Formulation and characterization of microspheres loaded with imatinib for sustained delivery

Biodegradable Long-Acting Injectables: Platform Technology and Industrial Challenges

Long-acting injectables have been used to benefit patients with chronic diseases. So far, several biodegradable long-acting platform technologies including drug-loaded polymeric microparticles, implants (preformed and in situ forming), oil-based solutions, and aqueous suspension have been established. In this chapter, we summarize all the marketed technology platforms and discuss their challenges regarding development including but not limited to controlling drug release, particle size, stability, sterilization, scale-up manufacturing, etc. Finally, we discuss important criteria to consider for the successful development of long-acting injectables.

A review on PLGA particles as a sustained drug-delivery system and its effect on the retina

In this review, the designs and recent developments of polymer-based drug delivery of Poly(lactic-co-glycolic acid) (PLGA) will be discussed for the possible treatment of age-related macular degeneration (AMD). PLGA is a versatile co-polymer that consists of synthetic lactic acid and glycolic acid monomers that are constructed to produce nanoparticles, microparticles, and scaffolds for the intraocular delivery of various drugs. As an FDA-approved polymer, PLGA has historically been well-suited for systemic slow-sustained release therapies due to its performance in biodegradability and biocompatibility. This review will examine recent in vitro and in vivo studies that provide evidence for PLGA-based particles as a therapeutic drug carrier for the treatment of AMD. Anti-angiogenic and antiproliferative effects of small peptides, small molecules, RNA molecules, and proteins within PLGA particles are briefly discussed. AMD is a leading cause of central vision loss in people over 55 years and the number of those afflicted will rise as the aging population increases. AMD has two forms that are often sequential. Dry AMD and wet AMD account for 85-90% and 10-15% of cases, respectively. The distinct categories of PLGA-based drug delivery vehicles are important for dispensing novel small molecules, RNA molecules, peptides, and proteins as a long-term effective treatment of AMD.

Multifaceted roles of pollen in the management of cancer

Oral drug delivery of microparticles demonstrates shortcomings like aggregation, decreased loading capacity and batch-to-batch variation, which limits its scale-up. Later, porous structures gained attention because of their large surface-to-volume ratio, high loading capacity and ability to carry biomacromolecules, which undergo degradation in GIT. But there are pitfalls like non-uniform particle size distribution, the impact of porogen properties, and harsh chemicals. To circumvent these drawbacks, natural carriers like pollen are explored in drug delivery, which withstands harsh environments. This property helps to subdue the acid-sensitive drug in GIT. It shows uniform particle size distribution within the species. On the other side, they contain phytoconstituents like flavonoids and polysaccharides, which possess various pharmacological applications. Therefore, pollen has the capability as a carrier system and therapeutic agent. This review focuses on pollen's microstructure, composition and utility in cancer management. The extraction strategies, characterisation techniques and chemical structure of sporopollenin exine capsule, its use in the oral delivery of antineoplastic drugs, and emerging cancer treatments like photothermal therapy, immunotherapy and microrobots have been highlighted. We have mentioned a note on the anticancer activity of pollen extract. Further, we have summarised the regulatory perspective, bottlenecks and way forward associated with pollen.

Preparation, Characterization, and Biological Evaluation of a Hydrophilic Peptide Loaded on PEG-PLGA Nanoparticles

The encapsulation of peptides and proteins in nanosystems has been extensively investigated for masking unfavorable biopharmaceutical properties, including short half-life and poor permeation through biological membranes. Therefore, the aim of this work was to encapsulate a small antimicrobial hydrophilic peptide (H-Ser-Pro-Trp-Thr-NH2, FS10) in PEG-PLGA (polyethylene glycol-poly lactic acid-co-glycolic acid) nanoparticles (Nps) and thereby overcome the common limitations of hydrophilic drugs, which because they facilitate water absorption suffer from rapid degradation. FS10 is structurally related to the well-known RNAIII inhibiting peptide (RIP) and inhibits S. aureus biofilm formation. Various parameters, including different method (double emulsion and nanoprecipitation), pH of the aqueous phase and polymeric composition, were investigated to load FS10 into PEG-PLGA nanoparticles. The combination of different strategies resulted in an encapsulation efficiency of around 25% for both the double emulsion and the nanoprecipitation method. It was found that the most influential parameters were the pH—which tailors the peptides charge—and the polymeric composition. FS10-PEG-PLGA nanoparticles, obtained under optimized parameters, showed size lower than 180 nm with zeta potential values ranging from −11 to −21 mV. In vitro release studies showed that the Nps had an initial burst release of 48−63%, followed by a continuous drug release up to 21 h, probably caused by the porous character of the Nps. Furthermore, transmission electron microscopy (TEM) analysis revealed particles with a spherical morphology and size of around 100 nm. Antimicrobial assay showed that the minimum inhibitory concentration (MIC) of the FS10-loaded Nps, against S. aureus strains, was lower (>128 µg/mL) than that of the free FS10 (>256 µg/mL). The main goal of this work was to develop polymeric drug delivery systems aiming at protecting the peptide from a fast degradation, thus improving its accumulation in the target site and increasing the drug-bacterial membrane interactions.

PLGA sustained-release microspheres loaded with an insoluble small-molecule drug: microfluidic-based preparation, optimization, characterization, and evaluation in vitro and in vivo

Microspheres play an important role in controlling drug delivery and release rate accurately. To realize the sustainable release of insoluble small-molecule drugs, a new three-phase flow-focusing microfluidic device was developed to produce the drug-loaded sustained-release microspheres which were prepared with bicalutamide (BCS class-II) as the model drug and poly(lactide-co-glycolide) (PLGA) as the carrier material. Under optimized prescription conditions, the microspheres showed a smooth surface and uniform size of 51.33 μm with a CV value of 4.43%. Sustained-release microspheres had a releasing duration of around 40 days in vitro without any initial burst release. The drug release mechanism of the microspheres was drug diffusion and polymer erosion. Meanwhile, the drug release of microspheres in vivo could be up to 30 days. Briefly, the microfluidic device in this study provides a new solution for the preparation of sustained-release microspheres for insoluble small-molecule drugs. PLGA sustained-release microspheres developed by the microfluidic device have good application prospects in precise delivery and sustainable release of insoluble small-molecule drugs.

Changing the daily injection of glatiramer acetate to a monthly long acting product through designing polyester-based polymeric microspheres

Introduction: Glatiramer acetate (GA) is a newly emerged therapeutic peptide to reduce the frequency of relapses in multiple sclerosis (MS). Despite its good performance in controlling MS, it is not widely used due to daily or biweekly subcutaneous injections due to rapid degradation and body clearance. Therefore, implant design with sustained release leads to prolonged biological effects by gradually increasing drug exposure and protecting GA from rapid local degradation. Methods: Different emulsion methods, PLGA type, surfactant concentration, drug/polymer ratio, drying processes, stirring method, and other variables in preliminary studies modified the final formulation. The release kinetics were studied through mechanistic kinetic models such as zero-order, Weibull, Higuchi, etc. In this study, all challenges for easy scale-up, methodological detail, and a simple, feasible setup in mass production were discussed. Results: The optimized formulation was obtained by 1:6 drug/PLGA, 0.5% w/w polyvinyl alcohol, and 0.75% w/w NaCl in the external aqueous phase, 1:10 continuous phase to dispersed phase ratio, and without any surfactant in the primary emulsion. The final freeze-dried particles presented a narrow distributed size of 1-10 µm with 7.29% ± 0.51 drug loading and zero-order release behavior with appropriate regression correlation (R2 98.7), complete release, and only 7.1% initial burst release. Conclusion: Therefore, to achieve improvement in patient compliance through better and longer efficacy, designing the parenteral sustained release microspheres (MPSs) of this immune modulator is a promising approach that should be considered.

PLGA-based biodegradable microspheres in drug delivery: recent advances in research and application

Biodegradable microspheres have been widely used in the field of medicine due to their ability to deliver drug molecules of various properties through multiple pathways and their advantages of low dose and low side effects. Poly (lactic-co-glycolic acid) copolymer (PLGA) is one of the most widely used biodegradable material currently and has good biocompatibility. In application, PLGA with a specific monomer ratio (lactic acid and glycolic acid) can be selected according to the properties of drug molecules and the requirements of the drug release rate. PLGA-based biodegradable microspheres have been studied in the field of drug delivery, including the delivery of various anticancer drugs, protein or peptide drugs, bacterial or viral DNA, etc. This review describes the basic knowledge and current situation of PLGA biodegradable microspheres and discusses the selection of PLGA polymer materials. Then, the preparation methods of PLGA microspheres are introduced, including emulsification, microfluidic technology, electrospray, and spray drying. Finally, this review summarizes the application of PLGA microspheres in drug delivery and the treatment of pulmonary and ocular-related diseases.

Preparation and quality by design assisted (Qb-d) optimization of bioceramic loaded microspheres for periodontal delivery of doxycycline hyclate

PLGA (Lactic- co-glycolic acid) coated chitosan microspheres loaded with hydroxyapatite and doxycycline hyclate complex were developed in the present study for periodontal delivery. A modified single emulsion method was adopted for the development of microspheres. Formulation was optimized on the basis of particle size, drug loading and encapsulation efficiency with the central composite design using 23 factorial design. Microspheres were optimized and electron microscopy revealed their spherical shape and porous nature. In-vitro study showed initial burst and then sustained release behavior of the formulation for 14 days. Further, in-vitro antibacterial study performed on E. coli (ATCC-25922) and S. aureus (ATCC-29213) revealed concentration dependent activity. Also, in-vitro cyto-toxicity assessment ensures biocompatibility of the formulation with the fibroblast's cells. Overall, the quality by design assisted PLGA microspheres, demonstrated the desired attributes and were found suitable for periodontal drug delivery.

Clinically established biodegradable long acting injectables: An industry perspective

Long acting injectable formulations have been developed to sustain the action of drugs in the body over desired periods of time. These delivery platforms have been utilized for both systemic and local drug delivery applications. This review gives an overview of long acting injectable systems that are currently in clinical use. These products are categorized in three different groups: biodegradable polymeric systems, including microparticles and implants; micro and nanocrystal suspensions and oil-based formulations. Furthermore, the applications of these drug delivery platforms for the management of various chronic diseases are summarized. Finally, this review addresses industrial challenges regarding the development of long acting injectable formulations.

Fasudil Loaded PLGA Microspheres as Potential Intravitreal Depot Formulation for Glaucoma Therapy

Rho-associated protein kinase (ROCK) inhibitors allow for causative glaucoma therapy. Unfortunately, topically applied ROCK inhibitors suffer from high incidence of hyperemia and low intraocular bioavailability. Therefore, we propose the use of poly (lactide-co-glycolide) (PLGA) microspheres as a depot formulation for intravitreal injection to supply outflow tissues with the ROCK inhibitor fasudil over a prolonged time. Fasudil-loaded microspheres were prepared by double emulsion solvent evaporation technique. The chemical integrity of released fasudil was confirmed by mass spectrometry. The biological activity was measured in cell-based assays using trabecular meshwork cells (TM cells), Schlemm’s canal cells (SC cells), fibroblasts and adult retinal pigment epithelium cells (ARPE-19). Cellular response to fasudil after its diffusion through vitreous humor was investigated by electric cell-substrate impedance sensing. Microspheres ranged in size from 3 to 67 µm. The release of fasudil from microspheres was controllable and sustained for up to 45 days. Released fasudil reduced actin stress fibers in TM cells, SC cells and fibroblasts. Decreased collagen gel contraction provoked by fasudil was detected in TM cells (~2.4-fold), SC cells (~1.4-fold) and fibroblasts (~1.3-fold). In addition, fasudil readily diffused through vitreous humor reaching its target compartment and eliciting effects on TM cells. No negative effects on ARPE-19 cells were observed. Since fasudil readily diffuses through the vitreous humor, we suggest that an intravitreal drug depot of ROCK inhibitors could significantly improve current glaucoma therapy particularly for patients with comorbid retinal diseases.

Quality by design thinking in the development of long-acting injectable PLGA/PLA-based microspheres for peptide and protein drug delivery

Adopting the Quality by Design (QbD) approach in the drug development process has transformed from "nice-to-do" into a crucial and required part of the development, ensuring the quality of pharmaceutical products throughout their whole life cycles. This review is discussing the implementation of the QbD thinking into the production of long-acting injectable (LAI) PLGA/PLA-based microspheres for the therapeutic peptide and protein drug delivery. Various key elements of the QbD approaches are initially elaborated using Bydureon®, a commercial product of LAI PLGA/PLA-based microspheres, as a classical example. Subsequently, the factors influencing the release patterns and the stability of the peptide and protein drugs are discussed. This is followed by a summary of the state-of-the-art of manufacturing LAI PLGA/PLA-based microspheres and the related critical process parameters (CPPs). Finally, a landscape of generic product development of LAI PLGA/PLA-based microspheres is reviewed including some major challenges in the field.

Lyophilisation Improves Bioactivity and Stability of Insulin-Loaded Polymeric-Oligonucleotide Nanoparticles for Diabetes Treatment

The oral bioavailability of therapeutic proteins is limited by the gastrointestinal barriers. Encapsulation of labile proteins into nanoparticles is a promising strategy. In order to improve the stability of nanoparticles, lyophilisation has been used to remove water molecules from the suspension. Although various cryoprotections were employed in the preparation of lyophilised nanoparticles, the selection of cryoprotectant type and concentration in majority of the developed formulation was not justified. In this study, nanoparticles were fabricated by cationic chitosan and anionic Dz13Scr using complex coacervation. The effect of cryoprotectant types (mannitol, sorbitol, sucrose and trehalose) and their concentrations (1, 3, 5, 7, 10% w/v) on physiochemical properties of nanoparticles were measured. Cellular assays were performed to investigate the impact of selected cryoprotectant on cytotoxicity, glucose consumption, oral absorption mechanism and gastrointestinal permeability. The obtained results revealed that mannitol (7% w/v) could produce nanoparticles with small size (313.2 nm), slight positive charge and uniform size distribution. The addition of cryoprotectant could preserve the bioactivity of entrapped insulin and improve the stability of nanoparticles against mechanical stress during lyophilisation. The gastrointestinal absorption of nanoparticles is associated with both endocytic and paracellular pathways. With the use of 7% mannitol, lyophilised nanoparticles induced a significant glucose uptake in C2C12 cells. This work illustrated the importance of appropriate cryoprotectant in conservation of particle physiochemical properties, structural integrity and bioactivity. An incompatible cryoprotectant and inappropriate concentration could lead to cake collapse and formation of heterogeneous particle size populations.

Regorafenib-loaded poly (lactide-co-glycolide) microspheres designed to improve transarterial chemoembolization therapy for hepatocellular carcinoma

Transarterial chemoembolization (TACE) has been widely introduced to treat hepatocellular carcinoma (HCC) especially for unresectable patients for decades. However, TACE evokes an angiogenic response due to the secretion of vascular endothelial growth factor (VEGF), resulting in the formation of new blood vessels and eventually tumor recurrence. Thus, we aimed to develop regorafenib (REGO)-loaded poly (lactide-co-glycolide) (PLGA) microspheres that enabled localized and sustained drug delivery to limit proangiogenic responses following TACE in HCC treatment. REGO-loaded PLGA microspheres were prepared using the emulsion-solvent evaporation/extraction method, in which DMF was selected as an organic phase co-solvent. Accordingly, we optimized the proportion of DMF, which the optimal ratio to DCM was 1:9 (v/v). After preparation, the microspheres provided high drug loading capacity of 28.6%, high loading efficiency of 91.5%, and the average particle size of 149 µm for TACE. IR spectra and XRD were applied to confirming sufficient REGO entrapment. The in vitro release profiles demonstrated sustained drug release of microspheres for more than 30 d To confirm the role of REGO-loaded microspheres in TACE, the cell cytotoxic activity on HepG2 cells and anti-angiogenic effects in HUVECs Tube-formation assay were studied in combination with miriplatin. Moreover, the microspheres indicated the potential of antagonizing miriplatin resistance of HepG2 cells in vitro. Pharmacokinetics preliminary studies exhibited that REGO could be sustainably released from microspheres for more than 30 d after TACE in vivo. In vivo anti-tumor efficacy was further determined in HepG2 xenograft tumor mouse model, demonstrating that REGO microspheres could improve the antitumor efficacy of miriplatin remarkably compared with miriplatin monotherapy. In conclusion, the obtained REGO microspheres demonstrated promising therapeutic effects against HCC when combined with TACE.

Recent research and development of local anesthetic-loaded microspheres

This review introduces the recent research and development in local anesthetic-loaded microsphere, as efficient microspheres formulation, the efficient microspheres: optimum preparation method, high loading efficiency, and ideal release rate.

Diosgenin-conjugated PCL–MPEG polymeric nanoparticles for the co-delivery of anticancer drugs: design, optimization, in vitro drug release and evaluation of anticancer activity

In this study, a polymeric nanoparticle-mediated dual anti-cancer drug delivery system was designed and developed.

Development of an analytical methodology for the analysis of priority cytostatics in water

The consumption of cytostatics has remarkably increased over the last years due to the high cancer incidence worldwide. In previous studies, seven cytostatics were already recognized to potentially induce chronic effects in aquatic organisms, taking into account their estimated concentrations in surface waters: cyclophosphamide (CYC), capecitabine (CAP), mycophenolic acid (MPA), imatinib (IMA), bicalutamide (BICA), prednisone (PRED) and 5-fluorouracil (5FU). The objective of the present study was to simultaneously analyse these 7 prioritized compounds, which have the highest chances to be found in surface and wastewaters. The analytical challenge relies in the determination of these very polar compounds, which have different chemical and structural properties. Solid-phase extraction with an Ultra Performance Liquid Chromatograph-Mass Spectrometer in electrospray ionization mixed mode (5-fluorouracil and bicalutamide in negative mode and the others in positive one) was developed to determine seven cytostatics in wastewater and surface water. Among eight tested cartridges with different sorbents and conditions, the best extraction performance was attained with Oasis WAX at pH 10, with recoveries ranging from 31 ± 4 (5FU) and 103 ± 17% (MPA). Regarding the chromatographic analysis, the best results were achieved with an XBridge amide column. The final analytical methodology was successfully applied for the analysis of real water samples, confirming the presence of risky cytostatics in surface and wastewaters.

Characterization, Stability and Biological Activity In Vitro of Cathelicidin-BF-30 Loaded 4-Arm Star-Shaped PEG-PLGA Microspheres

BF-30 is a single chain polypeptide of an N-segment with an α-helix from cathelicidin gene encoding, and it contains 30 amino acid residues, with a relative molecular mass and isoelectric point of 3637.54 and 11.79, respectively. Cathelicidin-BF-30 was entrapped in four-arm star-shaped poly(ethylene glycol-b-dl-lactic acid-co-glycolic acid) block copolymers (4-arm-PEG-PLGA) by a double-emulsion solvent-evaporation method. Three release phases of cathelicidin-BF-30loaded 4-arm-PEG-PLGA microspheres were observed, including an initial burst-release phase, followed by a lag phase with minimal drug release and finally a secondary zero-order release phase. The delivery system released BF-30 over more than 15 days in vitro. Furthermore, the material for preparing the microspheres has good biocompatibility and biodegradability. Additionally, based on the drug resistance of food pathogenic bacteria, the antibacterial effects of BF-30 on Shigella dysenteriae CMCC 51105 (Sh. dysenteriae CMCC 51105), Salmonella typhi (S. typhi) and Staphylococcus aureus (S. aureus) as well as the stability of the in vitro release of the BF-30-loded microspheres were studied. The α-helix secondary structure and antibacterial activity of released BF-30 were retained and compared with native peptide. These BF-30 loaded microspheres presented <10% hemolysis and no toxicity for HEK293T cells even at the highest tested concentration (150 μg/mL), indicating that they are hemocompatible and a promising delivery and protection system for BF-30 peptide.

Preparation of particulate polymeric therapeutics for medical applications

Particulate therapeutics fabricated from polymeric materials have become increasingly popular over the past several decades. Generally, polymeric systems are easy to synthesize and have tunable parameters, giving them significant potential for wide use in the clinic. They come in many different forms, including as nanoparticles, microparticles, and colloidal gels. In this review, we discuss the current preparation methods for each type of platform, as well as some representative applications. To achieve enhanced performance, lipid coatings and other surface modification techniques for introducing additional functionality are also mentioned. We hope that, by outlining the various methods and techniques for their preparation, it will be possible to provide insights into the utility of these polymeric platforms and further encourage their development for biomedical applications.

Controlled release and anti-proliferative effect of imatinib mesylate loaded sporopollenin microcapsules extracted from pollens of Betula pendula

Sporopollenin is a promising material for drug encapsulation due to its excellent properties; uniformity in size, non-toxicity, chemically and thermally resilient nature. Herein, morphologically intact sporopollenin microcapsules were extracted from Betula pendula pollens. Cancer therapeutic agent (imatinib mesylate) was loaded into the microcapsules. The encapsulation efficiency by passive loading technique was found to be 21.46%. Release behaviour of the drug from microcapsules was found to be biphasic, with an initial fast release followed by a slower rate of release. Imatinib mesylate release from the drug itself (control) was faster than from imatinib mesylate-loaded sporopollenin microcapsules. The release profiles for both free and entrapped drug samples were significantly slower and more controlled in PBS buffer (pH 7.4) than in HCl (pH 1.2) buffer. Cumulative drug release from IM-MES-loaded sporopollenin microcapsules was found to be 65% within 24h for PBS, whereas release from the control was completed within 1h. Also, a complete dissolution of control in HCl buffer was observed within first 30min. MTT assay revealed that drug-loaded microcapsules were effective on WiDr human colon carcinoma cell line. B. pendula sporopollenin can be suggested as an effective carrier for oral delivery of imatinib mesylate.

cmRNA/lipoplex encapsulation in PLGA microspheres enables transfection via calcium phosphate cement (CPC)/PLGA composites

In this study lipoplexes containing chemically modified messenger RNA (cmRNA) were incorporated into poly (lactic-co-glycolic acid) (PLGA) microspheres via water-in-oil-in-water (W/O/W) double emulsion solvent evaporation technique. The nanoparticle encapsulation by microparticle formation was optimized to achieve lipoplex release and maximum transfection efficiency in surrounding cells. It was possible to adjust characteristic features in surface topology and size of the PLGA-microspheres by varying the extent of lipoplex loading into the polymer matrix. The partial release of lipids and mRNA out of the microparticle system, their accumulation in cells and the production of encoded protein were visualized via fluorescence microscopy. These bioactive microspheres, containing cmRNA bearing lipoplexes, were developed for the incorporation of a therapeutic component into injectable calcium phosphate cements (CPC). Due to the incorporation of PLGA/lipoplex microspheres as a degradable entity, the porosity of the cement phase could additionally be adjusted. This approach of complex nanoparticle incorporation into polymer/cement composites represents a promising example for combining transcript therapy with biomechanical engineering.

A reformative shear precipitation procedure for the fabrication of vancomycin-loaded poly(lactide-co-glycolide) microspheres

This study reports the encapsulation of vancomycin, as a model hydrophilic drug, into poly(lactide-co-glycolide) microspheres using a novel reformative shear precipitation procedure. In contrast to the external aqueous phase used in the conventional microencapsulation technique based on emulsion solvent evaporation/extraction, the reformative shear precipitation procedure explored in this study uses a shear medium composed of glycerol as the viscous medium and ethanol as polymer antisolvent, which is relatively immiscible with the hydrophilic drug. This limits drug diffusion and leads to rapid microsphere solidification, which allows a large proportion of the hydrophilic drug to be encapsulated within the microspheres. The influence of various processing parameters, including polymer concentration, volume ratio of ethanol to glycerol in the shear medium, volume of aqueous drug solution, initial drug loading, and injecting rate of the drug-polymer emulsion, on the encapsulation efficiency and characteristics of resulting microspheres were investigated. The morphology and release characteristics, as well as mechanical, in vitro and in vivo behaviour of vancomycin-loaded poly(lactide-co-glycolide) microspheres prepared using the novel procedure were also investigated. The results demonstrated that the reformative shear precipitation procedure could achieve the loading of hydrophilic drugs into poly(lactide-co-glycolide) microspheres with high encapsulation efficiency, and the success of the procedure was largely influenced by the volume ratio of ethanol to glycerol in the shear medium. Vancomycin-loaded poly(lactide-co-glycolide) microspheres prepared using this procedure demonstrated favourable mechanical characteristics, antibacterial activity, and in vivo degradation behaviour which suggested their suitability for use as a sustained delivery system.

Formulation and evaluation of controlled release ethylcellulose and polyethylene glycol microspheres containing metoprolol tartrate

Metoprolol tartrate is rapidly absorbed from both gastric and intestinal regions, after oral administration. To retard the release rate of the metoprolol tartrate, microspheres were prepared with varying concentrations of a mixture containing ethylcellulose and polyethylene glycol-6000. The prepared microspheres were evaluated for various physicochemical characteristics and in vitro drug release. The percent yield of microspheres was in the range of 75.2-87.3%. The particle size of microspheres was found to be in the range of 73.2-85.5 μm. Fourier transform-infrared spectral analysis and differential scanning calorimetry concluded the absence of any interaction between the drug and the carriers. The release time profile of metoprolol tartrate from microspheres in 0.1 N hydrochloric acid solution was to the extent of 33.4-60.2%. The complete release of metoprolol tartrate occurred from MPT-3 and MPT-4 in phosphate buffer solution (pH 7.4) within 8 and 7 h, respectively, whereas the incomplete release (72.3%) occurred from MPT-1. Nearly, the complete release (98.5%) of metoprolol occurred from MPT-2 in 10 h. Formulation MPT-2 would be a preferred formulation. The release of metoprolol involves diffusion rate limited (R² = 0.9865) as a mechanism from drug release. The prepared microspheres of metoprolol tartrate eliminate the need for multiple dosing and provide patient compliance.

Sustained release of hydrophilic drug from polyphosphazenes/poly(methyl methacrylate) based microspheres and their degradation study

Drug delivery system is referred as an approach to deliver the therapeutic agents to the target site safely in order to achieve the maximum therapeutic effects. In this perspective, synthesis of three new polyphosphazenes and their blend fabrication system with poly(methyl methacrylate) is described and characterized with (1)H NMR, (31)P NMR, GPC and DSC. Furthermore, these novel blends were used to fabricate microspheres and evaluated for sustain release of hydrophilic drug (aspirin as model drug). Microspheres of the two blends showed excellent encapsulation efficacy (about 93%), controlled burst release (2.3% to 7.93%) and exhibited sustain in vitro drug release (13.44% to 32.77%) up to 218 h. At physiological conditions, the surface degradation of microspheres and diffusion process controlled the drug release sustainability. Furthermore, it was found that the degree of porosity was increased with degradation and the resulting porous network was responsible for water retention inside the microspheres. The percentage water retention was found to be interrelated with degradation time and percentage drug release.