Novel thermosensitive hydrogel composites based on poly(d,l‐lactide‐co‐glycolide) nanoparticles embedded in poly(n‐isopropyl acrylamide) with sustained drug‐release behavior

To reach sustained drug release, a new composite drug‐delivery system consisting of poly(d,l ‐lactide‐co‐glycolide) (PLGA) nanoparticles (NPs) embedded in thermosensitive poly(N‐isopropyl acrylamide) (PNIPAAm) hydrogels was developed. The PNIPAAm hydrogels were synthesized by free‐radical polymerization and were crosslinked with poly(ethylene glycol) diacrylate, and the PLGA NPs were prepared by a water‐in‐oil‐in‐water double‐emulsion solvent‐evaporation method. The release behavior of the composite hydrogels loaded with albumin–fluorescein isothiocyanate conjugate was studied and compared with that of the drug‐loaded neat hydrogel and PLGA NPs. The results indicate that we could best control the release rate of the drug by loading it to the PLGA NPs and then embedding the whole system in the PNIPAAm hydrogels. The developed composite hydrogel systems showed near zero‐order drug‐release kinetics along with a reduction or omission of initial burst release. The differential scanning calorimetry results reveal that the lower critical solution temperature of the developed composite systems remained almost unchanged (<1°C increase only). Such a characteristic indicated that the thermosensitivity of the PNIPAAm hydrogel was not distinctively affected by the addition of PLGA NPs. In conclusion, an approach was demonstrated for the successful preparation of a new hybrid hydrogel system having improved drug‐release behavior with retained thermosensitivity. The developed systems have enormous potential for many biotechnological applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40625.     

A multiple emulsion method for loading 5‐fluorouracil into a magnetite‐loaded nanocapsule: a physicochemical investigation

The preparation of 5‐fluorouracil (5‐FU) loaded poly(lactic‐co‐glycolic acid) (PLGA) biodegradable nanocapsules containing magnetite nanoparticles was studied through the modified multiple emulsion solvent evaporation method for magnetically controlled delivery of anticancer drugs. The morphology and size distribution of the prepared magnetite/PLGA nanocapsules were investigated by transmission and scanning electron microscopy. The micrographs showed that the magnetic nanocapsules were almost spherical in shape and their mean diameter was in the nanometer range with a narrow size distribution. Fourier transform infrared and ultraviolet–visible spectroscopy confirmed incorporation of 5‐FU molecules into the PLGA matrix. The magnetite content was assessed by thermogravimetric and magnetometry analysis and the results showed a magnetite content of 35 wt% with high magnetic responsivity. Magnetometry measurements showed superparamagnetic properties of the magnetic nanocapsules with a saturation magnetization of 13.7 emu g^?1. Such biodegradable magnetic nanocapsules could be considered as an appropriate choice for drug targeting. Furthermore, the influence of some important processing parameters such as PLGA concentration, initial loading of 5‐FU and poly(vinyl alcohol) concentration on drug content, encapsulation efficiency and in vitro drug release kinetics was investigated and optimized. The drug content and encapsulation efficiency of the magnetic nanocapsules were 4–7 wt% and 60%–80%, respectively, and the nanocapsules demonstrated controlled release of 5‐FU at 37 °C in a buffer solution. All samples exhibited a burst release at the initial stage and this burst release showed its close dependence on the formulation parameters. Copyright © 2012 Society of Chemical Industry     

Intrinsic factor and vitamin B12 complex‐loaded poly[lactic‐co‐(glycolic acid)] microspheres: preparation,characterization and drug release

BACKGROUND: Vitamin B12 is an essential vitamin required by all mammals. Absorption of vitamin B12 is facilitated by binding of intrinsic factor–vitamin B₁₂ complex to specific receptors in the ileum. In humans a deficiency of this vitamin or a lack of intrinsic factor leads to pernicious anaemia. The major objective of the present study was to prepare intrinsic factor–vitamin B12 complex‐loaded poly[lactic‐co‐(glycolic acid)] (PLGA)‐based microparticles and to investigate their release kinetics. RESULTS: PLGA copolymer was synthesized by the ring‐opening polymerization method and characterized using gel permeation chromatography, Fourier transform infrared spectroscopy and ¹H NMR. The glass transition temperature measurement showed a single T_g at 40 °C. The intrinsic factor–vitamin B12 complex‐loaded PLGA microspheres were prepared by a water‐in‐oil‐in‐water double emulsion solvent extraction/evaporation technique. An environmental scanning electron microscopy investigation demonstrated that the PLGA particles had a mean particle diameter of 38 µm. Interestingly, different drug release patterns (bi‐ and triphasic ones) were observed for vitamin B12‐loaded and intrinsic factor–vitamin B12 complex‐loaded microspheres. In contrast to the rapid release of vitamin B12 by itself, in vitro release tests showed that intrinsic factor and vitamin B12 in the complex were released from PLGA microspheres in a sustained manner over 15 days. CONCLUSION: PLGA microspheres can be an effective carrier for the intrinsic factor–vitamin B12 complex. Copyright © 2007 Society of Chemical Industry     

Surfactant‐free nanoparticles of poly(DL‐lactide‐co‐glycolide) prepared with poly(L‐lactide)/ poly(ethylene glycol)

Surfactant‐free nanoparticles of poly(DL ‐lactide‐co‐glycolide) (PLGA) nanoparticles were prepared with or without poly(L ‐lactide)‐poly(ethylene oxide) (LE) diblock copolymer (abbreviated as PLGA/LE and PLGA nanoparticles) by dialysis method. LE diblock copolymer was used to make PLGA nanoparticles to alternate conventional surfactant. The size of PLGA and PLGA/LE nanoparticles was 295.3 ± 171.3 and 307.6 ± 27.2 nm, respectively, suggesting LE diblock copolymer might be coated onto the surface of nanoparticles. Observation of scanning electron microscope (SEM) showed that PLGA/LE nanoparticles have spherical shapes ranging ～ 200–500 nm. In ¹H‐NMR study, characteristic peaks of the methyl protons of PLGA disappeared in D₂O, whereas characteristic peaks of the methyl proton of both PEG and PLGA were shown in both CDCl₃ and D₂O, indicating that LE diblock copolymer coated on the surface of the PLGA nanoparticles. The higher the initial content of drug, the higher the drug contents and the lower the loading efficiency. PLGA/LE nanoparticles at higher drug contents resulted in slower adriamycin·HCl (ADR) release rate than that of lower drug contents. Also, slower release rate of ADR was achieved by entrapped into the PLGA/LE nanoparticles, whereas LE polymeric micelles showed rapid ADR release. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1116–1123, 2003     

Preparation and drug release behaviors of 5‐fluorouracil loaded poly(glycolide‐co‐lactide‐co‐caprolactone) nanoparticles

5‐Fluorouracil (5‐Fu) loaded poly(glycolide‐co‐lactide‐co‐caprolactone) (PGLC) nanoparticles were prepared by modified spontaneous emulsification solvent diffusion method (modified‐SESD method) and characterized by dynamic light scattering, scanning electron microscopy and ¹H NMR determination. It was found that the obtained nanoparticles showed near spherical shape and was controllable with the radius range of 30–100 nm. Compared with the nanoparticles prepared by polylactide and poly (lactide‐co‐glycolide) (PLGA) under the similar preparation condition, yield of PGLC nanoparticles was the highest, which reached to about 100%. On the other hand, drug entrapment efficiency of PGLC nanoparticles was also higher than that of PLGA and PLLA nanoparticles. 5‐Fu release behavior of PGLC nanoparticles in vitro showed that 5‐Fu release of PGLC nanoparticles showed a near zero‐order release profile, and 5‐Fu release rate of PGLC nanoparticles was faster than that of PLLA and PLGA nanoparticles. According to degradation behavior of PGLC nanoparticles, it could be proposed that the kinetic of degradation controlled release played an important role in the release process of PGLC nanoparticles. It revealed that the PGLC nanoparticles could be a promising drug carrier. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

The polymer free volume as a controlling factor for drug release from poly(lactide‐co‐glycolide) microspheres

Drug release from poly(lactide‐co‐glycolide) (PLGA) microspheres is strongly determined by the pore structure of the particles. This study examines how swelling‐induced pore constriction delays the drug release and by which factors this process is controlled. Combination of different porosimetric and pycnometric methods enabled insight into the submicroscopic range of the pore structure and revealed that remarkably the polymer free volume plays a crucial role in drug release from PLGA microspheres. Surprisingly, the latter was shown to be inversely correlated to the degree of diffusional drug release. This can be explained by a swelling‐induced constriction of the macroporous channel system in the microspheres which is related to the availability of free volume. The hole free volume was shown to be well controllable by the manufacturing conditions. Thus, the study deepens comprehension of the mechanism of drug release from biodegradable microparticles and offers an effective approach for controlling the release behavior. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39740.     

Preparation of poly(DL‐lactide‐co‐glycolide) nanoparticles without surfactant

The preparation of poly(DL ‐lactide‐co‐glycolide) (PLGA) nanoparticles was performed by a dialysis method without surfactant or emulsifiers. The size of the PLGA nanoparticles prepared from dimethylacetamide (DMAc) as an initial solvent was smaller than that from acetone. The sizes of the PLGA nanoparticles from DMAc and acetone were 200.4 ± 133.0 and 642.3 ± 131.1 nm, respectively. The effects of the initial solvent selected to dissolve the copolymer and the lactide:glycolide ratio were investigated. The PLGA nanoparticles were spherical as revealed by the results of scanning electron microscopy and transmission electron microscopy observations. From these results it was shown that PLGA nanoparticles could be formed by the dialysis method without surfactant. The drug‐loading contents and efficiency were also dependent on the lactide:glycolide ratio and initial feeding amount of the drug. A higher lactide ratio resulted in higher drug loading and higher loading efficiency. However, a higher initial feeding amount of the drug resulted in higher drug loading and lower loading efficiency. Clonazepam was released for at least 2 days and the release rate was slower with a higher lactide:glycolide ratio and a larger amount of drug‐loading nanoparticles than that with a lower lactide:glycolide ratio and a smaller amount of drug‐loading nanoparticles. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2228–2236, 2001     

Modeling and closed‐loop control of particle size and initial burst of PLGA biodegradable nanoparticles for targeted drug delivery

An in‐house computer code based on artificial intelligence has been developed and applied in modeling and closed‐loop optimization of release behavior of Poly(lactic‐co‐glycolic acid) (PLGA) biodegradable particles. A series of micro‐ and nanoparticles were prepared via water‐in‐oil‐in‐water double emulsion to be loaded with albumin–fluorescein isothiocyanate conjugate as a typical drug. The interrelationship between input variables (molecular weight of polymer and stabilizer, polymer concentration, and sonication rate) and outputs (PLGA particle size and percentage of initial burst) was uncovered with the aid of artificial neural network modeling. The regression analysis confirmed acceptable correlation coefficients for the aforementioned responses, where the PLGA molecular weight played the most important role among the studied variables. Input variables needed to minimize PLGA size and PLGA initial burst were then obtained via multiobjective optimization performed by a genetic algorithm. PLGA nanoparticles were checked for particle size and particle size distribution using scanning electron micrographs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45145.     

Novel methyl cellulose‐grafted‐acrylamide/gelatin microspheres for controlled release of nifedipine

Naturally available carbohydrate polymers such as methylcellulose (MC) and gelatin (Ge) have been widely studied in the previous literature for controlled release (CR) applications. In this study, methyl cellulose‐g‐acrylamide/gelatin (MC‐g‐AAm/Ge) microspheres were prepared by water‐in‐oil (W/O) emulsion method and crosslinked with glutaraldehyde to encapsulate with nifedipine (NFD), an antihypertensive drug. The microspheres prepared were characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and laser particle size analyzer. DSC thermograms of NFD‐loaded AAm‐MC/Gel microspheres confirmed the molecular level distribution of NFD in the matrix. SEM indicated the formation of spherical particles. Swelling experiments supported the drug diffusion characteristics and release data of the matrices. Cumulative release data were analyzed using an empirical equation to understand the nature of transport of drug through the matrices. Controlled release characteristics of the matrices for NFD were investigated in pH 7.4 media. Drug was released in a controlled manner up to 12 h. Particle size and size distribution of the microspheres as studied by laser light diffraction particle size analyzer indicated their sizes to be around 120 μm. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of a drug‐delivery system based on melamine‐modified poly(vinyl acetate‐co‐maleic anhydride) hydrogel

Three‐dimensional polymeric networks, which quickly swell by imbibing a large amount of water or deswell in response to changes in their external environment, are called hydrogels. These types of polymeric materials are good potential candidates for drug‐delivery systems. In this study, we first synthesized poly(vinyl acetate‐co‐maleic anhydride) by free‐radical copolymerization. Then, they were modified with different molar ratios of melamine to prepare hydrogels that could be used in drug‐delivery systems. The hydrogels were characterized by Fourier transform infrared spectroscopy, ¹H‐NMR, differential scanning calorimetry, and scanning electron microscopy. In the second step, Ceftazidime antibiotic was loaded on selected hydrogels. The in vitro drug release was investigated and compared in three different media (HCl solution at pH = 3 and buffer solutions at pH 6.1and pH 8). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40389.     

Pilocarpine‐loaded poly(DL‐lactic‐co‐glycolic acid) nanoparticles as potential candidates for controlled drug delivery with enhanced ocular pharmacological response

The poor corneal residence time of pilocarpine, an alkaloid extracted from the leaves of the Jaborandi plant, limits its ocular application. The aim of this study was to develop, characterize, and evaluate the potential of pilocarpine entrapped by poly(DL ‐lactic‐co‐glycolic acid) (PLGA) nanoparticle carriers for ocular drug delivery. Pilocarpine‐loaded nanoparticles were prepared with a double‐emulsion (water in oil in water) method and characterized with transmission electron microscopy and X‐ray diffraction analysis. The nanoparticles exhibited an average size of 82.7 nm with an encapsulation efficiency of 57%. Stability studies showed the absence of agglomeration and constancy in the amount of drug entrapped; this indicated the solidity of these particles for long‐term use. The in vitro release studies conducted in simulated tear fluid showed the sustained release of pilocarpine. In vivo evaluation of the nanoparticles was done in a rabbit model with a miosis assay and compared to an equal dose of commercially available eye drops of pilocarpine (Pilocar drops). The in vivo miosis studies showed that the duration of miotic response increased by 40% for the nanoparticles and produced an almost 68% increase in total miotic response when compared to the eye drops. In conclusion, this study clearly demonstrated the potential of pilocarpine‐loaded PLGA nanoparticles for multiplying the therapeutic effect of ophthalmic drug delivery with enhanced bioavailability and pharmacological response. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and in vitro biological evaluation as antitumour drug carriers of folate‐targeted N‐isopropylacrylamide‐based nanohydrogels

Copolymeric nanohydrogels based on N‐isopropylacrylamide, N‐(pyridin‐4‐ylmethyl)acrylamide and tert‐butyl‐2‐acrylamidoethyl carbamate, synthesized by microemulsion polymerization, were characterized using Fourier transform infrared spectroscopy and their size (38–52 nm) determined using quasielastic light scattering. Folic acid was covalently attached to the nanohydrogels (1.40 ± 0.07 mmol g^?1). Tamoxifen (6.7 ± 0.2–7.3 ± 1.2 µg TMX mg^?1 nanohydrogel), a hydrophobic anticancer drug, and 5‐fluorouracil (7.7 ± 0.7–10.14 ± 1.75 µg 5‐FU mg^?1 nanohydrogel), a hydrophilic anticancer drug, were loaded into the nanohydrogels. Maximum in vitro TMX release (77–84% of loaded drug) depended on interactions of the drug with hydrophobic clusters of the nanogels; however, no nanogel/5‐FU interactions allowed total release of the loaded drug. The cytotoxicity of unloaded nanohydrogels in MCF7, T47D and HeLa cells was low. Cell uptake of nanogels without bound folic acid took place in the three cell types by unspecific internalization in a time‐dependent process. Cell uptake increased for folic acid‐targeted nanohydrogels in T47D and HeLa cells, which have folate receptors. The administration of 10 and 30 µmol L^?1 TMX by TMX‐loaded nanogels and 10 µmol L^?1 5‐FU by 5‐FU‐loaded nanogels was effective on the three cell types, and the best results were obtained for folic acid‐targeted nanohydrogels. Copyright © 2012 Society of Chemical Industry     

Poly(D,L‐lactide‐co‐glycolide)/poly(ethylenimine) blend matrix system for pH sensitive drug delivery

Poly(D ,L ‐lactide‐co‐glycolide) (PLGA) and poly(ethylenimine) (PEI) were blended and found to form a homogeneous pH sensitive matrix for drug release. Differential scanning calorimetry (DSC) studies of the PLGA/PEI blends showed a single glass transition temperature at all compositions. Fourier transform infrared spectroscopy (FTIR) demonstrated that the PLGA carbonyl peak at 1760 cm^?1 shifted to 1666 cm^?1 as a result of amide bond formation between the two polymers. This was confirmed by ¹³C nuclear magnetic resonance studies. A PLGA/PEI matrix of 90/10 weight ratio was chosen for evaluation for controlled drug release. Both hydrophobic β‐lapachone and hydrophilic rhodamine B showed pH dependent release profiles with faster release kinetics at lower pH values. The observed pH sensitive drug release was mainly attributed to two factors, pH dependent swelling and protonation of the PEI‐PLGA matrix. These results demonstrate utility of a PLGA/PEI matrix and its potential application in pH responsive drug delivery. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 89–96, 2006     

Effect of additives on release profile of leuprolide acetate in an in situ forming controlled‐release system: In vitro study

In situ forming drug delivery system is prepared by phase inversion technique using poly (D ,L ‐lactic‐co‐glycolide) and leuprolide acetate dissolved in N‐methyl‐2‐pyrrolidone. The effects of ethyl heptanoate and glycerol additives are important determinant as rate modifying agents on the drug release kinetics in biodegradable in situ forming porous systems of poly(D ,L ‐lactide‐co‐glycolide) (PLGA) in N‐methyl‐2‐pyrrolidone (NMP). The release performance and porous structure morphology are investigated by scanning electron microscopy and UV–visible spectroscopy techniques to study the effect of additives. The experimental results exhibit the crucial role of ethyl heptanoate and glycerol at different loadings (1, 3, and 5% w/w) on release profile of leuprolide acetate loaded on poly(D ,L ‐lactide‐co‐glycolide)hydroxylated (PLGA‐H). Both additives at different concentrations reduce the burst effect, while increasing duration of drug release. Ethyl heptanoate, however, shows stronger effect than glycerol. The results of morphological studies show that ethyl heptanoate reduces the porosity of the polymer surface and interconnected tear‐like structures of the bulk disappear while the sponge‐like structures are observed. In this system glycerol reduces the surface porosity intensively, while the interconnected tears change into channel‐like structures. Therefore, morphological results confirm the effect of additives on leuprolide release profile. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Controlled release of chlorpheniramine maleate through IPN beads of sodium alginate‐g‐methylmethacrylate

Controlled release of chlorpheniramine maleate drug, through sodium alginate‐g‐methylmethacrylate (NaAlg‐g‐MMA) interpenetrating polymeric network beads, has been investigated. Beads were prepared by precipitating the viscous solution of NaAlg‐g‐MMA in acetone followed by cross‐linking with glutaraldehyde. The beads were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Different formulations of beads were developed by varying amounts of MMA, cross‐linking agent, and drug concentration. DSC thermograms of chlorpheniramine maleate drug‐loaded NaAlg‐g‐MMA beads confirmed the molecular level distribution of drug in the polymer matrix. FTIR of beads confirm the grafting and cross‐linking, SEM of the beads suggested the formation of spherical particles. Swelling experiments on the beads provided an important information on drug diffusion properties. Release data have been analyzed using an empirical equation to understand the nature of transport of drug containing solution through the polymeric matrices. The controlled release characteristics of the matrices for chlorpheniramine maleate was investigated in pH 7.4 media. Drug was released in a controlled manner upto 12 h. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Flurbiprofen axetil loaded coaxial electrospun poly(vinyl pyrrolidone)–nanopoly(lactic‐co‐glycolic acid) core–shell composite nanofibers: Preparation,characterization, and anti‐adhesion activity

Flurbiprofen axetil (FA)‐loaded coaxial electrospun poly(vinyl pyrrolidone) (PVP)–nanopoly(lactic‐co‐glycolic acid) core–shell composite nanofibers were successfully fabricated by a facile coaxial electrospinning, and an electrospun drug‐loaded system was formed for anti‐adhesion applications. The FA, which is a kind of lipid microsphere nonsteroidal anti‐inflammatory drug, was shown to be successfully adsorbed in the PVP, and the formed poly(lactic‐co‐glycolic acid) (PLGA)/PVP/FA composite nanofibers exhibited a uniform and smooth morphology. The cell viability assay and cell morphology observation revealed that the formed PLGA/PVP/FA composite nanofibers were cytocompatible. Importantly, the loaded FA within the PLGA/PVP coaxial nanofibers showed a sustained‐release profile and anti‐adhesion activity to inhibit the growth of the IEC‐6 and NIH3T3 model cells. With the significantly reduced burst‐release profile, good cytocompatibility, and anti‐adhesion activity, the developed PLGA/PVP/FA composite nanofibers were proposed to be a promising material in the fields of tissue engineering and pharmaceutical science. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41982.     

Biodegradable poly(sebacic acid‐co‐ricinoleic‐ester anhydride) tamoxifen citrate implants: Preparation and in vitro characterization

The aim of this study was to prepare tamoxifen citrate loaded cylindrical polymeric implants for application at tumor sites. The implant was based on poly (sebacic acid‐co‐ricinoleic‐ester anhydride) 70 : 30 w/w [poly(SA‐RA) 70 : 30 w/w], a low‐melting, biodegradable, and biocompatible polymer. Implants were prepared by a standardized melt manufacturing method. Differential scanning calorimetry and scanning electron microscopy were used for implant characterization. In vitro drug release studies were performed in phosphate‐buffered saline (pH 7.4) at 37 ± 2°C. The drug content was estimated by high‐performance liquid chromatography. The differential scanning calorimetry studies showed that the tamoxifen citrate in the implants was in the amorphous state. The cumulative percentage of drug release from 10 and 20 wt % drug‐loaded poly(SA‐RA) 70 : 30 w/w implants after 30 days was found to be 42.36 and 62.60%, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and characterization of nanoparticulate poly(N‐isopropylacryl‐ amide) hydrogel for the controlled release of anti‐tumour drugs

BACKGROUND: Poly(N‐isopropylacrylamide) (PNIPA) nanohydrogels were synthesized by inverse microemulsion to be used for the controlled release of anti‐tumour drugs. Different methods were used to obtain drug‐loaded xerogels, and their effect on drug release was studied, and evaluated using mathematical modelling. RESULTS: Nanoparticulate hydrogels, with a z‐average diameter of 170 nm, were loaded with 5‐fluorouracil (5‐FU), methotrexate (MTX) or mitomycin C (MMC) by using spray drying (SD) and freeze drying (FD). Xerogels obtained by SD consisted of individual and independent particles, whereas particles established interactions in xerogels obtained by FD. Total drug release took place at 6 and 7 h from 5‐FU‐loaded and MMC‐loaded xerogels prepared by SD, whereas MTX was expelled from the xerogels formed using the SD process. Drug release was slower from xerogels prepared by FD: 5‐FU at 32 h, MMC at 120 h and MTX at 240 h. The Higuchi model most aptly fits the dissolution data. Non‐Fickian and Fickian release behaviour can be attributed to SD and FD formulations, respectively. CONCLUSION: The amount of drug loaded, the morphology of xerogels as well as the drug release characteristics not only depend on the drug but also mainly on the process used to obtain the drug‐loaded PNIPA xerogels. Copyright © 2008 Society of Chemical Industry     

Valproate‐Loaded hydrogel nanoparticles: Preparation and characterization

Developing a simple and efficient approach to formulate biodegradable nanoparticles for intravenous delivery of sodium valproate (a hydrophilic small molecule drug chronically used in epileptic patients), is the principal objective of the current study. To fabricate particles via ionotropic gelation approach, a polycation polymer (chitosan) along with a polyanion (tripolyphosphate) was utilized in the presence of sodium valproate, and the Taguchi experimental design method was drawn upon so as to determine the optimum conditions of nanoparticle generation. In the following step, the researchers investigated sodium valproate‐loaded nanoparticles to explore various features of the nanoparticles including drug loading parameters, particle size distribution, zeta‐potential, morphology, stability, yield, and in vitro drug release profile. Nanoparticles with sizes of 63 ± 1 nm (number‐based) and 79 ± 3.21 (volume‐based) were obtained with slightly negative zeta–potential, which was more positive in drug‐loaded nanoparticles than the unloaded ones. The TEM imaging of the hydrogel nanoparticles manifested spherical shapes and corroborated the size achieved via particle size analyzer. The loading efficiency, loading amount, and loading ratio were determined to be 21.81 ± 3.90%, 10.31 ± 1.82 (mg sodium valproate/g nanoparticle) and 23.70 ± 4.54%, respectively, in optimum conditions. Moreover, there was observed a gradual drug release for nearly a week consisting, in average, about 94.64 ± 2.71% of the nanoparticles' drug content. In a nutshell, the present study introduces a practical, simple, and effective ionotropic gelation approach to generate sodium valproate‐loaded nanoparticles, leaving open a window of promising prospects in the field of intravenous long‐term delivery of this chronically used drug. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Drug‐loaded polyurethane/clay nanocomposite nanofibers for topical drug‐delivery application

In this study, polyurethane/nanoclay nanocomposite nanofibrous webs were prepared by electrospinning. An antiseptic drug, chlorhexidine acetate (CA), was loaded onto montmorillonite clay and was then incorporated into polyurethane nanofibers. For comparison, the CA drug was loaded directly into the polyurethane solution dope used to electrospin the nanofibers. The emphasis was on investigating the effect of the drug loading into the nanoclay vis‐à‐vis direct drug loading on the drug‐release behavior of nanofibrous webs. The nanofibrous webs were also evaluated for other properties, such as moisture vapor transmission, porosity determination, contact angle measurement, and antibacterial activity, which are important for topical drug‐delivery application. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40230.