Unintended potential impact of perfect sink conditions on PLGA degradation in microparticles

Assessment of In Vitro Release Testing Methods for Colloidal Drug Carriers: The Lack of Standardized Protocols

Although colloidal carriers have been in the pipeline for nearly four decades, standardized methods for testing their drug-release properties remain to be established in pharmacopeias. The in vitro assessment of drug release from these colloidal carriers is one of the most important parameters in the development and quality control of drug-loaded nano- and microcarriers. This lack of standardized protocols occurs due to the difficulties encountered in separating the released drug from the encapsulated one. This review aims to compare the most frequent types of release testing methods (i.e., membrane diffusion techniques, sample and separate methods and in situ detection techniques) in terms of the advantages and disadvantages of each one and of the key parameters that influence drug release in each case.

Surface analysis of sequential semi-solvent vapor impact (SAVI) for studying microstructural arrangements of poly(lactide-co-glycolide) microparticles

Biodegradable poly(lactide-co-glycolide) (PLGA) microparticles have been used as long-acting injectable (LAI) drug delivery systems for more than three decades. Despite extensive use, few tools have been available to examine and compare the three-dimensional (3D) structures of microparticles prepared using different compositions and processing parameters, all collectively affecting drug release kinetics. Surface analysis after sequential semi-solvent impact (SASSI) was conducted by exposing PLGA microparticles to different semi-solvent in the liquid phase. The use of semi-solvent liquids presented practical experimental difficulties, particularly in observing the same microparticles before and after exposure to semi-solvents. The difficulties were overcome by using a new sequential semi-solvent vapor (SSV) method to examine the morphological changes of the same microparticles. The SASSI method based on SSV is called surface analysis of semi-solvent vapor impact (SAVI). Semi-solvents are the solvents that dissolve PLGA polymers depending on the polymer's lactide:glycolide (L:G) ratio. A sequence of semi-solvents was used to dissolve portions of PLGA microparticles in an L:G ratio-dependent manner, thus revealing different structures depending on how microparticles were prepared. Exposing PLGA microparticles to semi-solvents in the vapor phase demonstrated significant advantages over using semi-solvents in the liquid phase, such as in control of exposure conditions, access to imaging, decreasing the time for sequential exposure of semi-solvents, and using the same microparticles. The SSV approach for morphological analysis provides another tool to enhance our understanding of the microstructural arrangement of PLGA polymers. It will improve our comprehensive understanding of the factors controlling drug release from LAI formulations based on PLGA polymers.

Biopredictive tools for the development of injectable drug products

INTRODUCTION

Biopredictive release tests are commonly used in the evaluation of oral medicines. They support decision-making in formulation development and allow predictions of the expected in-vivo performances. So far, there is limited experience in the application of these methodologies to injectable drug products.

AREAS COVERED

Parenteral drug products cover a variety of dosage forms and administration sites including subcutaneous, intramuscular, and intravenous injections. In this area, developing biopredictive and biorelevant methodologies often confronts us with unique challenges and knowledge gaps. Here, we provide a formulation-centric approach and explain the key considerations and workflow when designing biopredictive assays. Also, we outline the key role of computational methods in achieving clinical relevance and put all considerations into context using liposomal nanomedicines as an example.

EXPERT OPINION

Biopredictive tools are the need of the hour to exploit the tremendous opportunities of injectable drug products. A growing number of biopharmaceuticals such as peptides, proteins, and nucleic acids require different strategies and a better understanding of the influences on drug absorption. Here, our design strategy must maintain the balance of robustness and complexity required for effective formulation development.

Drug formulations for localized treatment of Human Papillomavirus-induced lesions

BACKGROUND

The human papillomavirus (HPV) is responsible for over 90% of all cervical cancer cases. The use of vaginal gels is often indicated for local vaginal drug delivery. Previous studies have shown that Thymus vulgaris essential oil (TEO) exhibits anticancer properties besides antifungal and antibacterial properties. Its activity derives from a specific increase in free radicals and oxidative stress caused in cancer cells. Furthermore, mitoxantrone (MTX), an anthracenedione and C₈, an acridine orange derivative, were shown to inhibit the growth of the cervical cancer cell line HeLa.

RESULTS

The results showed that TEO + C₈ is the most promising formulation in terms of viscosity and osmolality properties in vaginal fluid simulant (VFS). The combined action of TEO with the compound's MTX and C₈ resulted in HeLa cell viability reduction compared with the effect obtained with the individual formulations containing each one of the compounds.

CONCLUSIONS

The formulation TEO + C₈ holds promise in terms of cost-benefit and topical application of the active compound for the HeLa cells.

Development and characterization of composition-equivalent formulations to the Sandostatin LAR® by the solvent evaporation method

Sandostatin long-acting release® (SLAR) is a long-acting injectable somatostatin analogue formulation composed of octreotide encapsulated in glucose-initiated poly(lactic-co-glycolic acid) (PLGA) microspheres. Despite the end of patent protection, SLAR remains resistant to generic competition likely due to complexity of production process, the uniqueness of the glucose star polymer, and the instability of octreotide in the formulation. Here, we describe development of glucose-PLGA-based composition-equivalent to SLAR formulations prepared by double emulsion-solvent evaporation method and the effect of variations in encapsulation variables on release kinetics and other formulation characteristics. The following encapsulation variables were adjusted at constant theoretical loading of 7.0% peptide: PLGA concentration, pH of inner water phase, and stirring rate. After final drying, the microspheres were examined with and without annealing at 50 °C under vacuum for 3 days. The loading and encapsulation efficiency (EE) of octreotide acetate, manufacturing yield, and in vitro drug release kinetics in PBStc (10 mM phosphate-buffered saline (PBS) with 1% triethyl citrate and 0.02% sodium azide at pH 7.4) were determined by UPLC. The in vitro release and acylation kinetics of octreotide for the solvent evaporation formulations prepared were similar to SLAR although the initial burst was slightly higher. Key formulation steps identified to maximize microsphere yield and minimize residual solvent and initial burst release included (a) addition of acetic acid to the peptide before preparation and (b) annealing the microspheres under vacuum after drying. Controlled release octreotide formulations prepared and investigated in this study could provide a better understanding of the effect of production variables on release performance and supply information useful for making progress in manufacturing of SLAR generic equivalents.

In-vitro drug release testing of parenteral formulations via an agarose gel envelope to closer mimic tissue firmness

Current in vitro drug-release testing of the sustained-release parenterals represents the in vivo situation insufficiently. In this work, a thin agarose hydrogel layer surrounding the tested dosage form was proposed to mimic the tissue. The method was applied on implantable formulations of different geometries (films, microspheres, and cylindrical implants); prepared from various polymers (several Resomer® grades or ethyl cellulose) and loaded with different model drugs: flurbiprofen, lidocaine or risperidone. The hydrogel layer did not possess any retarding effect on the released drug and acted as a physical restriction to swelling and/or plastic deformation of the tested dosage forms. This led to a different surface area available for drug-release compared with testing in release medium alone and correspondingly to significantly different release profiles of the majority of the formulations obtained between the two methods (e.g. t50% = 18 days in pure release medium vs. t50% = 26 days in gel-setup for risperidone loaded Resomer® 503 H films or t50% = 7 days vs. t50% = 19 days for risperidone loaded Resomer® 503 H microspheres). The limited space for swelling and the rigidity of the agarose gel might mimic the tight encapsulation of the dosage form in the tissue better than the conventional liquid medium.

In-situ forming gels containing fluorometholone-loaded polymeric nanoparticles for ocular inflammatory conditions

Thermosensitive gels have been developed and optimized in such a way that they become gels at corneal temperature and with a viscosity that allows the adequate release of the Fluorometholone (FMT)-loaded PLGA nanoparticles (NPs) in order to improve ocular anti-inflammatory efficacy against a commercial formulation. It has been shown that gels avoid burst release of the drug in the first hours with a slow and increasing profile after administration. NPs have maintained their average size and spherical shape within the gels as confirmed by transmission electron microscopy (TEM). In turn, the in-situ gelling of the formulations allows the administration in eye drops dosage form due to its state of sol at temperatures below 25 °C. Ocular tolerance studies have shown that no formulation causes eye irritation. The administration of the developed formulations has improved the precorneal residence time reflected in the ocular bioavailability, where deep tissues as aqueous humour and crystalline were reached. In conclusion, the use of thermosensitive gels for the topical application of NPs has demonstrated their effectiveness in the acute and preventive treatment of ocular inflammatory conditions.

Insight into Nanoscale Network of Spray-Dried Polymeric Particles: Role of Polymer Molecular Conformation

Poly(lactic- co-glycolic acid) (PLGA) microparticles represent a promising formulation approach for providing steady pharmacokinetic/pharmacodynamic profiles of therapeutic drugs for a long period. Understanding and controlling the supramolecular structure of PLGA microparticles at a molecular level is a prerequisite for the rational design of well-controlled, reproducible sustained-release profiles. Herein, we reveal the role of PLGA molecular conformation in particle formation and drug release. The nanoscale network of PLGA microparticles spray-dried using the solvents with distinct polarities was investigated by using NMR and neutron scattering. By employing chemometric method, we further demonstrate the evolution of nanoscale networks in spray-dried PLGA microparticles upon water absorption. Our results indicate that PLGA molecules form more chain entanglements during spray drying when using the solvents with low polarity, where PLGA molecule adopts a more flexible, extended conformation, resulting in the network being more resistant to water absorption in spray-dried PLGA microparticles. This work underlines the role of PLGA molecular conformation in controlling formation and evolution of nanoscale network of spray-dried PLGA microparticles and will have important consequences in achieving customized drug release from the PLGA microparticles.

Characterization and Preliminary Biological Evaluation of 3D-Printed Porous Scaffolds for Engineering Bone Tissues

Some basic requirements of bone tissue engineering include cells derived from bone tissues, three-dimensional (3D) scaffold materials, and osteogenic factors. In this framework, the critical architecture of the scaffolds plays a crucial role to support and assist the adhesion of the cells, and the subsequent tissue repairs. However, numerous traditional methods suffer from certain drawbacks, such as multi-step preparation, poor reproducibility, high complexity, difficulty in controlling the porous architectures, the shape of the scaffolds, and the existence of solvent residue, which limits their applicability. In this work, we fabricated innovative poly(lactic-co-glycolic acid) (PLGA) porous scaffolds, using 3D-printing technology, to overcome the shortcomings of traditional approaches. In addition, the printing parameters were critically optimized for obtaining scaffolds with normal morphology, appropriate porous architectures, and sufficient mechanical properties, for the accommodation of the bone cells. Various evaluation studies, including the exploration of mechanical properties (compressive strength and yield stress) for different thicknesses, and change of structure (printing angle) and porosity, were performed. Particularly, the degradation rate of the 3D scaffolds, printed in the optimized conditions, in the presence of hydrolytic, as well as enzymatic conditions were investigated. Their assessments were evaluated using the thermal gravimetric analyzer (TGA), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). These porous scaffolds, with their biocompatibility, biodegradation ability, and mechanical properties, have enabled the embryonic osteoblast precursor cells (MC3T3-E1), to adhere and proliferate in the porous architectures, with increasing time. The generation of highly porous 3D scaffolds, based on 3D printing technology, and their critical evaluation, through various investigations, may undoubtedly provide a reference for further investigations and guide critical optimization of scaffold fabrication, for tissue regeneration.

The effect of mechanical loads on the degradation of aliphatic biodegradable polyesters

Aliphatic biodegradable polyesters have been the most widely used synthetic polymers for developing biodegradable devices as alternatives for the currently used permanent medical devices. The performances during biodegradation process play crucial roles for final realization of their functions. Because physiological and biochemical environment in vivo significantly affects biodegradation process, large numbers of studies on effects of mechanical loads on the degradation of aliphatic biodegradable polyesters have been launched during last decades. In this review article, we discussed the mechanism of biodegradation and several different mechanical loads that have been reported to affect the biodegradation process. Other physiological and biochemical factors related to mechanical loads were also discussed. The mechanical load could change the conformational strain energy and morphology to weaken the stability of the polymer. Besides, the load and pattern could accelerate the loss of intrinsic mechanical properties of polymers. This indicated that investigations into effects of mechanical loads on the degradation should be indispensable. More combination condition of mechanical loads and multiple factors should be considered in order to keep the degradation rate controllable and evaluate the degradation process in vivo accurately. Only then can the degradable devise achieve the desired effects and further expand the special applications of aliphatic biodegradable polyesters.

Preparation and evaluation of posaconazole-loaded enteric microparticles in rats

OBJECTIVES

Posaconazole (POS) is an antifungal compound which has a low oral bioavailability. The aim of this study was to prepare POS enteric microparticles to enhance its oral bioavailability.

METHODS

POS enteric microparticles were prepared with hypromellose acetate succinate (HPMCAS) via the spray drying method. The solvent mixtures of acetone and ethanol used in the preparation of the microparticles were optimized to produce the ideal POS enteric microparticles. Multivariate data analysis using a principal component analysis (PCA) was used to find the relationship among the HPMCAS molecular characteristics, particle properties and drug release kinetics from the spray dried microparticles.

KEY FINDINGS

The optimal spray solvent mixtures were critical to produce the POS microparticles with the defined polymer entanglement index, drug surface enrichment, particle size and drug loading. The HPMCAS molecular characteristics affected the microscopic connectivity and diffusivity of polymer matrix and eventually influenced the drug release behavior, and enhanced the bioavailability of POS.

CONCLUSIONS

These studies suggested that the selection of suitable solvent mixtures of acetone and ethanol used in the spray drying of the microparticles was quite important to produce the entangled polymer structures with preferred polymer molecular properties of polymer coiling, overlap concentration and entanglement index. Additional studies on particle size and surface drug enrichment eventually produced HPMCAS-based enteric microparticles to enhance the oral bioavailability of POS.

Phenobarbital loaded microemulsion: development, kinetic release and quality control

ABSTRACT This study aimed to obtain and characterize a microemulsion (ME) containing phenobarbital (PB). The PB was incorporated in the proportion of 5% and 10% in a microemulsion system containing Labrasol(r), ethanol, isopropyl myristate and purified water. The physicochemical characterization was performed and the primary stability of the ME was evaluated. An analytical method was developed using spectrophotometry in UV = 242 nm. The kinetics of the in vitro release (Franz model) of the ME and the emulsion (EM) containing PB was evaluated. The incorporation of PB into ME at concentrations of 5 and 10% did not change pH and resistance to centrifugation. There was an increase in particle size, a decrease of conductivity and a change in the refractive index in relation to placebo ME. The ME remained stable in preliminary stability tests. The analytical method proved to be specific, linear, precise, accurate and robust. Regarding the kinetics of the in vitro release, ME obtained an in vitro release profile greater than the EM containing PB. Thus, the obtained ME has a potential for future transdermal application, being able to compose a drug delivery system for the treatment of epilepsy.

Controlled initial surge despite high drug fraction and high solubility

Potential connections between release profiles and solvent evaporation rates alongside polymer chemistry were elucidated for the release of tetracycline hydrochloride from two different poly (d, l-lactide-co-glycolide) (PLGA) film matrices containing high drug fractions (50%, 30%, and 15%), and prepared at two distinct solvent evaporation rates. At highest tetracycline concentrations (50%), (i) the early release rates were ≤0.5 μg/min in all cases; (ii) release was linear from systems fabricated with lower lactic content and slower solvent evaporation rate and bimodal from systems fabricated with higher lactic content and faster evaporation rate; (iii) surface fractions covered by the drug were similar at both evaporation rates for 85:15 PLGA but very different for 50:50 PLGA, leading to unexpectedly reduced early release from 50:50 PLGA than from 85:15 PLGA when both the matrices were fabricated using a slower evaporation rate. These features remained unaffected in case of low drug concentration. Results suggested that during the formation of the drug-polymer microstructure, the combined effect of polymer chemistry and solvent evaporation rate sets apart the surface characteristics and the initial release profiles of systems containing high drug fraction, and an appropriate combination of these parameters may be utilized to control the early stage of drug release.

Liver-targeting Resibufogenin-loaded poly(lactic-co-glycolic acid)-D-α-tocopheryl polyethylene glycol 1000 succinate nanoparticles for liver cancer therapy

Liver cancer remains a major problem around the world. Resibufogenin (RBG) is a major bioactive compound that was isolated from Chansu (also called toad venom or toad poison), which is a popular traditional Chinese medicine that is obtained from the skin secretions of giant toads. RBG has strong antitumor effects, but its poor aqueous solubility and its cardiotoxicity have limited its clinical use. The aim of this study was to formulate RBG-loaded poly(lactic-co-glycolic acid) (PLGA)-d-α-tocopheryl polyethylene glycol 1000 succinate nanoparticle (RPTN) to enhance the treatment of liver cancer. RPTN, RBG-loaded PLGA nanoparticle (RPN), and RBG/coumarin-6-loaded PLGA-d-α-tocopheryl polyethylene glycol 1000 succinate nanoparticle (RCPTN) were prepared. The cellular uptake of RCPTN by HepG2 and HCa-F cells was analyzed using confocal laser scanning microscopy. Apoptosis was induced in HepG2 cells by RPTN, RBG solution (RS), and 5-fluorouracil solution (used as the negative controls), as assayed using flow cytometry. LD₅₀ (median lethal dose) values were determined for RS and RPTN, and the liver-targeting properties were determined for RCPTN in intravenously injected mice. A pharmacokinetic study was conducted in rats, and the in vivo therapeutic effects of RPTN, RPN, and RS were examined in a mouse tumor model. The results showed that RCPTN simultaneously delivered both coumarin-6 and RBG into HepG2 and HCa-F cells. The ratio of apoptotic cells was increased in the RPTN group. The LD₅₀ for RPTN was 2.02-fold higher than the value for RS. Compared to RS, RPTN and RPN both showed a significant difference in vivo not only in the pharmacodynamic study but also in anticancer efficacy, and RPTN performed much better than RPN. The detection indexes for drug concentration and fluorescence inversion microscopy images both demonstrated that RCPTN was much better at targeting the liver than RS. The liver-targeting RPTN, which displayed enhanced pharmacological effects and decreased toxicity for the loaded drug RBG, is therefore a promising intravenous dosage form that may be useful in the treatment of liver cancer.

A Promising Emodin-Loaded Poly (Lactic-Co-Glycolic Acid)-d-α-Tocopheryl Polyethylene Glycol 1000 Succinate Nanoparticles for Liver Cancer Therapy

PURPOSE

Emodin (EMO) has multi-targets and multi-way antitumor effect, which was limited by the instability and poor solubility of EMO. The aim of this study was to formulate EMO-loaded poly (lactide-co-glycolide)-d-α-tocopheryl polyethylene glycol 1000 succinate (PLGA-TPGS) nanoparticles (EPTN) to increase the liver targeting of EMO for cancer therapy.

METHODS

EMO/coumarin-6-loaded PLGA-TPGS nanoparticles (ECPTN) and EMO-loaded PLGA nanoparticles (EPN) were also prepared as comparison. The cellular uptake of ECPTN by HepG2 and HCa-F cells was investigated using Confocal laser scanning microscopy. The apoptosis of HepG2 cells handled with EPTN was assayed by flow cytometry. The liver targeting property of ECPTN in mice was evaluated using the drug concentration determined by RP-HPLC and the freezing slices were investigated via fluorescence inversion microscopy. The blood samples were obtained from vein intubation to illustrate the pharmacokinetics process of EPTN. The tumor-bearing mice model was established to elucidate the in vivo therapeutic effect of EPTN.

RESULTS

The results demonstrated that ECPTN could be internalized by HepG2 and HCa-F cells respectively. The ratio of apoptosis cells was increased after dealing with EPTN. The detection indexes of drug concentration and fluorescence inversion microscopy images indicated ECPTN had an excellent effect on liver targeting property than EMO solutions (EMS). The pharmacokinetics process of EPTN showed obvious sustained-release effect than EMS. Compared with EPN, the in vivo antitumor activity of EPTN against tumor cells were better.

CONCLUSIONS

In conclusion, EPTN could be used in the treatment of liver cancer acted as a kind of promising intravenous dosage forms.

Mechanistic analysis of PLGA/HPMC-based in-situ forming implants for periodontitis treatment

In-situ forming implant formulations based on poly(lactic-co-glycolic acid) (PLGA), acetyltributyl citrate (ATBC), minocycline HCl, N-methyl pyrrolidone (NMP) and optionally hydroxypropyl methylcellulose (HPMC) were prepared and thoroughly characterized in vitro. This includes electron paramagnetic resonance (EPR), nuclear magnetic resonance ((1)H NMR), mass change and drug release measurements under different conditions, optical microscopy, size exclusion chromatography (SEC) as well as antibacterial activity tests using gingival crevicular fluid samples from periodontal pockets of periodontitis patients. Based on these results, deeper insight into the physico-chemical phenomena involved in implant formation and the control of drug release could be gained. For instance, the effects of adding HPMC to the formulations, resulting in improved implant adherence and reduced swelling, could be explained. Importantly, the in-situ formed implants effectively hindered the growth of bacteria present in the patients' periodontal pockets. Interestingly, the systems were more effectively hindering the growth of pathogenic bacterial strains (e.g., Fusobacterium nucleatum) than that of strains with a lower pathogenic potential (e.g., Streptococcus salivarius). In vivo, such a preferential action against the pathogenic bacteria can be expected to give a chance to the healthy flora to re-colonize the periodontal pockets.

Drug release from semisolid dosage forms: a comparison of two testing methods

The aim of the present work was to extend our previous in-vitro drug release studies using semisolid dermatological bases with non-impregnated cellulose acetate membranes. A comparison of the performances of two apparatuses, the more commonly used Franz cell and the new modified USP (mini paddle with ointment holding cell) systems were applied to this work. Five different semisolid as well as two marketed preparations containing 1% diclofenac sodium were used. Complex, slightly non-linear release curves indicating sink conditions were found. This was explained by the co-diffusion of excipients modifying the characteristics of the membrane and the receiving medium dynamically. Although our test model is, as a rule, not suitable to establish an in-vivo-in-vitro correlation, good qualitative as well as quantitative correlations were found within some types of dermatological bases. The correlation between the results of the two in-vitro methods also depends on the type of semisolids studied. The release curve characteristics and the amount of diclofenac sodium released at 6 h were measured. Their repeatability and reproducibility were calculated. The slopes and Q-values were correlated with in-vivo data. In general, the modified USP method provided more precise results than the Franz cell method.