Thermosensitive Copolymers Research Articles

Thermosensitive hybrid hydrogels with silica nanoparticle-cross-linked polymer networks

A simple methodology for the preparation of thermosensitive organic–inorganic hybrid hydrogels using silica nanoparticle-mediated polymer networks is described. A thermosensitive copolymer poly[N-isopropylacrylamide-co-(3-methacryloxypropyltrimethoxysilane)], (pNS), with reactive side chains (SiOCH3) was first synthesized by free radical polymerization using N-isopropylacrylamide (NIPAAm) and 3-methacryloxypropyltrimethoxysilane (MAPTS). Then, simple mixing of the aqueous solution of this copolymer with silica nanoparticle (SiP) suspensions at room temperature led to the formation of thermosensitive hybrid hydrogels cross-linked with silica nanoparticles (SiP) which did not require any other processing like washing for the removal of unreacted monomers and initiators. The effects of SiP content on gelation abilities, temperature-responsive behaviors, swelling and deswelling kinetics, and mechanical properties of the hydrogels were investigated. The results showed that transparent hybrid hydrogels with adjustable network structures were obtained within a few minutes to a couple of hours depending on the concentration of the copolymers and the silica nanoparticles. The hybrid hydrogels exhibited a lower critical solution temperature (LCST) of around 33°C with no significant deviation from conventional poly(N-isopropylacrylamide) hydrogels; the LCST was not significantly affected by the concentration of silica nanoparticles (which in these systems serve as the cross-linkers). In addition, the hydrogels showed significantly large equilibrium swelling ratios, improved mechanical strength, and suitable deswelling behavior, which can easily be tuned by varying the composition of the hybrid hydrogels.

Π–Π Stacking Increases the Stability and Loading Capacity of Thermosensitive Polymeric Micelles for Chemotherapeutic Drugs

Thermosensitive amphiphilic block copolymers self-assemble into micelles above their lower critical solution temperature in water, however, the micelles generally display mediocre physical stability. To stabilize such micelles and increase their loading capacity for chemotherapeutic drugs, block copolymers with novel aromatic monomers were synthesized by free radical polymerization of N-(2-benzoyloxypropyl methacrylamide (HPMAm-Bz) or the corresponding naphthoyl analogue (HPMAm-Nt), with N-(2-hydroxypropyl) methacrylamide monolactate, using a polyethylene glycol based macroinitiator. The critical micelle temperatures and critical micelle concentrations decreased with increasing the HPMAm-Bz/Nt content. The micelles of 30-50 nm were prepared by heating the polymer aqueous solutions from 0 to 50 °C and were colloidally stable for at least 48 h at pH 7.4 and 37 °C. Paclitaxel and docetaxel encapsulation was performed by mixing drug solutions in ethanol with polymer aqueous solutions and heating from 0 to 50 °C. The micelles had a drug loading capacity up to 34 wt % for docetaxel, which is among the highest loadings reported for polymeric micelles, with loaded micelle sizes ranging from 60 to 80 nm. The micelles without aromatic groups almost completely released loaded paclitaxel in 10 days, whereas the HPMAm-Bz/Nt containing micelles released 50% of the paclitaxel at the same time, which showed a better retention for the drug of the latter micelles. (1)H solid-state NMR spectroscopy data are compatible with π-π stacking between aromatic groups. The empty micelles demonstrated good cytocompatibility, and paclitaxel-loaded micelles showed high cytotoxicity to tumor cells. In conclusion, the π-π stacking effect introduced by aromatic groups increases the stability and loading capacity of polymeric micelles.

Toxicity andin vivobiological effect of the nanoparticular self-supported hydrogel of a thermosensitive copolymer for non-invasive drug delivery

Injectable thermosensitive hydrogels provide local non-invasive platforms for sustained drug release,tissue engineering and cellular immunity. As a long-term implant, the toxicity and in vivo biological effect should be concerned.Previously we developed a novel type of injectable nanoparticular self-supported hydrogel (PECT NPs(Gel))of PEG and pendent cycle ethers modified poly(ε-caprolactone) triblock copolymer (PECT), which could sustainedly release PECT or drug-loaded PECT nanoparticles with the hydrogel disassembly and provided efficient antitumor activity and significant decrease of side effects. Herein, the aim of this work was to reveal the toxicity and in vivo biological effect of PECT nanoparticles and PECT NPs(Gel). In vitro cytotoxicity indicated no cell cytotoxicity was observed when the concentration of PECT nanoparticle was up to 500 µg/mL, and also nomutagenic effect and no genotoxicity were observed.In vivo intravenous injection of PECT nanoparticles demonstrated that the LD50 was approximate high to 2.564 g/kg, and compared with the control mice, the mice treated with daily administration of PECT nanoparticles showed no difference in the physical or behavioral alterations, body weight changes, biochemical and hematological parameters as well as organ coefficients. The in vivo chronic effect of PECT NPs(Gel)confirmed no toxic lesions to animals in a whole period of three months even the dosage was high to 20 g/kg. These findings indicated PECT nanoparticles and PECT NPs(Gel) were of well biocompatibility and did not provoke any side effect to body, which represented a new class of injectable and non-invasive systemic or site-specific delivery carrier.

Nonlinear depression of the lower critical solution temperatures in aqueous solutions of thermo‐sensitive random copolymers

ABSTRACTWe develop a theoretical model of cooperative hydration to clarify the molecular origin of the observed nonlinear depression of the lower critical solution temperature (LCST) in the aqueous solutions of thermosensitive random copolymers and find the monomer composition at which LCST shows a minimum. Phase diagrams of poly(N‐isopropylacrylamide‐co‐N,N‐diethylacrylamide) copolymer solutions are theoretically derived on the basis of the theory of cooperative hydration by introducing the microscopic structure parameter η which characterizes the distribution of the monomer sequences along the chains. We compared them with the experimental data of LCST of random copolymers with various monomer compositions and also of the diblock copolymers with equimolar monomer composition. The transition temperature shifts to lower than those of homopolymer counterparts when the monomer sequence of the chains has an alternative tendency. On the contrary, for the blocky polymers such as diblock copolymers, the transition temperature remains almost the same as those of the homopolymers. Thus, the nonlinear effect in phase separation appears when the average block length of the copolymers is shorter than the average sequence length of the cooperative hydration. The degree of hydration is calculated as a function of the temperature and polymer concentration for varied distribution of the copolymer compositions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1112–1123

Poly(N-isopropylacrylamide-co-hydroxyethylacrylamide) thermosensitive microspheres: The size of microgels dictates the pulsatile release mechanism

Poly(N-isopropylacrylamide-co-N-hydroxyethylacrylamide) (poly(NIPAAm-co-HEAAm)) was prepared as a new thermosensitive copolymer possessing a sharp phase transition around the human body temperature. The effect of the copolymer concentration on the lower critical solution temperature (LCST) was determined under physiological conditions by cloud point (CP) and differential scanning calorimetric (DSC) methods. Then, thermosensitive microspheres were prepared from preformed copolymers by chemical cross-linking of hydroxyl groups with glutaraldehyde at a temperature situated slightly below LCST of the copolymer solution. The volume phase transition temperature (VPTT) of corresponding cross-linked microspheres was determined from swelling degree-temperature curve. The microspheres were loaded with model drug indomethacin by the solvent evaporation method. The DSC analysis proved that the drug is molecularly dispersed in the polymer network. Finally, the influence of the microsphere size on drug release was investigated. It was established that microspheres with the diameter ranging between 5 and 60μm release the drug with almost the same rate below (in the swollen state) and above the VPTT (in the collapsed state). On the contrary, microspheres with the diameter ranging between 125 and 220μm release a significantly higher amount of indomethacin below than above the VPTT. This different behavior is enough to assure a pulsatile release mechanism when the temperature changes cyclically below and above the VPTT. However, both small and large microspheres release a large amount of the drug during the collapsing process.

Nucleation and growth of micellar polycrystals under time-dependent volume fraction conditions

We study the freezing kinetics of colloidal polycrystals made of micelles of Pluronic F108, a thermosensitive copolymer, to which a small amount of silica nanoparticles of size comparable to that of the micelles are added. We use rheology and calorimetry to measure Tc, the crystallization temperature, and find that Tc increases with the heating rate \dot{T} used to crystallize the sample. To rationalize our results, we first use viscosity measurements to establish a linear mapping between temperature T and the effective volume fraction, {\phi}, of the micelles, treated as hard spheres. Next, we reproduce the experimental \dot{T} dependence of the crystallization temperature with numerical calculations based on standard models for the nucleation and growth of hard spheres crystals, classical nucleation theory and the Johnson-Mehl-Avrami-Kolmogorov theory. The models have been adapted to account for the peculiarities of our experiments: the presence of nanoparticles that are expelled in the grain boundaries, and the steady increase of T and hence {\phi} during the experiment. We moreover show that the polycrystal grain size obtained from the calculations is in good agreement with light microscopy data. Finally, we find that the {\phi} dependence of the nucleation rate for the micellar polycrystal is in remarkable quantitative agreement with that found in previous experiments on colloidal hard spheres. These results suggests that deep analogies exist between hard-sphere colloidal crystals and Pluronics micellar crystals, in spite of the difference in particle softness. More generally, our results demonstrate that crystallization processes can be quantitatively probed using standard rheometry.

Effect of Heating Rate on the Pathway for Vesicle Formation in Salt-Free Aqueous Solutions of Thermosensitive Cationic Diblock Copolymers

Amphiphilic diblock copolymers composed of a thermo-responsive poly(2-isopropyl-2-oxazoline) (PIPOZ) block (Mn = 7000 g/mol) linked to a poly(3-acrylamidopropyl)trimethylammonium chloride) (PAMPTMA) block (Mn = 3500 or 8200 g/mol) were prepared by cationic ring-opening polymerization (PIPOZ block) and subsequent atom transfer radical polymerization (PAMPTMA block). Salt-free dilute aqueous solutions of the diblock copolymers underwent a reversible phase transition upon heating past 40 °C that led to the formation of vesicles, as established by light scattering (LS) and transmission electron microscopy (TEM) studies of solutions heated to 60 °C. The pathway toward vesicles varied depending on the heating rate. A slow heating rate (0.2 °C/min) led to the formation of small spheres as the temperature reached 40 °C; the spheres grew in size as the temperature increased and eventually converted into vesicles by diffusion of some hydrophilic charged blocks toward the center. Upon application of a fast heating rate (0.7 °C/min or faster), the copolymers formed rod-like and/or worm-like micelles at 40 °C and, at higher temperature, oblate membranes that closed up into vesicles. The kinetic control of the pathway toward vesicles may be attributed to the existence of several metastable states in the system, by analogy with studies of the isothermal self-assembly of diblock copolymers in selective solvents.

Removal of metal ions from aqueous effluents involving new thermosensitive polymeric sorbent

In this work, new thermosensitive copolymers bearing phosphonated groups were synthesized and used to remove metal pollution. Sorption properties are brought by hydrolyzed (dimethoxyphosphoryl)methyl 2-methylacrylate (hMAPC1) monomer. N-n-propylacrylamide (NnPAAm) led to the thermoresponsive properties of the copolymers. Low lower critical solution temperature (LCST) values were observed, ranging between 20 and 25 °C depending on the molar ratio of each monomer in the copolymer. Sorption properties of these copolymers towards nickel ions were evaluated for increasing temperatures (10-40 °C), Ni ion concentrations of 20 mg L(-1) and pH values between 3 and 7. Best results were observed for temperatures just lower than the LCST (20 °C), when the copolymer was fully soluble in water solution. For temperature higher than the LCST, phosphonic diacid groups accessibility was considerably reduced by the precipitation of the thermosensitive part of the copolymer leading to lower sorption properties. In these conditions, the highest Ni removal by the copolymer was observed for pH = 7, when there was almost no competition between the sorption of H(+) and Ni(2+) ions on the phosphonic acid groups. These optimal conditions enabled removal of about 70% of the nickel in the synthetic effluent.

Thermosensitive behavior in cell culture media and cytocompatibility of a novel copolymer: poly(N-isopropylacrylamide-co-butylacrylate)

Cell sheet technology is a promising step forward in tissue engineering. Cell sheets are usually generated using Poly(N-isopropylacrylamide) hydrogels due to their swelling change around the lower critical solution temperature (LCST). Nevertheless, LCST can be affected by cell culture medium components and therefore it is necessary to ensure that the polymer preserves its thermosensitivity under these conditions. We propose a novel thermosensitive crosslinked-copolymer: Poly(N-isopropylacrylamide-co-butylacrylate). This copolymer is shown to be cytocompatible and thermosensitive under cell culture medium conditions, and besides, it can be synthesized inexpensively. Thermosensitivity was investigated by determining the LCST with differential scanning calorimetry and swelling/ratio measurements. Cytocompatibility and capacity to deliver cell sheets were studied employing 3T3 and human oral epithelial cells. In conclusion, we obtained a thermosensitive copolymer that allows cell sheet formation/detachment by using a simple and low-cost polymerization method. Furthermore, crosslinking allows easy manipulation of cell sheets growing on the copolymer for potential in situ applications.

Preparation of injectable and thermoresponsive hydrogel based on penta-block copolymer with improved sol stability and mechanical properties

New biocompatible, biodegradable and thermosensitive penta-block copolymer poly (N-isopropylacrylamide)–b-poly (∊-caprolactone)–b-poly ethylene glycol–b-poly (∊-caprolactone)–b-poly (N-isopropylacrylamide) (PNIPAAm–PCL–PEG–PCL–PNIPAAm) was synthesized by a combination of controlled ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). This penta-block copolymer undergoes reversible sol–gel transitions between room temperature (22 °C) and human body temperature (37 °C). By incorporation of poly (N-isopropylacrylamide) (PNIPAAm) block at the end of PCL–PEG–PCL (PCEC) triblock copolymer, the resulting PNIPAAm–PCEC–PNIPAAm penta-block copolymer achieves improved mechanical properties and high sol stability while keeping its thermogelling property in the range of physiological temperatures 20–50 °C. The mechanical properties of these materials as a function of temperature were measured by rheometry. To confirm the sol stability, the crystalizability of penta-block copolymer was analyzed by the XRD. The sol-to-gel transition temperature of block copolymer aqueous solution is controllable by varying the composition and molecular weight of PEG and PNIPAAm. Their physicochemical properties in aqueous media were characterized by 1H NMR spectroscopy and GPC techniques. This amphiphilic copolymer is self-assembled into spherical micelles in aqueous solution at room temperature. The critical micelle concentration (CMC) of these amphiphilic block copolymers was studied by fluorescence techniques. The size distribution and thermal responses of the polymeric micelles and aggregation to hydrogel in higher temperature were investigated by dynamic light scattering (DLS). The synthesized copolymer showed no apparent cytotoxicity on normal cells. In vitro release studies showed that the anticancer agent Na-HCl is effectively loaded and released by the temperature sensitive PNIPAAm–PCEC–PNIPAAm penta-block copolymer.

<i>In Vitro</i> Studies of NIPAAM-MAA-VP Copolymer-Coated Magnetic Nanoparticles for Controlled Anticancer Drug Release*

Thermosensetive poly(N-isopropylacrylamide)-based magnetic nanoparticles were synthesized by free radical polymerization of N-isopropylacrylamide (NIPPAMs), methacrylic acid (MAA), and vinyl pyrrolidone (VP) in the presence of methylene-bis-acrylamide as cross linking agent. The Fe3O4 magnetic nanoparticls were prepared by chemical precipitation of Fe salts in the ratio of 1:2 under alkaline and inert condition. Thermosensitive crosslinked P (NI-PAAM-MAA-VP) copolymers were characterized by FT-IR and H-NMR. The pH and thermosensitive copolymer was used for preparation of drug loaded magnetic nanoparticles, and doxorubicin (DOX) was used as a typical anticancer drug. The amount of the loaded drug and drug release amount were determined by UV measurements. Scanning electron microscopy (SEM) and lower critical solution temperature (LCST) were used to determine the particle surface morphology and the phase transition temperature of the nanoparticles respectively. The release behavior of DOX at pH = 7.4 and 37°C was studied. The result indicated that this thermosensetive magnetic nanoparticle has a high drug loading capacity and favorable linear release property for DOX without initial burst release. Thus this system is promising for the application in targeted smart anticancer drug delivery.

Dual responsive micelles based on poly[(R)-3-hydroxybutyrate] and poly(2-(di-methylamino)ethyl methacrylate) for effective doxorubicin delivery

We present novel pH and thermo-sensitive amphiphilic triblock copolymers with two hydrophilic poly(2-(di-methylamino)ethyl methacrylate) (DMAEMA) blocks flanking a central hydrophobic poly[(R)-3-hydroxybutyrate] block. The release of doxorubicin from the micelles can be controlled by pH and temperature triggers. Using this system, extremely long duration sustained drug release was achieved, better than most micelle systems currently described in the literature. Sustained release of the drug was achieved at pH 7 and 37 °C. Cytotoxicity tests of the copolymers showed that they have significantly lower toxicity towards fibroblast cells compared with the PDMAEMA homopolymer. The doxorubicin-loaded micelles were effective in controlling the growth of HeLa cells. The results demonstrated that the copolymers could be potentially used in chemotherapeutic applications.

A reconstituted "two into one" thermosensitive hydrogel system assembled by drug-loaded amphiphilic copolymer nanoparticles for the local delivery of paclitaxel.

Combination delivery systems composed of injectable hydrogels and drug-incorporated micelles or nanoparticles with tunable and convenient properties for clinical operation and storage are urgently demanded in regional cancer chemotherapy to prolong and control drug release, enhance antitumor efficiency and decrease side effects. Previously, we developed a novel thermosensitive amphiphilic triblock copolymer, poly(ε-caprolactone-co-1,4,8-trioxa[4.6]spiro-9-undecanone)-poly(ethylene glycol)-poly(ε-caprolactone-co-1,4,8-trioxa[4.6]spiro-9-undecanone) (PECT), and fabricated a reconstituted "two into one" combination system of thermosensitive injectable hydrogel PTX/PECTGel, assembled from paclitaxel (PTX)-loaded PECT nanoparticles (NPs). PTX/PECTGel could be stored as freeze-dried powders of paclitaxel-loaded PECT NPs, which could be reconstituted into aqueous fluid dispersions at ambient temperature just by mixing with water after gentle stirring for several minutes, and form a hydrogel at the injected site in vivo. Herein, the drug release, in vivo morphology, antitumor efficiency and pharmacokinetic properties of PTX/PECTGel were evaluated. The PTX/PECTGel combination system could continuously release PTX in a near linear manner over 42 days in vitro, and simultaneously, PTX/PECT NPs containing 75% of the total released PTX could dissociate from the PTX/PECTGel. PTX/PECTGel exhibited remarkable in vitro anti-proliferative activities against Ehrlich ascites carcinoma (EAC) cancer cells. The peritumorally or intratumorally injected PECT gel could cover the entire surface or fill up the interior space of the tumor, respectively. A single peritumoral injection of the PTX/PECTGel formulation at a low dosage of 10 mg kg-1 could completely inhibit the growth of an EAC tumor inoculated in Balb/c mice after the first week, and the inhibition could be sustained for more than 21 days. The plasma pharmacokinetic study demonstrated that PTX/PECTGel could greatly decrease the systemic exposure of PTX, as confirmed by the rather low plasma concentration. On the other hand, the PTX concentration in normal tissues with the intratumoral injection of PTX/PECTGel was approximately 2 μg g-1, which was 3-10 times lower than that with the intraperitoneal or intratumoral injection of Taxol®, implying fewer off-target side effects. These data confirmed that the PTX/PECTGel combination local delivery system could vastly prolong the in vitro and in vivo paclitaxel release, enhance the local tumor inhibition effect and lower the systemic exposure and tissue distribution of paclitaxel. Hence, the "two into one" PTX/PECTGel system holds underlying value for regional cancer chemotherapy.

Sequential thermo-induced self-gelation and acid-triggered self-release process of drug-conjugated nanoparticles: a strategy for the sustained and controlled drug delivery to tumors.

A novel strategy was purposed to sustainedly deliver drug-loaded nanoparticles (NPs) to tumor sites and further enhance intracellular drug release. NPs with the ability of sequential self-gelation and self-release in response to a tumor-specific microenvironment were developed, which involved the conjugation of doxorubicin (DOX) on a thermosensitive amphiphilic copolymer (poly(ε-caprolactone)-b-poly(ethylene glycol)-b-poly(ε-caprolactone), PCEC) via acid-cleavable hydrazone linkages. The conjugate (PCEC-co-DOX) can self-assemble into micelle-like NPs in water. Moreover, the freeze-dried PCEC-co-DOX NP powder with good dispersibility in water can easily be constructed into an injectable NP aqueous dispersion at ambient temperature, making it convenient for storage and clinical applications. After injection, the dispersion can in situ thermosensitively self-gelate, anchoring large amounts of NPs at the tumor site. Subsequently, the formed NP self-supported gel can sustainedly release NPs themselves in an acidic tumor microenvironment. The released DOX-co-PCEC NPs were taken up by tumor cells and finally realized in intracellular drug release by the acid-triggered cleavage of the hydrazone bond. Compared with the repeated injection of free DOX, a single peritumoral injection of DOX-co-PCEC NP aqueous dispersion achieved a similar tumor inhibition effect but exhibited lower systemic toxicity. In vivo biodistribution studies indicated that DOX delivered by the DOX-co-PCEC NP hydrogel accumulated mainly in tumor tissue rather than in healthy tissue in mice treated with a single peritumoral injection. These results suggest that the design presented here provides a promising nanomedicine platform for cancer therapy.

Enhanced and sustained topical ocular delivery of cyclosporine A in thermosensitive hyaluronic acid-based in situ forming microgels

For nearly a decade, thermoresponsive ophthalmic in situ gels have been recognized as an interesting and promising ocular topical delivery vehicle for lipophilic drugs. In this study, a series of thermosensitive copolymers, hyaluronic acid-g-poly(N-isopropylacrylamide) (HA-g-PNIPAAm), was synthesized, by coupling carboxylic end-capped PNIPAAm to aminated hyaluronic acid through amide bond linkages, and was used as a potential carrier for the topical ocular administration of cyclosporine A (CyA). The lower critical solution temperature of HA-g-PNIPAAm59 in aqueous solutions was measured as 32.7°C, which was not significantly affected by the polymer concentration. Moreover, HA-g-PNIPAAm59 microgels showed a high drug loading efficiency (73.92%) and a controlled release profile that are necessary for biomedical application. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) observations showed that HA-g-PNIPAAm microgels were spherical in shape with homogeneous size. Based on the result of the eye irritation test, the HA-g-PNIPAAm microgels formulation was shown to be safe and nonirritant for rabbit eyes. In addition, HA-g-PNIPAAm microgels achieved significantly higher CyA concentration levels in rabbit corneas (1455.8 ng/g of tissue) than both castor oil formulation and commercial CyA eye drops. Therefore, these newly described thermoresponsive HA-g-PNIPAAm microgels demonstrated attractive properties to serve as pharmaceutical delivery vehicles for a variety of ophthalmic applications.

Design and functioning of new thermosensitive copolymers of linear and meshwork structure

A new approach to the synthesis of thermosensitive polymers was realized, it is based on the radical copolymerization of monomers with a significant difference in the hydrophilic-hydrophobic balance of the structure. A wide range of new thermosensitive copolymers was received, which at a certain ratio of hydrophilic and hydrophobic units in macrochain display properties that are typical for thermosensitive polymers. Aqueous solutions of copolymers are characterized by lower critical temperature of dissolution, and polymer meshworks on their base show ability to termo-induced collapse, that’s value can adjust within wide limits by varying the composition of the copolymer. The main regularities of physico-chemical behavior of the derived copolymers were determined.

Self-Association of a Thermosensitive Amphiphilic Block Copolymer Poly(N-isopropylacrylamide)-b-poly(N-vinyl-2-pyrrolidone) in Aqueous Solution upon Heating

The self-association behavior of a thermosensitive amphiphilic block copolymer, poly(N-isopropylacrylamide)-b-poly(N-vinyl-2-pyrrolidone) (PNIPAM-b-PNVP) in water upon heating was investigated by static and dynamic light scattering (SLS and DLS), small-angle X-ray scattering (SAXS), and pulsed field gradient NMR (PFG-NMR). Combining SLS and DLS with SAXS and PFG-NMR, we conclude that above 40 °C, the unimer or a few arms star micelle of the copolymer coexists with large spherical particles of uniform density, which should be regarded as concentrated-phase droplets produced by a liquid–liquid phase separation. The spherical particles of PNIPAM-b-PNVP samples with the PNIPAM content less than 0.32 became smaller with increasing temperature. This temperature dependence was explained in terms of the packing parameter for amphiphiles.

Removal of nickel ions from aqueous solution by low energy-consuming sorption process involving thermosensitive copolymers with phosphonic acid groups

In order to remove metal ions from wastewaters, thermosensitive copolymers bearing sorption properties toward metal cations were prepared by free radical copolymerization between the N-n-propylacrylamide (NnPAAm) and the (dimethoxyphosphoryl)methyl 2-methylacrylate (MAPC1), followed by a hydrolysis of the phosphonated esters into phosphonic diacid groups (hMAPC1). The thermosensitivity and the sorption abilities of the resulting poly(NnPAAm-stat-hMAPC1) copolymers were studied. Lower Critical Solution Temperatures (LCST) of these copolymers ranged from 22°C to 26°C, depending on the molar ratio of phosphonated monomers and were lower than those obtained with usual poly(N-isopropylacrylamide)-based polymers. The influence of both the temperature and the pH on the sorption properties of the copolymers was evaluated for Ni2+ cations. The most interesting results were obtained for temperatures around the LCST, i.e. when the proximity of the complexing groups favored the sorption of metallic cations. Concerning the pH effect, the maximum sorption capacity was obtained at pH 7, i.e. in the absence of competition between the sorption of H+ and Ni2+ ions on the phosphonic acid groups. The influence of the molar ratio of metal ions and phosphonate moieties was also studied and different sorption mechanisms were proposed.

The triblock copolymers hydrogel through intracameral injection may be a new potential ophthalmic drug delivery with antiscaring drugs after glaucoma filtration surgery

The hyperplasia of fiber cell at operation area cause scarring lead to the failure after glaucoma filtration surgery. People are looking for more safe and effective way to advance the success rate in operation. There are many researches demonstrated that ophthalmic drug delivery system can be a treatment. Among this, some biodegradable and thermosensitive triblock copolymers hydrogel are novel candidate for ocular drug release system. But whether they can be used to restrain the hyperplasia of fiber cell through intracameral injection after glaucoma filtration surgery, the research have not been reported. So it suggested a new hypothesis for intracameral injection of the triblock copolymers hydrogel as a new potential in situ sustained ophthalmic drug delivery system with antiscaring formation after glaucoma filtration surgery. Indicating that the new nanomaterials through intracameral injection treating complication of glaucoma filtration surgery is hoped to be a creative and promising ophthalmic drug delivery system in the future.

Collapse of hydrogels based on copolymers of N-isopropylacrylamide and sodium vinylsulfonate

This paper describes the investigation of the behavior of polyelectrolyte thermosensitive hydrogels based on copolymers of N-isopropylacrylamide and sodium vinylsulfonate at different temperatures. The influence of ionogenic groups on the swollen gel-collapsed gel phase transition was studied by means of highly sensitive differential scanning calorimetry. It was demonstrated that the presence of ionogenic groups in the thermosensitive copolymer influences the reversibility and the amplitude of gel collapse, as well as the temperature, enthalpy, and increment of the transition heat capacity.