-2-methyl-N-(5-methyl-1,3-thiazol-2-yl)-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide; DMF, N,N-dimethylformamide), [Cu(HISO)₂] (H₂ISO, 4-hydroxy-2-methyl-N-(5-methylisoxazol-3-yl)-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide), and [Cu(HTEN)₂(H₂O)₂] (H₂TEN, 4-hydroxy-2-methyl-N-pyridin-2-yl-2H-thieno[2,3-e][1,2]thiazine-3-carboxamide 1,1-dioxide), were loaded on CMH2 hydrogel (co-1:10-poly(N-methacryloyl-l-histidine-co-N-isopropylacrylamide) cross-linked with N,N′-ethylene-bis-acrylamide (EBA) 2%) and the kinetics of release of Cu-HPIR species in several media were studied. The release of Cu(HPIR)₂ in DMSO from CMH2 hydrogel after swelling and loading from DMSO followed a diffusion controlled process. The release of Cu(HPIR)/Cu(HPIR)₂ from dried CMH2 hydrogel after swelling and loading from THF solution, then soaking into water/DMSO 95:5 v/v (pH 5.6) followed a relaxation controlled and diffusion controlled mechanism. The amount of Cu(HPIR)₂ released in the medium reached 0.03 μg Cu/mg gel/mL, i.e. ca 0.8 μM within 48 h that compares well with the IC₅₀ values reported for metal based drugs like carboplatin (diammino(1,1-cyclobutandicarboxylato)platinum(II)) against certain human tumor cell lines. The release studies performed by monitoring both the absorbance values at 362 nm (sensitive to metal-bound HPIR⁻) and the content of Cu via AAS, showed an excellent agreement with the Cu(HPIR)₂ or Cu(HPIR)₂ stoichiometry, depending on the delivery medium. Corresponding studies were performed for other Cu(oxicam-H)₂ species in different delivery media.