Multiple hour antifibrotic drug release enabled by a thermosensitive quadpolymer

Injectable drug delivery for uterine fibroid therapy is an ambitious, possibly fertility-preserving concept, that could meet the challenges associated with the structure of these tumors and their location in the uterus. This study was conducted to advance a thermosensitive injectable quadpolymer for effective sustained release of anti-fibrotic drug formulations and to evaluate the feasibility of its use for delivery of the anti-fibrotic drug pirfenidone as a therapy to reduce fibroid cell proliferation. A series of quadpolymers were prepared by free radical polymerization of N-isopropylacrylamide (NIPAM) with different amounts of polylactic acid functionalized hydroxyethyl methacrylate (HEMA-PLA), acrylic acid (AAc), and methacrylate functionalized hyperbranched polyglycerol (HPG-MA) to optimize the sol-gel phase transition temperature and mechanical stiffness. Poly(NIPAM-co-HEMA-PLA-co-AAc-co-HPG-MA) with feed ratio (83-7-1-9), at 17% w/v, readily formed an aqueous solution that could be manipulated by syringe at room temperature. The quadpolymer also rapidly formed a stable gel at physiological body temperature, and partially biodegraded over time as confirmed by several spectroscopic characterization techniques. To evaluate the potential range of utility, quadpolymer 83-7-1-9 was loaded in-vitro with caffeine (a prototype hydrophilic drug) or the hydrophobic drug pirfenidone. Pirfenidone-loaded quadpolymer 83-7-1-9 formulations released 50% of drug loaded in double the time as compared to other reported liposome and nanoparticle injectable pirfenidone formulations. Furthermore, treatment of cultured fibroid cells with pirfenidone-loaded quadpolymer 83-7-1-9 formulations confirmed that activity of pirfenidone was preserved and proliferation of fibroid cells was inhibited. These results support that quadpolymer 83-7-1-9 is a promising candidate to be further developed for localized delivery of drugs for uterine fibroid therapy.

Ecofriendly Controlled-Release Insecticide Carrier: pH-/Temperature-Responsive Rosin-Derived Hydrogels for Avermectin Delivery against Mythimna separata (Walker)

The exploration of environmentally friendly, less toxic, sustained-release insecticide is increasing with the growing demand for food to meet the requirements of the expanding population. As a sustained-release carrier, the unique, environmentally friendly intelligent responsive hydrogel system is an important factor in improving the efficiency of insecticide utilization and accurate release. In this study, we developed a facile approach for incorporating the natural compound rosin (dehydroabietic acid, DA) and zinc ions (Zn2+) into a poly(N-isopropylacrylamide) (PNIPAM) hydrogel network to construct a controlled-release hydrogel carrier (DA-PNIPAM-Zn2+). Then, the model insecticide avermectin (AVM) was encapsulated in the carrier at a drug loading rate of 36.32% to form AVM@DA-PNIPAM-Zn2+. Surprisingly, the smart controlled carrier exhibited environmental responsiveness, strongly enhanced mechanical properties, self-healing ability, hydrophobicity, and photostability to ensure a balance between environmental friendliness and the precision of the drug release. The release experiments showed that the carboxyl and amide groups in the polymer chains alter the intermolecular forces within the hydrogel meshes and ingredient diffusion by changing temperatures (25 and 40 °C) and pH values (5.8, 7.4, and 8.5), leading to different release behaviors. The insecticidal activity of the AVM@DA-PNIPAM-Zn2+ against oriental armyworms was good, with an effective minimum toxicity toward aquatic animals. Therefore, AVM@DA-PNIPAM-Zn2+ is an effective drug delivery system against oriental armyworms. We anticipate that this ecofriendly, sustainable, smart-response carrier may broaden the utilization rosin and its possible applications in the agricultural sector.

Morphological transitions of cationic PISA particles by salt, triflate ions and temperature; comparison of three polycations

Three strong polycation stabilizers, poly((vinylbenzyl) trimethylammonium chloride), PVBTMAC, poly((2-(methacryloyloxy)ethyl)trimethylammonium chloride), PMOTAC, and poly((3-acrylamidopropyl) trimethylammonium chloride), PAMPTMAC have been synthesized with reversible addition-fragmentation chain transfer, RAFT, reactions. Solubilities of the polycations...

Synthesis, characterization and in vitro cytotoxicity studies of poly-N-isopropyl acrylamide gel nanoparticles and films

In this work, we show synthesis that leads to thermoreponsive poly-N-isopropyl acrylamide (pNIPAM) nanogels with sizes below 100 nm, irrespectively of the surfactant to crosslinker ratio. We also show that in many environments the temperature induced pNIPAM collapse at Lower Critical Solution Temperature (LCST) of 32.5 °C is accompanied by gel nanoparticles' aggregation. Thus, the proper information on the nanoparticle (NP) structure and deswelling can be obtained only if the routinely measured hydrodynamic radius is supplemented by information on the molecular weight, which can be obtained from the intensity of scattered light. We measured the dynamics and reversibility of the deswelling and subsequent aggregation processes. Furthermore, we show that the highly concentrated pNIPAM gel NPs reversibly form bulk hydrogel networks of varied interconnected porous structure. We show, that in case of drying pNIPAM gel NPs above the LCST, it is possible to obtain films with 20-fold increase in storage modulus (G') compared to hydrogel networks measured at room temperature. They exhibit temperature hysteresis behavior around LCST of 32.5 °C similar to pNIPAM films. Finally, we show that these hydrogel films, lead to extended proliferation of cells across three different types: fibroblast, endothelial and cancer cells. Additionally, none of the films exhibited any cytotoxic effects. Our study brings new insights into physicochemical characterization of pNIPAM gel NPs and networks behavior in realistic conditions of in vitro measurements, especially by means of dynamic light scattering as well as final unique properties of both gel NPs and formed porous films for possible tissue engineering applications.

CE and asymmetrical flow-field flow fractionation studies of polymer interactions with surfaces and solutes reveal conformation changes of polymers

Amphiphilic diblock copolymers consisting of a hydrophobic core containing a polymerized ionic liquid and an outer shell composed of poly(N-isoprolylacrylamide) were investigated by capillary electrophoresis and asymmetrical flow-field flow fractionation. The polymerized ionic liquid comprised poly(2-(1-butylimidazolium-3-yl)ethyl methacrylate tetrafluoroborate) with a constant block length (n = 24), while the length of the poly(N-isoprolylacrylamide) block varied (n = 14; 26; 59; 88). Possible adsorption of the block copolymer on the fused silica capillary, due to alterations in the polymeric conformation upon a change in the temperature (25 and 45 °C), was initially studied. For comparison, the effect of temperature on the copolymer conformation/hydrodynamic size was determined with the aid of asymmetrical flow-field flow fractionation and light scattering. To get more information about the hydrophilic/hydrophobic properties of the synthesized block copolymers, they were used as a pseudostationary phase in electrokinetic chromatography for the separation of some model compounds, that is, benzoates and steroids. Of particular interest was to find out whether a change in the length or concentration of the poly(N-isoprolylacrylamide) block would affect the separation of the model compounds. Overall, our results show that capillary electrophoresis and asymmetrical flow-field flow fractionation are suitable methods for characterizing conformational changes of such diblock copolymers.

Thermoresponsive behavior of poly[trialkyl-(4-vinylbenzyl)ammonium] based polyelectrolytes in aqueous salt solutions

A systematic method to induce thermoresponsive behavior for polycations with salts from the reversed Hofmeister series is introduced.

Molecular Mass Affects the Phase Separation of Aqueous PEG-Polycation Block Copolymer

Mechanisms of the phase separation and remixing of cationic PEG-containing block copolymers have been investigated in aqueous lithium triflate solutions. The polycation was poly(vinylbenzyl trimethylammonium triflate). We have previously reported on one such block copolymer, which upon cooling of a hot clear solution first underwent phase separation into a turbid colloid and, later, partially cleared again with further cooling. To better understand the balance of various interactions in the solutions/dispersions, a series of polymers with varying DP of the cationic block was synthesized. From one of the polymers, the alkyl end group (a fragment of the chain transfer agent) was removed. The length of the cationic block affected critically the behavior, but the hydrophobic end group had a minimal effect. Polymers with a short cationic block turn cloudy and partially clear again during a temperature decrease, whereas those with a long cationic block phase separate and slowly precipitate and remix only when heated. Phase separation takes place via particle formation, and we suggest different mechanisms for colloidal stabilization of particles composed of short or long chains.

Poly(2-propyl-2-oxazoline)s in Aqueous Methanol: To Dissolve or not to Dissolve

At room temperature, poly(N-isopropylacrylamide) (PNIPAM) is soluble in water and methanol, but it is not soluble in certain water/methanol mixtures. This phenomenon, known as cononsolvency, has been explored in great detail experimentally and theoretically in an attempt to understand the complex interactions occurring in the ternary PNIPAM/water/co-nonsolvent system. Yet little is known about the effects of the polymer structure on cononsolvency. To address this point, we investigated the temperature-dependent solution properties in water, methanol, and mixtures of the two solvents of poly(2-cyclopropyl-2-oxazoline) (PcyPOx) and two structural isomers of PNIPAM (M_n ∼ 11 kg/mol): poly(2-isopropyl-2-oxazoline) (PiPOx) and poly(2-n-propyl-2-oxazoline) (PnPOx). The phase diagram of the ternary water/methanol/poly(2-propyl-2-oxazolines) (PPOx) systems, constructed based on cloud point (T_CP) measurements, revealed that PnPOx exhibits cononsolvency in water/methanol mixtures. In contrast, methanol acts as a cosolvent for PiPOx and PcyPOx in water. The enthalpy, ΔH, and temperature, T_max, of the coil-to-globule transition of the three polymers in various water/methanol mixtures were measured by high-sensitivity differential scanning calorimetry. T_max follows the same trends as T_CP, confirming the cononsolvency of PnPOx and the cosolvency of PiPOx and PcyPOx. ΔH decreases linearly as a function of the methanol content for all PPOx systems. Ancillary high-resolution ¹H NMR spectroscopy studies of PPOx solutions in D₂O and methanol-d₄, coupled with DOSY and NOESY experiments revealed that the n-propyl group of PnPOx rotates freely in D₂O, whereas the rotation of the isopropyl and cyclopropyl groups of PiPOx and PcyPOx, respectively, is limited due to steric restriction. This factor appears to play an important role in the case of the PPOxs/water/methanol ternary system.

Functional Surfaces through Controlled Assemblies of Upper Critical Solution Temperature Block and Star Copolymers

Endowing surfaces with multiple advanced functionalities, such as temperature-controlled swelling or the triggered release of functional small molecules, is attractive for a large variety of applications ranging from smart textiles to advanced biomedical applications. This Invited Feature Article summarizes recent advances in the development of upper critical solution temperature (UCST) behavior of copolymers in aqueous solutions and compares the fundamental differences between lower critical solution temperature (LCST) and UCST transitions. The effect of polymer chemistry and architecture on UCST transitions is discussed for block copolymer micelles (BCMs) and star polymers in solution and assembled at surfaces. The inclusion of such nanocontainers (i.e., BCMs and star polymers) in layer-by-layer (LbL) coatings and how to control their responsive behavior through deposition conditions and binding partners is explored. Finally, the inclusion and temperature-triggered release of functional small molecules is explored for nanocontainers in LbL coatings. Taken together, UCST nanocontainers containing LbL films are promising building blocks for the development of new generations of practical, functional surface coatings.

Thermosensitive hydrogels a versatile concept adapted to vaginal drug delivery

Vaginal drug delivery represents an attractive strategy for local and systemic delivery of drugs otherwise poorly absorbed after oral administration. The rather dense vascular network, mucus permeability and the physiological phenomenon of the uterine first-pass effect can all be exploited for therapeutic benefit. However, several physiological factors such as an acidic pH, constant secretion, and turnover of mucus as well as varying thickness of the vaginal epithelium can impact sustained drug delivery. In recent years, polymers have been designed to tackle challenges mentioned above. In particular, thermosensitive hydrogels hold great promise due to their stability, biocompatibility, adhesion properties and adjustable drug release kinetics. Here, we discuss the physiological and anatomical uniqueness of the vaginal environment and how it impacts the safe and efficient vaginal delivery and also reviewed several thermosensitive hydrogels deemed suitable for vaginal drug delivery by addressing specific characteristics, which are essential to engage the vaginal environment successfully.

Facile synthesis of thermo-, pH-, CO2- and oxidation-responsive poly(amido thioether)s with tunable LCST and UCST behaviors

Multi-responsive N-substituted poly(amido thioether) copolymers synthesized by one-pot amine–thiol–acrylate polyaddition could exhibit composition-dependent and stimuli-triggered single or double thermoresponsivity.

pH responsive highly branched poly(N-isopropylacrylamide) with trihistidine or acid chain ends

Thermally responsive highly branched poly(N-isopropyl acrylamide)s (HB-PNIPAM) were prepared and end-functionalised to give polymers with acid or trihistidine end groups. ​The ionisation of the end groups affects the swelling of desolvated globules.

RAFT synthesis of triply responsive poly[N-[2-(dialkylamino)ethyl]acrylamide]s and their N-substitute determined response

The thermo- and pH/CO₂-responsive poly[N-[2-(dialkylamino)ethyl]acrylamide]s containing a polyacrylamide backbone but different N-substitutes of dialkylamine were synthesized and their solution properties were comparatively checked.