Engineering polymer blend microparticles: An investigation into the influence of polymer blend distribution and interaction

Polymer type effect on PLGA-based microparticles preparation by solvent evaporation method with single emulsion system using focussed beam reflectance measurement

AIM

This study aimed to investigate the effect of polymer type on solidification rate of PLGA polymeric microparticles and particle size/distribution of the emulsion droplets/hardened PLGA polymeric microparticles during solvent evaporation process using FBRM (Focussed Beam Reflectance Measurement).

METHODS

PLGA polymeric microparticles were prepared by an O/W solvent evaporation method using various PLGA polymers, including PLGA Resomer® RG503H, RG502H and RG752H. The particle size mean, chord length distribution (CLD), and chord count of the emulsion droplets/hardened microparticles were monitored by FBRM. The morphology of polymeric microparticles were characterised by optical microscopy and scanning electron microscopy (SEM).

RESULTS

The transformation of the emulsion droplets into solid microparticles occurred within the first 30 (± 1.04), 34 (± 1.15) and 37 (± 0.82) min and square weighted mean chord lengths are 64.08 (± 3.18), 52.36 (± 5.27) and 42.18 (± 4.61) µm when PLGA Resomer® RG503H, RG502H and RG752H were used respectively. Larger square weighted mean chord length of PLGA polymeric microparticles gave lower chord counts. PLGA RG752H microparticles gave smallest square weighted mean chord length and the chord counts was the highest. The CLDs measured by FBRM showed that a larger particle size mean gave longer CLD and a lower peak of particle number. SEM data revealed that the morphology of microparticles was influenced by type and physical properties of polymer.

CONCLUSIONS

FBRM can be employed for online monitoring of the shift in the microparticle CLD and detect transformation of the emulsion droplets into solid microparticles during the solvent evaporation process. The microparticle CLD and transformation process were strongly influenced by polymer type.

Impact of dispersion time interval and particle size on release profiles of propranolol HCl and carbamazepines from microparticle blends system

The objective of this study was to investigate the effect of dispersion time interval (DTI) on physicochemical properties of drug following the incorporation of propranolol HCl (Pro) and carbamazepine (CBZ) within ethyl cellulose (EC) microparticle blends using solvent evaporation method. The first Pro emulsion and second CBZ oil phase were dispersed in an external aqueous phase, with DTI of 0 and 60 min. The morphology of microparticle blends were characterized by SEM. The particle size mean of the emulsion droplets/hardened microparticles were monitored by FBRM. Encapsulation efficiency (EE) and in vitro drug release were also investigated. The resulting microparticle blends were spherical and formed two populations. The particle size mean of microparticle blends ranged from 113.27 µm to 122.42 µm. The EE was 77.28% to 78.64% for Pro and 96.48% to 98.64% for CBZ. FBRM studies showed that the size of microparticle blend prepared as W/O/W (Pro) and O/W (CBZ) system with DTI of 60 min and stirring time 4 h were larger than those prepared with DTI of 0 min. In vitro drug release studies after 28 days that revealed the CBZ release (58.72%) was faster than Pro release (43.16%). Investigation on surface morphology by SEM showed that the second drug CBZ which added as the oil phase in the W/O/W emulsion system had blocked the pores on the surface Pro microparticles prepared from the first primary emulsion, therefore affecting the drug release. This blocking effects of second drug (CBZ) on first emulsion microparticles (Pro) depended on the DTI. This phenomenon is only applicable if the first primary emulsion is W/O/W system.

Real-time particle size analysis using focused beam reflectance measurement as a process analytical technology tool for continuous microencapsulation process

The online real-time particle size analysis of the microencapsules manufacturing process using the continuous solvent evaporation method was performed using focused beam reflectance measurement (FBRM). In this paper, we use FBRM measurements to investigate the effects of polymer type and compare the size distributions to those obtained using other sizing methods such as optical microscope and laser diffraction. FBRM was also utilized to measure the length-weighted chord length distribution (CLD) and particle size distribution (PSD) online during particle solidification, which could not be done with laser diffraction or nested sieve analysis. The chord lengths and CLD data were taken at specific times using an online FBRM probe mounted below the microparticle. The timing of the FBRM determinations was coordinated with the selection of microparticle samples for particle size analysis by optical microscope and laser diffraction calculation as a reference. For all three produced batches tested, FBRM, laser diffraction, and sieve analysis yielded similar results. Hardening time for the transformation of emulsion droplets into solid microparticles occurred within the first 10.5, 19, 25, 30, and 55 min, according to FBRM results. The FBRM CLDs revealed that a larger particle size mean resulted in a longer CLD and a lower peak of particle number. The FBRM data revealed that the polymer type had a significant impact on microparticle CLD and the transformation process.

Gene Signature-Based Approach Identified MEK1/2 as a Potential Target Associated With Relapse After Anti-TNFα Treatment for Crohn's Disease

BACKGROUND

Anti-tumor necrosis factor alpha (anti-TNFα) therapy has become the mainstay of therapy for Crohn's disease (CD). However, post-therapy, the recurrence rate is still high. The aim of this study was to dissect the molecular mechanism for recurrence of CD treated with anti-TNFα therapy and investigate novel therapeutic options that could induce complete remission.

METHODS

We re-analyzed publicly available mucosal gene expression data from CD patients pre- and post-infliximab therapy to extract the transcriptional differences between responders and healthy controls. We used a systematic computational approach based on identified differences to discover novel therapies and validated this prediction through in vitro and in vivo experimentation.

RESULTS

We identified a set of 3545 anti-TNFα therapy-untreatable genes (TUGs) that are significantly regulated in intestinal epithelial cells, which remain altered during remission. Pathway enrichment analysis of these genes clearly showed excessive growth state and suppressed terminal differentiation, whereas immune components were clearly resolved. Through in silico screening strategy, we observed that MEK inhibitors were predicted to revert expression of genes dysregulated in infliximab responders. In vitro transcriptome analysis demonstrated that selective MEK1/2 inhibitor significantly normalized reference genes from TUGs. In addition, in vitro functional study proved that MEK1/2 inhibitor facilitated intestinal epithelial differentiation. Finally, using murine colitis model, administration of MEK1/2 inhibitor significantly improved diarrhea and histological score.

CONCLUSIONS

Our data revealed the abnormalities in anti-TNFα responders' CD colons that would be cause of recurrence of CD. Also, we provided evidence regarding MEK1/2 inhibitor as a potential treatment against CD to achieve sustainable remission.

Inner layer-embedded contact lenses for pH-triggered controlled ocular drug delivery

Contact lenses (CLs) are ideally suited for controlled ocular drug delivery, but are limited by short release duration, poor storage stability and low drug loading. In this study, we present a novel inner layer-embedded contact lens capable of pH-triggered extended ocular drug delivery with good storage stability. Blend film of ethyl cellulose and Eudragit S100 was used as the inner layer, while pHEMA hydrogel was used as outer layer to fabricate inner layer-embedded contact lens. Using diclofenac sodium(DS) as a drug model, influence of polymer ratio in the blend film, EC viscosity, drug/polymer ratio, inner layer thickness and outlayer thickness of pHEMA hydrogel on drug release behavior was studied and optimized for daily use. The pH-triggered drug eluting pattern enables the inner layer-embedded contact lens being stored in phosphate buffer solution pH 6.8 with ignorable drug loss and negligible changes in drug release pattern. In vivo pharmacokinetic study in rabbits showed sustained drug release for over 24 h in tear fluid, indicating significant improvement in drug corneal residence time. A level A IVIVC was established between in vitro drug release and in vivo drug concentration in tear fluid. In conclusion, this inner layer embedded contact lens design could be used as a platform for extended ocular drug delivery with translational potential for both anterior and posterior ocular diseases therapy.

Evaluate the ability of PVP to inhibit crystallization of amorphous solid dispersions by density functional theory and experimental verify

In this study, we used density functional theory (DFT) to predict polymer-drug interactions, and then evaluated the ability of poly (vinyl pyrrolidone) (PVP) to inhibit crystallization of amorphous solid dispersions by experimental-verification. Solid dispersions of PVP/resveratrol (Res) and PVP/griseofulvin (Gri) were adopted for evaluating the ability of PVP to inhibit crystallization. The density functional theory (DFT) with the B3LYP was used to calculate polymer-drug and drug-drug interactions. Fourier transform infrared spectroscopy (FTIR) was used to confirm hydrogen bonding interactions. Polymer-drug miscibility and drug crystallinity were characterized by the modulated differential scanning calorimetry (MDSC) and X-ray powder diffraction (XRD). The release profiles were studied to investigate the dissolution advantage. DFT results indicated that E_PVP-Res>E_Res-Res (E: represents hydrogen bonding energy). A strong interaction was formed between PVP and Res. In addition, Fourier transform infrared spectroscopy (FTIR) analysis showed hydrogen bonding formed between PVP and Res, but not between PVP and Gri. MDSC and XRD results suggested that 70-90wt% PVP/Res and PVP/Gri solid dispersions formed amorphous solid dispersions (ASDs). Under the accelerated testing condition, PVP/Res dispersions with higher miscibility quantified as 90/10wt% were more stable than PVP/Gri dispersions. The cumulative dissolution rate of 90wt% PVP/Res dispersions still kept high after 90days storage due to the strong interaction. However, the cumulative dissolution rate of PVP/Gri solid dispersions significantly dropped because of the recrystallization of Gri.

Coatings of Eudragit® RL and L-55 Blends: Investigations on the Drug Release Mechanism

In a previous study, generally lower drug release rates from RL:L55 blend coated pellets in neutral/basic release media than in acidic release media were reported. The aim of this study was to obtain information on the drug release mechanism of solid dosage forms coated with blends of Eudragit® RL (RL) and Eudragit® L-55 (L55). Swelling experiments with free films were analyzed spectroscopically and gravimetrically to identify the physicochemical cause for this release behavior. With Raman spectroscopy, the swelling of copolymer films could be monitored. IR spectroscopic investigations on RL:L55 blends immersed in media at pH 6.8 confirmed the formation of interpolyelectrolyte complexes (IPECs) that were not detectable after swelling in hydrochloric acid pH 1.2. Further investigations revealed that these IPECs decreased the extent of ion exchange between the quaternary ammonium groups of RL and the swelling media. This is presumably the reason for the previously reported decreased drug permeability of RL:L55 coatings in neutral/basic media as ion exchange is the determining factor in drug release from RL coated dosage forms. Gravimetric erosion studies confirmed that L55 was not leached out of the film blends during swelling in phosphate buffer pH 6.8. In contrast to all other investigated films, the 4:1 (RL:L55) blend showed an extensive swelling within 24 h at pH 6.8 which explains the reported sigmoidal release behavior of 4:1 blend coated pellets. These results help to understand the release behavior of RL:L55 blend coated solid dosage forms.

Optimization of sustained release aceclofenac microspheres using response surface methodology

Polymeric microspheres containing aceclofenac were prepared by single emulsion (oil-in-water) solvent evaporation method using response surface methodology (RSM). Microspheres were prepared by changing formulation variables such as the amount of Eudragit® RS100 and the amount of polyvinyl alcohol (PVA) by statistical experimental design in order to enhance the encapsulation efficiency (E.E.) of the microspheres. The resultant microspheres were evaluated for their size, morphology, E.E., and in vitro drug release. The amount of Eudragit® RS100 and the amount of PVA were found to be significant factors respectively for determining the E.E. of the microspheres. A linear mathematical model equation fitted to the data was used to predict the E.E. in the optimal region. Optimized formulation of microspheres was prepared using optimal process variables setting in order to evaluate the optimization capability of the models generated according to IV-optimal design. The microspheres showed high E.E. (74.14±0.015% to 85.34±0.011%) and suitably sustained drug release (minimum; 40% to 60%; maximum) over a period of 12h. The optimized microspheres formulation showed E.E. of 84.87±0.005 with small error value (1.39). The low magnitudes of error and the significant value of R(2) in the present investigation prove the high prognostic ability of the design. The absence of interactions between drug and polymers was confirmed by Fourier transform infrared (FTIR) spectroscopy. Differential scanning calorimetry (DSC) and X-ray powder diffractometry (XRPD) revealed the dispersion of drug within microspheres formulation. The microspheres were found to be discrete, spherical with smooth surface. The results demonstrate that these microspheres could be promising delivery system to sustain the drug release and improve the E.E. thus prolong drug action and achieve the highest healing effect with minimal gastrointestinal side effects.

Influence of some formulation variables on the optimization of pH-dependent, colon-targeted, sustained-release mesalamine microspheres

The aim of this work was to understand the influence of different formulation variables on the optimization of pH-dependent, colon-targeted, sustained-release mesalamine microspheres prepared by O/O emulsion solvent evaporation method, employing pH-dependent Eudragit S and hydrophobic pH-independent ethylcellulose polymers. Formulation variables studied included concentration of Eudragit S in the internal phase and the ratios between; internal to external phase, drug to Eudragit S and Eudragit S to ethylcellulose to mesalamine. Prepared microspheres were evaluated by carrying out in vitro release studies and determination of particle size, production yield, and encapsulation efficiency. In addition, morphology of microspheres was examined using optical and scanning electron microscopy. Emulsion solvent evaporation method was found to be sensitive to the studied formulation variables. Particle size and encapsulation efficiency increased by increasing Eudragit S concentration in the internal phase, ratio of internal to external phase, and ratio of Eudragit S to the drug. Employing Eudragit S alone in preparation of the microspheres is only successful in forming acid-resistant microspheres with pulsatile release pattern at high pH. Eudragit S and ethylcellulose blend microspheres were able to control release under acidic condition and to extend drug release at high pH. The stability studies carried out at 40°C/75% RH for 6 months proved the stability of the optimized formulation. From the results of this investigation, microencapsulation of mesalamine in microspheres using blend of Eudragit S and ethylcellulose could constitute a promising approach for site-specific and controlled delivery of drug in colon.