Dual crosslinked carboxymethyl sago pulp/pectin hydrogel beads as potential carrier for colon‐targeted drug delivery

Carboxymethyl sago pulp (CMSP)/pectin hydrogel beads were synthesized by calcium crosslinking and further crosslinked by electron beam irradiation to form drug carrier for colon‐targeted drug. Sphere‐shaped CMSP/pectin 15%/5% hydrogel beads is able to stay intact for 24 h in swelling medium at pH 7.4. It shows pH‐sensitive behavior as the swelling degree increases as pH increases. Fourier transform infrared spectroscopy analysis confirmed the absence of chemical interaction between hydrogel beads and diclofenac sodium. Differential scanning calorimetric and X‐ray diffraction studies indicate the amorphous nature of entrapped diclofenac sodium. The drug encapsulation efficiency is up to about 50%. Less than 9% of drug has been released at pH 1.2 and the hydrogel beads sustain the drug release at pH 7.4 over 30 h. This shows the potential of CMSP/pectin hydrogel beads as carrier for colon‐targeted drug. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43416.     

Formation of silk fibroin hydrogel and evaluation of its drug release profile

Silk hydrogels are interesting materials to be used as matrix in controlled drug delivery devices. However, methods to accelerate fibroin gelation and allow the drug incorporation during the hydrogel preparation are needed in literature. In this article we report the preparation of silk fibroin hydrogels with addition of several contents of ethanol, used to accelerate fibroin gelation kinetics, and we also evaluate the potential of these hydrogels to be used as matrices for drug delivery. Chemical and conformational properties did not change despite the amount of ethanol incorporated in the hydrogel. Hydrogels containing diclofenac sodium dissolved in ethanol showed a faster initial release of the drug than hydrogels with the drug dissolved in water but equilibrium was reached later. This indicates a more sustained drug delivery from hydrogels in which the model drug was dissolved in ethanol. Fibroin hydrogels confirm their promising use as biopolymeric matrices for controlled drug release. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41802.     

Preparation of a biodegradable poly(vinyl alcohol)–starch composite film and its application in pesticide controlled release

With the herbicide 2,4‐dichlorophenoxyacetic acid (2,4‐D) as a model drug, a series of poly(vinyl alcohol)–starch (PVA–ST) composite films for controlled drug release were prepared by a casting method. The morphology, structure, and release properties were systematically investigated. The results show that when the PVA–ST composite film containing 2,4‐D (PSD) was immersed in water, the drug‐release rate was high, whereas the introduction of sodium montmorillonite (Na‐MMT) and an alginate ion‐crosslinking structure to PSD significantly reduced the release rate and maintained the sustained release of the model drug for a longer period. A leaching experiment through the soil layer showed that the PSD drug‐loaded film with Na‐MMT and the alginate ion‐crosslinking structure (PSDMA) possessed good release properties. The cumulative leached amount of the herbicide 2,4‐D after eight irrigations was reduced to 57.6% from 100%. In addition, the PSDMA film showed favorable mechanical and thermal properties. This composite film is expected to have potential applications in the fields of agriculture, drug delivery, and more. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45051.     

In situ incorporation of monodisperse drug nanoparticles into hydrogel scaffolds for hydrophobic drug release

The effective and locally sustained delivery of hydrophobic drug with hydrogels as carriers is still a challenge owing to the inherent incompatibility of hydrophilic hydrogel network and hydrophobic drug. One promising approach is to use porous hydrogels to encapsulate and deliver hydrophobic drug in the form of nanoparticles to the disease sites. However, this approach is currently limited by the inability to load concentrated hydrophobic drug nanoparticles into the hydrogels because of the severe nanoparticle aggregation during the loading process. In this article, we firstly designed and fabricated efficient drug nanoparticles embedded hydrogels for hydrophobic drug delivery by incorporating monodisperse silybin (hydrophobic drug for liver protection) nanoparticles into acrylated hyaluronic acid (HA‐AC) based hydrogels through in situ cross‐linking. The silybin nanoparticles embedded hydrogel scaffolds proved to be a good sustained release system with a long period of 36 h. The drug release from this hybrid hydrogels could be modulated by tuning HA‐AC concentration, cross‐linking ratio, chain length of cross‐linker and drug loading amount. The different kinetic models were applied, and it was observed that the release profile of silybin best followed the Hixson‐Crowell model for the release of drug from the hydrogels embedding silybin nanoparticles. It could be envisioned that this process would significantly advance the potential applications of hydrogel scaffolds mediated hydrophobic drug delivery in clinical therapies. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43111.     

Synthesis of a cellulose‐based hydrogel network: Characterization and study of urea fertilizer slow release

In the present study, we synthesized a low‐cost biodegradable hydrogel based on cellulose in order to perform controlled release of fertilizer. For this purpose, the cellulose was modified and crosslinked with urea. Then the prepared hydrogel underwent loading with the fertilizer in order to study the controlled release. Characterization of the samples was carried out by Fourier Transform Infrared (FT‐IR) spectroscopy, elemental analysis, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM). The hydrogel showed a good swelling behavior in distilled water, tap water, and 0.9% NaCl solution. Besides, water holding and water retention behavior of the hydrogel was investigated. Finally, the release of fertilizer from the loaded hydrogel was studied and showed excellent controlled release. According to the results, this hydrogel can be employed as a suitable moisture‐holding additive in the soil for agricultural purposes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42935.     

Silk fibroin membranes with self-assembled globular structures for controlled drug release

In this paper, we have evaluated the incorporation of a drug model and its release from silk fibroin (SF) membranes, analyzing the morphological, chemical, barrier, and biological properties. SF self-assembled into stable globular structures, encapsulating the drug, when diclofenac sodium (DS) was incorporated into SF solution prior to membranes preparation. The membranes showed biostatic action and prevented microorganism permeation. Kinetic studies indicate that DS was released in 120 min, with Fickian diffusion as the main mechanism of release. Results of this paper emphasize the potential of SF in wound healing, with good barrier and biological properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48763.     

Synthesis and characterization of star‐shaped PLLA with sorbitol as core and its microspheres application in controlled drug release

The purpose of this study was to investigate the suitability of a six‐arm star‐shaped poly(l ‐lactide)s (s‐PLLA) as controlled drug carriers for hydrophobic drug molecules. First, s‐PLLA was synthesized by ring‐opening polymerization of l ‐lactide using sorbitol as initiator and stannous octoate as catalyst. The structure and molecular weight (M_w) of s‐PLLA was characterized with ¹H NMR, ¹³C NMR, and GPC. Second, rifampicin (RIF) used as a model drug was encapsulated within the microspheres of s‐PLLA via oil‐in‐water emulsion/solvent evaporation technique. The morphology, drug encapsulation efficiency (EE), and in vitro release behavior of the prepared microspheres were studied in details. Results indicated that the average diameters of s‐PLLA microspheres can be controlled between 8 and 20 µm by varying the copolymer's concentration or M_w . The EE of RIF was mainly determined by the concentration of s‐PLLA. The in vitro study showed that the burst release behavior can be depressed by increasing the M_w of the s‐PLLA. Present work suggests that the synthesized s‐PLLA could be used as a new material for drug delivery. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42213.     

Thermoresponsive/low‐fouling Zwitterionic hydrogel for controlled drug release

A controlled/ living free‐radical polymerization technique was introduced to prepared a homogeneous poly(N‐isopropylacrylamide)‐g‐poly(sulfobetaine methacrylate) hydrogel (RG) possessing a highly porous architecture via two steps. Compared to a poly(N‐isopropylacrylamide)‐co‐poly(sulfobetaine methacrylate) hydrogel (CG) prepared by conventional radical polymerization, RG exhibited a much faster shrinking rate (it lost over 72% of the water in 15 min) in response to the temperature changes. The release behaviors of tetracycline hydrochloride (TCHC) of the hydrogels indicated the TCHC release from the RG could be prolonged to 48 h at 37°C; this was much longer than that for CG (5 h at 37°C). Bovine serum albumin (BSA) was chosen as the model protein to examine the low‐fouling properties of the RG. The BSA adsorption data showed that improved antifouling properties could be achieved by the RG at both 25 and 37°C. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39816.     

Enzymatic degradability and release properties of graphene oxide/silk fibroin nanocomposite films

The structure evolution of silk fibroin (SF) in the nanocomposite films with graphene oxide (GO) was investigated and related to the enzymatic degradability and release property. The interaction with GO was found to induce conformation transition of SF from random coil to β-sheet. However, the surface binding constrained the rearrangement of the silk chains, leading to a decrease of β-sheet when GO content was more than 1.0%. The crystal structure of SF played a key role in the degradation of GO/SF composites. The preferential degradation of the hydrophilic blocks resulted in a faster degradation of SF films with higher β-sheet content. The addition of GO to SF matrix led to a slower release and a reduction of the burst release of RhB, the model compound. The release profile was well fitted to the Rigter–Peppas equation, from which the characteristic constant decreased and the diffusional exponent increased with increasing GO content but quickly leveled off when GO content was more than 1.0%. Degradation of the composites had little influence on the characteristic constant of RhB release, however, led to an increased diffusional exponent, which was more evident for the composites with higher β-sheet content.     

Theophylline‐loaded pectin‐based hydrogels. I. Effect of medium pH and preparation conditions on drug release profile

In this study, a series of theophylline‐loaded calcium pectin gel films were prepared in three different Ca⁺² concentrations with three different methods for wound dressing applications. Drug release performance of the films were investigated in four different medium pH in order to mimic wound healing pH conditions. Hydrogel films were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy and atomic force microscopy. Their absorbency (fluid handling), swelling behavior, dehydration rate, dispersion characteristic, dressing pH determination, water vapor permeability, oxygen permeability, surface contact angle, flexibility, Shore A hardness, mean mass per unit area and thickness were determined. The effect of the hydrogels on wound healing was evaluated with an in vitro wound healing assay. After evaluating all data, we suggested that the hydrogel film prepared with swelling method using 7% or 10% crosslinker and dried at 26 °C is more suitable for controlled drug release process. We showed that between pH 3.25 and 7.12 the form of the hydrogel did not change, and drug release was continuous. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46731.     

Self‐assembling chitosan hydrogel: A drug‐delivery device enabling the sustained release of proteins

The development of a self‐assembling hydrogel, prepared from maleimide‐modified and thiolated chitosan (CS), is described. Under mild reaction conditions, the natural CS polymer was coupled with either maleimide or sulfhydryl moieties in a one‐step synthesis. Subsequently, these CS polymers spontaneously formed a covalently crosslinked CS hydrogel when mixed. The three‐dimensional network structure was visualized with scanning electron microscopy. The swelling and degradation behavior was evaluated, and viscosity measurements were conducted. The gel was loaded with the model protein albumin, and prolonged release was achieved. These properties were preserved after lyophilization and rehydration. This makes the hydrogel a promising scaffold for biological wound dressings for the treatment of chronic wounds. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45638.     

Novel blend microspheres of poly(3‐hydroxybutyrate) and Pluronic F68/127 for controlled release of 6‐mercaptopurine

The objective of this article is to investigate the controlled release characteristics of 6‐mercaptopurine (6‐MP) loaded microspheres prepared from the blends of poly(3‐hydroxybutyrate) (PHB) and Pluronic F68/127 by the oil‐in‐water emulsion‐solvent evaporation technique. Formulations were prepared by taking different ratios of individual polymer components to achieve a maximum 79% encapsulation and extending the release time up to 24 h. Differential scanning calorimetry (DSC) suggested reduction in crystallanity of PHB after blending with Pluronic F127. The absence of chemical interactions between 6‐MP and the blend matrix was confirmed by Fourier transform infrared (FTIR) spectroscopy, while the size of microspheres measured by optical microscopy ranged between 30 and 47 μm. X‐ray diffraction (XRD) confirmed the crystalline nature of 6‐MP even after encapsulation and surface morphology of the microspheres was investigated by scanning electron microscopy (SEM). In vitro release of 6‐MP at 37°C in pH 7.4 phosphate buffer media indicated a dependence on the composition of Pluronic in the blend. The release data have been fitted to empirical equations to understand the release profile of 6‐MP. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40196.     

Kinetics of drug release from drug carrier of polymer/TiO2 nanotubes composite—pH dependent study

This study was to investigate the kinetics of drug release from polymer/TiO₂ nanotubes composite. Lidocaine and carprofen were selected as model drugs to represent weak base and weak acid drugs, respectively. Mathematical models used to fit the in vitro drug release experimental data indicate that at higher pH, the drug release was first order diffusion controlled. At lower pH, the release of the two drugs exhibits two staged controlled release mechanism. The first phase is due to drug diffusion and the second stage is a result of poly(lactic‐co‐glycolic acid) (PLGA) polymer degradation. The rate of drug release from polymer/TiO₂ nanotubes drug carrier was mainly controlled by three pH dependent factors: the solubility of the drug, the degree of polymer swelling/degradation, and the electrostatic force between polymer and drug. This study suggests that controlled release could be achieved for polymer/TiO₂ nanotubes drug carrier via the modulation of pK_a values of polymers and drug solubility. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41570.     

Effect of urea and formamide plasticizers on starch/PVA bioblend sheets

The starch/polyvinyl alcohol (PVA) bioblend sheets containing urea and formamide as plasticizers were prepared through melt processing in presence of water. The experiments indicated that urea and formamide plasticizers could form strong hydrogen bonds with starch/PVA molecules. Urea exhibited better plasticizing effect than formamide. Urea also could greatly destroy the crystal structures of PVA component in the blends, leading to the decreased crystallinity of the blends. Formamide was a good solvent for urea and could prevent urea separating from the blends, resulting in the improved stability of plasticizing systems. The blends exhibited good flexibility. Therefore, the incorporation of both urea and formamide into starch/PVA blends could exhibit synergistic effects to ensure the blends with both good plasticizing effect and the stability of the plasticizing systems. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42311.     

Biodegradable starch particles for controlled release applications: Swelling and leaching mechanisms

Starch-extruded particles have only found infrequent use as delivery systems for active ingredients. We have previously shown that these particles are attractive for releasing hydrophobic compounds in water media. Here, we cover a range of amylose–amylopectin ratios and evaluate the presence of the thyme essential oil (TEO) as active compound to understand the dominant release mechanism in relation to the physicochemical properties of the starch matrices. Starch blends with high amylopectin content (1.8 and 15% amylose) could not be shaped into regular particles. For amylose contents higher than 28%, the equilibrium degree of swelling in water decreased with increasing amylose contents, from nearly 300% for an amylose content of 28–90% at an amylose content of 70%. For both lowest amylose contents, 1.8 and 15%, leaching of solids and disintegration of the particles resulted in a low apparent degree of swelling. The presence of TEO reduces the degree of swelling of the gelatinized starch matrix. This is explained by the formation of thymol–amylose complexes, which is confirmed by Fourier transform infrared spectroscopy analysis and X-ray diffraction.     

Tetracycline release from chitosan/fish‐scale‐based membranes

In this study, we aimed to develop new biocompatible membranes on the basis of chitosan (CHIT) and fish scale powder (ESC) from the species Leporinus elongatus. The possibility of using the uncrosslinked membrane (ESC/CHIT) and membrane crosslinked with sodium tetraborate (ESC/CHIT‐B) for tetracycline release was investigated. The drug‐release kinetics were studied at 30 and 37°C in phosphate buffered saline (pH 7.4). For ESC/CHIT, the drug release was faster, about 6 days, whereas the release time of tetracycline impregnated in ESC/CHIT‐B was about 7 days. The in vitro release behavior of tetracycline from both membranes followed the Peppas and Higuchi kinetic models. The kinetics of drug release from ESC/CHIT were regarded as a coupled diffusion/polymer relaxation mechanism, whereas drug release from ESC/CHIT‐B seemed to be controlled by polymer relaxation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39943.     

In vitro nifedipine release from poly(lactic acid)/chitosan nanoparticles loaded with nifedipine

In this study, nanoparticles based on poly(lactic acid) (PLA), chitosan (CS), and nifedipine (NIF) were prepared by an emulsion method with poly(ethylene oxide) (PEO) as an emulsifier. We investigated the most suitable conditions for preparing the poly(lactic acid)/chitosan/nifedipine nanoparticles (PCNs) by changing the distilled water volume, PEO content, and PLA/CS ratio. NIFs with different contents were loaded into poly(lactic acid)/chitosan nanoparticles (PCs) to study in vitro drug‐delivery systems. The PCNs were characterized with a Zetasizer particle size analyzer, field emission scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, and X‐ray diffraction (XRD) methods. From the obtained results of the particle size parameters of the PCNs, the most suitable conditions for the preparation of the PCNs were found. The FTIR spectroscopy and XRD results show that NIF was loaded into the PCs. The PCNs had major basic particle sizes in the range 20–40 nm. NIF release from the PCNs was studied as a function of the pH of the immersed solution, the immersion time, and the NIF content. The kinetics of drug release were investigated and are reported to determine the type of release mechanism. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43330.     

Thermogravimetric and Fourier‐transform infrared analyses on the cure behavior of polycardanol containing epoxy groups cured by electron beam

In this study, the curing behavior of polycardanol containing epoxy groups (diepoxidized polycardanol) was exploited in terms of thermal stability and the cure reaction conversion by means of thermogravimetric analysis and Fourier‐transform infrared spectroscopy, respectively. The effect of photo‐initiator type and concentration and electron beam absorption dose in the presence of cationic photo‐initiators (triarylsulfonium hexafluorophosphate (P‐type) and triarylsulfonium hexafluoroantimanate (Sb‐type) on the cure behavior of diepoxidized cardanol (DEC) resin was investigated. The thermal stability of DEC with Sb‐type photo‐initiator was higher than that with P‐type one, being increased with increasing the concentration and electron beam absorption dose. The conversion of cure reaction was gradually increased with increasing the dose, showing the maximum at 800 kGy. The results revealed that Sb‐type photo‐initiator, the concentration of 2 or 3 wt %, and electron beam absorption dose of about 800 kGy may be preferable for initiating epoxy ring opening in the DEC molecules as well as for efficiently curing the DEC resin by electron beam irradiation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41599.     

Effects of drug and polymer molecular weight on drug release from PLGA‐mPEG microspheres

This study investigated the effects of drug and polymer molecular weight on release kinetics from poly (g ‐co‐glycolic acid)‐methoxypoly(ethyleneglycol) (PLGA‐mPEG) microspheres. Bovine serum albumin (BSA, 66 kDa), lysozyme (LZ, 13.4 kDa), and vancomycin (VM, 1.45 kDa) were employed as the model drugs, and encapsulated in PLGA‐mPEG microspheres of different molecular weight. Release of macromolecular BSA was mainly dependent on diffusion of drug at/ near the surface of the matrix initially and dependent on degradation of matrix at later stages, while, the small drug of vancomycin seemed to depend totally on diffusion for the duration of the release study. The release behavior of lysozyme was similar to bovine serum albumin, except a shorter lag period. PLGA‐mPEG molecular weight also affected the release behavior of bovine serum albumin and lysozyme, but not obviously. PLGA‐mPEG microspheres in smaller molecular weight seemed to degrade more quickly to obtain a mass lose and matrix erosion, and thus, an accelerated release rate of bovine serum albumin and lysozyme. Vancomycin released much faster than bovine serum albumin and lysozyme, and exhibited no lag period, as it is thought to be diffusion‐controlled. Besides, vancomycin showed no difference in release behavior as PLGA‐mPEG molecular weight change. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41431.     

Study of a nanocomposite starch–clay for slow‐release of herbicides: Evidence of synergistic effects between the biodegradable matrix and exfoliated clay on herbicide release control

In this article a nanocomposite based on starch gel, a renewable polymer, and montmorillonite clay (MMT) is proposed as a host system for the slow‐delivery of a hydrophobic herbicide loaded in very high contents (50% in total weight), where the nanocomposite structure controls the release by imposing diffusional barriers to the active compound. The herbicide release rate in water showed that nanocomposites presented higher retentions than the neat samples (herbicide‐loaded starch or MMT), revealing a cooperative or synergic effect between the constituents. Biodegradation essays also revealed this cooperative behavior, showing longer biodegradation periods for the nanocomposite than the pristine materials. Also, a two‐step release was noticed, where the first step was controlled by starch (short periods) and the second was played by MMT (longer times). The nanocomposite structural analysis gave evidence that the release behavior is governed by the interaction between the constituents, even at very high herbicide contents. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41188.