Characterization and Optimization of PLA Stereocomplexed Hydrogels for Local Gene Delivery Systems.

Localized gene delivery still remains as a challenging therapeutic method due to the multiple hurdles to overcome. One of the significant factors is a development of a matrix to carry and safely deliver genes at the local site in a controlled manner and then exit and disintegrate harmlessly. This report describes the structural and mechanistic studies on the in-situ forming hydrogels composed of the PEI/DNA multi-layered micelles to apply for gene therapy. The stereocomplexation-driven hydrogel systems from the DNA-loaded and DNA-free PLA-PEG-PLA triblock copolymer micelles that include enantiomeric polylactide blocks exhibited a sol-to-gel transitions between room and body temperatures. These hydrogels have well-described structure and compositions, and improved mechanical properties. Furthermore, the investigation of their degradation profiles and chemical analysis indicated the faster acidic degradation and stepwise degradation process of these micelle-hydrogel systems.

Inkjet Printed Parallel Plate Capacitors Using PVP Polymer Dielectric Ink on Flexible Polyimide Substrates.

Inkjet printing (IJP) is an exciting new additive manufacturing technology that promises monolithic electronic circuit fabrication of $\mu \mathrm{m}$ thin low-cost large-area electronic low-cost body-worn flexible sensors. In this work, we demonstrate inkjet printed multilayer metal-dielectric-metal capacitors on flexible polyimide (PI) substrate by formulating a custom dielectric ink based on Poly 4-vinylphenol (PVP). Silver nanoparticle ink was used for printing theconductive parallel metal plates. We also demonstrate control over the capacitance values by varying the design parameters and succeeded in printing capacitors in the range 8.8 pF to 467 pF, with excellent repeatability on flexible PI substrates. A functional LC circuit using these printed capacitors has been designed and demonstrated to have a resonance frequency of 24.3 MHz. These results are a vital step forward towards monolithic printing of flexible electronic circuits using IJP technique formany applications such as body-worn sensors.

In vitro and in vivo evaluations of a novel post-electrospinning treatment to improve the fibrous structure of chitosan membranes for guided bone regeneration.

Electrospun chitosan membranes have been investigated for guided bone regeneration but are susceptible to swelling, dissolution, and loss of biomimetic nanofiber structure due to residual acid salts. A novel process was investigated for acidic salt removal from chitosan electrospun in 70% trifluoroacetic acid (TFA) by treating with triethylamine (TEA)/acetone and di-tert-butyl dicarbonate (tBOC) instead of the common Na2CO3 treatment. TFA salt removal and nanofiber structure stabilization were confirmed by EDS, FTIR, 19F NMR and electron microscopy before and after soaking in water. Membrane degradation after 4 weeks in PBS with 100 µg ml-1 lysozyme and osteoblastic proliferation were similar between TEA/tBOC-treated and Na2CO3-treated membranes. A simulated surgical tear test using surgical tacks showed that the peak tensile tear strength of the TEA/tBOC-treated chitosan membranes (62.1 ± 1.9 N mm-1) was significantly greater than a commercial polylactic acid (PLA) membrane (13.4 ± 0.4 N mm-1), similar to one commercial collagen membrane (55.3 ± 7.5 N mm-1) but lower than another commercial collagen membrane (133.9 ± 21.5 N mm-1). Rat 8 mm critical-sized calvarial defects covered with TEA/tBOC-treated chitosan membranes prevented soft tissue infiltration and supported new bone growth (15.76 ± 10.28%) similar to a commercial collagen membrane (16.08 ± 10.69%) at 12 weeks based on microCT analyses. Hence our novel TEA/tBOC process significantly improved nanofiber structure and mechanical strengths of electrospun chitosan membranes as compared to Na2CO3 treated membranes, without affecting in vitro degradation or cytocompatibility, improved membrane mechanical properties to be greater than a commercial PLA membrane and to be in range of commercial collagen membranes and supported calvarial bone defect healing similar to collagen. Thus TEA/tBOC-treated chitosan membranes exhibit many characteristics and properties that strongly support their potential for use in guided bone regeneration.