Preparation Process Of Microspheres Research Articles

OPTIMIZATION AND CHARACTERIZATION OF MICROSPHERES OF BERBERINE HYDROCHLORIDE USING BOX-BEHNKEN DESIGN

Objective: The current work sought to optimize Berberine hydrochloride (BBH)-loaded microspheres by examining the link between design parameters and experimental results. Methods: BBH-loaded microspheres were prepared by using the water-in-oil emulsion cross-linking process and optimized with a three-factor, three-level Box-Behnken design (BBD). Grafted gum polyvinyl alcohol (PVA) ratio (w/w) (A), Revolutions per minute (RPM) (B), and Span 20 (%) (C) were independent variables. The dependent variables were Percent Entrapment Efficiency (% EE) (R1), Percent Drug Loading (% DL) (R2), and Particle Size (µm) (R3). The generated polynomial equations and response surface plots were used to relate the dependent and independent variables. Microscopic examination, %EE, and % DL were determined to evaluate the optimized formulation. Fourier transforms infrared (FT-IR) spectroscopy studies and stability studies of optimized formulation were also carried out. Results: The optimized formulation (FMS6) had a polymer content of 2% w/v [Grafted gum (36.96): PVA (63.04)], a span 20 (0.78 %), and a prepared at the speed of 1225.92 rpm. The observed responses were close to the improved formulation's predicted values. The particle size, % EE, and % DL were found to be 1.10 µm, 82.79% and 16.48%, respectively. FT-IR spectroscopy study indicated that the drug was entrapped in microspheres. Conclusion: BBD provides a systematic approach to optimize the BBH microsphere preparation process. Additionally, the stability study results confirmed that FMS6 is not only the ideal formulation but also stable, ensuring its suitability for practical applications.

Machine learning in accelerating microsphere formulation development.

Microspheres have gained much attention from pharmaceutical and medical industry due to the excellent biodegradable and long controlled-release characteristics. However, the drug release behavior of microspheres is influenced by complicated formulation and manufacturing factors. The traditional formulation development of microspheres is intractable and inefficient by the experimentally trial-and-error methods. This research aims to build a prediction model to accelerate microspheres product development for small-molecule drugs by machine learning (ML) techniques. Two hundred eighty-six microsphere formulations with small-molecule drugs were collected from the publications and pharmaceutical company, including the dissolution temperature at both 37 ℃ and 45 ℃. After the comparison of fourteen ML approaches, the consensus model achieved accurate predictions forthevalidation set at 37 ℃ and 45 ℃ (R2 = 0.880 vs. R2 = 0.958), indicating the good performance to predict the in vitro drug release profiles at both 37 ℃ and 45 ℃. Meanwhile, themodels revealed the feature importance of formulations, which offered meaningful insights to the microspheres development. Experiments of microsphere formulations further validated the accuracy of theconsensus model. Furthermore, molecular dynamics (MD) simulation provided a microscopic view of the preparation process of microspheres. In conclusion, the prediction model of microsphere formulations for small-molecule drugs was successfully built with high accuracy, which is able to accelerate microspheres product development and promote the quality control of microspheres for the pharmaceutical industry.

Preparation and properties of nano-SiO2/lipase/polycaprolactone composite microsphere and its application in controlling the degradation of polylactic acid fiber membrane

Polylactic acid (PLA) fiber membrane needs to match the wound healing time when used as a medical adhesive membrane. In order to adjust the degradation cycle of PLA fiber, the composite microspheres of nano-SiO2/lipase/polycaprolactone (PCL) with degradation regulation function were designed and prepared. And then the composite microspheres were added into PLA fiber membrane to verify the degradation regulation function. The results showed that: the optimal preparation process of microspheres was obtained as follows: 5 mg/mL SiO2/lipase complex concentration, 10 mg/mL PCL concentration, 1000 r/min emulsification speed and 600 r/min curing speed. The amount of enzyme, loading in the microspheres, can be regulated in the range of 10.24%–11.29%. And the drug-loaded microspheres had a good sustained release effect. Finally, it was verified that the microspheres could accelerate the degradation rate of PLA fiber membrane.

Minocycline Hydrochloride Controlled-release Microsphere Preparation Process Optimization Based on the Robust Design Method.

The objective of the present study is to establish a robust preparation method that could steadily produce minocycline hydrochloride (MCH) microspheres regardless of used polymer types. Taguchi's Robust Experimental Design methodology was employed to optimize the process parameters for MCH-loaded poly(D,L-lactide-co-glycolide) (PLGA) microspheres. In the experimental design, seven controllable factors, i.e., preparation method, pH of the aqueous phase, volume of the aqueous phase, volume of dichloromethane, rotation speed, temperature, and amount of polyvinyl alcohol, were considered for the optimization of process parameters. PLGA types with different lactide/glycolide ratios were considered the uncontrollable (noise) factor. Based on the L18 orthogonal array, 18 experimental runs were conducted for each type of PLGA. The encapsulation efficiency (EE) and in vitro release rate were evaluated for all the prepared formulations. Regardless of the PLGA type with different lactic/glycolic acid ratios, microspheres prepared via the solid-in-oil-in-water (S/O/W) method, showed a much higher EE and faster drug release than the microspheres prepared via the co-solvent method. Preparation methods, pH of the aqueous phase, and volume of the aqueous phase were the most influencing parameters on the EE. The confirmation experiment results indicated that the signal-to-noise ratio increased by 5.76 db from that of an initial condition. The release of minocycline was fastest with the PLGA (50:50) microspheres, followed by PLGA (75:25) and PLGA (85:15). Although the interaction between the selected factors in the evaluation was ignored, the orthogonal array design of the experiment based on Taguchi's robust experimental design methodology was sufficient to optimize the process parameters for the PLGA microspheres of MCH. The S/O/W was the main factor affecting the EE. Microspheres prepared via the S/O/W method exhibited a higher EE and faster drug release than the microspheres prepared via co-solvent method. The pH and volume of the aqueous phase were also effective parameters on the EE. A robust experimental design has been successfully applied to the optimization of the process parameters for microsphere preparation.

Development of Arteannuin B Sustained-Release Microspheres for Anti-Tumor Therapy by Integrated Experimental and Molecular Modeling Approaches.

Arteannuin B (AB) has been found to demonstrate obvious anti-tumor activity. However, AB is not available for clinical use due to its very low solubility and very short half-life. This study aimed to develop AB long sustained-release microspheres (ABMs) to improve the feasibility of clinical applications. Firstly, AB-polylactic-co-glycolic acid (PLGA) microspheres were prepared by a single emulsification method. In vitro characterization studies showed that ABMs had a low burst release and stable in vitro release for up to one week. The particle size of microspheres was 69.10 μm (D50). The drug loading is 37.8%, and the encapsulation rate is 85%. Moreover, molecular dynamics modeling was firstly used to simulate the preparation process of microspheres, which clearly indicated the molecular image of microspheres and provided in-depth insights for understanding several key preparation parameters. Next, in vivo pharmacokinetics (PK) study was carried out to evaluate its sustained release effect in Sprague-Dawley (SD) rats. Subsequently, the methyl thiazolyl tetrazolium (MTT) method with human lung cancer cells (A549) was used to evaluate the in vitro efficacy of ABMs, which showed the IC50 of ABMs (3.82 μM) to be lower than that of AB (16.03 μM) at day four. Finally, in vivo anti-tumor activity and basic toxicity studies were performed on BALB/c nude mice by subcutaneous injection once a week, four times in total. The relative tumor proliferation rate T/C of AMBs was lower than 40% and lasted for 21 days after administration. The organ index, organ staining, and tumor cell staining indicated the excellent safety of ABMs than Cis-platinum. In summary, the ABMs were successfully developed and evaluated with a low burst release and a stable release within a week. Molecular dynamics modeling was firstly applied to investigate the molecular mechanism of the microsphere preparation. Moreover, the ABMs possess excellent in vitro and in vivo anti-tumor activity and low toxicity, showing great potential for clinical applications.

Optimized parameters for the preparation of silk fibroin drug-loaded microspheres based on the response surface method and a genetic algorithm-backpropagation neural network model.

Using silk fibroin as the base material, the drug-loaded microspheres are prepared by an emulsification method. In order to determine the drug-loading and drug-release performance parameters of the microspheres, the central composite design method is used to design and investigate the effects of the parameters of the microsphere preparation process, such as the oil-water ratio, stirring temperature, and stirring rate, on the microsphere particle size, drug-loading rate, and drug release rate. The "overall desirability" is taken as a comprehensive evaluation index, and the response surface method (RSM) and genetic algorithm-backpropagation (GA-BP) neural network GA-BP model are used to predict and evaluate the parameters of the drug-loaded microsphere preparation process. The root-mean-square error values obtained from the RSM and BP-GA model experiments are 0.000325 and 0.00022, respectively. The results show that the BP-GA model has better prediction accuracy and optimization ability than the RSM. The optimal microsphere preparation process conditions were determined to be as follows: a water-oil ratio of 10:1, at a temperature of 45°C with stirring at a speed of 400 rpm, the particle size of the microspheres is 1.392 μm, the drug-loading rate is 3.218%, and the drug release rate is 51.991%. The results of this study indicate that this approach is an effective method for the optimization of the parameters of the drug-loaded microsphere preparation process.

Preparation and Characterization of Polyamide‐6/Reduced Graphene Oxide Composite Microspheres

AbstractAn effective method of in‐situ anionic ring‐opening polymerization of caprolactam (CL) is adopted to prepare polyamide‐6 (PA6)/reduced graphene oxide (RGO) composite microspheres utilizing reaction‐induced phase inversion of polymer pairs PA6/polystyrene (PS) with the presence of graphene oxide (GO). The reduction of GO with CL as reducing agent in the preparation process of microspheres is studied in detail. The morphology, functional groups, crystallization properties and thermal stability of PA6‐based composite microspheres are analyzed by different techniques (i. e. SEM, TEM, FTIR, DSC and TGA). Results indicate that both crystallinity and melting temperature of PA6/RGO composite microspheres are improved by RGO inclusion, and the thermal property of PA6/RGO microspheres is obviously better than that of neat PA6 microspheres.

Effect of pH on polyethylene glycol (PEG)-induced silk microsphere formation for drug delivery

The effects of changing solution pH in the range of 3.6–10.0 during a one-step silk microsphere preparation process, by mixing silk and polyethylene glycol (PEG), was assessed. The microspheres prepared at low pH (3.6) showed a more homogeneous size (1–3μm) and less porous texture than those prepared at neutral pH. High pH (10.0) inhibited microsphere formation, yielding small and inhomogeneous microspheres. Compared to neutral pH, low pH also increased the content of silk crystalline β-sheet structure from approx. 30% to above 40%. As a result, the microspheres produced at low pH were more thermally stable as well as resistant to chemical (8M urea) and enzymatic (protease XIV) degradation when compared to microspheres prepared at neutral pH. Doxorubicin hydrochloride (DOX) and curcumin (CUR) were successfully loaded in silk microspheres via control of solution pH. The loading efficiency of DOX was approx. 95% at pH7.0 and approx. 60% for CUR at pH3.6, attributed to charge-charge interactions and hydrophobic interactions between the silk and drug molecules, respectively. When PBS, pH7.4, was used as a medium for release studies, the pH3.6 microspheres released both drugs more slowly than the pH7.0 microspheres, likely due to the high content of crystalline β-sheet structure that enhanced drug-silk interactions as well as restricted drug molecule diffusion.

Addition of Zinc Improves the Physical Stability of Insulin in the Primary Emulsification Step of the Poly(lactide-co-glycolide) Microsphere Preparation Process

In this study, the effect of zinc on insulin stability during the primary emulsification step of poly(lactide-co-glycolide) microspheres preparation by the water-in-oil-in-water (w/o/w) double emulsion solvent evaporation technique was evaluated. Insulin was emulsified at homogenization speeds of 5000 and 10,000 rpm. Insulin was extracted from the primary w/o emulsion by a method previously reported from our laboratory and analyzed by comprehensive analytical techniques. The differential scanning calorimetry thermograms of insulin with zinc showed a single peak around 83 °C with calorimetric enthalpy values similar to native insulin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of extracted insulin showed a single intense band around 6 kDa, demonstrating the preservation of primary structure. High performance liquid chromatography (HPLC) analysis revealed that no degradation products were formed during the homogenization process. Insulin aggregates residing at the w/o interfaces were found to be of non-covalent nature. In addition, observation of a single characteristic peak for insulin at m/z 5808 in the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrum confirmed the absence of insulin degradation products and covalent dimers. Presence of zinc preserved the secondary structure of insulin as indicated by circular dichroism. In conclusion, these results show that with the addition of zinc, insulin stability can be improved during the primary emulsification step.

An assessment of the interactions between diclofenac sodium and ammonio methacrylate copolymer using thermal analysis and Raman spectroscopy

The objective of the work was to assess the possible interactions between the model drug diclofenac sodium (DS) and the water-insoluble ammonio methacrylate copolymer (AMC). Films with different drug/polymer ratios were therefore prepared by the solvent casting method and investigated as a preformulation study towards sustained release microparticles. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to investigate the dispersed/dissolved state of the DS in the preparation, the thermal stability and the properties of DS-containing AMC films; and Raman spectroscopy was used to confirm the possible interactions between DS and AMC. Thermoanalytical studies confirmed that the DS could behave as a plasticizer, which was indicated by decreasing glass transition temperature ( T g) of the AMC, depending on its dispersity level in the AMC matrix. Partially solid solutions were formed at DS/AMC ratios of 1:12, 1:8 and 1:6. The DS was mainly crystalline at DS/AMC ratio of 1:4, while it remained crystalline at a ratio of 1:2. The Raman spectra confirmed that none of the major structural changes revealed any significant difference, which can indicate a strong ionic interaction between the DS and the AMC. The investigations provided good facilities for the selection of a DS/AMC ratio, in the preformulation study of the microsphere preparation process, in conformity with the therapeutic aim.

An Interesting Phenomenon in Dispersion Polymerisation of Styrene: The Relationship between Conversion and Quantity of Microspheres

A phenomenon which has been ignored in most previous research, i.e., the relationship between conversion and the actual amount of microspheres in the dispersion polymerisation of styrene, has been researched. This led to a discussion of the polymerisation mechanism and the microsphere preparation process. The results showed that the actual amount of microspheres was always lower than the conversion, and the ratio of the two was different in different media. They also showed that with the decreasing polarity and solubility parameter of the medium, the conversion of styrene gradually reduced, and the character of the polymerisation was partly emulsion and partly solution. The average diameter and distribution of the microspheres in ethanol-water, ethanol, isopropanol and butanol were investigated too, and it was found that they increased with increasing polarity of the medium.

Preparation of poly( dl-lactide- co-glycolide) microspheres encapsulating all-trans retinoic acid

Poly( dl-lactide- co-glycolide) (PLGA) microspheres containing all-trans retinoic acid (atRA) were prepared by o/w solvent evaporation method and various preparation parameters, such as poly(vinyl alcohol) (PVA) concentration in aqueous solution, PVA MW, drug weight, solvent, polymer MW, and polymer weight, on the characteristics of microspheres and drug release were investigated. PVA concentration in water phase was a critical factor in making microspheres consistently with smooth surface and round shape. In our study, at least 2% (w/v) of PVA in aqueous solution was necessary for making microspheres with round shape. The particle size of microspheres ranged 10–100 μm. AtRA was slowly released from PLGA microspheres over 30 days. Sterilization of microspheres by ethylene oxide (EO) gas at 37 °C did not significantly affect the characteristics of drug release or its morphology. Cell growth inhibition of atRA was affected by preparation process of microspheres rather than the EO-gas sterilization process. These results indicate that PLGA microspheres containing atRA are acceptable for controlled release devices for use in the treatment of brain tumor.

Lysozyme stability in primary emulsion for PLGA microsphere preparation: effect of recovery methods and stabilizing excipients.

To investigate the conformational stability of a model protein, lysozyme, in the primary emulsion phase of the microsphere preparation process. The conformational stability of lysozyme during primary emulsification was assessed by differential scanning calorimetry (DSC) and enzymatic activity assay. PEG 400 was used to separate lysozyme from water-in-oil (w/o) emulsion containing poly(lactideco-glycolide) (PLGA). No significant changes in the recovery of lysozyme were observed due to increasing sonication time from 20 to 60 s at 40 W or increasing intensity from 40 to 60 W for 20 s. By using the method involving PEG 400, lysozyme recovery in the presence of PLGA was increased from 11.8% to 709%. Hydroxypropyl-beta-cyclodextrin (HP-beta-CD) increased lysozyme recovery from 35% to 70% at low lysozyme concentration (20 mg/ml), and from 70% to 77% at high lysozyme concentration (100 mg/ml) in the presence of PLGA. Sugars such as trehalose and mannitol failed to increase lysozyme recovery. DSC results suggested the retention of the conformational structure of the recovered lysozyme, which was supported by an enzymatic activity assay. HP-beta-CD was found to be a promising stabilizer that protected lysozyme during the primary emulsification. Protein recovery method with the help of PEG 400 allowed the study of protein stability in w/o emulsions in the presence of PLGA. DSC provided supplementary information on the conformational changes of lysozyme during emulsification.

Peptide containing microspheres from low molecular weight and hydrophilic poly( d, l-lactide-co-glycolide)

Biodegradable poly( d, l-lactide-co-glycolide) (PLGA) polymers of molecular weight lower than 30 000 Da and free terminal carboxylic acid end groups were evaluated for incorporation of a peptide. These low molecular weight hydrophilic polymers require characterization for carboxylic acid content and fraction of water soluble polymer, both of which significantly affected the structure and peptide incorporation. The polymers from different suppliers have different properties due to their methods of synthesis. The glass transition temperature increased with increase in the molecular weight, where as the carboxylic acid content and the bulk density of the microspheres decreased with an increase in the molecular weight. The particle size of the microspheres increased with molecular weight. The total yield of microspheres decreased with an increase in the water soluble fraction of the polymer. The 75:25 lactide/glycolide polymers showed a decrease in peptide incorporation with molecular weight but the 50:50 did not. The peptide not incorporated into the microsphere was extracted by the aqueous continuous phase during the microsphere preparation. Microspheres with higher molecular weight show lower initial peptide release. The peptide incorporation in low molecular weight polymers can be controlled by modification in the microsphere preparation process. The results suggest that peptide microspheres can be prepared from low molecular weight hydrophilic lactide/glycolide polymers.

Novel vaginal delivery systems for calcitonin: II. Preparation and characterization of HYAFF® microspheres containing calcitonin

Microspheres prepared from hyaluronan esters (HYAFF®) have been evaluated as a novel delivery system for the vaginal administration of salmon calcitonin (sCT). HYAFF® microspheres containing sCT were prepared by a solvent extraction method. Spherical microspheres of about 10 mm in diameter with smooth surfaces were obtained. An HPLC method was developed for the determination of sCT incorporated into the microspheres. The efficiency of incorporation was high, with approximately 80 to 90% of the peptide recovered by extraction from the microspheres. Quantification of the extracted peptide in vivo confirmed that the biological activity of sCT was unaffected by the microsphere preparation process.