Structurally Tunable pH-responsive Phosphine Oxide Based Gels by Facile Synthesis Strategy

Abstract

Design and synthesis of nanostructured responsive gels have attracted increasing attention, particularly in the biomedical domain. Polymer chain configurations and nanodomain sizes within the network can be used to steer their functions as drug carriers. Here, a catalyst-free facile one-step synthesis strategy is reported for the design of pH-responsive gels and controlled structures in nanoscale. Transparent and impurity free gels were directly synthesized from trivinylphosphine oxide (TVPO) and cyclic secondary diamine monomers via Michael addition polymerization under mild conditions. NMR analysis confirmed the consumption of all TVPO and the absence of side products, thereby eliminating post purification steps. The small-angle X-ray scattering (SAXS) elucidates the nanoscale structural features in gels, that is, it demonstrates the presence of collapsed nanodomains within gel networks and it was possible to tune the size of these domains by varying the amine monomers and the nature of the solvent. The fabricated gels demonstrate structure tunability via solvent–polymer interactions and pH specific drug release behavior. Three different anionic dyes (acid blue 80, acid blue 90, and fluorescein) of varying size and chemistry were incorporated into the hydrogel as model drugs and their release behavior was studied. Compared to acidic pH, a higher and faster release of acid blue 80 and fluorescein was observed at pH 10, possibly because of their increased solubility in alkaline pH. In addition, their release in phosphate buffered saline (PBS) and simulated body fluid (SBF) matrix was positively influenced by the ionic interaction with positively charged metal ions. In the case of hydrogel containing acid blue 90 a very low drug release (<1%) was observed, which is due to the reaction of its accessible free amino group with the vinyl groups of the TVPO. In vitro evaluation of the prepared hydrogel using human dermal fibroblasts indicates no cytotoxic effects, warranting further research for biomedical applications. Our strategy of such gel synthesis lays the basis for the design of other gel-based functional materials.

Fabrication of Cellulase Catalysts Immobilized on a Nanoscale Hybrid Polyaniline/Cationic Hydrogel Support for the Highly Efficient Catalytic Conversion of Cellulose

“…PCL ( M n = 80 000) and piperazine were obtained from Sigma-Aldrich (United Kingdom). TVPO was synthesized according to a published work . Analytical grade phosphoric acid, ethanol, methanol, hydrochloric acid, acetone, chloroform, and dimethylformamide (DMF) were purchased from Merck (Germany).…”

“…Preparation of the Electrospun PCL Nano-HG. To prepare uniform nanofibers, PCL was dissolved in a mixed solvent containing chloroform and DMF with a ratio of 90:10 at a concentration of 8% w/v and stirred at ambient temperature for 24 h. Subsequently, four different amounts of piperazine and TVPO (10,25,50, and 75%) in a 1:1 molar ratio mixture (monomers of HG) were added to the 8% w/v PCL solution, based on the previous study, 27 and stirred for 3 h at room temperature to form a homogeneous solution. The well-mixed solution was pumped through an electrospinning machine using a syringe pump.…”

“…A 0.2 M solution of aniline hydrochloride was prepared by dissolving the monomer in 1 M HCL. Then, the PHG web, as well as the HG (prepared based on the previous study 27 ), were immersed in an aniline hydrochloride solution for 6 h. To improve the reaction yield, a stoichiometric molar ratio of 1.25 of ammonium peroxydisulfate: monomer was selected. Polymerization was performed by the dropwise addition of APS to the already prepared monomer solution containing the PHG and HG under continuous shaking (130 rpm) at 5 °C for 30 min.…”

“…The simplicity of the manufacturing process and the ability to control the fiber diameter make this technique extremely attractive to develop solid supports. As the HG formed by mixing two monomers does not have a specific shape, 27 electrospun PCL was used as a scaffold to generate nanofibers with a high specific surface area in this study. To select the appropriate concentration of PCL for electrospinning, 7, 8, and 9% w/v of PCL solutions were prepared.…”

“…In a recent study, , a cationic HG was prepared via the Michael addition reaction of trivinylphosphine oxide (TVPO) and piperazine under ambient conditions. In addition to the existing reports on the effects of phosphine-containing polymers on controlling the size and shape of polymers, the synthesized gel showed other excellent properties, including response to external stimuli (pH, ionic strength, chemicals, and their combinations), easy penetration of water-soluble chemicals, and effective retention of biomolecular activity.…”