Hydration changes of poly(2-(2-methoxyethoxy)ethyl methacrylate) during thermosensitive phase separation in water

Enhanced Solubility and Bioavailability of Clotrimazole in Aqueous Solutions with Hydrophobized Hyperbranched Polyglycidol for Improved Antifungal Activity

The poor solubility of clotrimazole in the aqueous medium and the uncontrolled removal of the drug-loaded suppository content limit its effectiveness in the treatment of vulvovaginal candidiasis. We present here the aqueous formulations of clotrimazole in the form of non-Newtonian structured fluids, i.e., Bingham plastic or pseudoplastic fluids constructed of hyperbranched polyglycidol, HbPGL, with a hydrophobized core with aryl groups such as phenyl or biphenyl. The amphiphilic constructs were obtained by the modification of linear units containing monohydroxyl groups with benzoyl chloride, phenyl isocyanate, and biphenyl isocyanate, while the terminal 1,2-diol groups in the shell were protected during the modification step, followed by their deprotection. The encapsulation of clotrimazole within internally hydrophobized HbPGLs using a solvent evaporation method followed by water addition resulted in structured fluids formation. Detailed Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) analyses performed for aryl-HbPGLs with clotrimazole revealed the difference in drug compatibility among polymers. Clotrimazole in biphenyl-enriched HbPGL, unlike phenyl derivatives, was molecularly distributed in both the dry and the hydrated states, resulting in transparent formulations. The shear-thinning properties of the obtained fluid formulations make them injectable and thus suitable for the intravaginal application. Permeability tests performed with the usage of the Franz diffusion cell showed a 5-fold increase in the permeability constant of clotrimazole compared to drugs loaded in a commercially available disposable tablet and a 50-fold increase of permeability in comparison to the aqueous suspension of clotrimazole. Furthermore, the biphenyl-modified HbPGL-based drug liquid showed enhanced antifungal activity against both Candida albicans and Candida glabrata that was retained for up to 7 days, in contrast to the phenyl-HbPGL derivatives and the tablet. With their simple formulation, convenient clotrimazole/biphenyl-HbPGL formulation strategy, rheological properties, and enhanced antifungal properties, these systems are potential antifungal therapeutics for gynecological applications. This study points in the synthetic direction of improving the solubility of poorly water-soluble aryl-enriched pharmaceuticals.

In situ insight into the self-assembly evolution of ABA-type block copolymers in water during the gelation process using infrared spectroscopy and near-infrared spectroscopy

As a kind of thermo-responsive hydrogel, amphiphilic block copolymers are widely investigated. However, the molecular mechanism of their structural change during the gelation process is still limited. Here, a well-controlled triblock copolymer poly(N,N-dimethylacrylamide)-b-poly(diacetone acrylamide)-b-poly(N,N-dimethylacrylamide) (PDMAA-b-PDAAM-b-PDMAA) was synthesized. Its optical microrheology results suggest a gelation temperature range from 42 to 50 °C, showing a transition from viscosity to elasticity. The morphological transition from spheres to worms occurs. Temperature-dependent IR spectra through two-dimensional correlation spectroscopy (2D-COS) and the Gaussian fitting technique were analyzed to obtain the transition information of the molecular structure within the triblock copolymer. The N-way principal component analysis (NPCA) on the temperature-dependent NIR spectra was performed to understand the molecular interaction between water and the copolymer. The intramolecular hydrogen bonds within the hydrophobic PDAAM block tend to dissociate with temperature, resulting in improved hydration and a relative volume increase of the PDAAM block. The dissociation of intermolecular hydrogen bonds within the PDAAM block was the driving force for the morphological transition. Moreover, the hydrophilic PDMAA block dehydrates with temperature, and three stages can be found. The dehydration rate of the second stage with temperature from 42 to 50 °C was obviously higher than those in the lower (first stage) and higher (third stage) temperature ranges.

The Belousov-Zhabotinsky Reaction in Thermoresponsive Core-Shell Hydrogel Microspheres with a Tris(2,2'-bipyridyl)ruthenium Catalyst in the Core

The Belousov-Zhabotinsky (BZ) reaction shows temporal or spatiotemporal structures such as redox oscillation of the catalyst, [ruthenium(II)tris(2,2'-bipyridine)][PF₆]₂ ([Ru(bpy)₃][PF₆]₂). In this study, autonomously oscillating hydrogel microspheres (microgels) were investigated, which show swelling/deswelling oscillation induced by the redox oscillation of the BZ reaction inside the gel. Despite the periodically and autonomously induced oscillation that does not require an external stimulus, it has not been possible to perform any manipulation of the oscillatory behavior over time. The results of the present study show that it is possible to reversibly switch the microgel oscillations from an "on" active state of the BZ reaction to an "off" inactive state by changing the temperature in combination with thermoresponsive microgels. To realize on-demand switching, the construction of double-shell structures is crucial; the thermoresponsive first shell allows the microgels to modulate the diffusion of the substrates or intermediates in the BZ reaction, while the second shell maintains colloidal stability under high temperatures and high ion concentrations. The functionalized double-shell microgels were prepared via multistep seeded precipitation polymerization. The oscillatory switching behavior of the BZ reaction was observed directly and evaluated by ultraviolet-visible (UV-vis) spectroscopy. The central concept of this study, i.e., "on-off switching" can be expected to benefit the development of advanced bioinspired materials.

Water-Templated, Polysaccharide-rich Bioartificial 3D Microarchitectures as Extra-Cellular Matrix Bioautomatons

This is the first report of exploiting the "quasi-spherical" shape of water molecules for recapitulating a true human extracellular matrix (ECM). Herein, water behaved as a quasi-spherical porogen, for engineering polysaccharide-rich and chemically defined 3D-microarchitecture, with semi-interpenetrating networks (S-IPNs). Furthermore, their viscoelastic behavior along with a heterogeneous, fibroporous morphology, facilitated instructive, self-remodeling of the bioartificial scaffolds, thence effectively permitting and promoting the growth of 3D tumor spheroids of divergent origins. The hybrid composites displayed reproducible, uniform tumor spheroids with a Z-depth of ∼65 ± 2 μm in case of human adenocarcinoma (DLD-1) and ∼54 ± 3 μm for human glioblastoma cells (U-251) (vs. nonuniform spheroids, on Agarose matrix). Thereafter, their capacity for anticancer drug screening was examined using limited cancer drugs. The conflicting drug screening results for Etoposide's reduced efficacy on glioblastoma cells cultured on our 3D matrix could be ascribed to decreased drug access and thus lower ingression. Nonetheless, adenocarcinoma's resistance to Camptothecin was paralleled. Moreover, their potential for real-time, high-content, phenotypic precision oncology was affirmed by the exceptional transparency of the synthesized composite. Since this 3D microarchitecture typifies ECM bioautomaton, this matrix can also be wielded for precision oncology.

Solubility behaviour of random and gradient copolymers of di- and oligo(ethylene oxide) methacrylate in water: effect of various additives

Poly[oligo(ethylene oxide)] based gradient and random copolymers with different compositions are synthesized via Cu-based atom transfer radical polymerization. The solubility behavior of these copolymers in pure water and in the presence of different salts, surfactants and ethanol is investigated. According to dynamic light scattering results, the lower critical solution temperature (LCST) depends on the structure of the copolymer and changes slightly in the presence of additives. Good cosolvents like ethanol can increase the LCST through dissolving the collapsed copolymer chains to some extent. The same effect is observed for surfactants that make the copolymer solution more stable by preventing aggregation. Above a certain concentration of surfactant, depending on the copolymer structure, the solution is stable at all temperatures (no LCST). The effect of salts on the solubility of the copolymers follows the Hofmeister series and it is related linearly to the salt concentration. Based on their affinity to the copolymer, the salts can increase or decrease the LCST. There is a considerable difference in phase transition changes for gradient or random copolymers after salt addition. While both copolymers show a two-step phase transition in the presence of different salts, the changes in the hydrodynamic radius and normalized scattering intensity are rather broad for random compared to gradient copolymers. Contrary to what was expected, varying the cations has no distinguishable effect on the LCST for both copolymers. All chlorides decrease the LCST. This decrease is almost the same for gradient copolymers and fluctuates for random copolymers.

Understanding the role of water in the aggregation of poly(N,N-dimethylaminoethyl methacrylate) in aqueous solution using temperature-dependent near-infrared spectroscopy

For understanding the role of water in the aggregation of polymers, the variation of water structures with the structural change of polymers in the process of aggregation was studied by temperature-dependent near-infrared (NIR) spectroscopy. The NIR spectra of the aqueous poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) solutions of different concentrations were measured at different temperatures. The spectral changes of the polymer and water with temperature were analyzed by N-way principal component analysis (NPCA). It was found that, at low concentration, the chains of the polymer tend to form a loose hydrophobic structure below 36 °C and then aggregate into a micelle at a lower critical solution temperature (LCST) of around 39 °C. In the process of the aggregation, the water species with two hydrogen bonds (S2) increases gradually before 36 °C and then a sudden decrease occurs after that temperature. The results clearly indicate that water species S2 plays an important role in the formation of the intermediate, i.e., the loose hydrophobic structure of the polymer chains linked by the two hydrogen bonds of S2 water. When the temperature increases, the dissociation of the hydrogen bonds enables the intermediate to be destroyed to form a micelle structure. For the high concentration solution, however, the spectral information of S2 was not found in the aggregation, suggesting direct formation of the micelle from the dehydrated chains.

Bioinactive semi-interpenetrating network gel layers: zwitterionic polymer chains incorporated in a cross-linked polymer brush

A thin gel layer with thermo-responsive polymer brushes and semi-interpenetrating PCMB exhibited the switching of bio-inert properties depending on temperature.

Nanocomposite Microgels for the Selective Separation of Halogen Compounds from Aqueous Solution

Nanocomposite microgels that selectively adsorb and release halogen compounds were developed. These nanocomposite microgels consist of poly(2-methoxyethyl acrylate) (pMEA) and a poly(oligo ethylene glycol methacrylate) hydrogel matrix. Therefore, the methoxy groups of the former are crucial for the halogen bonding, while the presence of the latter adds colloidal stability and allows controlled uptake/release of the halogen compounds. Such nanocomposite microgels may not only be used as dispersed carriers, but also in films and columnar formations. Thus, these unprecedented polymer/polymer nanocomposite microgels resolve a variety of problems associated with, e.g., the removal of halogen compounds from wastewater, or with the delivery of halogen-containing drugs.

The role of hydrophobic hydration in the LCST behaviour of POEGMA300 by all-atom molecular dynamics simulations

The role of hydrophobic hydration in the LCST phase transition of POEGMA₃₀₀ by means of the breakage of cage-like water formations around the side chains.

Multitemperature Responsive Self-Folding Soft Biomimetic Structures

Untethered, millimeter-scale, stimuli-responsive shape change structures are critical to the function of autonomous devices, smart materials, and soft robotics. Temperature in a range compatible with physiological or ambient environmental conditions is an excellent cue to trigger actuation of soft structures for practical biomimetic applications. Previously, a range of thermally responsive self-folding soft structures has been described and utilized in a variety of applications from tissue engineering to minimally invasive surgery. In order to extend these concepts to more complex devices, thermally responsive bilayer structures composed of poly[oligo (ethylene glycol) methyl ether methacrylate] (POEGMA) gels that swell at three different temperatures are described. The lower critical solution temperature and volume transition temperature of POEGMA are tuned by varying the side chain length and the extent of copolymerization. The swelling properties of the POEGMA gels are characterized and a multilayer photopatterning process is described that is used to create soft biomimetic structures that change shape in a sequential manner while displaying multistate behaviors.

Antimicrobial colloidal hydrogels assembled by graphene oxide and thermo-sensitive nanogels for cell encapsulation

Hydrogels are promising 3D materials that have demonstrated increasing applications in the encapsulation and delivery of drugs and cells. Herein we report an injectable colloidal hydrogel that directly assembled by graphene oxide (GO) and thermo-sensitive nanogels (tNG). The pH dependent hydrogen bonding interactions between the carboxyl and oxethyl groups induce the reversible assembly of GO and nanogels. The hydrogel is mouldable and can be shaped into different macroscopic objects, and the mechanical strengths are tunable with pH and temperature adjustment. The hybrid hydrogel by its own possesses high antibacterial activity, and demonstrates responsive drug release behaviour and high viability of 3D encapsulated cells. We expect this hybrid colloidal hydrogel can serve as an interesting scaffold for active cargo delivery and cell culture.

Adsorption and Aggregation Properties of Homogeneous Polyoxypropylene-Polyoxyethylene Alkyl Ether Type Nonionic Surfactants

Homogeneous polyoxypropylene (PO)-polyoxyethylene (EO) alkyl ether type nonionic surfactants comprising alkyl, EO, and PO chains with identical chain length distributions (C_nEO_xPO_y; alkyl chain length n = 10, 12, 14, or 16; EO chain length x = 4, 6, or 8; and PO chain length y = 1, 2, or 3) were synthesized from homogeneous polyoxyethylene alkyl ether bromide and monosodium polyoxypropylene by Williamson ether synthesis. The adsorption and aggregation properties of these surfactants were characterized (cloud point, surface tension, dynamic light scattering, small-angle X-ray scattering, polarization microscopy, and cryogenic transmission electron microscopy) and compared to those of conventional homogeneous EO alkyl ether type nonionic surfactants (C_nEO_x). The introduction of a PO chain to the EO terminal group of the C_nEO_x species lowered the cloud points, especially for x = 6. Contrary to our expectations, the C_nEO_xPO_y surfactants adsorbed efficiently at the air/water interface, despite their complex structure (hydrophobic alkyl chain/hydrophilic EO chain/hydrophobic PO chain). They also displayed excellent micelle-forming ability in solution. Furthermore, the C_nEO_x species formed small micelles in solution at low concentrations and the structures transformed to hexagonal liquid crystals as the surfactant concentration increased. Conversely, C_nEO_xPO_y maintained a micellar structure even at high concentrations. Notably, the introduction of a PO chain into the C_nEO_x surfactant controlled the formation of aggregates with a higher-order structure (hexagonal liquid crystals).

Reversible Size Modulation of Aqueous Microgels via Orthogonal or Combined Application of Thermo- and Phototriggers

Aqueous microgels that respond orthogonally to external temperature and light stimuli and to a combination of both stimuli were developed. N-Vinylcaprolactam (VCL) was copolymerized with small feed amounts (<5 mol %) of 4-[(4-methacryloyloxy)phenylazo] benzenesulfonic acid (ABSA) and cross-linked with N,N'-methylenebis(acrylamide) (BIS) to synthesize monodisperse and colloidally stable P(VCL-BIS-ABSA) microgels. The volume phase transition information on the microgels under both orthogonal and combined application of temperature and light stimuli was investigated in situ by dynamic light scattering (DLS) instrument. Modeling of this information by the Flory-Rehner theory describes and aids the preliminary understanding of the main features in the volume phase transition of these photoresponsive microgels. Interestingly, the microgels rapidly deswell upon UV irradiation (λ = 365 nm), even as the trans-ABSA pendant groups are converted to the more polar cis state. The variation in the content of the pendant azobenzene groups in the microgels allows for reversible modulation of the phototriggered volume change. We propose that the approach of the sulfonic acid groups of cis-ABSA toward the polymer backbone causes the disruption of hydrogen bonding interactions between water molecules and the carbonyl groups of VCL.

Understanding the thermosensitivity of POEGA-based star polymers: LCST-type transition in water vs. UCST-type transition in ethanol

The lower critical solution temperature (LCST) transition in water and the upper critical solution temperature (UCST) transition in ethanol of poly(oligo(ethylene glycol) acrylate) (POEGA)-based core cross-linked star (CCS) polymers have been investigated and compared by employing turbidity, dynamic light scattering (DLS), (1)H NMR and FTIR measurements. Macroscopic phase transitions in water and in ethanol were observed to occur when passing through the transition temperature, as revealed by DLS and turbidity measurements. Analysis by IR indicated that the interactions between the polymer chains and solvent molecules in water are stronger than those in ethanol such that the CCS polymer arm chains in water adopt more extended conformations. Moreover, hydrophobic interaction among the aliphatic groups plays a predominant role in the LCST-type transition in water whereas weak solvation of the polymer chains results in the UCST-type transition in ethanol. Additionally, the LCST-type transition in water was observed to be much more abrupt and complete than the UCST-type transition in ethanol, as suggested by (1)H NMR and IR at the molecular level. Finally, an abnormal "forced hydration" phenomenon was observed during the LCST transition upon heating. This study provides a detailed understanding of the subtle distinctions between the thermal transitions of CCS polymers in two commonly used solvents, which may be useful to guide future materials design for a wide range of applications.

The influence of selected NSAIDs on volume phase transition in poly(2-(2-methoxyethoxy)ethyl methacrylate) hydrogels

Hydrogels exhibiting Volume Phase Transition (VPT) are considered as useful biomaterials for the preparation of various drug delivery systems.

Multi-responsive (diethylene glycol)methyl ether methacrylate (DEGMA)-based copolymer systems

RAFT polymerisation was used to synthesise stimuli-responsive DEGMA-based copolymer systems, and their solution properties and aggregation behaviour were then studied.

On the abnormal “forced hydration” behavior of P(MEA-co-OEGA) aqueous solutions during phase transition from infrared spectroscopic insights

During the phase separation of POEGA in water, C–H groups exhibit dehydration, whereas CO and C–O–C groups present “forced hydration”.

Pseudo-graft polymer based on adamantyl-terminated poly(oligo(ethylene glycol) methacrylate) and homopolymer with cyclodextrin as pendant: its thermoresponsivity through polymeric self-assembly and host–guest inclusion complexation

Thermoresponsivity and self-assembly of a pseudo-graft polymer based on Ad-terminated poly(oligo(ethylene glycol) methacrylate) and homopolymer with CD pendants.

Infrared spectroscopic study on hydration and chiral interaction of temperature-responsive polymer with L-proline moieties

We studied the hydration of a temperature-responsive polymer containing L-proline moieties (poly(acryloyl-L-proline methyl ester), PAProM) by using infrared spectroscopy. Red shifts of ν(C-H) bands and blue shifts of amide and ester carbonyl bands of PAProM during temperature-induced phase separation indicate that the alkyl, amide, and ester groups are partially dehydrated. The population of the amide carbonyls forming hydrogen bonds (H-bonds) with two water molecules decreased from 63 to 33%, while that of the ester carbonyls forming one H bonding decreased from 100 to 84%. We labeled the methyl groups of PAProM by introducing deuterium (poly(acryloyl-L-proline methyl-d3 ester, PAProMd3) to clarify hydration change of the labeled groups. Red shifts of three ν(C-D) bands appearing at 2000-2200 cm(-1) clearly showed that the methyl groups at the end of side chains also dehydrated as well as the alkyl groups on the main chain. As for the effects of additives, methanol raised the phase separation temperature (Tp) of PAProM. The IR spectra show that the average number of H bonds to the amide and ester carbonyls decreases with increasing methanol concentration and that the water molecules surrounding the alkyl groups of PAProM are replaced by methanol molecules. The increase in Tp suggests that the favorable effect of the latter is superior to the unfavorable effect of the former. On the other hand, malic acid (MA) reduced Tp of PAProM. Moreover, a chiral interaction occurs; that is, Tp was lower in the presence of d-isomer than L-isomer. The analysis of the amide band revealed that the d-isomer associates more effectively with the amide carbonyls of PAProM than the L-isomer does.