Liquid crystal droplet design by using pseudopeptidic bottlebrush polymer additives

Liquid crystal (LC) droplets are promising candidates for sensing applications due to their high sensitivity to surface anchoring changes, resulting in readily detectable optical effects. Herein, we have designed and synthesized amino acid-based bottlebrush polymers and investigated their impact on LC director configurations in the droplets. The pseudopeptidic bottlebrush polymers with an aromatic (phenyl) and aliphatic appendages are synthesized using ring-opening metathesis polymerization (ROMP). Polymer dispersed liquid crystal (PDLC) samples are prepared by employing pseudopeptidic bottlebrush polymers and 4-cyano-4'-pentylbiphenyl (5CB) LC via solvent-induced phase separation (SIPS) technique. Due to π-π stacking, the phenyl group favours radial configuration, whereas the repulsion between 5CB and aliphatic groups induces molecular alignment leading to bipolar droplet arrangement. The impact of various pendant groups attached to the polymer on the prepared PDLC sample's surface characteristics and free energy components is illustrated. The sensing capability of 5CB dispersed in pseudopeptidic bottlebrush polymers for various pH solutions is investigated using polarizing optical microscopy (POM). The PDLC samples are moderately permeable to water and sensitive to different pH solutions. The results demonstrate a simplified and straightforward approach for preparing LC-based biosensors and chemical sensors.

Poly(vinyl alcohol boric acid)-Diclofenac Sodium Salt Drug Delivery Systems: Experimental and Theoretical Studies

The main aim of the paper was to simulate the drug release by a multifractal theoretical model, as a valuable method to assess the drug release mechanism. To do this, drug delivery films were prepared by mixing poly(vinyl alcohol boric acid) (PVAB) and diclofenac (DCF) sodium salt drug in different mass ratios from 90/10 to 70/30, in order to obtain drug delivery systems with different releasing rates. The different drug content of the three systems was confirmed by energy-dispersive spectroscopy (EDAX) analysis, and the encapsulation particularities were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and polarized optical microscopy (POM) techniques. The ability of the PVAB matrix to anchor the DCF was assessed by Fourier transform infrared (FTIR) spectroscopy. The in vitro release of the diclofenac sodium salt from the formulations was investigated in biomimetic conditions (pH = 7.4 and 37°C) by UV-Vis spectroscopy, measuring the absorbance of the drug at 275 nm and fitting the results on a previously drawn calibration curve. An estimation of the drug release kinetics was performed by fitting three traditional mathematical models on experimental release data. Further, the drug delivery was simulated by the fractal theory of motion, in which the release dynamics of the polymer-drug complex system is described through various Riccati-type "regimes." To explain such dynamics involved multifractal self-modulation in the form of period doubling, quasiperiodicity, intermittency, etc., as well as multifractal self-modulation of network type. Standard release dynamics were explained by multifractal behaviors of temporary kink type. The good correlation between the traditional mathematical models and the new proposed theoretical model demonstrated the validity of the multifractal model for the investigation of the drug release.

Polyvinyl alcohol boric acid - A promising tool for the development of sustained release drug delivery systems

The paper deals with the design and investigation of the morphology, in vitro drug release and biocompatibility of some new formulations based on polyvinyl alcohol boric acid (PVAB) and diclofenac sodium salt (DCF), with the aim to explore the ability of PVAB to act as a matrix for controlled drug delivery systems. A series of three formulations was obtained by mixing the drug and the polymeric matrix in different mass ratios, with high drug content from 10% w/w to 30% w/w. Their structural and supramolecular characterization, performed by FTIR spectroscopy and X-ray diffraction, revealed important physical interactions between the drug and the polymeric matrix. The morphological data, obtained by X-ray diffraction, polarized optical microscopy and scanning electron microscopy revealed the presence of the drug into the PVAB polymeric matrix, as micrometric polycrystals with a mean diameter in the range 10-15 μm, depending on the drug/polymer ratio. The investigation of their surface peculiarities indicated highly hydrophilic surfaces with a water to air contact angle between 29.9 and 41.4 deg and a surface free energy of 45.6-54.2 N/m². The in vitro release kinetics was monitored by UV-VIS spectroscopy and the cytotoxic effect was investigated in vitro on fibroblasts and HeLa cells. The PVAB proved excellent cytocompatibility, a relative cell viability of the fibroblasts higher than 90% being recorded for concentrations of PVAB up to 7.5% w/v. The drug has been strongly anchored into the electron deficient PVAB matrix, fact which led to its prolonged release up to 5 days. These findings recommend PVAB as a versatile tool for the development of sustained release drug delivery systems with real chances to cross the gap from theory to applications.