Principles of encapsulating hydrophobic drugs in PLA/PLGA microparticles

Automated PET-RAFT Polymerization Towards Pharmaceutical Amorphous Solid Dispersion Development

In pharmaceutical oral drug delivery development, about 90% of drugs in the pipeline have poor aqueous solubility leading to severe challenges with oral bioavailability and translation to effective and safe drug products. Amorphous solid dispersions (ASDs) have been utilized to enhance the oral bioavailability of poorly soluble active pharmaceutical ingredients (APIs). However, a limited selection of regulatory-approved polymer excipients exists for the development and further understanding of tailor-made ASDs. Thus, a significant need exists to better understand how polymers can be designed to interact with specific API moieties. Here, we demonstrate how an automated combinatorial library approach can be applied to the synthesis and screening of polymer excipients for the model drug probucol. We synthesized a library of 25 random heteropolymers containing one hydrophilic monomer (2-hydroxypropyl acrylate (HPA)) and four hydrophobic monomers at varied incorporation. The performance of ASDs made by a rapid film casting method was evaluated by dissolution using ultra-performance liquid chromatography (UPLC) sampling at various time points. This combinatorial library and rapid screening strategy enabled us to identify a relationship between polymer hydrophobicity, monomer hydrophobic side group geometry, and API dissolution performance. Remarkably, the most effective synthesized polymers displayed slower drug release kinetics compared to industry standard polymer excipients, showing the ability to modulate the drug release profile. Future coupling of high throughput polymer synthesis, high throughput screening (HTS), and quantitative modeling would enable specification of designer polymer excipients for specific API functionalities.

Biodegradable Nanocomposite Microcapsules for Controlled Release of Urea

Urea is the most used fertilizer around the world as the main source of nitrogen to soil and plants. However, the administration of nitrogen dosage is critical, as its excess can be harmful to the environment. Therefore, the encapsulation of urea to achieve control on its release rates has been considered in several areas. In this work, encapsulation of urea by biodegradable polymer poly(3-hydroxybutyrate) (PHB) and its nanocomposites, namely PHB/MMT and PHB/OMMT, producing microcapsules by emulsion method is carried out. MMT and OMMT refer to Brazilian clays in a natural state and organophilized, respectively. In addition, the microcapsules are thus prepared to have their physicochemical characteristics investigated, then tested for biodegradation. Increment of microcapsules’ crystallinity due to the increased amount of poly(vinylacetate) (PVA), as emulsifier agent in the continuous phase, was confirmed by X-ray diffractometry (XRD) and atomic force microscopy (AFM). The presence of urea within microcapsules was verified by XRD, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The soil biodegradation assessments showed that PHB/OMMT microcapsules present higher degradation rates in sandy soils. The overall results suggest that the composites performed better than neat PHB and are very promising; moreover, PHB/OMMT microcapsules proved to be the best candidate for the controlled-release of urea in soils.

Key Factor Study for Generic Long-Acting PLGA Microspheres Based on a Reverse Engineering of Vivitrol®

The FDA (U.S. Food and Drug Administration) has approved only a negligible number of poly(lactide-co-glycolide) (PLGA)-based microsphere formulations, indicating the difficulty in developing a PLGA microsphere. A thorough understanding of microsphere formulations is essential to meet the challenge of developing innovative or generic microspheres. In this study, the key factors, especially the key process factors of the marketed PLGA microspheres, were revealed for the first time via a reverse engineering study on Vivitrol^® and verified by the development of a generic naltrexone-loaded microsphere (GNM). Qualitative and quantitative similarity with Vivitrol^®, in terms of inactive ingredients, was accomplished by the determination of PLGA. Physicochemical characterization of Vivitrol^® helped to identify the critical process parameters in each manufacturing step. After being prepared according to the process parameters revealed by reverse engineering, the GNM demonstrated similarity to Vivitrol^® in terms of quality attributes and in vitro release (f₂ = 65.3). The research on the development of bioequivalent microspheres based on the similar technology of Vivitrol^® will benefit the development of other generic or innovative microspheres.

Doxycycline hyclate-loaded in situ forming gels composed from bleached shellac, Ethocel, and Eudragit RS for periodontal pocket delivery

Polymeric material plays an important role as a matrix former in the modulation of drug release of antimicrobial-loaded in situ forming gel (ISG) for efficient periodontitis treatment. This study was conducted to compare three polymers, namely bleached shellac (BS), Ethocel (EC) and Eudragit RS (ERS), as matrix formers of doxycycline hyclate (DH)-loaded solvent exchange-induced ISG. All prepared ISGs, except 25% EC ISG, exhibited the Newtonian flow behaviour. Transformation from solution into matrix-like was achieved rapidly within 5 min. Increasing the amount of these polymers extended the release of DH. DH-loaded EC and ERS ISG systems exhibited high antimicrobial activity, and all ISGs were effective in inhibiting the growth of Staphylococcus aureus, Escherichia coli, Streptococcus mutans, Porphyromonas gingivalis and Candida albicans. By comparison, the DH-loaded ERS ISG, through the solvent exchange mechanism, was found to be ease in injection with low viscosity and sustained the release with higher concentration, meanwhile, it also exhibited interesting in vitro degradability and antimicrobial activities. Therefore, the DH-loaded ERS ISG exhibited a potential use for localized periodontal drug delivery system for the treatment periodontitis.

A comparison of acyl-moieties for noncovalent functionalization of PLGA and PEG-PLGA nanoparticles with a cell-penetrating peptide

Noncovalent functionalization with acylated cell-penetrating peptides achieves an efficient cellular uptake of PLGA and PEG-PLGA nanoparticles.

Stimulus-cleavable chemistry in the field of controlled drug delivery

This review comprehensively summarises stimulus-cleavable linkers from various research areas and their cleavage mechanisms, thus provides an insightful guideline to extend their potential applications to controlled drug release from nanomaterials.

The influence of nanodelivery systems on the antioxidant activity of natural bioactive compounds

Bioactive compounds may lose their antioxidant activity (e.g., phenolic compounds) at elevated temperatures, enhanced oxidative conditions and severe light exposures so they should be protected by various strategies such as nano/microencapsulation methods. Encapsulation technology has been employed as a proper method for using antioxidant ingredients and to provide easy dispersibility of antioxidants in all matrices including food and pharmaceutical products. It can improve the food fortification processes, release of antioxidant ingredients, and extending the shelf-life and bioavailability of them when ingested in the intestine. In this study, our main goal is to have an overview of the influence of nanoencapsulation on the bioactivity and bioavailability, and cellular activities of antioxidant ingredients in different delivery systems. Also, the effect of encapsulation process conditions, storage conditions, carrier wall materials, and release profile on the antioxidant activity of different natural bioactives are explained. Finally, analytical techniques for measuring antioxidant activity of nanoencapsulated ingredients will be covered.

The effect of polymer blends on initial release regulation and in vitro-in vivo relationship of peptides loaded PLGA-Hydrogel Microspheres

The aim of this study was to resolve the lag time problem for peptides loaded PLGA-Hydrogel Microspheres (PLGA-gel-Ms) by blending low molecular PLGA (Mw. 1 kDa) into PLGA (Mw. 10 kDa) as an intrinsic porogen, and then assess the in vitro-in vivo relationship (IVIVR). Here, Goserelin acetate (GOS) was chosen as the model peptides. When compared to additional types of porogen, the intrinsic porogen avoided impurities remaining and protected the bioactivities of the peptides. By adding 10% PLGA (Mw. 1 kDa), the lag time was eliminated both in vitro and in vivo with a desirable EE (97.04% ± 0.51%). The release mechanisms were found to be: a) initial GOS release mainly controlled by pores diffusion and b) autocatalysis of PLGA (Mw. 1 kDa) which increased the quantity of aqueous pores, as revealed by SEM images. To solve the challenges caused by multiphasic release profiles, for the first time the Segmented phases IVIVR were proposed and developed, and showed improved linear fitting effects and supported the proposed release mechanisms. The application of PLGA blends could provide a new insight into PLGA microsphere initial release rate regulation.

Recent advances in the formulation of PLGA microparticles for controlled drug delivery

Polymeric microparticles (MPs) are recognized as very popular carriers to increase the bioavailability and bio-distribution of both lipophilic and hydrophilic drugs. Among different kinds of polymers, poly-(lactic-co-glycolic acid) (PLGA) is one of the most accepted materials for this purpose, because of its biodegradability (due to the presence of ester linkages that are degraded by hydrolysis in aqueous environments) and safety (PLGA is a Food and Drug Administration (FDA)-approved compound). Moreover, its biodegradability depends on the number of glycolide units present in the structure, indeed, lower glycol content results in an increased degradation time and conversely a higher monomer unit number results in a decreased time. Due to this feature, it is possible to design and fabricate MPs with a programmable and time-controlled drug release. Many approaches and procedures can be used to prepare MPs. The chosen fabrication methodology influences size, stability, entrapment efficiency, and MPs release kinetics. For example, lipophilic drugs as chemotherapeutic agents (doxorubicin), anti-inflammatory non-steroidal (indomethacin), and nutraceuticals (curcumin) were successfully encapsulated in MPs prepared by single emulsion technique, while water-soluble compounds, such as aptamer, peptides and proteins, involved the use of double emulsion systems to provide a hydrophilic compartment and prevent molecular degradation. The purpose of this review is to provide an overview about the preparation and characterization of drug-loaded PLGA MPs obtained by single, double emulsion and microfluidic techniques, and their current applications in the pharmaceutical industry.Graphic abstract.

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.

Interfacial tension effects on the properties of PLGA microparticles

Many types of long-acting injectables, including in situ forming implants, preformed implants, and polymeric microparticles, have been developed and ultimately benefited numerous patients. The advantages of using long-acting injectables include greater patient compliance and more steady state drug plasma levels for weeks and months. However, the development of long-acting polymeric microparticles has been hampered by the lack of understanding of the microparticle formation process, and thus, control of the process. Of the many parameters critical to the reproducible preparation of microparticles, the interfacial tension (IFT) effect is an important factor throughout the process. It may influence the droplet formation, solvent extraction, and drug distribution in the polymer matrix, and ultimately drug release kinetics from the microparticles. This mini-review is focused on the IFT effects on drug-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles.

Scaling Laws in the Diffusive Release of Neutral Cargo from Hollow Hydrogel Nanoparticles: Paclitaxel-Loaded Poly(4-vinylpyridine)

We study the nonequilibrium diffusive release of electroneutral molecular cargo encapsulated inside hollow hydrogel nanoparticles. We propose a theoretical model that includes osmotic, steric, and short-range polymer-cargo attractions to determine the effective cargo-hydrogel interaction, u_eff*, and the effective diffusion coefficient of the cargo inside the polymer network, D_eff*. Using dynamical density functional theory (DDFT), we investigate the scaling of the characteristic release time, τ_1/2, with the key parameters involved in the process, namely, u_eff*, D_eff*, and the swelling ratio. This effort represents a full study of the problem, covering a broad range of cargo sizes and providing predictions for repulsive and attractive polymer shells. Our calculations show that the release time through repulsive polymer networks scales with q²e^βu_eff*/D_eff* for βu_eff* ≫ 1. In this case, the cargo molecules are excluded from the shell of the hydrogel. For attractive shells, the polymer retains the cargo molecules on its internal surface and its interior, and the release time grows exponentially with the attraction strength. The DDFT calculations are compared to an analytical model for the mean first passage time, which provides an excellent quantitative description of the kinetics for both repulsive and attractive shells without fitting parameters. Finally, we apply the method to reproduce experimental results on the release of paclitaxel from hollow poly(4-vinylpyridine) nanoparticles and find that the slow release of the drug can be explained in terms of the strong binding attraction between the drug and the polymer.

Recent Advances on Antitumor Agents-loaded Polymeric and Lipid-based Nanocarriers for the Treatment of Brain Cancer

In 2016, there were 17.2 million cancer cases, which caused 8.9 million deaths worldwide. Of all cancers, ranked by absolute years of life lost, brain and central nervous system cancers were classified in the nine positions between 2006 and 2016. Glioblastoma is the most common malignant primary brain tumor and comprises 80% of malignant tumours. The therapeutic approach usually involves the combination of surgery and radiotherapy, which present a high risk for the patient and are not always effective in the most aggressive cases. Chemotherapy commonly includes a specific number of cycles given over a set period of time, in which patients receive one drug or a combination of different compounds. The difficulty of access for the neurosurgeon to remove the tumor, the limitation of the penetration of the antitumor agents caused by the blood-brain barrier and the serious adverse effects of these drugs significantly compromise the therapeutic success in these patients. To solve these problems and improve the effectiveness of existing treatments, as well as new molecules, the use of nanotechnology is arousing much interest in the last decades in this field. The use of polymeric and lipid-based nanosystems is one of the best alternatives for the central delivery of drugs due to their versatility, easy manufacturing, biocompatibility, biodegradability and drug targeting, among other virtues. Thus, in this review, we will explore the recent advances in the latest anticancer agent's development associated with polymeric and lipid-based nanocarriers as a novel tools for the management of brain tumors.

Phenomenology of the Initial Burst Release of Drugs from PLGA Microparticles

Poly(lactic-co-glycolic acid) (PLGA) is the most prevalent polymer drug delivery vehicle in use today. There are about 20 commercialized drug products in which PLGA is used as an excipient. In more than half of these formulations, PLGA is used in the form of microparticles (with sizes in the range between 60 nm and 100 μm). The primary role of PLGA is to control the kinetics of drug release toward achieving sustained release of the drug. Unfortunately, most drug-loaded PLGA microparticles exhibit a common drawback: an initial uncontrolled burst of the drug. After 30 years of utilization of PLGA in controlled drug delivery systems, this initial burst drug release still remains an unresolved challenge. In this Review, we present a summary of the proposed mechanisms responsible for this phenomenon and the known factors affecting the burst release process. Also, we discuss examples of recent efforts made to reduce the initial burst release of the drug from PLGA particles.

Fabrication of biodegradable particles with tunable morphologies by the addition of resveratrol to oil in water emulsions

Particles for biomedical applications can be produced by emulsifying biocompatible polymers dissolved in an organic solvent in water. The emulsion is then transferred to an extraction bath that removes the solvent from the dispersed droplets, which leads to polymer precipitation and particle formation. Typically, the particles are smooth and spherical, likely because the droplets remain fluid throughout the solvent extraction process allowing minimization of surface area as the volume decreases. Few modifications to this technique exist that alter the spherical geometry, even though particle performance, from drug delivery to engaging cells of the body, can be tuned with morphology. Here we demonstrate that incorporation of resveratrol, with the aid of ethanol, into the oil phase of an emulsion of poly(lactide-co-glycolide) and dichloromethane in aqueous poly(vinyl alcohol) leads to a crumpled particle morphology. Video microscopy of particle formation revealed that during solvent extraction the droplet crumples in on itself, which does not occur when only ethanol is added to the emulsion. It is unclear why this occurs with resveratrol, but its hydroxyl groups appear to be optimally positioned because removal of the 4' hydroxyl or addition of a 3' hydroxyl resulted in a loss of crumpled particle morphology. We demonstrate that particle morphology can be tuned from that of a crumpled sheet of paper to a deflated sphere by switching out ethanol for a different cosolvent. We quantify the degree of particle deformation with surface area calculated from krypton adsorption isotherms and BET theory and find surface area correlates with resveratrol loading in the particle. Furthermore, spherical particles are achieved when ethyl acetate is used in lieu of dichloromethane and a cosolvent. We propose that during solvent extraction, resveratrol accumulates at the droplet surface where it inhibits polymer chain motion necessary to maintain a spherical geometry and the role of cosolvent is to redistribute resveratrol from the droplet bulk to its surface. This method of producing nonspherical particles extends to polycaprolactone and poly(L-lactic acid) and is compatible with the encapsulation of a hydrophobic fluorescent dye, suggesting hydrophobic bioactive agents could be encapsulated. Taken together, we demonstrate an ability to control morphology of biocompatible polymer particles produced by the widely practiced oil-in-water/solvent extraction protocol via the addition of resveratrol and a cosolvent to the oil phase. The methodology reported is straight forward, and scalable, and expected to be of utility in applications in which a deviation from the default smooth, spherical morphology is desired.

Nanoceria: Metabolic interactions and delivery through PLGA-encapsulation

Cerium oxide nanoparticles (nanoceria) have recyclable antioxidative activity. It has numerous potential applications in biomedical engineering, such as mitigating damage from burns, radiation, and bacterial infection. This mitigating activity is analogous to that property of metabolic enzymes such as superoxide dismutase (SOD) and catalase - scavengers of reactive oxygen species (ROS). Therefore, nanoceria can protect cells from environmental oxidative stress. This therapeutic effect prompted studies of nanoceria and metabolic enzymes as a combination therapy. The activity and structure of SOD, catalase, and lysozyme were examined in the presence of nanoceria. A complementary relationship between SOD and nanoceria motivated the present work, in which we explored a method for simultaneous delivery of SOD and nanoceria. The biocompatibility and tunable degradation of poly(lactic-co-glycolic acid) (PLGA) made it a candidate material for encapsulating both nanoceria and SOD. Cellular uptake studies were conducted along with a cytotoxicity assay. The antioxidative properties of PLGA-nanoceria-SOD particles were verified by adding H₂O₂ to cell culture and imaging with fluorescent markers of oxidative stress. Our results suggest that PLGA is a suitable encapsulating carrier for simultaneous delivering nanoceria and SOD together, and that this combination effectively reduces oxidative stress in vitro.

Nano, micro particulate and cosmetic delivery systems of polylactic acid: A mini review

BACKGROUND

Poly lactic acid and its copolymers are considered to be the preferred substrates for drug delivery devices. Poly lactic acid is a biocompatible, biodegradable and nontoxic polymer. It was approved by Food and Drug Administration and thought to be among the most attractive polymeric candidates intended for controlling drug delivery. It was utilized for the development of devices for the delivery of small molecules, proteins, genes, vaccines, anticancer drugs, and macromolecules.

OBJECTIVES AND METHODS

This manuscript lists the different techniques for synthesizing poly lactic acid-based nano and microparticles such as emulsion-based methods, precipitation-based methods, direct compositing methods, in situ forming micro-particles, and microfluidic technique.

CONCLUSIONS

In addition, it describes the application and use of poly lactic acid in biomedical and cosmetic delivery systems.

Continuous in-line homogenization process for scale-up production of naltrexone-loaded PLGA microparticles

Injectable, long-acting drug delivery systems provide effective drug concentrations in the blood for up to 6 months. Naltrexone-loaded poly(lactide-co-glycolide) (PLGA) microparticles were prepared using an in-line homogenization method. It allows the transition from a laboratory scale to scale-up production. This research was designed to understand how the processing parameters affect the properties of the microparticles, such as microparticle size distributions, surface and internal morphologies, drug loadings, and drug release kinetics, and thus, to control them. The in-line homogenization system was used at high flow rates for the oil- and water-phases, e.g., 100 mL/min and 400 mL/min, respectively, to continuously generate microparticles. A high molecular weight (148 kDa) PLGA at various concentrations was used to generate oil-phases with a range of viscosities and also to compare with a 64 and 79 kDa at a single, high concentration. The uniformity of the microparticles was found to be related to the viscosity of the oil-phase. As the viscosity of the oil-phase increased from 52.6 mPa∙s to 4046 mPa∙s, the span value (a measure of uniformity) increased from 1.24 to 3.1 for the microparticles generated at the homogenization speed of 2000 RPM. Increasing the PLGA concentration from 5.58% to 16.85% showed a corresponding rise in the encapsulation efficiency from 74.0% to 85.8% and drug loading (DL) from 27.4% to 31.7% for the microparticles made with the homogenization speed of 2000 RPM. These increases may be due to a faster shell formulation, enabling PLGA microparticles to entrap more naltrexone into the structure. A higher DL, however, shortened the drug release duration from 56 to 42 days. The changes in morphology of the microparticles during different phases of the in vitro release study were also studied for three types of microparticles made with different PLGA concentrations and molecular weights. As PLGA microparticles went through structural changes, the surface showed raisin-like wrinkled morphologies within the first 10 days. Then, the microparticles swelled to form smooth surfaces. The in-line approach produced PLGA microparticles with a highly reproducible size distribution, DL, and naltrexone release rate.

Biodegradable Flame Retardants for Biodegradable Polymer

To improve sustainability of polymers and to reduce carbon footprint, polymers from renewable resources are given significant attention due to the developing concern over environmental protection. The renewable materials are progressively used in many technical applications instead of short-term-use products. However, among other applications, the flame retardancy of such polymers needs to be improved for technical applications due to potential fire risk and their involvement in our daily life. To overcome this potential risk, various flame retardants (FRs) compounds based on conventional and non-conventional approaches such as inorganic FRs, nitrogen-based FRs, halogenated FRs and nanofillers were synthesized. However, most of the conventional FRs are non-biodegradable and if disposed in the landfill, microorganisms in the soil or water cannot degrade them. Hence, they remain in the environment for long time and may find their way not only in the food chain but can also easily attach to any airborne particle and can travel distances and may end up in freshwater, food products, ecosystems, or even can be inhaled if they are present in the air. Furthermore, it is not a good choice to use non-biodegradable FRs in biodegradable polymers such as polylactic acid (PLA). Therefore, the goal of this review paper is to promote the use of biodegradable and bio-based compounds for flame retardants used in polymeric materials.

Potential Toxicity of Iron Oxide Magnetic Nanoparticles: A Review

The noteworthy intensification in the development of nanotechnology has led to the development of various types of nanoparticles. The diverse applications of these nanoparticles make them desirable candidate for areas such as drug delivery, coasmetics, medicine, electronics, and contrast agents for magnetic resonance imaging (MRI) and so on. Iron oxide magnetic nanoparticles are a branch of nanoparticles which is specifically being considered as a contrast agent for MRI as well as targeted drug delivery vehicles, angiogenic therapy and chemotherapy as small size gives them advantage to travel intravascular or intracavity actively for drug delivery. Besides the mentioned advantages, the toxicity of the iron oxide magnetic nanoparticles is still less explored. For in vivo applications magnetic nanoparticles should be nontoxic and compatible with the body fluids. These particles tend to degrade in the body hence there is a need to understand the toxicity of the particles as whole and degraded products interacting within the body. Some nanoparticles have demonstrated toxic effects such inflammation, ulceration, and decreases in growth rate, decline in viability and triggering of neurobehavioral alterations in plants and cell lines as well as in animal models. The cause of nanoparticles' toxicity is attributed to their specific characteristics of great surface to volume ratio, chemical composition, size, and dosage, retention in body, immunogenicity, organ specific toxicity, breakdown and elimination from the body. In the current review paper, we aim to sum up the current knowledge on the toxic effects of different magnetic nanoparticles on cell lines, marine organisms and rodents. We believe that the comprehensive data can provide significant study parameters and recent developments in the field. Thereafter, collecting profound knowledge on the background of the subject matter, will contribute to drive research in this field in a new sustainable direction.

Meloxicam-loaded solvent exchange-induced in situ forming beta-cyclodextrin gel and microparticle for periodontal pocket delivery

The in situ forming system has attracted attention for periodontitis treatment owing to its sustainable drug release localisation at a periodontal pocket. Given its low aqueous solubility, beta-cyclodextrin (β-CD) may serve as a matrix former of solvent exchange-induced in situ forming gel (ISG) and microparticle (ISM). Meloxicam (Mex)-loaded-β-CD ISG and ISM were prepared using β-CD in dimethyl sulphoxide (ISG) as the internal phase and camellia oil comprising 5% glyceryl monostearate as the external phase (ISM). Mex-loaded β-CD systems comprising 40% β-CD were easily injected via a 24-gauge needle. During solvent exchange with phosphate buffer saline (pH 6.8), the highly concentrated β-CD ISG promoted the phase inversion of β-CD aggregates into matrix-like. Upon exposure to aqueous phase, the ISM system comprising 40% β-CD transformed into microparticles and extended the drug release to 7 days with minimised initial burst release following Fickian diffusion. Moreover, the potential degradability was evident from the high weight loss. High maximum deformation force with high viscous character initiated the slow diffusion rate of the solvent from the ISM system. Therefore, 40% β-CD ISM is a potential local Mex-controlled release system of anti-inflammatory drug for periodontitis treatment.

Rapamycin-PLGA microparticles prevent senescence, sustain cartilage matrix production under stress and exhibit prolonged retention in mouse joints

Osteoarthritis (OA) is a joint disease characterized by progressive damage of articular cartilage and the adjoining subchondral bone. Chondrocytes, the primary cells of the cartilage, have limited regenerative capacity and when they undergo stress due to trauma or with aging, they senesce or become apoptotic. Rapamycin, a potent immunomodulator, has shown promise in OA treatment. It activates autophagy and is known to prevent senescence. However, its clinical translation for OA is hampered due to systemic toxicity as high and frequent doses are required. Here, we have fabricated rapamycin encapsulated poly(lactic-co-glycolic acid) (PLGA) based carriers that induced autophagy and prevented cellular senescence in human chondrocytes. The microparticle (MP) delivery system showed sustained release of the drug for several weeks. Rapamycin microparticles protected in vitro cartilage mimics (micromass cultures) from degradation, allowing sustained production of sGAG, and demonstrated a prolonged senescence preventive effect under oxidative and genomic stress conditions. These microparticles also exhibited a residence time of ∼30 days after intra-articular injections in murine knee joints. Such particulate systems are promising candidates for intra-articular delivery of rapamycin for the treatment of osteoarthritis.

A sensitive in vitro performance assay reveals the in vivo drug release mechanisms of long-acting medroxyprogesterone acetate microparticles

Today, a growing number of subcutaneously administered depot formulations enable continuous delivery of poorly soluble compounds over a longer time period. The modified liberation is considered to be a rate-limiting step in drug absorption and thus impacts therapeutic efficacy and product safety. In the present approach, a mechanism-based pharmacokinetic model of the commercial microparticle formulation depo-subQ provera 104™ (Sauter mean diameter of 5.08 ± 1.63 µm) was established. The model was verified using human pharmacokinetic data from three different clinical trials. Further, the effects of drug release, injection site and patient population on the pharmacokinetic profile were investigated. For this purpose, the drug release was assessed using the novel dispersion releaser technology, whereby a biorelevant medium reflecting major characteristics of the subcutaneous tissue (including ion background, buffer capacity and protein concentration) was used. The established model provided an effective prediction of the key pharmacokinetic parameters, including C_max, T_max and AUC_all. Only in presence of 55% of fetal bovine serum (using a novel simulated subcutaneous interstitial fluid), the release assay was capable to discriminate between microparticles before and after storage.

Predicting the Miscibility and Rigidity of Poly(lactic-co-glycolic acid)/Polyethylene Glycol Blends via Molecular Dynamics Simulations

The addition of polyethylene glycol (PEG) chains to poly(lactic-co-glycolic acid) (PLGA) matrices is extensively used to modulate the biodegradation, drug loading and release, mechanical properties, and chemical stability of the original system. Multiple parameters, including the molecular weight, relative concentration, polarity, and solubility, affect the physicochemical properties of the polymer blend. Here, molecular dynamics simulations with the united-atom 2016H66 force field are used to model the behavior of PLGA and PEG chains and thus predict the overall physicochemical features of the resulting blend. First, the model accuracy is validated against fundamental properties of pure PLGA and PEG samples. In agreement with previous experimental and theoretical observations, the PLGA solubility results to be higher in acetonitrile than in water, with Flory parameters ν_ACN = 0.63 ± 0.01 and ν_W = 0.21 ± 0.02, and the Young’s modulus of PLGA and PEG equal to Y = 2.0 ± 0.43 and 0.32 ± 0.34 GPa, respectively. Next, four PEG/PLGA blending regimes are identified by varying the relative concentrations and molecular weights of the individual polymers. The computational results demonstrate that at low PEG concentrations (<8% w/w), homogeneous blends are generated for both low and high PEG molecular weights. In contrast, at comparable PEG and PLGA concentrations (∼50% w/w), short PEG chains are only partially miscible whereas long PEG chains segregate within the PLGA matrix. This behavior has been confirmed experimentally via differential scanning calorimetry and is in agreement with previous observations. Finally, the computed Young’s modulus of PLGA/PEG blends is observed to decrease with the PEG content returning the lowest values for the partial and fully segregated regimens (Y ≈ 1.3 GPa). This work proposes a computational scheme for predicting the physicochemical properties of PLGA/PEG blends paving the way toward the rational design of polymer mixtures for biomedical applications.

Microencapsulation of luteinizing hormone-releasing hormone agonist in poly (lactic-co-glycolic acid) microspheres by spray-drying

A spray drying technique was developed to prepare injectable and biodegradable poly(lactic-co-glycolic acid) (PLGA) microspheres encapsulating a model luteinizing hormone-releasing hormone agonist (LHRHa)-based peptide, leuprolide. Various spray drying parameters were evaluated to prepare 1-month controlled release formulations with a similar composition to the commercial Lupron Depot® (LD). A single water-in-oil emulsion of aqueous leuprolide/gelatin solution in PLGA 75/25 acid capped (13 kDa Mw) dissolved in methylene chloride (DCM) was spray-dried before washing the microspheres in cold ddH2O and freeze-drying. The spray-drying microencapsulation was characterized by: particle size/distribution (span), morphology, drug/gelatin loading, encapsulation efficiency, and residual DCM and water content. Long-term release was tested over 9 weeks in PBS + 0.02% Tween 80 + 0.02% sodium azide pH 7.4 (PBST) at 37 °C. Several physical-chemical parameters were monitored simultaneously for selected formulations, including: water uptake, mass loss, dry and hydrated glass transition temperature, to help understand the related long-term release profiles and explore the underlying controlled-release mechanisms. Compared with the commercial LD microspheres, some of the in-house spray-dried microspheres presented highly similar or even improved long-term release profiles, providing viable long-acting release (LAR) alternatives to the LD. The in vitro release mechanism of the peptide was shown to be controlled either by kinetics of polymer mass loss or by a second process, hypothesized to involve peptide desorption from the polymer. These data indicate spray drying can be optimized to prepare commercially relevant PLGA microsphere formulations for delivery of peptides, including the LHRHa, leuprolide.

Qualification of Non-Halogenated Organic Solvents Applied to Microsphere Manufacturing Process

As a non-halogenated dispersed solvent, ethyl acetate has been most commonly used for the manufacturing of poly-d,l-lactide-co-glycolide (PLGA) microspheres. However, ethyl acetate-based microencapsulation processes face several limitations. This study was aimed at proposing ethyl formate as an alternative. Evaluated in this study was the solvent qualification of ethyl formate and ethyl acetate for microencapsulation of a hydrophobic drug into PLGA microspheres. An oil-in-water emulsion solvent extraction technique was developed to load progesterone into PLGA microspheres. Briefly, right after emulsion droplets were temporarily stabilized, they were subject to primary solvent extraction. Appearing semisolid, embryonic microspheres were completely hardened through subsequent secondary solvent extraction. Changes in process parameters of the preparative technique made it possible to manipulate the properties of emulsion droplets, progesterone behavior, and microsphere quality. Despite the two solvents showing comparable Hansen solubility parameter distances toward PLGA, ethyl formate surpassed ethyl acetate in relation to volatility and water miscibility. These features served as advantages in the microsphere manufacturing process, helping produce PLGA microspheres with better quality in terms of drug crystallization, drug encapsulation efficiency, microsphere size homogeneity, and residual solvent content. The present ethyl formate-based preparative technique could be an attractive method of choice for the production of drug-loaded PLGA microspheres.

Current advances in the development of novel polymeric nanoparticles for the treatment of neurodegenerative diseases

Effective intervention is essential to combat the coming epidemic of neurodegenerative (ND) diseases. Nanomedicine can overcome restrictions of CNS delivery imposed by the blood-brain barrier, and thus be instrumental in preclinical discovery and therapeutic intervention of ND diseases. Polymeric nanoparticles (PNPs) have shown great potential and versatility to encapsulate several compounds simultaneously in controlled drug-delivery systems and target them to the deepest brain regions. Here, we critically review recent advances in the development of drugs incorporated into PNPs and summarize the molecular changes and functional effects achieved in preclinical models of the most common ND disorders. We also briefly discuss the many challenges remaining to translate these findings and technological advances successfully to current clinical settings.

Development of 6-Thioguanine conjugated PLGA nanoparticles through thioester bond formation: Benefits of electrospray mediated drug encapsulation and sustained release in cancer therapeutic applications

Polymeric nanoparticle-based successful delivery of hydrophobic drugs is highly desirable for its controlled and sustained release at the disease site, which is a challenge with the current synthesis methods. In the present study, an electrospray mediated facile one-step synthesis approach is explored in which a solution mixture of a hydrophobic drug, 6-thioguanine (Tg) and a biocompatible FDA approved polymer, Poly (d, l-lactide-co-glycolide) (PLGA) is injected in an applied electric field of suitable intensity to prepare drug encapsulated PLGA nanoparticles, PLGA-Tg with high yield. In order to explore the effect of external electric field on Tg loading and delivery applications, the nanoparticles are characterized using EDX, AFM, FESEM, TEM, FTIR, Raman, fluorescence, and mass spectroscopy techniques. The characterization studies indicate that the electric field mediated synthesis exhibits spherical nanoparticles with a homogenous core size distribution of ~60 nm, high encapsulation (~97.22%) and stable conjugation of Tg (via thioester linkages) with PLGA molecules in the presence of the applied electric field. The kinetic study demonstrates the 'anomalous diffusion' (non-Fickian diffusion) release mechanism in which Tg escapes from PLGA matrix with a slow, but steady diffusion rate and the sustained drug release profile continues for 60 days. To check the biological activity of the encapsulated Tg, in-vitro cell studies of the PLGA-Tg are performed on HeLa cells. The MTT assay shows significant cell death after 48 h of treatment, and the cellular internalization of the drug-loaded nanoparticles occurs through pinocytosis mediated uptake, which is established by the AFM analysis. The Raman and mass spectroscopy studies suggest that the PLGA-Tg nanoparticles are rapidly hydrolyzed inside cell cytoplasm to release Tg which initiates apoptosis-mediated cell death confirmed by as DNA fragmentation and membrane blebbing studies. The results clearly emphasize the benefits of electrospray based synthesis of polymeric nanodrug formulation through the formation of chemical bonds between polymer and drug molecules that could be easily implemented in the design and development of an effective nanotherapeutic platform with no typical 'burst effect,' prolonged release profile, and significant toxicity to the cancer cells.

A smart approach to enable preclinical studies in pharmaceutical industry: PLGA-based extended release formulation platform for subcutaneous applications

Objective: Validation of a prospective new therapeutic concept in a proof of concept study is costly and time-consuming. In particular, pharmacologically active tool compounds often lack suitable pharmacokinetic (PK) properties for subsequent studies. The current work describes a PLGA-based formulation platform, encapsulating different preclinical research compounds into extended release microparticles, to optimize their PK properties after subcutaneous administration.Significance: Developing a PLGA-based formulation platform offers the advantage of enabling early proof of concept studies in pharmaceutical research for a variety of preclinical compounds by providing a tailor-made PK profile.Methods: Different model compounds were encapsulated into PLGA microparticles, utilizing emulsification solvent evaporation or spray drying techniques. Formulations aiming different release rates were manufactured and characterized. Optimized formulations were assessed in in vivo studies to determine their PK properties, with the mean residence time (MRT) as one key PK parameter.Results: Utilizing both manufacturing methods, tested tool compounds were encapsulated successfully, with a drug load between 5% and 40% w/w, and an extended release time up to 250 h. In the following PK studies, the MRT was extended by a factor of 90, resulting in prolonged coverage of the required target through level. This approach was confirmed to be equally successful for additional internal compounds, verifying a general applicability of the platform.Conclusion: For different active pharmaceutical ingredients (API), an optimized, tailor-made PK profile was obtained utilizing the described formulation platform. This approach is applicable for a variety of pharmacologically active tool compounds, reducing timelines and costs in preclinical research.

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.

Optimization of the Single Emulsion Method for Encapsulation of a Cancer Drug in Nanoparticles

The goal of this study is to apply and optimize the single emulsion technique for encapsulation of an anti-tumor drug, Di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT), in nanoparticles (NPs) of poly(lactic-co-glycolic acid) (PLGA), as a step towards targeted delivery of this drug. We previously showed that the nanoprecipitation technique can effectively produce PLGA NPs carrying this drug. Here, we aim to examine the single emulsion technique as an alternative for the preparation of these NPs and to compare the resultant NPs to those from nanoprecipitation. We fabricated NPs with variations in (i) injection rate, (ii) the amount of surfactant poly (vinyl alcohol) (PVA) in aqueous phase, and (iii) concentration of PLGA in the organic phase. These NPs were characterized for size, surface potential, and encapsulation efficiency. The results revealed that increasing the injection rate (from manual addition to 90 mL/hr via syringe pump) greatly reduced the size of NPs (by 48%) and decreasing the PVA concentration in the aqueous phase (from 5 to 1% w/v) further reduced the NP size (by 32%) to 329 nm. All tested NP formulations had negative surface potential, suggesting good colloidal stability for these NPs. Focusing on the optimal injection rate and PVA percentage, we found that reducing the concentration of PLGA, from 100 to 1 mg/mL, significantly reduced the NP size to 136 nm, which is close to the optimal range for cancer therapeutic delivery. NPs produced by this method had a high encapsulation efficiency of 77% for Dp44mT and reducing the PLGA concentration slightly lowered this value to 74%. Overall, these NPs were comparable to those produced by nanoprecipitation and can thus, serve as an effective alternative for delivery of Dp44mT to cancer cells.