Polylactide-Based Nonisocyanate Polyurethanes: Preparation, Properties Evaluation and Structure Analysis.

This study investigated the successful synthesis and characterization of nonisocyanate polyurethanes (NIPUs) based on polylactide. The NIPUs were synthesized by a condensation reaction of oligomers with hard segments (HSs) and synthesized carbamate-modified polylactic acid containing flexible segments (FSs). The oligomers with HSs were prepared from phenolsulfonic acid (PSA) or a mixture of PSA and hydroxynaphthalenesulfonic acid (HNSA), urea and formaldehyde. The mixing of oligomeric compounds with different amounts of formaldehyde was carried out at room temperature. Obtained NIPU samples with different hard segment content were tested for their mechanical and thermal properties. The tensile strength (TS) of all NIPU samples increased with an increasing amount of HSs, attaining the maximum value at an HS:FS ratio of 1:3. Samples prepared from PSA and HNSA showed higher tensile strength (TS) without significant change in elongation at break compared to the samples based only on PSA. Thermogravimetric analysis data indicated an absence of weight loss for all samples below 100 °C, which can be considered a safe temperature for using NIPU materials. Maximum degradation temperatures reached up to 385 °C. Fourier transform infrared spectroscopy results confirmed the existence of expected specific groups as well as the chemical structure of the prepared polyurethanes. DSC analysis showed the existence of two characteristic phase transitions attributed to the melting and crystallization of hard segments in the NIPU samples.

Chitosan/dialdehyde cellulose hydrogels with covalently anchored polypyrrole: Novel conductive, antibacterial, antioxidant, immunomodulatory, and anti-inflammatory materials.

In this work, conductive composite hydrogels with covalently attached polypyrrole (PPy) nanoparticles are prepared. Hydrogels are based on partially re-acetylated chitosan soluble at physiological pH without any artificial structural modifications or need for an acidic environment, which simplifies synthesis and purification. Low-toxic and sustainable dialdehyde cellulose (DAC) was used for crosslinking chitosan and covalent anchoring of PPy colloidal particles. The condensation reaction between DAC and PPy is reported for the first time and improves not only the anchoring of PPy particles but also control over the properties of the final composite. The soluble chitosan and PPy particles are shown to act in synergy, which improves the biological properties of the materials. Prepared composite hydrogels are non-cytotoxic, non-irritating, antibacterial, can capture reactive oxygen species often related to excessive inflammation, have conductivity similar to human tissues, enhance in vitro cell growth (migration assay), and have immunomodulatory effects related to the stimulation of neutrophils and macrophages. The covalent attachment of PPy also strengthens the hydrogel network. The aldol condensation as a method for PPy covalent anchoring thus presents an interesting possibility for the development of advanced biomaterials in the future.

Controlled Drug Delivery Device for Cornea Treatment and Novel Method for Its Testing.

A new solution for local anesthetic and antibiotic delivery after eye surgery is presented. A contact lens-shaped collagen drug carrier was created and loaded by Levofloxacin and Tetracaine with a riboflavin crosslinked surface layer, thus impeding diffusion. The crosslinking was confirmed by Raman spectroscopy, whereas the drug release was investigated using UV-Vis spectrometry. Due to the surface barrier, the drug gradually releases into the corneal tissue. To test the function of the carrier, a 3D printed device and a new test method for a controlled drug release, which mimics the geometry and physiological lacrimation rate of the human eye, were developed. The experimental setup with simple geometry revealed that the prepared drug delivery device can provide the prolonged release profile of the pseudo-first-order for up to 72 h. The efficiency of the drug delivery was further demonstrated using a dead porcine cornea as a drug recipient, without the need to use live animals for testing. Our drug delivery system significantly surpasses the efficiency of antibiotic and anesthetic eyedrops that would have to be applied approximately 30 times per hour to achieve the same dose as that delivered continuously by our device.

New approach to prepare cytocompatible 3D scaffolds via the combination of sodium hyaluronate and colloidal particles of conductive polymers.

Bio-inspired conductive scaffolds composed of sodium hyaluronate containing a colloidal dispersion of water-miscible polyaniline or polypyrrole particles (concentrations of 0.108, 0.054 and 0.036% w/w) were manufactured. For this purpose, either crosslinking with N-(3-dimethylaminopropyl-N-ethylcarbodiimide hydrochloride and N-hydroxysuccinimid or a freeze-thawing process in the presence of poly(vinylalcohol) was used. The scaffolds comprised interconnected pores with prevailing porosity values of ~ 30% and pore sizes enabling the accommodation of cells. A swelling capacity of 92-97% without any sign of disintegration was typical for all samples. The elasticity modulus depended on the composition of the scaffolds, with the highest value of ~ 50 kPa obtained for the sample containing the highest content of polypyrrole particles. The scaffolds did not possess cytotoxicity and allowed cell adhesion and growth on the surface. Using the in vivo-mimicking conditions in a bioreactor, cells were also able to grow into the structure of the scaffolds. The technique of scaffold preparation used here thus overcomes the limitations of conductive polymers (e.g. poor solubility in an aqueous environment, and limited miscibility with other hydrophilic polymer matrices) and moreover leads to the preparation of cytocompatible scaffolds with potentially cell-instructive properties, which may be of advantage in the healing of damaged electro-sensitive tissues.

Gas-phase fragmentation of 1-adamantylbisimidazolium salts and their complexes with cucurbit[7]uril studied using selectively 2 H-labeled guest molecules.

RATIONALE: Bisimidazolium salts (BIMs) represent an interesting family of ditopic ligands that are used in the construction of supramolecular systems with hosts based on cyclodextrins or cucurbit[n]urils. Understanding the fragmentation mechanism of individual BIMs and how this mechanism changes after complexation with cucurbit[n]urils can bring new insight into the intrinsic host-guest relationship, thereby allowing utilization of mass spectrometry to describe binding behavior. METHODS: Selectively 2 H-labeled bisimidazolium salts were prepared and fully characterized by spectroscopic methods. All MSn experiments were conducted in the positive-ion mode using an electrospray ionization (ESI) ion-trap mass spectrometer. The structures of the proposed fragments were supported by theoretical optimizations performed at the B3LYP/6-31G(d) level of density functional theory (DFT) using the Spartan'14 program. RESULTS: Using selectively deuterium-labeled isotopologues of two adamantylated bisimidazolium salts and DFT calculations, we describe the fragmentation pathways of bisimidazolium salts. The release of two important adamantane moieties, [C11 H17 ]+ and C11 H16 , from M2+ was determined, although the former was strongly preferred. In contrast, when M2+ was complexed with CB7, the neutral loss of the C11 H16 fragment was favored. The fragmentation pattern strongly depended on the steric hindrance of the M2+ guest against slippage of the CB7 unit over the guest molecular axle. CONCLUSIONS: The structures of two adamantane-based fragments and the mechanisms of their formation were rationalized. Two distinct geometric arrangements for the adamantane cage inside the CB7 cavity were hypothesized to explain the differences in the fragmentation patterns for guests with minimal, moderate, and high steric hindrance. This finding brings new insight into the understanding of intrinsic behavior of the adamantane-based guests inside the CB7 cavity.