Gellan xanthan gels have been shown to be excellent carriers for growth factors and as matrices for several tissue engineering applications. Gellan xanthan gels along with chitosan nanoparticles of 297 ± 61 nm diameter, basic fibroblast growth factor (bFGF), and bone morphogenetic protein 7 (BMP7) were employed in a dual growth factor delivery system to promote the differentiation of human fetal osteoblasts. An injectable system with ionic and temperature gelation was optimized and characterized. The nanoparticle loaded gels showed significantly improved cell proliferation and differentiation due to the sustained release of growth factors. A differentiation marker study was conducted, analyzed, and compared to understand the effect of single vs dual growth factors and free vs encapsulated growth factors. Dual growth factor loaded gels showed a higher alkaline phosphatase and calcium deposition compared to single growth factor loaded gels. The results suggest that encapsulation and stabilization of growth factors within nanoparticles and gels are promising for bone regeneration. Gellan xanthan gels also showed antibacterial effects against Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis, the common pathogens in implant failure.

Infections are both frequent and costly in hospitals around the world, leading to longer hospital stays, overuse of antibiotics, and excessive costs to the healthcare system. Moreover, antibiotic resistant organisms, such as Pseudomonas aeruginosa are increasing in frequency, leading to 1.7 million infections per year in USA hospitals, and 99,000 deaths, both due to the evolution of antibiotic resistance and the formation of biofilms on medical devices. In particular, respiratory infections are costly, deadly to 4.5 million persons per year worldwide, and can spread to the lungs through the placement of endotracheal tubing. In this study, towards a reduction in infections, solid lipid nanoparticles were formulated from free fatty acids, or natural lipophilic constituents found in tissues of the body. A strategy was developed to target infections by producing coatings made of non-toxic chemistries lauric acid and oleic acid delivered by core-shell solid lipid nanoparticles that act against bacteria by multiple mechanisms at the nanoscale, including disruption of bacteria leading to DNA release, and reducing the adhesion of dead bacteria to ~1%. This is the first such study to explore an anti-infection surface relying on these multi-tier strategies at the nanoscale.

Porous anodic alumina template has been employed, in the presence of a precipitation reaction involving Ca(OH) 2 and H 3 PO 4 , to form calcium phosphate based tubular structures. These structures are amorphous in nature and can be recovered by etching the sacrificial alumina membrane. Full characterization of these structures has been done using X-ray diffraction, electron microscopy and FTIR. In addition, their biocompatibility has been tested on L929 mouse fibroblast cells using MTT assay and the cellular internalization of these nanotubes has also been evaluated using rhodamine 6G dye tagged nanotubes in the presence of fibroblast cells. The studies also suggest that the nanotubes are non-toxic to fibroblasts and can be taken up easily by mammalian cells. Such tubes may serve as vehicles for drugs and growth factors, and for tissue repair including bone regeneration.

Synovial inflammation, angiogenesis and joint degradation are the hallmarks of inflammatory arthritis progression. Angiostatic targeting is an extensively studied potential therapeutic option for inflammatory arthritis. Studies have confirmed that surface-active phospholipids (SAPLs), predominantly phosphatidylcholines (PCs), are responsible for the lubricating properties of lubricin in joints. Paclitaxel, a potent antineoplastic agent in cancer chemotherapy, has been shown to inhibit several processes associated with arthritis development such as angiogenesis, neutrophil activation and collagenase expression but is limited by systemic toxicity. This study was aimed at designing a surface-active phospholipid mimetic nanocarrier system and assessing its efficacy for intra-articular delivery of paclitaxel in rat joints. Dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) liposomes were prepared using a thin-film hydration method and characterized for size, morphology, drug encapsulation and in vitro release. DPPC liposomes of a size of 311 ± 57 nm and 92 ± 0.6% paclitaxel encapsulation were developed. In vitro release studies showed a short initial burst phase and a sustained release profile with a cumulative release of 18 ± 0.36% of the drug by 60 h in phosphate-buffered saline (PBS). The efficacy of the intra-articular formulation was evaluated in antigen-induced arthritic rat models and compared with direct injections of paclitaxel. After a 28-day period, intra-articular paclitaxel delivered in liposomes led to a significant improvement in gait scores and synovial inflammation in rats compared to the control, as seen in histopathology studies. Reduction in inflammation in the experimental group was confirmed by evaluating TNFα levels in serum samples. This study suggests feasibility of using surface-active phospholipid based carriers for local, intra-articular therapy of paclitaxel in arthritis.

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