pH- and thermo-responsive solution behavior of amphiphilic, linear triblock terpolymers

PnBA-b-PNIPAM-b-PDMAEA Thermo-Responsive Triblock Terpolymers and Their Quaternized Analogs as Gene and Drug Delivery Vectors

In this work, the ability of thermo-responsive poly [butyl acrylate-b-N-isopropylacrylamide-b-2-(dimethylamino) ethyl acrylate] (PnBA-b-PNIPAM-b-PDMAEA) triblock terpolymer self-assemblies, as well as of their quaternized analogs (PnBA-b-PNIPAM-b-QPDMAEA), to form polyplexes with DNA through electrostatic interactions was examined. Terpolymer/DNA polyplexes were prepared in three different amine over phosphate group ratios (N/P), and linear DNA with a 2000 base pair length was used. In aqueous solutions, the terpolymers formed aggregates of micelles with mixed PNIPAM/(Q)PDMAEA coronas and PnBA cores. The PnBA-b-PNIPAM-b-PDMAEA terpolymers' micellar aggregates were also examined as carriers for the model hydrophobic drug curcumin (CUR). The complexation ability of the terpolymer with DNA was studied by UV-Vis spectroscopy and fluorescence spectroscopy by investigating ethidium bromide quenching. Fluorescence was also used for the determination of the intrinsic fluorescence of the CUR-loaded micellar aggregates. The structural characteristics of the polyplexes and the CUR-loaded aggregates were investigated by dynamic and electrophoretic light scattering techniques. Polyplexes were found to structurally respond to changes in solution temperature and ionic strength, while the intrinsic fluorescence of encapsulated CUR was increased at temperatures above ambient.

Recyclable DNA-Derived Polymeric Sensor: Ultrasensitive Detection of Hg(II) Ions Modulated by Morphological Changes

Going beyond organic solvent as the solubilizer for small-molecular organic probes motivates exploration of water-soluble polymeric sensors. In this respect, dye-derived thermal-responsive polymeric sensors are an attractive direction, but for its practical application, it is limited by sensor recycling because only irreversible change in the structure of the recognition unit for many sensors can trigger the appearance of the detection signal. Here, we established the oligonucleotide-derived thermal-responsive polymeric sensor, TBC-P1, which overcame this fundamental limitation. The TBC-P1 sensor was based on reversible binding between oligonucleotides and Hg²⁺ ions, and easy sensor separation via tuning temperature, achieving the Hg²⁺ detection in a cost-effective and green manner. The TBC-P1 sensor displayed specific and rapid sensing properties toward Hg²⁺ ions in pure aqueous media via turn-off fluorescence emission, with a limit of detection as low as 0.65 nM (much lower than the presently reported dye-derived polymeric sensors). This high detection sensitivity was further enhanced (with LOD = 0.17 nM) via warming to yield spherical micelles, in which the oligonucleotide-containing thermoresponsive PNIPAM block forming a hydrophobic core amplified the fluorescence signals. Treating the Hg²⁺-trapped micelles with cysteine (Cys) led to competition-induced release of these combined Hg²⁺ ions and then thermally precipitating and recycling polymeric sensor TBC-P1. This oligonucleotide-derived thermalresponsive polymeric sensor will open a universal avenue for sensor recycling, which will achieve the goal of reducing cost and improving detection sensitivity of sensors.

Synthesis and physicochemical properties of dual-responsive acrylic acid/butyl acrylate cross-linked nanogel systems

HYPOTHESIS

A cross-linked amphiphilic nanogel containing a high mole% of hydrophilic pH-responsive moiety can provide enhanced functionality regarding stimuli-responsiveness, water-dispersibility, hydrophobic substance loading, and structural stability under harsh environmental conditions. These nanogels could be synthesized using a one-pot procedure for large-scale applications. Moreover, the interplay of various interaction forces in these colloidal systems is being investigated.

EXPERIMENTS

Model nanogels consisting of acrylic acid-butyl acrylate-ethylene glycoldimethacrylate were synthesized using an emulsion copolymerization via a seeded semi-batch process under an acidic condition. The structures were assessed by Fourier transform infrared spectroscopy and potentiometric-conductometric titrations. Zeta potential, field-emission scanning electron microscopy, and transmission electron microscopy were used to evaluate the dispersion stability, size distribution, and structural distribution, respectively. Their stimuli-responsive behavior was studied by combining static and dynamic light scattering and titration analyses.

FINDINGS

Monodisperse nanospheres of approximately 150 nm were successfully prepared by implementing a one-pot practical pathway. These nanogels displayed a dual thermo- and pH-responsive behavior, reflecting the high efficiency of physical cross-linking make it ideal for drug delivery and oil industry applications. Moreover, a novel symmetric pH-activated morphology transformation behavior was revealed. Accordingly, a compositional distribution was proposed and assessed by exploring the polymerization process.

Synthesis and self-assembly of a carborane-containing ABC triblock terpolymer: morphology control on a dual-stimuli responsive system

Amphiphilic triblock terpolymers have attractive applications in the preparation of nanoparticles with controlled morphology.