Preparation and evaluation of waxes/fat microspheres loaded with lithium carbonate for controlled release

Recent advances in microbeads-based drug delivery system for achieving controlled drug release

Novel drug delivery system endows a beneficial method for achieving a desired drug concentration at the appropriate site in the body. The concept of targeted drug delivery has been emerged to localize the drug in the targeted tissue of interest while reducing the relative concentration of the medication in the surrounding tissues. This could be easily accomplished by using different multi-particulate dosage forms like pellets, granules, microcapsules, liposomes, beads. But the major drawbacks associated with them are the use of harsh chemicals and an elevated temperature for their preparation. Preparation of microbeads by ionotropic gelation and emulsion gelation method overcomes these problems by neither using harsh chemicals nor elevated temperature for their preparation. Thus, this can be proved to be a better alternative over other dosage forms. Several parameters were studied in terms of their morphology, particle size, encapsulation efficiency, swelling ratio, mucoadhesivity, etc. The endeavor of present article is toward presenting a wider perspective of the comprehensive knowledge available in the field of microbeads. Thus, the intent of this review is to recapitulate the relevance of microbeads.

Lipospheres for Simultaneous Controlled Release and Improved Pharmacokinetic Profiles of Saxagliptin-Enalapril: Formulation, Optimization, and Comparative In Vitro-In Vivo Evaluation

The current study aims at formulating and optimizing lipospheres (LS) by the Box-Behnken design (BBD) from safe biodegradable carnauba wax (CW) to co-administer saxagliptin (SG) and enalapril (EP) for co-existing chronic hypertensive diabetes in order to overcome inadequacies of conventional modes of drug administration. Optimized liposphere formulation (OLF) was selected by a numerical optimization procedure and a comparative in vivo pharmacokinetic study of OLF and commercial brands was also performed. Discrete, free-flowing, spherical, smooth-surface LS having a size range of 5-10 μm and zeta potential of - 20 to - 30 mV were successfully formulated. Compatibility studies by FTIR and DSC proved the lack of interaction of components while XRD suggested the transformation of crystalline drugs to amorphous form. Outcomes of dependent optimizing variables like percentage yield (30-90%), EP-release (32-92%), and SG-release (28-95%) followed a polynomial quadratic model. Pharmacokinetics studies indicated a significantly lower C_max of EP (125.22 ± 6.32) and SG (75.63 ± 3.85) and higher mean T_max values (9.4 h for EP and 10.73 h for SG) from OLF in comparison with reference brands of EP (257.54 ± 8.23 ng/mL) and SG (393.66 ± 2.97 ng/mL). Additionally, a potential rise in half-life and MRT of SG and EP was achieved reaching approximately 2- to 3-fold higher than noted for reference brands. Importantly, the enhanced T_max and AUC_0-24 specified the achievement of enhanced bioavailability of both drugs from LS. Consequently, such an innovative approach could not only control drug release in both in vitro and in vivo analyses but also maintain plasma drug concentration for a longer time without maximizing C_max leading towards effective management of chronic illnesses.

Microencapsulation of retinyl palmitate by melt dispersion for cosmetic application

Retinyl palmitate was encapsulated in wax matrix by melt dispersion for the purpose of economic and sustainable cosmeceutical formulation with minimum use of synthetic chemicals. We evaluated the effect of different process variables of microencapsulation by melt dispersion. In this study, a three level definitive screening design was applied, where the microcapsule properties were analysed through statistical analysis to understand the effect of four process variables: type of wax, theoretical loading capacity, surface concentration and stirring speed. Microparticles were characterised for size using image analysis; loading capacity and encapsulation efficiency using ultraviolet-visible spectroscopy; antioxidant activity through DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. Melt dispersion method was effective to produce microcapsules with a spherical shape and mean size as small as 28 µm. The encapsulation efficiency ranged 60-80%. Theoretical loading capacity (p-value = 0.00232, significance level, α = 1%) and surfactant% (p = 0.0573, α = 10%) were found to be the most significant factors to control the actual loading capacity and size of microcapsules.

Sustained release biodegradable solid lipid microparticles: Formulation, evaluation and statistical optimization by response surface methodology

For preparing nebivolol loaded solid lipid microparticles (SLMs) by the solvent evaporation microencapsulation process from carnauba wax and glyceryl monostearate, central composite design was used to study the impact of independent variables on yield (Y1), entrapment efficiency (Y2) and drug release (Y3). SLMs having a 10-40 μm size range, with good rheological behavior and spherical smooth surfaces, were produced. Fourier transform infrared spectroscopy, differential scanning calorimetry and X-ray diffractometry pointed to compatibility between formulation components and the zeta-potential study confirmed better stability due to the presence of negative charge (-20 to -40 mV). The obtained outcomes for Y1 (29-86 %), Y2 (45-83 %) and Y3 (49-86 %) were analyzed by polynomial equations and the suggested quadratic model were validated. Nebivolol release from SLMs at pH 1.2 and 6.8 was significantly (p < 0.05) affected by lipid concentration. The release mechanism followed Higuchi and zero order models, while n > 0.85 value (Korsmeyer- Peppas) suggested slow erosion along with diffusion. The optimized SLMs have the potential to improve nebivolol oral bioavailability.

Design of phosphated cross-linked microspheres of bael fruit gum as a biodegradable carrier

Present work was aimed at designing of phosphated cross-linked microspheres of bael fruit gum (BFG) by emulsification method using sodium-tri-meta phosphate as a cross-linking agent for treatment of colon cancer using 5-fluorouracil as model drug. Stirring speed was found to be 1,000 rpm for about 5 h to be optimal to obtain reproducible microspheres. It was found that there is an increase in particle size as polymer concentration is increased whereas a reduction in particle size was observed as there is increase in stirring speed. Cross-linked BFG microspheres were successfully prepared by emulsification method. Optimum surfactant concentration was found to be 2 % w/w. Scanning electron microscopy studies showed that the drug-loaded microspheres were non-aggregated and in spherical shape. Differential scanning calorimetry and Fourier transform infrared-spectroscopy studies showed that drug and excipients are compatible. Release studies showed that drug release was more profound in cecal medium induced with enzymes causing degradation of the cross linked BFG than that of the release showed in simulated intestinal fluid. Stability studies showed that there were no significant changes in the drug content and physical appearance of microspheres.

Sustained release microspheres of ropinirole hydrochloride: effect of process parameters

An emulsion solvent evaporation method was employed to prepare microspheres of ropinirole hydrochloride, a highly water soluble drug, by using ethylcellulose and PEG with the help of 32 full factorial design. The microspheres were made by incorporating the drug in a polar organic solvent, which was emulsified using liquid paraffin as an external oil phase. Effects of various process parameters such as viscosity of the external phase, selection of the internal phase, surfactant selection and selection of stirring speed were studied. Microspheres were evaluated for product yield, encapsulation efficiency and particle size. Various drug/ethylcellulose ratios and PEG concentrations were assayed. In vitro dissolution profiles showed that ethylcellulose microspheres were able to control release of the drug for a period of 12 h.

Preparation, Characterization and in vivo Evaluation of Parenteral Sustained Release Microsphere Formulation of Zopiclone

The aim of this study was to prepare zopiclone-loaded polycaprolactone microspheres by emulsion solvent evaporation technique with different drug-to-carrier ratios {MP 1 (1:1), MP 2 (1:2), MP 3 (1:3), and MP 4 (1:4)}, characterize and evaluate the in vivo performance. The microspheres were characterized for particle size, surface morphology, drug excipient compatibility, percentage yield, drug entrapment, and in vitro release kinetics. Pharmacokinetics and pharmacodynamics were evaluated after parenteral administration so as to determine the sustained action of the drug after one-time administration of the formulation in a rat model. Of four formulations prepared, MP 2, i.e., 1:2 (drug-polymer) ratio was selected as the optimized formulation based on particle size, particle shape, and the release behavior. The size of microspheres was found to be ranging from 5.4 to 12.1 µm. The shape of microspheres was found to be spherical by SEM. Among the four formulations, MP 2 (1:2) showed maximum percentage yield of 75% ± 2.68%. There was no interaction between drug and polymer by FT-IR study. In the in vitro release study, formulation MP 2 (1:2) showed 86.5% drug release and was found to be sustained for 10 days. The microsphere formulations were able to sustain the release of drug both in vitro and in vivo. Pharmacodynamic study (Maze apparatus) indicated that the anxiolytic activity shown by zopiclone microspheres was significant when compared to the zopiclone solution given daily.

Design and characterization of sustained release ketoprofen entrapped carnauba wax microparticles

CONTEXT

Ketoprofen is a non-steroid anti-inflammatory drug (NSAID) used in the treatment of rheumatic diseases and in mild to moderate pain. Ketoprofen has a short biological half-life and the commercially available conventional release formulations require dosages to be administered at least 2-3 times a day. Due to these characteristics, ketoprofen is a good candidate for the preparation of controlled release formulations.

OBJECTIVES

In this work, a multiparticulate-sustained release dosage form containing ketoprofen in a carnauba wax matrix was developed.

METHODS

Particles were prepared by an emulsion congealing technique. System variables were optimized using fractional factorial and response surface experimental design. Characterization of the particles included size and morphology, flow rate, drug loading and in vitro drug release.

RESULTS

Spherical particles were obtained with high drug load and sustained drug release profile. The optimized particles had an average diameter of approximately 200 µm, 50% (w/w) drug load, good flow properties and prolonged ketoprofen release for more than 24 h.

CONCLUSIONS

Carnauba wax microspheres prepared in this work represent a new multiparticulate-sustained release system for the NSAID ketoprofen, exhibiting good potential for application in further pharmaceutical processes.

Encapsulation and characterization of controlled release flurbiprofen loaded microspheres using beeswax as an encapsulating agent

The aim of the present study was to extend the use of flurbiprofen in clinical settings by avoiding its harmful gastric effects. For this purpose, we designed the controlled release solid lipid flurbiprofen microspheres (SLFM) by emulsion congealing technique. Drug was entrapped into gastro resistant biodegradable beeswax microspheres which were prepared at different drug/beeswax ratios 1:1, 1:2 and 1:3 using gelatin and tween 20 as emulsifying agents. The effect of emulsifiers and the effect drug/beeswax ratios were studied on hydration rate, encapsulating efficiency, micromeritic properties, scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (X-RD) analysis and in vitro drug release at pH 1.2 for 2 h and at pH 6.8 for 10 h. SEM revealed that microspheres made with tween 20 were smooth while microspheres made with gelatin showed porous morphology, however, they were all spherical in nature. The practical yield (recovery) showed a dependence on drug-beeswax ratio and it was variable from 53 to 84%. High loading encapsulating efficiency of flurbiprofen from 8 to 94% was achieved. FTIR and DSC analysis confirmed the absence of any drug polymer interaction indicating drug stability during microencapsulation. X-RD of pure flurbiprofen shows sharp peaks, which decreases on encapsulation, indicating decrease in the crystallinity of drug in microspheres. The micromeritic studies confirmed the presence of excellent and good flow properties of microspheres. Entrapment efficiency, morphology, practical yield, hydration rate, flow properties demonstrated their dependence on the HLB value of emulsifiers and emulsifiers with higher HLB were found more appropriate for effective microencapsulation of flurbiprofen. The release kinetics followed zero order mechanism of drug release at pH 6.8. Release pattern depends on the morphology of flurbiprofen microspheres and amount of beeswax used in the microspheres preparation. The microspheres prepared with high HLB values i.e., tween 20 showed effective control of drug release from microspheres. The absence of drug release at pH 1.2 proved the suitability of beeswax for its use as a gastro resistant material.

Microencapsulation of flavors in carnauba wax

The subject of this study is the development of flavor wax formulations aimed for food and feed products. The melt dispersion technique was applied for the encapsulation of ethyl vanillin in wax microcapsules. The surface morphology of microparticles was investigated using scanning electron microscope (SEM), while the loading content was determined by HPLC measurements. This study shows that the decomposition process under heating proceeds in several steps: vanilla evaporation occurs at around 200 °C, while matrix degradation starts at 250 °C and progresses with maxima at around 360, 440 and 520 °C. The results indicate that carnauba wax is an attractive material for use as a matrix for encapsulation of flavours in order to improve their functionality and stability in products.

Preparation, evaluation and bioavailability studies of indomethacin-bees wax microspheres

The present study envisages the preparation of microspheres containing indomethacin (IM) as model drug and bees wax as carrier, and to compare the in vitro release and pharmacokinetics of prepared IM formulation with commercially available oral formulation MicrocidSR. The microsphere formulations were prepared by meltable emulsified dispersion and cooling induced solidification. Surface morphology of microspheres has been evaluated using scanning electron microscopy (SEM). The SEM images revealed the spherical shape of microspheres and more than 98.0% of the isolated microspheres were in the size range 115-855 mum. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy studies indicated that the drug after encapsulation with bees wax was stable and compatible. A single dose randomized complete cross over study of IM (75 mg) microspheres was carried out on 8 healthy Albino sheeps. Plasma IM concentrations and other pharmacokinetic parameters obtained were statistically analyzed. The T (max), C (max), AUC(O-24) and T (1/2) values of MicrocidSR and optimized formulation were 3.0 h, 2038 +/- 51.31 ng/ml, 9528 +/- 129.65 ng/ml h(-1), and 2.59 +/- 0.02 h(-1); and 3.2 h, 1940 +/- 22.61 ng/ml, 8751 +/- 41.32 ng/ml h(-1), and 2.68 +/- 0.02 h(-1), respectively. Beeswax microspheres showed controlled release and it can be concluded that both the prepared formulation and MicrocidSR are bioequivalent.