Bone cement based nanohybrid as a super biomaterial for bone healing

A novel nanohybrid based on bone cement has been developed which is capable of healing fractured bone in 30 days, one-third of the time required for the natural healing process. Nanohybrids of bone cement based on poly( methyl methacrylate) (PMMA), currently used as a grouting material in joint replacement surgery, were prepared by simple mixing with organically modified layered silicates of varying chemical compositions. The temperature arising from exothermic polymerization in one of the nanohybrids is 12 degrees C lower than that in pure bone cement, thus circumventing the reported cell necrosis that occurs during implantation with pure bone cement. The thermal stability and mechanical superiority of this nanohybrid were verified in terms of its higher degradation temperature, better stiffness, superior toughness, and significantly higher fatigue resistance compared with pure bone cement; these properties make it appropriate for use as an implant material. The biocompatibility and bioactivity of the nanohybrid were confirmed using cell adhesion, cell viability, and fluorescence imaging studies. Osteoconductivity and bone bonding properties were monitored in vivo in rabbits through radiographic imaging and histopathological studies of growing bone and muscle near the surgery site. The observed dissimilarity of the properties of two different nanoclays used as fillers were visualized through interactions measured using spectroscopic techniques. Studies of the influence of different elements on bioactivity showed a higher efficiency for the nanoclay containing greater amounts of iron

In the Crucible: When development, poverty and fundamentalism combine

Bina Srinivasan looks at the many contradictions that unfold on the lives of women, specially on the Dalit, adivasi and economically vulnerable communities of women, as they employ strategies of survival in a world that increasingly seeks to push them into the margins. Development (2007) 50, 122–126. doi:10.1057/palgrave.development.1100366

Methotrexate-Loaded Four-Arm Star Amphiphilic Block Copolymer Elicits CD8⁺ T Cell Response against a Highly Aggressive and Metastatic Experimental Lymphoma

We have synthesized a well-defined four-arm star amphiphilic block copolymer [poly­(DLLA)-<i>b</i>-poly­(NVP)]₄ [star-(PDLLA-<i>b</i>-PNVP)₄] that consists of d,l-lactide (DLLA) and <i>N</i>-vinylpyrrolidone (NVP) via the combination of ring-opening polymerization (ROP) and xanthate-mediated reversible addition–fragmentation chain transfer (RAFT) polymerization. Synthesis of the polymer was verified by ¹H NMR spectroscopy and gel permeation chromatography (GPC). The amphiphilic four-arm star block copolymer forms spherical micelles in water as demonstrated by transmission electron microscopy (TEM) and ¹H NMR spectroscopy. Pyrene acts as a probe to ascertain the critical micellar concentration (cmc) by using fluorescence spectroscopy. Methotrexate (MTX)-loaded polymeric micelles of star-(PDLLA₁₅-<i>b</i>-PNVP₁₀)₄ amphiphilic block copolymer were prepared and characterized by fluorescence and TEM studies. Star-(PDLLA₁₅-<i>b</i>-PNVP₁₀)₄ copolymer was found to be significantly effective with respect to inhibition of proliferation and lysis of human and murine lymphoma cells. The amphiphilic block copolymer causes cell death in parental and MTX-resistant Dalton lymphoma (DL) and Raji cells. The formulation does not cause hemolysis in red blood cells and is tolerant to lymphocytes compared to free MTX. Therapy with MTX-loaded star-(PDLLA₁₅-<i>b</i>-PNVP₁₀)₄ amphiphilic block copolymer micelles prolongs the life span of animals with neoplasia by reducing the tumor load, preventing metastasis and augmenting CD8⁺ T cell-mediated adaptive immune responses

Tailored Chemical Properties of 4‑Arm Star Shaped Poly(d,l‑lactide) as Cell Adhesive Three-Dimensional Scaffolds

Biodegradable poly­(lactic acid) (PLA) is widely used to fabricate 3D scaffolds for tissue regeneration. However, PLA lacks cell adhering functional moieties, which limit its successful application in tissue engineering. Herein, we have tailored the cell adhesive properties of star shaped poly­(d,l-lactide) (ss-PDLLA) by grafting gelatin to their 4 arms. Grafting of gelatin on PDLLA backbone was confirmed by ¹H NMR and FTIR. The synthesized star shaped poly­(d,l-lactide)-<i>b</i>-gelatin (ss-pLG) exhibited enhanced wettability and protein adsorption. The modification also facilitated better cell adhesion and proliferation on their respective polymer coated 2D substrates, compared to their respective unmodified ss-PDLLA. Further, 3D scaffolds were fabricated from gelatin grafted and unmodified polymers. The fabricated scaffolds were shown to be cytocompatible to 3T3-L1 cells and hemocompatible to red blood cells (RBCs). Cell proliferation was increased up to 2.5-fold in ss-pLG scaffolds compared to ss-PDLLA scaffolds. Furthermore, a significant increase in cell number reveals a high degree of infiltration of cells into the scaffolds, forming a viable and healthy 3D interconnected cell community. In addition to that, burst release of docetaxal (DTX) was observed from ss-pLG scaffolds. Hence, this new system of grafting polymers followed by fabricating 3D scaffolds could be utilized as a successful approach in a variety of applications where cell-containing depots are used

Osteoconductive Amine-Functionalized Graphene–Poly(methyl methacrylate) Bone Cement Composite with Controlled Exothermic Polymerization

Bone cement has found extensive usage in joint arthroplasty over the last 50 years; still, the development of bone cement with essential properties such as high fatigue resistance, lower exothermic temperature, and bioactivity has been an unsolved problem. In our present work, we have addressed all of the mentioned shortcomings of bone cement by reinforcing it with graphene (GR), graphene oxide (GO), and surface-modified amino graphene (AG) fillers. These nanocomposites have shown hypsochromic shifts, suggesting strong interactions between the filler material and the polymer matrix. AG-based nanohybrids have shown greater osteointegration and lower cytotoxicity compared to other nanohybrids as well as pristine bone cement. They have also reduced oxidative stress on cells, resulting in calcification within 20 days of the implantation of nanohybrids into the rabbits. They have significantly reduced the exothermic curing temperature to body temperature and increased the setting time to facilitate practitioners, suggesting that reaction temperature and settling time can be dynamically controlled by varying the concentration of the filler. Thermal stability and enhanced mechanical properties have been achieved in nanohybrids vis-à-vis pure bone cement. Thus, this newly developed nanocomposite can create natural bonding with bone tissues for improved bioactivity, longer sustainability, and better strength in the prosthesis