Functionality of chitosan-halloysite nanocomposite films for sustained delivery of antibiotics: The effect of chitosan molar mass

This study was designed to investigate functionality of tetracycline-loaded chitosan-halloysite nanocomposite films, with focus on evaluating the influence of chitosan molar mass on films applicability for sustained local antibiotic delivery. The films were prepared by casting and solvent evaporation using low, medium, and high molar mass chitosan. SEM analysis revealed compact, nonporous and rough surface of the nanocomposite films due to the presence of halloysite agglomerates and tetracycline crystals. Increasing chitosan molar mass led to higher values of elongation at break (from 21.65 ± 2.65 to 34.48 ± 2.34%), tensile strength (from 134.8 ± 13.21 to 246.36 ± 14.69 MPa), and elastic modulus (from 633.79 ± 128.37 to 716.55 ± 60.76 MPa) of the nanocomposite films. FT-IR, XRPD, and thermal analyses confirmed molar mass dependent chitosan-halloysite interactions and improved thermal stability of the nanocomposite films in comparison with chitosan films. The nanocomposite films released tetracycline in a sustained manner, with the slowest release achieved from the films consisting of low molar mass chitosan. Chitosan molar mass was confirmed to be a functionality-related characteristic of chitosan-halloysite nanocomposite films as potential sustained-release carriers for topical delivery of antibiotics. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48406.     

Transparent low‐density polyethylene/starch nanocomposite films

Low‐density polyethylene (LDPE)/starch nanocomposite films were prepared by melt extrusion process. The first step includes the preparation of starch–clay nanocomposite by solution intercalation method. The resultant product was then melt mixed with the main matrix, which is LDPE. Maleic anhydride‐grafted polyethylene (MAgPE), produced by reactive extrusion, was used as a compatibilizer between starch and LDPE phases. The effects of using compatibilizer, clay, and plasticizers on physico‐mechanical properties were investigated. The results indicated that the initial intercalation reaction of clay layers with starch molecules, the conversion of starch into thermoplastic starch (TPS) by plasticizers, and using MAgPE as a compatibilizer provided uniform distribution of both starch particles and clay layers, without any need of alkyl ammonium treatment, in LDPE matrix. The nanocomposite films exhibited better tensile properties compared to clay‐free ones. In addition, the transparency of LDPE film did not significantly change in the presence of TPS and clay particles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Orange peel‐derived pectin jelly and corn starch‐based biocomposite film with layered silicates

Orange peel‐derived pectin jelly/corn starch‐based biocomposite films with and without layered silicates (LSs) were prepared using melt extrusion followed by film die casting. To enhance interfacial compatibility, corn starch and LSs were chemically modified. Regardless of chemical modification or LS weight content, different pectin jelly‐to‐starch weight ratios (63/37, 60/40, 57/43, and 54/46) were considered to formulate the ingredients of biocomposite films in light of Taguchi‐based predictions. X‐ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), scanned electron microscopy (SEM) and transmission electron microscopy (TEM) were systematically used to characterize corn starch, LSs, and biocomposite films. Among all the films considered, pectin jelly/modified (15%) starch‐based biocomposite film (54/46 w/w) containing 0.25 wt % of pristine LSs was found to be the most promising in terms of texture structure and mechanical integrity. Furthermore, creep recovery, hydrophobicity, and water vapor and oxygen gas transmission rates of the most promising biocomposite film were experimentally determined. Based on the findings obtained, the overall performance of the biocomposite film was evaluated and weighed against the overall performance of a low‐density polyethylene film. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40654.     

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.     

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.     

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.     

Polyurethane‐incorporated chitosan/alginate core–shell nano‐particles for controlled oral insulin delivery

Chitosan (CS) and polyurethane‐chitosan (PU‐CS) nano‐particles (NPs) were prepared for the core formation by complex coacervation method whereas alginate (ALG) and PU‐ALG were crosslinked by ionic gelation method to form the protective shell‐layer over the core. Effects of PU incorporation either within the core or shell or both were investigated by different in vitro and in vivo parameters. Fourier transform infrared (FTIR) spectroscopy of different compositions of nano‐particles showed distinct characteristic peaks for CS, PU, and ALG, indicating their presence in variable ratios. Significance of polyurethane‐incorporated systems towards insulin encapsulation efficiency, swelling parameters, insulin release, and in vivo pharmacological effect were also studied. Particle sizes, zeta potential, morphological analysis, mucoadhesion study, and in vivo acute toxicity studies of these core–shell nano‐particles were also performed. Bioavailability of insulin ranged from 9.04% to 11.6% for polyurethane‐incorporated chitosan‐alginate core–shell nano‐particle formulations which was significantly higher than the insulin bioavailability of basic CS/ALG core–shell nano‐particle system. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46365.     

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.     

Lignin‐polyethylene glycol matrices and ethylcellulose to encapsulate highly soluble herbicides

The blending of lignin with polyethylene glycol (PEG) allowed us to obtain formulations with controlled release properties in which metribuzin have been successfully trapped with encapsulation efficiency higher than 85%. Moreover, the modification of the lignin's viscoelastic properties by the addition of PEG led to obtain herbicide formulations with active ingredient contents lower than 15%, suitable for its application in soil. Fourier transformed infrared spectroscopy and differential scanning calorimetry studies indicated the compatibility between polymers and metribuzin in lignin‐based controlled release formulations (CRFs). Lignin‐based formulations were coated in a Wurster‐type fluidized‐bed equipment using ethylcellulose and dibutylsebacate. Scanning electron microscope pictures showed a homogeneous film in ethylcellulose‐coated CRFs. The kinetic release studies showed that the release rate of metribuzin was mainly controlled either by selecting the granule size of controlled release lignin‐PEG matrixes, or by changing the thickness of coating film for ethylcellulose coated CRFs. These results could help to increase the efficiency of delivery of the highly soluble herbicide metribuzin and prevent the environmental pollution derived from its use. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41422.     

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.     

Hydroxypropylmethyl cellulose‐based sponges loaded self‐microemulsifying curcumin: Preparation,characterization, and in vivo oral absorption studies

Novel hydroxypropylmethyl cellulose (HPMC)‐based sponges containing self‐microemulsifying curcumin (SME‐Cur) were prepared by a freeze drying method using different grades of HPMC (E5 LV, E15 LV, E50 LV, A15 LV, and A4C). The physical properties and drug release from these carriers were characterized and compared among the different formulations. The mean pore size values of the sponges from image analysis ranged from 43.36 ± 4.54 to 123.22 ± 8.19 nm. An increase in the concentration or viscosity of the HPMC, resulted in denser sponges and a slower drug release. The average microemulsion droplet size from the optimal sponge formulation was 34.80 ± 0.1 nm, and the curcumin was almost completely released within 120 min. The AUC after oral administration of the liquid and solid SME‐Cur were 7‐ and 5‐fold greater than that of the curcumin powder in the rabbit, respectively. The results demonstrated that the HPMC‐based sponges loaded with SME‐Cur could be efficiently used to enhance the oral bioavailability and might be useful as they could be administered at a lower dose compared to normal curcumin powder. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42966.     

Spray‐drying microencapsulation of β‐carotene by soy protein isolate and/or OSA‐modified starch

Microencapsulation is an effective strategy to improve the storage stability of β‐carotene. This article investigated the potential and effectiveness of soy protein isolate (SPI) and octenylsuccinic anhydride‐modified starch (MS), alone or in combination (1:1, w/w), to encapsulate β‐carotene by spray drying. The results indicated that the microcapsule with MS exhibited much lower encapsulation efficiency (NE) and poorer dissolution behavior, but much better redispersion behavior, than that with SPI or its blends with MS. The NE was basically unaffected by total solid content (TC) or core/wall ratio; increasing the TC impaired the dissolution and/or redispersion behavior. The dispersion behavior was closely associated with the morphology of the microcapsules. The encapsulated β‐carotene suffered a progressive loss upon storage under high humid or temperature environment, but it exhibited extraordinary stability at low temperatures (e.g., 4°C). The β‐carotene degradation was independent of sunlight. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40399.     

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.     

Fabrication of starch‐g‐poly(l‐lactic acid) biocomposite films: Effects of the shear‐mixing and reactive‐extrusion conditions

In this study, we developed a new approach for the fabrication of a green poly(l ‐lactic acid)‐grafted starch (St‐g‐PLA) copolymer and nanocomposite (St‐g‐PLA/organoclay)‐based films via shear‐mixing and reactive‐extrusion systems. The chemical and physical structures, thermal behavior, and morphology of the synthesized blends and some other parameters were examined by Fourier transform infrared spectroscopy and ¹³C cross‐polarization/magic angle spinning NMR spectroscopy, X‐ray diffraction, thermogravimetric analysis–derivative thermogravimetry, and scanning electron microscopy, respectively. Significant increases in the mechanical and permeability properties were evident in the high value of grafted poly(lactic acid) molar percentages and high exfoliation of organoclay. The biodegradability of films were investigated under aerobic composting conditions through the measurement of the temperature, moisture, pH, consumed O₂ value, and carbon dioxide produced. This new strategy mainly improved the good adhesion between both phases, and it was an interesting method for the production of environmentally friendly biocomposites that could easily be scaled up for commercial production with the potential for replacing petroleum‐based plastics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44490.     

Freezing/thawing effects on the exfoliation of montmorillonite in gelatin‐based bionanocomposite

Freezing/thawing is used as a new method to elaborate exfoliated gelatin‐Montmorillonite (MMT) bionanocomposites. The data of X‐ray diffraction and transmission electron microscopy indicate that freezing/thawing is an effective approach to exfoliate the clay for concentrations higher than 5 mass% in gelatin matrix. In addition, after freezing/thawing process to introduce, the crystallinity (triple‐helix content) of gelatin‐MMT bionanocomposites is improved, revealing that freezing/thawing method has the advantages for gelatin molecules to renature into triple‐helix. Specially, the data of Fourier transform infrared indicate that freezing/thawing may be induce more hydrogen bond interactions in gelatin‐MMT bionanocomposites due to the better dispersion of MMT. The mechanical measurements and thermogravimetric analysis show that gelatin‐MMT bionanocomposites prepared by freezing/thawing display enhanced mechanical properties and thermal stability in comparison with the ones prepared by conventional blending at the same clay content. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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.     

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.     

Self‐aggregated nanoparticles of N‐dodecyl,N′‐glycidyl(chitosan) as pH‐responsive drug delivery systems for quercetin

In this study, pH‐responsive amphiphilic chitosan (CS) nanoparticles were used to encapsulate quercetin (QCT) for sustained release in cancer therapy. The novel CS derivatives were obtained by synthesis with 2,3‐epoxy‐1‐propanol, also known as glycidol, followed by acylation with dodecyl aldehyde. Characterization was performed by spectroscopic, viscosimetric, and size‐determination methods. Critical aggregation concentration, morphology, entrapment efficiency, drug release profile, cytotoxicity, and hemocompatibility studies were also carried out. The average size distribution of the self‐assembling nanoparticles measured by dynamic light scattering ranged from 140 to 300 nm. In vitro QCT release and Korsmeyer–Peppas model indicated that pH had a major role in drug release. Cytotoxicity assessments indicated that the nanoparticles were non‐cytotoxic. 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay further revealed that QCT‐loaded nanoparticles could inhibit MCF‐7 cell growth. In vitro erythrocyte‐induced hemolysis indicated the good hemocompatibility of the nanoparticles. These results suggest that the synthesized copolymers might be potential carriers for hydrophobic drugs in cancer therapy. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45678.     

Effect of five saturated fatty acids on the properties of sweet‐potato‐starch‐based films

To fully explore the influences of saturated fatty acids (SFAs) on the properties of sweet‐potato‐starch (SPS)‐based films, five SFAs were chosen to add to SPS. The SPS‐based films were prepared by casting. The microstructure, mechanical, optical, water vapor barrier, and thermal properties of the films were investigated. The 2.0% (w/w, on the basis of starch) SFA significantly changed the SPS pasting characteristics in the peak viscosity, breakdown, and other feature point viscosity values as determined by a Rapid Visco Analyser. The amylose molecular weights decreased as measured by high‐performance size exclusion chromatography. A thermal study with differential scanning calorimetry suggested that the addition of SFA increased the onset temperature and peak temperature. Scanning electronic microscope (SEM) images showed a continuous and uniform structure in the films with SFA. The SPS–SFA composite films showed lower light transmission and elongation at break than the control. Compared with the control films, the addition of SFA increased the tensile strength and decreased the water vapor permeability of the films. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41380.     

Graphene oxide/poly(ethylene glycol)/chitosan gel with slow‐release lubrication applied on textured surface

Graphene oxide/poly(ethylene glycol) (GO/PEG) composites that have biocompatibility and biodegradability properties have been prepared to improve the lubrication of artificial joints, but they would be rapidly degraded and absorbed by the human body if injected. To prolong the lubrication effect, GO/PEG lubricants were mixed into a chitosan (CS) sol, and then the GO/PEG/CS sol was added to the dimpled texture of a Co‐Cr‐Mo alloy and transformed into a gel to slowly release GO/PEG lubricants. The results of friction experiments showed that the average friction coefficient of the slow‐release solution is below 0.025, especially when under pressure, and the gel in the texture also has a good lubrication effect. Meanwhile, the FTIR and UV–vis of the slow‐release solution indicated that it is likely to contain GO, PEG, and CS, which are associated with each other via hydrogen bonds and may form a particular structure, leading to good slow‐release lubrication. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45818.