The ability to print defined patterns of cells and extracellular-matrix components in three dimensions has enabled the engineering of simple biological tissues, however bioprinting functional solid organs is beyond the capabilities of current biofabrication technologies. An alternative approach would be to bioprint the developmental precursor to an adult organ, using this engineered rudiment as a template for subsequent organogenesis in vivo. Here we demonstrate that developmentally inspired hypertrophic cartilage templates can be engineered in vitro using stem cells within a supporting gamma-irradiated alginate bioink incorporating Arg-Gly-Asp (RGD) adhesion peptides.Furthermore, these soft tissue templates can be reinforced with a network of printed polycaprolactone fibres, resulting in a ~350 fold increase in construct compressive modulus providing the necessary stiffness to implant such immature cartilaginous rudiments into load bearing locations. As a proofof-principal, multiple-tool biofabrication was used to engineer a mechanically reinforced cartilaginous template mimicking the geometry of a vertebral body, which in vivo supported the development of a vascularized bone organ containing trabecular-like endochondral bone with a supporting marrow structure. Such developmental engineering approaches could be applied to the biofabrication of other solid organs by bioprinting pre-cursors that have the capacity to mature into their adult counterparts over time in vivo.3

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Magnetite/gold (Fe(3)O(4)/Au) hybrid nanoparticles were synthesized from a single iron precursor (ferric chloride) through a green chemistry route using grape seed proanthocyanidin as the reducing agent. Structural and physicochemical characterization proved the nanohybrid to be crystalline, with spherical morphology and size ~35 nm. Magnetic resonance imaging and magnetization studies revealed that the Fe(3)O(4) component of the hybrid provided superparamagnetism, with dark T(2) contrast and high relaxivity (124.2 ± 3.02 mM(-1) s(-1)). Phantom computed tomographic imaging demonstrated good X-ray contrast, which can be attributed to the presence of the nanogold component in the hybrid. Considering the potential application of this bimodal nanoconstruct for stem cell tracking and imaging, we have conducted compatibility studies on human Mesenchymal Stem Cells (hMSCs), wherein cell viability, apoptosis, and intracellular reactive oxygen species (ROS) generation due to the particle-cell interaction were asessed. It was noted that the material showed good biocompatibility even for high concentrations of 500 μg/mL and up to 48 h incubation, with no apoptotic signals or ROS generation. Cellular uptake of the nanomaterial was visualized using confocal microscopy and prussian blue staining. The presence of the nanohybrids were clearly visualized in the intracytoplasmic region of the cell, which is desirable for efficient imaging of stem cells in addition to the cytocompatible nature of the hybrids. Our work is a good demonstrative example of the use of green aqueous chemistry through the employment of phytochemicals for the room temperature synthesis of complex hybrid nanomaterials with multimodal functionalities.

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a b s t r a c tPoly(lactic acid) (PLA)/chitosan (CS) nanoparticles were prepared by emulsion method for anti-HIV drug delivery applications. The prepared PLA/CS nanoparticles were characterized using DLS, SEM, and FTIR. The hydrophilic antiretroviral drug Lamivudine was loaded into PLA/CS nanoparticles. The encapsulation efficiency and in-vitro drug release behaviour of drug loaded PLA/CS nanoparticles were studied using UV spectrophotometer. In addition, the cytotoxicity of the PLA/CS nanoparticles using MTT assay was also studied. The in-vitro drug release studies showed that drug release rate was lower in the acidic pH when compared to alkaline pH. This may due to repulsion between H + ions and cationic groups present in the polymeric nanoparticles. Drug release rate was found to be higher in the 6% drug loaded formulation when compared to 3% drug loaded formulation. These results indicated that the PLA/CS nanoparticles are a promising carrier system for controlled delivery of anti-HIV drugs.

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In this study, we evaluated the role of fiber size scale in the adhesion and spreading potential of human mesenchymal stem cells (hMSCs) on electrospun poly(caprolactone) (PCL) nanofibrous and microfibrous scaffolds. The effect of in vivo regulators in inducing osteogenic differentiation of hMSCs on PCL nanofibrous scaffolds was investigated using osteogenic differentiation marker gene expression and matrix mineralization. Here, we report for the first time the influence of in vivo regulators in an in vitro setting with hMSCs for bone tissue engineering on PCL nanofibrous matrices. Our results indicated that hMSCs attached and spread rapidly on nanofibrous scaffolds in comparison to microfibrous PCL. Further, hMSCs proliferated well on the nanofibrous scaffolds. The cells on the nanofibrous PCL were found to differentiate into the osteoblast lineage and subsequently mineralize upon addition of in vivo osteogenic regulators. The attachment and spreading of hMSCs were more effective on the nanofibers compared with the microfibers despite the lower protein surface coverage (total adsorbed protein per unit fiber surface area) on nanofibers.

Regeneration of complex bone defects remains a significant clinical challenge. Multi-tool biofabrication has permitted the combination of various biomaterials to create multifaceted composites with tailorable mechanical properties and spatially controlled biological function. In this study we sought to use bioprinting to engineer nonviral gene activated constructs reinforced by polymeric micro-filaments. A gene activated bioink was developed using RGD-γ-irradiated alginate and nano-hydroxyapatite (nHA) complexed to plasmid DNA (pDNA). This ink was combined with bone marrow-derived mesenchymal stem cells (MSCs) and then co-printed with a polycaprolactone supporting mesh to provide mechanical stability to the construct. Reporter genes were first used to demonstrate successful cell transfection using this system, with sustained expression of the transgene detected over 14 days postbioprinting. Delivery of a combination of therapeutic genes encoding for bone morphogenic protein and transforming growth factor promoted robust osteogenesis of encapsulated MSCs in vitro, with enhanced levels of matrix deposition and mineralization observed following the incorporation of therapeutic pDNA. Gene activated MSC-laden constructs were then implanted subcutaneously, directly postfabrication, and were found to support superior levels of vascularization and mineralization compared to cell-free controls. These results validate the use of a gene activated bioink to impart biological functionality to three-dimensional bioprinted constructs.