Temperature/pH/magnetic triple‐sensitive nanogel–hydrogel nanocomposite for release of anticancer drug

Hydrogels, nanogels and nanocomposites show increasing potential for application in drug delivery systems due to their good chemical and physical properties. Therefore, we were encouraged to combine them to produce a new compound with unique properties for a long‐term drug release system. In this regard, the design and application of a nanocomposite hydrogel containing entrapped nanogel for drug delivery are demonstrated. To this aim, we first prepared an iron oxide nanocomposite nanogel based on poly(N‐isopropylacrylamide)‐co‐((2‐dimethylaminoethyl) methacrylate) (PNIPAM‐co‐PDMA) grafted onto sodium alginate (NaAlg) as a biocompatible polymer and iron oxide nanoparticles (ION) as nanometric base (PND/ION‐NG). This was then added into a solution of PDMA grafted onto NaAlg. Through dropwise addition of mixed aqueous solution of iron salts into the prepared polymeric solution, a novel hydrogel nanocomposite with excellent pH, thermal and magnetic responsivity was fabricated. The synthesized samples were fully characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy with energy‐dispersive X‐ray analysis, vibrating sample magnetometry and atomic force microscopy. A mechanism for the formation of PNIPAM‐co‐PDMA/NaAlg‐ION nanogel–PDMA/NaAlg‐ION hydrogel and PND/ION nanogel is suggested. Swelling capacity was measured at various temperatures (25 to 45 °C), pH values (from 2 to 11) and magnetic field and under load (0.3 psi) and the dependence of swelling properties of the nanogel–hydrogel nanocomposite on these factors was well demonstrated. The release rate of doxorubicin hydrochloride (DOX) as an anticancer drug was studied at different pH values and temperatures in the presence and absence of a magnetic field. The results showed that these factors have a high impact on drug release from this nanocomposite. The result showed that DOX release could be sustained for up to 12.5 days from these nanocomposite hydrogels, significantly longer than that achievable using the constituent hydrogel or nanogel alone (<1 day). The results indicated that the nanogel–hydrogel nanocomposite can serve as a novel nanocarrier for anticancer drug delivery. © 2019 Society of Chemical Industry     

In vitro and in vivo investigational studies of a nanocomposite‐hydrogel‐based dressing with a silver‐coated chitosan wafer for full‐thickness skin wounds

A nanocomposite reservoir‐type hydrogel dressing of poly vinyl alcohol (PVA) was fabricated by a freeze–thaw method and loaded with silver‐nanoparticle‐coated chitosan wafers (Ag–CHWs). The Ag–CHWs were synthesized by a sonication technique with silver nitrate (AgNO₃) and chitosan powder. Scanning electron microscopy images showed silver nanoparticles (AgNPs) with a size range of 10 ± 4 nm on the surface of the chitosan wafers, and the antibacterial efficacy (minimum inhibitory concentration) of the Ag–CHWs was measured against Pseudomonas aeruginosa (32 µg/mL), Staphylococcus aureus, (30 µg/mL) and Escherichia coli (32 µg/mL). The antimicrobial PVA hydrogel showed an improved tensile strength (～0.28 MPa) and gel content (～92%) in comparison with the blank hydrogels. Full‐thickness‐excision wound studies of the nanocomposite dressing on Wistar rats revealed enhanced wound contraction, improved inflammation response, re‐epithelization rate, neoangiogenesis, and granulation tissue formation in comparison to the control group. A flexible, biocompatible, nanocomposite reservoir dressing not only established the chitosan as a stabilizer but also proved the efficacious and safe utility of AgNPs toward chronic wound management. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43472.     

Preparation and characterization of acrylic acid/itaconic acid hydrogel coatings containing silver nanoparticles

Hydrogel silver nanocomposites have been used in applications with excellent antibacterial performance. Acrylic acid (AA)/itaconic acid (IA) hydrogels silver nanocomposites were prepared and applied as a coating on a textile substrate. Hydrogel matrices were synthesized first by the polymerization of an AA/IA aqueous (80/20 v/v) solution and mixed with 2‐2‐azobis(2‐methylpropionamide) diclorohydrate and N,N′‐methylene bisacrylamide until the hydrogel was formed. Silver nanoparticles were generated throughout the hydrogel networks with an in situ method via the incorporation of the silver ions and subsequent reduction with sodium borohydride. Cotton (C) and cotton/polyester (CP) textile fibers were then coated with these hydrogel silver nanocomposites. The influence of these nanocomposite hydrogels on the properties of the textile fiber were investigated by infrared spectroscopy (attenuated total reflectance), scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and antibacterial tests against Pseudomona aeruginosa and Staphylococcus aureus. The better conditions, in which no serious aggregation of the silver nanoparticles occurred, were determined. It was proven that the textiles coated with hydrogels containing nanosilver had an excellent antibacterial abilities. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2713–2721, 2013     

Layer‐by‐layer assembled hydrogel nanocomposite film with a high loading capacity

The layer‐by‐layer assembly technique is a method that widely used in the preparation of nanostructured multilayer ultrathin films. We fabricated a hydrogel nanocomposite film by alternating the deposition of a core–shell poly[(dimethylimino)(2‐hydroxy‐1,3‐propanedily) chloride] (PDMIHPC)–laponite solution and poly(acrylic acid). The growth of the deposition procedure was proven by ultraviolet–visible spectroscopy and spectroscopic ellipsometry. The surface morphology of the films was observed by scanning electron microscopy. The films could reversibly load and release methylene blue (MB) dye, which was used as an indicator. It took about 4.5 h to reach loading equilibrium at pH 9.0. The loading capacity of the film for MB was as large as 4.48 μg/cm² per bilayer because of the introduction of the core–shell PDMIHPC–laponite as a film component. Nearly 90% of MB was released at pH 3.0 or in a 300 mM NaCl solution within 2.5 h. The loading and release processes were greatly influenced by the ionic strength and pH value of the MB solution. The hydrogel nanocomposite film showed good pH‐triggered loading‐release reversibility and suggested potential applications in controlled drug‐delivery systems and smart materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39352.     

Synthesis and characterization of novel silver/L‐phenylalanine‐based optically active polyacrylate nanocomposite

Novel bioactive and optically active poly(N‐acryloyl‐L ‐phenylalanine) (PAPA) was synthesized by atom transfer radical polymerization. PAPA‐silver (Ag) nanocomposites have been successfully prepared via in situ reducing Ag⁺ ions anchored in the polymer chain using hydrazine hydrate as reducing agent in an aqueous medium. By controlling of the amount of Ag⁺ ions introduced, we have produced an organic/inorganic nanocomposite containing Ag nanoparticles with well controlled size. Nanocomposites were characterized by X‐ray diffraction (XRD), UV–Vis spectrophotometry, transmission electron microscopy, and Fourier transform infrared. XRD pattern showed presence of Ag nanoparticles. The PAPA/Ag nanocomposites with 1 : 10 silver nitrate (AgNO₃) : PAPA ratio revealed the presence of well‐dispersed Ag nanoparticles in the polymer matrix. All of these Ag nanoparticles formed are spherical and more than 80% of them are in the range of 15–25 nm. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Linear low‐density polyethylene‐g‐poly(acrylic acid)/(organo‐montmorillonite) hydrogel composite as hydrogel electrolytes for zinc–carbon batteries

A hydrogel composite that has been prepared by using waste linear low‐density polyethylene, acrylic acid, and organo‐montmorillonite (LLDPE‐g‐PAA/OMMT) is used as a hydrogel electrolyte. An absorbency test was used to determine the percentage of ZnCl₂ solution absorbed by the hydrogel composite. The swelling behavior of the hydrogel composite in the ZnCl₂ solution was then studied. The highest absorbency was recorded when the concentration of ZnCl₂ solution was 3 M. The conductivity of ZnCl₂‐hydrogel composite electrolytes is dependent on the solution's concentration. A mixture of ZnCl₂ solution with hydrogel composite yields a good hydrogel composite electrolyte with a conductivity of 0.039 S cm^?1 at 3 M ZnCl₂. The hydrogel composite electrolyte was used to produce zinc‐carbon cells. The fabricated cell gives capacity of 7.8 mAh, has an internal resistance of 9.9 Ω, a maximum power density of 15.78 mWcm^?2, and a short‐circuit current density of 43.75 mAcm^?2 for ZnCl₂‐hydrogel composite electrolytes. J. VINYL ADDIT. TECHNOL., 22:279–284, 2016. © 2014 Society of Plastics Engineers     

Two‐step synthesis and properties of a magnetic‐field‐sensitive modified maltodextrin‐based hydrogel

A magnetic‐field‐sensitive modified maltodextrin‐based hydrogel (ferrogel) was synthesized. Fourier transform infrared and ¹³C‐CP/MAS NMR spectral analyses confirmed the efficiency of the gelling process. X‐ray diffraction analysis revealed the appearance of new crystalline planes in the hydrogel diffractograms after embedding of magnetite nanoparticles. Magnetization curves and Mössbauer analysis revealed that the magnetic hydrogel has a high lattice strain due to bonded iron atom covalence. Moreover, some magnetite molecules embedded in the hydrogel ensure a degree of paramagnetism and iron atoms exhibiting oxidation states alternating between 2 and 3 in the final material. Scanning electron microscopy and energy‐dispersive X‐ray analysis revealed that no phase separation occurred between the magnetite nanoparticles and crosslinked hydrogel, indicating excellent dispersion throughout the hydrogel. Moreover, the average pore sizes decreased on increasing the amount of magnetite inside the polymer network. The results of compression stress versus strain revealed that the elasticity of the magnetic hydrogel was increased on increasing the amount of magnetite nanoparticles. Finally, kinetic studies revealed that the diffusion mechanism of water in the hydrogel is driven by anomalous release with a tendency towards the occurrence of macromolecular relaxation. Copyright © 2011 Society of Chemical Industry     

Silver Nanoparticles Loaded Thermoresponsive Hybrid Nanofibrous Hydrogel as a Recyclable Dip‐Catalyst with Temperature‐Tunable Catalytic Activity

Silver nanoparticles (AgNPs) loaded thermoresponsive nanofibrous hydrogel is fabricated by electrospinning the aqueous solution containing the metal nanoparticles and poly((N‐isopropylacrylamide)‐co‐(N‐hydroxymethylacrylamide)) copolymer, followed by heat treatment. To avoid negative effect of the stabilizer or the residual reductant on their performances, the AgNPs of less than 5 nm size are synthesized through reducing Ag⁺ ions in the spinning solution by UV irradiation. The prepared nanofibrous hydrogel with desirable stability in aqueous medium has significant thermoresponsive property, and can reach its swelling or deswelling equilibrium state within 15 s with the medium temperature changing between 25 and 50 °C alternately. The smart nanofibrous hydrogel as a dip‐catalyst has the catalysis for the reduction of 4‐nitrothiophenol to 4‐aminothiophenol by NaBH₄, and its catalytic activity can be rapidly tuned by temperature. Moreover, it can be facilely recycled from the reaction system at least four times, without any loss of its catalytic activity.     

Preparation of chitosan‐graft‐(methyl methacrylate)/Ag nanocomposite with antimicrobial activity

It has been found that composites of chitosan (CS) and Ag nanoparticles can exhibit excellent antibacterial activities. However, the weak mechanical performances of these composite materials limit their wide application. Grafting of vinyl monomers onto CS is one of the most effective methods to improve the performances of CS without sacrificing its properties. A nanocomposite of chitosan‐graft‐(methyl methacrylate) (CS‐g‐MMA) containing Ag nanoparticles was prepared by in situ chemical reduction of Ag ions in an aqueous acetic acid solution of CS and graft copolymerization of MMA onto CS. Transmission electron micrographs, X‐ray diffraction patterns and UV‐visible spectra of the nanocomposite confirmed the formation of Ag nanocrystals. X‐ray photoelectron spectroscopy proved that Ag? O bonds exist in the composite. Thermogravimetric analysis/differential scanning calorimetry showed that the decomposition temperature of CS was 319.8 °C while that of the CS‐g‐MMA/Ag composite shifted to a higher temperature of 422.1 °C. Antimicrobial experiments showed that the antimicrobial rates of the CS‐g‐MMA/Ag composite to E. coli, B. subtilis, S. aureus and P. aeruginosa were 93–98%. CS molecules can act as stabilizing agents to prevent the aggregation of Ag nanoparticles in the process of synthesizing CS‐g‐MMA/Ag nanocomposites. The antimicrobial activity of the as‐prepared nanocomposites is higher than that of CS alone. Copyright © 2009 Society of Chemical Industry     

Characterization and determination of swelling and diffusion characteristics of poly(n‐vinyl‐2‐pyrrolidone) hydrogels in water

Hydrogels in the form of rods with varying crosslink densities and three‐dimensional network structures were prepared from Poly(N‐vinyl‐2‐pyrrolidone) (PVP)/water and PVP/water/persulfate systems by irradiation with γ rays at ambient temperature. Average molecular weights between crosslinks, percent swelling, swelling equilibrium values, diffusion/swelling characteristics (i.e., the structure of network constant, the type of diffusion, the initial swelling rate, swelling rate constant), and equilibrium water content were evaluated for both hydrogel systems. Water diffusion to the hydrogel is a non‐Fickian type diffusion and diffusion coefficients vary from 6.56 × 10⁻⁷ to 2.51 × 10⁻⁷cm²min⁻¹ for PVP and 6.09 × 10⁻⁷ to 2.14 × 10⁻⁷ cm²min⁻¹ for PVP/persulfate hydrogel systems. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 994–1000, 2000     

Properties and application of poly(methacrylic acid‐co‐dodecyl methacrylate‐cl‐N,N‐methylene bisacrylamide) hydrogel immobilized Bacillus cereus MTCC 8372 lipase for the synthesis of geranyl acetate

A range of fatty acid esters is now being produced commercially with immobilized microbial lipases (glycerol ester hydrolases; EC) in nonaqueous solvents. In this study, a synthetic hydrogel was prepared by the copolymerization of methacrylic acid and dodecyl methacrylate in the presence of a crosslinker, N,N‐methylene bisacrylamide. A purified alkaline thermotolerant bacterial lipase from Bacillus cereus MTCC 8372 was immobilized on a poly(methacrylic acid‐co‐dodecyl methacrylate‐cl‐N,N‐methylene bisacrylamide) hydrogel by an adsorption method. The hydrogel showed a 95% binding efficiency for the lipase. The bound lipase was evaluated for its hydrolytic potential toward various p‐nitrophenyl acyl esters with various C chain lengths. The bound lipase showed optimal hydrolytic activity toward p‐nitrophenyl palmitate at a pH of 8.5 and a temperature of 55°C. The hydrolytic activity of the hydrogel‐bound lipase was enhanced by Hg²⁺, Fe³⁺, and NH ions at a concentration of 1 mM. The hydrogel‐bound lipase was used to synthesize geranyl acetate from geraniol and acetic acid in n‐heptane. The optimization of the reaction conditions, such as catalyst loading, effect of substrate concentration, solvent (n‐pentane, n‐hexane, n‐heptane, n‐octane, and n‐nonane), reaction time, temperature, molecular sieve (3 Å × 1.5 mm) and scale up (at 50‐mL level), was studied. The immobilized lipase (25 mg/mL) was used to perform an esterification in n‐alkane(s) that resulted in the synthesis of approximately 82.8 mM geranyl acetate at 55°C in n‐heptane under continuous shaking (160 rpm) after 15 h when geraniol and acetic acid were used in a ratio of 100 : 100 mM. The addition of a molecular sieve (3 Å × 1.5 mm) to the reaction system at a concentration of 40 mg/mL in reaction volume (2 mL) resulted in an increase in the conversion of reactants into geranyl acetate (90.0 mM). During the repetitive esterification under optimum conditions, the hydrogel‐bound lipase produced ester (37.0 mM) after the eighth cycle of reuse. When the reaction volume was scaled up to 50 mL, the ester synthesized was 58.7 mM under optimized conditions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Gum Acacia‐cl‐poly(acrylamide)@carbon nitride Nanocomposite Hydrogel for Adsorption of Ciprofloxacin and its Sustained Release in Artificial Ocular Solution

In the present work, a nanocomposite hydrogel is designed consisting of gum acacia, poly(acrylamide) and carbon nitride by facile microwave approach. This nanocomposite hydrogel is sensitive to environmental stimuli which is essential for its application in environmental remediation and as a drug delivery system. The effects of carbon nitride percentage and microwave Watt variation on swelling capacity of gum acacia‐cl‐poly(acrylamide)@carbon nitride (Ga‐cl‐PAM@C₃N₄) nanocomposite hydrogel are analyzed. The structural characterizations are considered by numerous techniques such as FTIR (Fourier transform infra‐red spectroscopy), X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, and elemental mapping. Batch experiment is performed for remediation of ciprofloxacin (CIP) drug from water. Various parameters such as effect of ciprofloxacin doses, Ga‐cl‐PAM@C₃N₄ nanocomposite hydrogel dosage, pH, time and temperature for adsorption of CIP on gum acacia‐cl‐poly(acrylamide)@carbon nitride nanocomposite hydrogel is examined. Maximum adsorption capacity of Ga‐cl‐PAM@C₃N₄ nanocomposite hydrogel observed is 169.49 mg g^?1 at pH 6.4. The drug loading and drug release capacity of Ga‐cl‐PAM@C₃N₄ nanocomposite hydrogel is investigated for ciprofloxacin. Drug release is monitored in artificial ocular solution (pH 8), saline (pH 5.5), acetate buffer (pH 2.2), and distilled water. Maximum drug release is observed in artificial ocular solution.     

Nanocomposites of Surface‐Modified BaTiO3 Nanoparticles Filled Ferroelectric Polymer with Enhanced Energy Density

We report nanocomposites of increased dielectric permittivity, enhanced electric breakdown strength and high‐energy density based on surface‐modified BaTiO₃ (BT) nanoparticles filled poly(vinylidene fluoride) polymer. Polyvinylprrolidone (PVP) is used as the surface modification agent and homogeneous nanocomposite films have been prepared by solution casting processing. The dielectric permittivity of the nanocomposite with treated BT is higher than those with untreated BT and reaches the maximum value of 77 (1 kHz) at BT concentration of 55 vol%. The electric breakdown strength of the nanocomposite is greatly enhanced to 336 MV/m at BT concentration of 10 vol% and the calculated energy density is 6.8 J/cm³. The results indicate that using PVP as surface modification agent can greatly enhance the dielectric permittivity and electric breakdown strength of the ceramic–polymer nanocomposite and achieve high‐energy density for energy storage and power capacitor applications.     

Enhanced photoresponse and photocatalytic activities of graphene quantum dots sensitized Ag/TiO2 thin film

TiO₂ thin films were fabricated through hydrothermal method. Silver nanoparticles were loaded on TiO₂ thin films via photoreduction technique. Subsequently, the graphene quantum dots (GQDs) were spin‐coated on the Ag/TiO₂ nanocomposites thin films. The crystal structure, surface morphology and UV‐vis absorbance were tested by XRD, SEM and ultraviolet‐visible spectrophotometer. These results indicated that Ag nanoparticles and GQDs are anchored on the TiO₂ nanorods. Absorbance of Ag/TiO₂ and GQDs/Ag/TiO₂ nanocomposite thin films have been extended into the visible region. Visible‐light response of the samples were investigated by electrochemical workstation. The photoresponse of the sample can be enhanced by sensitization of the Ag nanoparticles and GQDs. The enhanced visible‐light response may be due to the surface plasmon resonance of silver nanoparticles and visible absorbance of GQDs. The highest photocatalytic activity has been observed in the 9‐GQDs/Ag/TiO₂ composite thin film. The efficient charge separation and transportation can be achieved by introducing the Ag nanoparticles and GQDs in the TiO₂ thin film.     

Photocatalytic degradation of C.I. Acid Orange 7 by TiO2 nanoparticles immobilized onto/into chitosan‐based hydrogel

Photocatalytic degradation of dye C.I. Acid Orange 7 in aqueous solution using TiO₂/hydrogel nanocomposite under solar light simulating source was studied. Hydrogel based on chitosan, itaconic and methacrylic acid was modified with colloidal TiO₂ nanoparticles synthetized by acidic hydrolysis of TiCl₄ and commercial Degussa P25 TiO₂ nanoparticles. SEM/EDX analysis confirmed the presence of TiO₂ nanoparticles onto/into hydrogel. It was found that both types of photocatalysts efficiently removed the dye from solution, but sorption rates and photodegradation efficiency were higher in the case of colloidal TiO₂ nanoparticles. They ensured complete discoloration of dye solution. The efficiency of the reused TiO₂/hydrogel nanocomposite showed that photodegradation activity was maintained at satisfactory level after three repeated cycles of illumination. POLYM. COMPOS., 35:806–815, 2014. © 2013 Society of Plastics Engineers     

Synthesis and characterization of a porous poly(hydroxyethylmethacrylate‐co‐ethylene glycol dimethacrylate)‐based hydrogel device for the implantable delivery of insulin

Poly(hydroxyethylmethacrylate‐co‐ethylene glycol dimethacrylate) [poly(HEMA‐co‐EGDMA)]‐based hydrogel devices were synthesized by a free‐radical polymerization reaction with 2‐hydroxyethylmethacrylate as the monomer, different concentrations of ethylene glycol dimethacrylate (EGDMA) as the crosslinking agent, and ammonium persulfate/N,N,N′,N′‐tetra‐methyl ethylenediamine as the free‐radical initiator. The porosity of the poly(HEMA‐co‐EGDMA) hydrogels was controlled with water as the porogen. The Fourier transform infrared spectrum of poly(HEMA‐co‐EGDMA) showed absorption bands associated with ? C?O stretching at 1714 cm^?1, C? O? C stretching vibrations at 1152 cm^?1, and a broad band at 3500–3800 cm^?1 corresponding to ? OH stretching. Atomic force microscopy studies showed that the hydrogel containing 67% water had pores in the range of 3500–9000 nm, whereas the hydrogel containing 7% water did not show measurable pores. The hydrogel synthesized with 1% EGDMA showed 50% thallium‐201 release within the first 30 min and about 80% release within 60 min. In vitro insulin‐release studies suggested that the hydrogel with 27% water showed sustained release up to 120 min, whereas the hydrogels with 47 and 67% water showed that nearly all of the insulin was released within 60 min. Hydrogel devices synthesized with 27% water and filled with insulin particles showed sustained release for up to 8 days, whereas the hydrogels synthesized with 47 and 67% water released insulin completely within 3 days of administration. Animal studies suggested that the hydrogel devices synthesized with 27% water and filled with insulin‐loaded particles (120 IU) were able to control blood glucose levels for up to 5 days after implantation. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Ag‐nanocomposite based on carboxymethylcellulose for humidity detection: Green synthesis and sensing performances

A novel highly sensitive Ag‐nanocomposite for humidity detection has been successfully prepared. Initially, cellulose isolated from Tunisian palm date petiole was converted to carboxymethyl cellulose (CMC) as biomatrix under heterogeneous conditions. The synthesized product was thoroughly characterized by means of FT‐IR spectroscopy, viscosity analysis, and high performance size exclusion chromatography multiangle laser light scattering. CMC was used as reducing and stabilizing agent to prepare CMC‐stabilized silver nanoparticles via a rapid green method. The bioreduction of silver ions under different experimental conditions, including Ag⁺ concentration and pH, was investigated. Optimal experimental conditions provided a long‐term stable colloidal suspension and well‐dispersed spherical shape Ag NPs with a size ranging from 13 to 28 nm. Ag‐nanocomposite coated quartz microbalance crystal was used as sensitive layer for humidity detection. A comparative study showed that the immobilized metallic nanostructures greatly reduced changes in visco‐elastic properties, increased surface area as well as surface local charge density of the CMC. Consequently, sensor performances were greatly enhanced: better stability even at higher relative humidity (RH), good reproducibility and linearity (11–98% RH), low hysteresis characteristics, and rapid response and recovery times (14 and 6 s, respectively) were obtained. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43686.     

Breathing‐in/breathing‐out approach to preparing nanosilver‐loaded hydrogels: Highly efficient antibacterial nanocomposites

The key objective of developing novel materials for hygienic living conditions is to lower the risk of transmitting diseases and biofouling. To this end, a number of silver–hydrogel nanocomposite systems are under development. In this study, we attempted a unique strategy to prepare silver‐nanoparticle‐loaded poly(acrylamide‐co‐N‐vinyl‐2‐pyrolidone) hydrogel composites. To load nanosilver particles into such a nonionic hydrogel, a novel breathing‐in/breathing‐out (BI–BO) approach was employed. As the number of BI–BO cycles increased, the amount of the silver nanoparticles loaded into these hydrogels also increased. This behavior was obvious and was confirmed by ultraviolet–visible spectroscopy and thermal analysis. Furthermore, the hydrogel–silver‐nanoparticle composites were confirmed with Fourier transform infrared spectroscopy and transmission electron microscopy studies. Antibacterial studies of these hydrogel–silver nanocomposites showed excellent results against Escherichia coli. The antibacterial activity increased with the number of BI–BO cycles, and samples that underwent three BI–BO cycles showed optimal bactericidal activity. The degree of crosslinking and the silver content had a great influence on the antibacterial efficacy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of Ag nanoparticles in the presence of low generational poly(ester‐amine) dendrimers

Stable Ag nanoparticles of 10–20 nm were prepared by reduction of AgNO₃ with NaBH₄ in water solution in the presence of low generational hydroxyl‐ terminated poly(ester‐amine) dendrimer G1.0 (OH)₁₆ and amino‐terminated poly(ester‐amine) dendrimer G1.5 (NH₂)₈ by optimizing preparation conditions. UV–vis absorption spectra and transmission electron microscopy were adopted to characterize absorption properties of Ag⁺/dendrimer complex, Ag/dendrimer nanocomposite aqueous solutions, and the morphology of the formed Ag nanoparticles, respectively. The results showed that the size of the Ag particles increased with Ag⁺/dendrimer molar ratio, and the size of Ag nanoparticles in Ag/G1.0 (OH)₁₆ system was larger than that of Ag nanoparticles in Ag/G1.5 (NH₂)₈ system, while the polydispersities of two systems were similar. Moreover, the Ag/G1.5 (NH₂)₈ nanocomposite system was more stable than the Ag/G1.0 (OH)₁₆ one. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 422–426, 2007     

Preparation and characterization of poly(ϵ‐caprolactone‐co‐p‐dioxanone)–poly(ethylene glycol)–poly(ϵ‐caprolactone‐co‐p‐dioxanone)/bioactive inorganic particle nanocomposites

With an aim to develop injectable hydrogel with improved solution stability and enhanced bone repair function, thermogelling poly(ε‐caprolactone‐co‐p‐dioxanone)‐poly(ethylene glycol)‐poly(ε‐caprolactone–co‐p‐dioxanone) (PECP)/bioactive inorganic particle nanocomposites were successfully prepared by blending the triblock copolymer (PECP) with nano‐hydroxyapatite (n‐HA) or nano‐calcium carbonate (n‐CaCO₃). The hydrogel nanocomposites underwent clear sol–gel transitions with increasing temperature from 0 to 50°C. The obtained hydrogel nanocomposites were investigated by ¹H NMR, FT‐IR, TEM, and DSC. It was found that the incorporation of inorganic nanoparticles into PECP matrix would lead to the critical gelation temperature (CGT) shifting to lower values compared with the pure PECP hydrogel. The CGT of the hydrogel nanocomposites could be effectively controlled by adjusting PECP concentration or the content of inorganic nanoparticles. The SEM results showed that the interconnected porous structures of hydrogel nanocomposites were potentially useful as injectable scaffolds. In addition, due to the relatively low crystallinity of PECP triblock copolymer, the aqueous solutions of the nanocomposites could be stored at low temperature (5°C) without crystallization for several days, which would facilitate the practical applications. The PECP/bioactive inorganic particle hydrogel nanocomposites are expected to be promising injectable tissue engineering materials for bone repair applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013