Higuchi Equation Research Articles

Tamibarotene-Loaded PLGA Microspheres for Intratumoral Injection Administration: Preparation and Evaluation.

Tamibarotene (Am80) has good curative effect on advanced hepatocellular carcinoma (HCC). To improve the therapeutic efficacy furtherly, we prepared tamibarotene-loaded PLGA microspheres (Am80-PLGA-MS) for intratumoral injection. Firstly, Am80-PLGA-MS were prepared by emulsion-solvent evaporation method. Subsequently, microspheres were characterized by particle size analysis, drug loading (DL), and entrapment efficiency (EE). Finally, the drug release characteristics in vitro, pharmacokinetic, and pharmacodynamics were studied separately. According to results obtained, microspheres were spherical with a uniform particle size 7.04±0.03μm and its EE and DL were 82.23±0.74 and 11.74±0.11%, respectively. In vitro, Am80-PLGA-MS can release drug for 14days and its release behavior was fitted with the Higuchi equation. In pharmacokinetic studies, the t1/2β, MRT, and AUC of microspheres were 15.43-fold, 8.62-fold, and 9.98-fold those of Am80 solution, respectively, which revealed that the utilization of drug was improved obviously. The pharmacodynamics studies showed that the tumor doubling time, growth inhibition rate, and specific growth rate of tumor of Am80-PLGA-MS were 1.34 times, 2.63 times, and 0.72 times those of drug solution, respectively, indicating that the inhibitory effect on tumor by the microspheres was significantly improved. In summary, Am80-PLGA-MS are promising carrier to enhance the inhibitory effect on tumor, which will provide significantly clinical value for treatment of HCC.

Effect of drying method on mechanical, thermal and water absorption properties of enzymatically crosslinked gelatin hydrogels.

Enzymatically crossliked gelatin hydrogel was submitted to two different drying methods: air drying and freeze drying. The resulting polymeric tridimensional arrangement (compact or porous, respectively) led to different thermal and swelling properties. Significant differences (p < 0.05) on thermal and mechanical characteristics as well as swelling in non-enzymatic gastric and intestinal simulated fluids (37 ºC) were detected. Water absorption data in such media was modelled according to Higuchi, Korsmeyer-Peppas, and Peppas-Sahlin equations. Freeze dried hydrogel showed Fickian diffusion behavior while air dried hydrogels presented poor adjustment to Higuchi model suggesting the importance of the relaxation mechanism at the beginning of swelling process. It was possible to conclude that the same gelatin hydrogel may be suitable to different applications depending on the drying process used.

Formulation optimization of scutellarin-loaded HP-β-CD/chitosan nanoparticles using response surface methodology with Box–Behnken design

The aim of this paper is to investigate and optimize the preparation of scutellarin (SCU)-loaded HP-β-CD/chitosan (CS) nanoparticles (CD/CS-SCU-NPs). CD/CS-SCU-NPs were prepared by ionic cross-linking method and the process and formulation variables were optimized using response surface methodology (RSM) with a three-level, three factor Box–Behnken design (BBD). The independent variables were the added amounts of CS, sodium tripolyphosphate (TPP) and Pluronic F-68 during the preparation. Dependent variables (responses) were particle size and entrapment efficiency. Mathematical equations and respond surface plots were used to correlate independent and dependent variables. The preparation process and formulation variables were optimized to achieve minimum particle size and maximum entrapment efficiency by calculating the overall desirability value (OD). The optimized NP formulation was characterized for particle size, PDI, zeta potential, entrapment efficiency and in vitro drug release. According to the results, an optimized CD/CS-SCU-NP formulation was prepared. Results for particle size, PDI, zeta potential and entrapment efficiency were found to be around 200 nm, 0.5, 25 mV, and 70% respectively. For in vitro study, the release of SCU from the NPs exhibited a biphasic release and was in accordance with Higuchi equation. The optimized preparation was simple with the probability for industrialization. The combination use of RSM, BBD and overall desirability values could provide a promising application for incorporating CD into CS nanoparticles as drug delivery carrier and help develop lab-scale procedures.

Preparation and characterization of beta-glucan particles containing a payload of nanoembedded rifabutin for enhanced targeted delivery to macrophages.

β-glucan particles (GP) are polymeric carbohydrates, mainly found as components of cell wall fungi, yeast, bacteria and also in cereals such as barley and oat, and have been recently shown to have application in macrophage-targeted drug delivery. The aim of this study was to prepare and characterize GP containing a large payload of Rifabutin (RB), an anti-tuberculosis drug effective against MDR-TB at lower MIC than Rifampicin. GP were prepared from yeast cells by acidic and alkaline extraction were either spray dried or lyophilized, prior to RB loading and alginate sealing. The FTIR and 13C-NMR spectra of the GP confirmed a β-(1→3) linked glucan structure, with a triple-helical conformation. The spray dried GP exhibited better characteristics in terms of uniformity, size range (2.9 to 6.1 µm) and more than 75 % particles were below 3.5 μm. The RP-HPLC analysis of spray dried GP revealed drug entrapment and drug loading up to 81.46 ± 4.9 % and ~40.5 ± 1.9 %, respectively, as compared to those dried by lyophilization. Electron microscopy showed nearly spherical and porous nature of GP, and the presence of drug 'nanoprecipitates' filling the pore spaces. The formulation showed adequate thermal stability for pharmaceutical application. The particles were readily phagocytosed by macrophage(s) within 5 min of exposure. Drug release occurred in a sustained manner via diffusion, as the release kinetics best fit for drug release was obtained using Higuchi's equation. Thus, the spray dried GP-based-formulation technology holds promise for enhanced targeted delivery of anti-TB drug(s) to macrophage within a therapeutic window for the clearance of intracellular bacteria.

Effect of solid lipid’s structure on nanostructured lipid carriers encapsulated with sun filter: characterisation, photo-stability and in vitro release

Three series of solid lipid are formulated in nanostructured lipid carriers (NLC) system, which encapsulated with sun filter to evaluate the effect on the physicochemical properties of the nanocarriers. Production is performed by ultrasonication–homogenisation, analysis by particle size, zeta potential (ZP), transmission electron microscope, Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD). Moreover, the encapsulation efficiency, ultraviolet performance and in vitro release are also investigated. The particle sizes of NLCs are between 185 and 225 nm and the polydispersity index is lower than 0.4, ZP from −56.4 to −78.6 mV, and the particles are spherical and in homogenous shading. All prepared NCLs encapsulated the sun filter and the EE are higher than 73%. DSC analysis revealed α- to β-polymorphic modification existed in the system of fatty alcohol and fatty acid. However, α, β and β′-polymorphic modifications are exist in the system of cetyl palmitate (PC). Compared with conventional emulsion, all NLCs displayed perfect photo-protective property, especially for the alcohol system. The photo-stability studies showed that the all NLCs have the ability to improve the photo-stability of sunscreens. The in vitro release study suggested all three NLCs displayed sustained release profile and they were fit well with Higuchi equation.

Preparation and in vitro release evaluation of slow releasing intrauterine silicone rubber bar made of Panax notoginseng and Rubia cordifolia

To prepare the intrauterine slow release silicone rubber bar made of Panax notoginseng and Rubia cordifolia, and finish its preliminary evaluation of in vitro releasing properties. The open mill method was used for plasticating of silicone rubber. The process parameters of the silicone rubber and drugs mixing were optimized by orthogonal test. The parameters of silicone rubber vulcanization was optimized by single factor test. The preliminary evaluation of in vitro release performance of the silicone rubber bar was conducted with ginsenoside Rg₁, ginsenoside Rb₁, notoginsenoside R₁, purpurin and rubimaillin as the indexes. The results showed that optimum technologic parameters for silicone rubber and drugs mixing：the roller spacing 2 mm; speed ratio 1∶1.2; front roller temperature 55-60 ℃; rear roll temperature 50-55 ℃; and mixing time 20 min. The optimum parameters for silicone rubber vulcanization：temperature 90 ℃, and time 60 min. The studies on release process in vitro revealed that the release process of silicone rubber bar was in line with the Higuchi equations. After 90 days, the cumulative release of ginsenoside Rg₁, ginsenoside Rb₁ and notoginsenoside R₁ was 46.7%, and the cumulative release of purpurin and rubimaillin was 51.9%. The preparation method can be applied to the preparation of silicone rubber bar, with slow release characteristics.

Preparation and evaluation of gastric adhesive-floating pellets for Bolo leaf phenols

Gastric adhesive-floating pellets for Bolo leaf phenols (BLP) were prepared by extrusion-spheronization method, with chitosan as skeleton bioadhesive material, and stearyl alcohol as help-bleaching agent to evaluate its in vitro adhesivity, floatability and in vivo retention situation, and investigate its in vitro release characteristics. The in vitro adhesivity and floatability were evaluated respectively by in vitro tissue retention method and visual observation method. The retention of pellets in rats was investigated by in vivo tissue retention method and in vivo imaging of small animals. In addition, the in vitro release of p-coumaric acid and caffeic acid as the index components in pellets were evaluated. Results showed that the in vitro adhesivity of the prepared gastric adhesive-floating pellets reached (73.2±3.4)%, and the pellets could float immediately in simulated gastric fluid for more than 12 h; the retention rate of adhesive-floating pellets in rats reached more than 40% after 6 h, while the retention rate of common reference pellets was decreased by 15% as compared with the gastric adhesive-floating pellets, with significant difference (P<0.01); the drug in vitro release time can reach more than 6 h, and the drug release behaviors were lined with Higuchi equation. In vivo and in vitro studies showed that, the gastrointestinal bioadhesive and floating pellets prepared in this study have good bioadhesivity, floatability and good sustained release characteristics.

Cationic nioplexes-in-polysaccharide-based hydrogels as versatile biodegradable hybrid materials to deliver nucleic acids.

Two polysaccharide-based hydrogels made of only κ-carrageenan (4%; w/v) or of a mixture of methylcellulose:κ-carrageenan (2%; w/v) were used to encapsulate cationic nioplexes. These vesicular particles were made of a synthetic aminolipid and polysorbate-80 (Tween-80), as a non-ionic surfactant agent. According to oscillatory rheological measurements, the presence of nioplexes did not compromise the mechanical integrity of the gels. In vitro niosomal release experiments demonstrated the liberation of nioplexes up to 24 h, and the curves were fitted according to Higuchi, Korsmeyer-Peppas and Weibull equation models, which indicated Fickian-diffusion controlled mechanisms. Besides nioplexes, cervical cancer cells were also entrapped within the biohydrogels. Cell release confirmed that these materials did not affect the cell viability, allowing cells to spread and proliferate after 24 h. The applicability of these biocompatible hydrogels was also extended to gene delivery. In this regard, the best silencing activities were found when cationic niosomes were complexed with antisense oligonucleotides in KC hydrogels. Nioplexes were able to release through the hydrogel and promoted silencing of luciferase expression in the presence of serum without using commercially available cationic lipids. Overall, the formation of such hybrid materials by integrating cationic nioplexes within biodegradable hydrogels provides a new perspective for the delivery of macromolecular therapeutics.

A PLGA-PEG-PLGA Thermosensitive Gel Enabling Sustained Delivery of Ropivacaine Hydrochloride for Postoperative Pain Relief.

Postoperative pain is a complex physiological response to disease and tissue injury. Moderate-to-severe pain typically occurs within 48 h after surgery. Amino amide local anesthetics are widely applied to manage postoperative pain, and they have high efficacy, a low risk for addiction and limited side effects. However, these anesthetics also have short half-lives, often necessitating continuous injection to obtain satisfactory pain relief. In the current work, we used a poly(lactic-co-glycolic acid) (PLGA)-polyethylene glycol (PEG)-PLGA (PLGA-PEG-PLGA) temperature-sensitive gel to deliver a local anesthetic, ropivacaine hydrochloride (RP), to prolong its analgesic effect. We investigated the influence of polymer and drug concentration on gelation temperature and the in vitro drug release rate from the temperature-sensitive gel. RP-loaded PLGA-PEG-PLGA solution is a liquid at room temperature and forms a gel at temperatures slightly lower than body temperature. With regard to the gel's drug release rate, 37.5, 51.3 and 72.6% of RP was released at 12, 24 and 48 h, respectively. This in vitro drug release profile conformed to the Higuchi equation. To assess pain control efficacy when using the gel, we evaluated the mechanical paw withdrawal reflex threshold, thermal pain threshold and incision cumulative pain scores in a rat incisional model. The results showed that the anti-pain effect of a single injection of RP-loaded gel at the incision site lasted for 48 h, which is significantly longer than the effect produced by injection of RP solution alone. The use of RP-loaded thermosensitive gels could provide a promising method for managing postoperative pain.

Sustained-release solid dispersion of pelubiprofen using the blended mixture of aminoclay and pH independent polymers: preparation and in vitro/in vivo characterization

The present study aimed to develop the sustained-release oral dosage form of pelubiprofen (PEL) by using the blended mixture of 3-aminopropyl functionalized-magnesium phyllosilicate (aminoclay) and pH-independent polymers. The sustained-release solid dispersion (SRSD) was prepared by the solvent evaporation method and the optimal composition of SRSD was determined as the weight ratio of drug: Eudragit® RL PO: Eudragit® RS PO of 1:1:2 in the presence of 1% of aminoclay (SRSD(F6)). The dissolution profiles of SRSD(F6) were examined at different pHs and in the simulated intestinal fluids. The drug release from SRSD(F6) was limited at pH 1.2 and gradually increased at pH 6.8, resulting in the best fit to Higuchi equation. The sustained drug release from SRSD(F6) was also maintained in simulated intestinal fluid at fasted-state (FaSSIF) and fed-state (FeSSIF). The structural characteristics of SRSD(F6) were examined by using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR), indicating the change of drug crystallinity to an amorphous form. After oral administration in rats, SRSD(F6) exhibited the prolonged drug exposure in plasma. For both PEL and PEL-transOH (active metabolite), once a day dosing of SRSD(F6) achieved oral exposure (AUC) comparable to those from the multiple dosing (3 times a day) of untreated drug. In addition, the in vivo absorption of SRSD(F6) was well-correlated with the in vitro dissolution data, establishing a good level A in vitro/in vivo correlation. These results suggest that SRSD(F6) should be promising for the sustained-release of PEL, thereby reducing the dosing frequency.

Development and evaluation of Ketoprofen sustained release matrix tablet using Hibiscus rosa-sinensis leaves mucilage

Currently, the use of natural gums and mucilage is of increasing importance in pharmaceutical formulations as valuable drug excipient. Natural plant-based materials are economic, free of side effects, biocompatible and biodegradable. Therefore, Ketoprofen matrix tablets were formulated by employing Hibiscus rosa-sinensis leaves mucilage as natural polymer and HPMC (K100M) as a synthetic polymer to sustain the drug release from matrix system. Direct compression method was used to develop sustained released matrix tablets. The formulated matrix tablets were evaluated in terms of physical appearance, weight variation, thickness, diameter, hardness, friability and in vitro drug release. The difference between the natural and synthetic polymers was investigated concurrently. Matrix tablets developed from each formulation passed all standard physical evaluation tests. The dissolution studies of formulated tablets revealed sustained drug release up to 24h compared to the reference drug Apo Keto® SR tablets. The dissolution data later were fitted into kinetic models such as zero order equation, first order equation, Higuchi equation, Hixson Crowell equation and Korsmeyer-Peppas equation to study the release of drugs from each formulation. The best formulations were selected based on the similarity factor (f2) value of 50% and more. Through the research, it is found that by increasing the polymers concentration, the rate of drug release decreased for both natural and synthetic polymers. The best formulation was found to be F3 which contained 40% Hibiscus rosa-sinensis mucilage polymer and showed comparable dissolution profile to the reference drug with f2 value of 78.03%. The release kinetics of this formulation has shown to follow non-Fickian type which involved both diffusion and erosion mechanism. Additionally, the statistical results indicated that there was no significant difference (p>0.05) between the F3 and reference drug in terms of MDT and T50% with p-values of 1.00 and 0.995 respectively.

Organogels as novel carriers for dermal and topical drug delivery vehicles

Aminoalcohol based bis-(aminoalcohol)oxalamides (BAOAs) (1,6-amino alcohol=leucinol, isoleucinol, valinol, phenylglycinol, phenylalaninol and 2-amino-1-butanol) have been explored to develop drug depot systems and illustrated as a novel dermal and topical drug delivery vehicle for non-steroidal anti-inflammatory drug molecules. FAE's (Fatty acid ethyl and isopropyl esters) with different chain lengths, ethyl laurate, ethyl myristate, ethyl palmitate, isopropyl laurate, isopropyl myristate, isopropyl palmitate, have been chosen as they are biocompatible organic fluids used typically in cosmetic industry. Ibuprofen (Ib), acting as a model drug, was entrapped in the supramolecular organogels. The release behavior of Ib molecules in the supramolecular organogels was investigated by using UV–vis spectroscopy. The influence of the organogelator and drug concentration, pH values of the accepting media, and nature of solvent (different FAE's) on the release behavior of Ib was investigated under static conditions. The results indicated that the release rate of Ib from the supramolecular organogels was effectively retarded with an increase of the organogelator concentration. Also, the release rates of Ib increased on increasing the Ib content. Furthermore, the release behavior of Ib was found to be different at various pH values in buffers as accepting media. The study of the release kinetics indicated that the release behavior of Ib was in accord with the Higuchi equation and the diffusion-controlled mechanism involved in the Fickian model. These observations indicate that bis-(aminoalcohol)oxalamides gels may act as delivery vehicles for non-steroidal anti-inflammatory drug molecules and also show that the release profiles for such systems can be fine-tuned by the correct choice of gelator-FAE combination.

Thermal treatments affect breakage kinetics and calcium release of fish bone particles during high-energy wet ball milling

Effects of thermal treatments on breakage and calcium release of fish bone particles during high-energy wet ball milling were investigated. Heating temperature (55–130 °C) showed much more obvious influences on the breakage and calcium release than heating time (20–60 min). As heating temperature increased from 55 °C to 120 °C, fish bone matrix became more porous, and mechanical parameters of fish bone remarkably decreased (p < 0.05). Furthermore, particle size of the fish bone after milling reached a limit (approximate 110 nm) in a shorter time and calcium release was enhanced. Regardless of heating time, size of the fish bone particles was not significantly different (p > 0.05) between the samples treated with 120 °C and 130 °C during milling, while calcium release was higher for the latter sample. Breakage kinetics and calcium release of fish bone particles were fitted with the first-order exponential decay function and the Higuchi equation, respectively.

The role of surfactants in the formulation of elastic liposomal gels containing a synthetic opioid analgesic.

Transdermal drug delivery systems have made significant contributions to the medical community, but have yet to completely substitute oral or parenteral delivery. Recently, various strategies have been used to augment the transdermal delivery of therapeutics. Primarily, they include iontophoresis, electrophoresis, sonophoresis, chemical permeation enhancers, microneedles, and vesicular systems. Among these strategies, elastic liposomes appear promising. Elastic vesicle scaffolds have been developed and evaluated as novel topical and transdermal delivery systems, with an infrastructure consisting of hydrophobic and hydrophilic moieties together, and as a result, such scaffolds can accommodate drug molecules with a wide range of solubility. High deformability of these vesicles provides for better penetration of intact vesicles. This system is much more efficient at delivering low- and high-molecular-weight drugs to the skin in terms of quantity and depth. In this work, elastic liposomes of Tramadol HCl were prepared using a solvent evaporation method with different surfactants and were characterized using microscopy, and particle size, shape, drug content, ex vivo release, and zeta potential were also calculated. The prepared elastic liposomes were found to be in the range of 152.4 nm with a zeta potential of −22.4 mV; the entrapment efficiencies of the selected formulation was found to be 79.71%±0.27%. All formulations in the form of a gel were evaluated for physicochemical properties and were found to be homogeneous with no grittiness, and the pH of all formulations was found to be neutral. The optimized selected elastic liposomal formulation followed the Higuchi equation and Fickian diffusion and released the drug for a period of 24 hours. The overall results provide much promise for the continued investigation of deformable vesicles as transdermal drug carriers.

In Vitro Interaction Between Oral Hypoglycemic Drug And Herbal Sex Stimulants: Drug Interactions

Sexual dysfunction is a common, underappreciated complication of diabetes. Male sexual dysfunction among diabetic patients can include disorders of libido, ejaculatory problems, and erectile dysfunction (ED). All three forms of male dysfunction can cause significant bother for diabetic patients and can affect their quality of life. Diabetic patients take oral hypoglycemic drug to control their diabetic as well as take herbal sex stimulants to control to increase the libido. The combined use of herbs and drugs has increased the possibility of herb-drug interactions. The study was undertaken to explore the herb-drug interactions. To investigate the herbdrug interactions an in vitro dissolution study in different simulated pH medium were performed. In this study gliclazide containing tablet of 80mg as oral hypoglycemic drug and different herbal sex stimulants available in local market were used. The release mechanism was explored and explained with zero order, first order and Higuchi equations to identify drug interaction. Higher percentage release of gliclazide was found at simulated phosphate buffer of pH 7.4 compared to gastric medium of pH 1.2 and also in presence of herbal sex stimulants. Increased release pattern of gliclazide by concomitant administration of herbal sex stimulants gives slightly higher absorption, which gives the indication of herb-drug interactions.

Post-use assay of vaginal rings (VRs) as a potential measure of clinical trial adherence

Adherence measurement for microbicide use within the clinical trial setting remains a challenge for the HIV prevention field. This paper describes an assay method used for determining residual dapivirine levels in post-use vaginal rings from clinical trials conducted with the Dapivirine Vaginal Matrix Ring-004 developed by the International Partnership for Microbicides to prevent male to female HIV transmission. Post-use assay results from three Ring-004 clinical trials showed that of the 25mg drug load, approximately 4mg of dapivirine is released from the matrix ring over a 28-day use period. Data obtained by both in vitro and in vivo studies indicate that dapivirine is released according to a diffusion mechanism, as determined by conformance of both data sets to the Higuchi equation. This, coupled with the low variability associated with batch production over two manufacturing sites and 20 batches of material, provides evidence that post-use ring analysis can contribute to the assessment of adherence to ring use. Limitations of this method include the potential of intra-participant and inter-participant variability and uncertainty associated with measuring the low amount of dapivirine actually released relative to the drug load. Therefore, residual drug levels should not serve as the only direct measurement for microbicide adherence in vaginal ring clinical trials but should preferably be used as part of a multi-pronged approach towards understanding and assessing adherence to vaginal ring use.

A novel tetrandrine-loaded chitosan microsphere: characterization and in vivo evaluation.

In this study, novel tetrandrine-loaded chitosan microspheres were prepared by the emulsion cross-linking method. The systems were then characterized for physicochemical properties and in vitro drug release. In addition, the pharmacokinetics and tissue distribution of microspheres were further verified in animal models. Particle-size distribution indicated that the size of microspheres was within the range of 7–15 μm, with a median diameter of 12.4 μm. The drug loading and entrapment efficiency of the formulation were 34.6%±12.5% and 87.3%±9.7% (mean ± SD), respectively. In vitro release showed a typical sustained and long-term drug release behavior. The Higuchi equation was the model that fit best with release data. Maintaining a relatively constant plasma concentration in the long-term drug treatment is an outstanding pharmacokinetic advantage of tetrandrine microspheres in vivo. Moreover, compared with tetrandrine solution, tetrandrine microspheres produced a lower drug concentration in the heart, liver, and kidneys. This indicated that the microspheres used in this study were preferable for targeting lung tissue versus other tissues. No damage to the tissues of the lung was found in histopathological examination.

The effect of surfactant above and below the critical micelle concentration (CMC) and the mathematical models used to determine the kinetics of drug release from the matrix system

The liberation of propranolol HCl from a controlled release matrix, containing the hydrophilic polymer, sodium carboxymethylcellulose (NaCMC) and the hydrophobic polymer, Eudragit RL 100 (RL 100) as excipients, was studied. The influences of surface active agents on the dissolution rate of the drug were examined. Tablets were made by direct compression methods. The dissolution tests were performed by using the basket method. The incorporation of the cationic surfactants within the matrices increased the drug release until the critical micelle concentration (CMC). While, after the CMC, the increase in drug release was to a lesser extent. The incorporation of the anionic surfactants reduced the release rate of the drug from the matrices. At the CMC, the percent of drug release from the matrices were approximately the same with the matrices without the surfactants. While an increase in drug release was observed above the CMC of the anionic surfactants. The data obtained from in vitro drug release studies were plotted according to three kinetic models to study the release kinetic. These were zero order release, the first order release and the Higuchi equation. Zero order release of the drug was observed in all the formulations. The release mechanism was influenced considerably by the ratio of the excipients. Key words: Propranolol HCl, controlled release, critical micelle concentration (CMC), dissolution, dissolution rate kinetics, surfactant.

Dendritic multi-walled carbon nanotube with thermoresponsive shells: A good carrier for anticancer drugs

In this research, multi-walled carbon nanotubes (MWCNTs) were modified by dendritic macromonomer. Herein, polyamidoamine with acrylamide end groups was incorporated on MWCNTs. Afterwards, poly(N-isopropylacrylamide), (PNIPAM), was grafted on polyamidoamine in a facile synthesis. Then, doxorubicin as anticancer drug was loaded on this nanocarrier. The drug release was studied at below and above the lower critical solution temperature of PNIPAM, (LCST 32°C), 27°C and 37°C, respectively. At 37°C (body temperature) the polymer shell dehydrated and the drug release increased. The profile of drug release was expressed by Higuchi's equation which indicated that the drug release mechanism was diffusion controlled.

Preparation and characterization of gatifloxacin-loaded sodium alginate hydrogel membranes supplemented with hydroxypropyl methylcellulose and hydroxypropyl cellulose polymers for wound dressing.

Introduction:The aim of this study is to evaluate gatifloxacin-loaded sodium alginate hydrogel membranes, supplemented with glycerol (a plasticizer), glutaraldehyde (a cross-linking agent), and hydroxypropyl methylcellulose (HPMC) or hydroxypropyl cellulose (HPC) polymers, as potential wound dressing materials based on their physicochemical properties and the sustain-release phenomenon.Materials and Methods:The physicochemical properties of the prepared hydrogel membranes were evaluated by several methods including Fourier transform infrared and differential scanning calorimetry. Different techniques were used to assess the swelling behavior, tensile strength and elongation, % moisture absorption, % moisture loss, water vapor transmission rate (WVTR), and microbial penetration for the hydrogel membranes. In vitro gatifloxacin release from the hydrogel membranes was examined using the United States Pharmacopeia XXIII dissolution apparatus. Four kinetics models (zero-order, first-order, Higuchi equation, and Korsmeyer-Peppas equation) were applied to study drug release kinetics.Results:The addition of glycerol, glutaraldehyde, HPMC, and HPC polymers resulted in a considerable increase in the tensile strength and flexibility/elasticity of the hydrogel membranes. WVTR results suggest that hydrated hydrogel membranes can facilitate water vapor transfer. None of the hydrogel membranes supported microbial growth. HPMC-treated and HPC-treated hydrogel membranes allow slow, but sustained, release of gatifloxacin for 48 h. Drug release kinetics revealed that both diffusion and dissolution play an important role in gatifloxacin release.Conclusions:Given their physicochemical properties and gatifloxacin release pattern, HPMC-treated and HPC-treated hydrogel membranes exhibit effective and sustained drug release. Furthermore, HPMC-treated and HPC-treated hydrogel membranes possess physiochemical properties that make them effective and safe wound dressing materials.