Influence of secondary preparative parameters and aging effects on PLGA particle size distribution: a sedimentation field flow fractionation investigation

Recent Advances in the Surface Functionalization of PLGA-Based Nanomedicines

Therapeutics are habitually characterized by short plasma half-lives and little affinity for targeted cells. To overcome these challenges, nanoparticulate systems have entered into the disease arena. Poly(d,l-lactide-co-glycolide) (PLGA) is one of the most relevant biocompatible materials to construct drug nanocarriers. Understanding the physical chemistry of this copolymer and current knowledge of its biological fate will help in engineering efficient PLGA-based nanomedicines. Surface modification of the nanoparticle structure has been proposed as a required functionalization to optimize the performance in biological systems and to localize the PLGA colloid into the site of action. In this review, a background is provided on the properties and biodegradation of the copolymer. Methods to formulate PLGA nanoparticles, as well as their in vitro performance and in vivo fate, are briefly discussed. In addition, a special focus is placed on the analysis of current research in the use of surface modification strategies to engineer PLGA nanoparticles, i.e., PEGylation and the use of PEG alternatives, surfactants and lipids to improve in vitro and in vivo stability and to create hydrophilic shells or stealth protection for the nanoparticle. Finally, an update on the use of ligands to decorate the surface of PLGA nanomedicines is included in the review.

New Advances and Applications in Field-Flow Fractionation

Field-flow fractionation (FFF) is a family of techniques that was created especially for separating and characterizing macromolecules, nanoparticles, and micrometer-sized analytes. It is coming of age as new nanomaterials, polymers, composites, and biohybrids with remarkable properties are introduced and new analytical challenges arise due to synthesis heterogeneities and the motivation to correlate analyte properties with observed performance. Appreciation of the complexity of biological, pharmaceutical, and food systems and the need to monitor multiple components across many size scales have also contributed to FFF's growth. This review highlights recent advances in FFF capabilities, instrumentation, and applications that feature the unique characteristics of different FFF techniques in determining a variety of information, such as averages and distributions in size, composition, shape, architecture, and microstructure and in investigating transformations and function.

Design of Non-Haemolytic Nanoemulsions for Intravenous Administration of Hydrophobic APIs

Among advanced formulation strategies, nanoemulsions are considered useful drug-delivery systems allowing to improve the solubility and the bioavailability of lipophilic drugs. To select safe excipients for nanoemulsion formulation and to discard any haemolytic potential, an in vitro miniaturized test was performed on human whole blood. From haemolysis results obtained on eighteen of the most commonly used excipients, a medium chain triglyceride, a surfactant, and a solubilizer were selected for formulation assays. Based on a design of experiments and a ternary diagram, the feasibility of nanoemulsions was determined. The composition was defined to produce monodisperse nanodroplets with a diameter of either 50 or 120 nm, and their physicochemical properties were optimized to be suitable for intravenous administration. These nanoemulsions, stable over 21 days in storage conditions, were shown to be able to encapsulate with high encapsulation efficiency and high drug loading, up to 16% (w/w), two water practically insoluble drug models: ibuprofen and fenofibrate. Both drugs may be released according to a modulable profile in sink conditions. Such nanoemulsions appear as a very promising and attractive strategy for the efficient early preclinical development of hydrophobic drugs.

Therapeutic potential of polypeptide-based conjugates: Rational design and analytical tools that can boost clinical translation

The clinical success of polypeptides as polymeric drugs, covered by the umbrella term "polymer therapeutics," combined with related scientific and technological breakthroughs, explain their exponential growth in the development of polypeptide-drug conjugates as therapeutic agents. A deeper understanding of the biology at relevant pathological sites and the critical biological barriers faced, combined with advances regarding controlled polymerization techniques, material bioresponsiveness, analytical methods, and scale up-manufacture processes, have fostered the development of these nature-mimicking entities. Now, engineered polypeptides have the potential to combat current challenges in the advanced drug delivery field. In this review, we will discuss examples of polypeptide-drug conjugates as single or combination therapies in both preclinical and clinical studies as therapeutics and molecular imaging tools. Importantly, we will critically discuss relevant examples to highlight those parameters relevant to their rational design, such as linking chemistry, the analytical strategies employed, and their physicochemical and biological characterization, that will foster their rapid clinical translation.

Controlling Size and Fluorescence of Dye-Loaded Polymer Nanoparticles through Polymer Design

Nanoprecipitation is a straightforward yet powerful technique to synthesize polymer nanoparticles loaded with various biologically active compounds or contrast agents. Particle formation in this approach is kinetically controlled, and various assembly parameters have been used to control the size distribution and properties of the formed nanoparticles. Here, the influence of the nature of the polymer on the formation of nanoparticles in nanoprecipitation is studied systematically by varying its hydrophobicity and charge over a broad range. For this, methacrylate copolymers with different types and fractions of hydrophobic, hydrophilic, and charged side groups are synthesized. Nanoprecipitation of these polymers shows that particle size increases with increasing global hydrophobicity of the polymers. At the same time, both hydrophilic and charged groups reduce particle size. In this way, we achieve control over particle size from ∼10 to 200 nm. Furthermore, the effect of the polymer nature on the photophysical properties of nanoparticles loaded with a fluorescent dye, a rhodamine B derivative with a bulky hydrophobic counterion (fluorinated tetraphenylborate), is studied. It is found that the hydrophobic/hydrophilic balance of the polymer modulates to a large extent the spectral properties and fluorescence quantum yield of the dye encapsulated at high concentration, which reflects changes in the dye aggregation within the polymer matrix. Thus, we show how polymer chemistry can tune kinetically controlled formation of nanoparticles and encapsulation of the load. The concepts introduced here should be valuable tools for the design of nanoparticles for imaging and drug-delivery applications.

Targeted delivery of immune therapeutics to lymph nodes prolongs cardiac allograft survival

The targeted delivery of therapeutic drugs to lymph nodes (LNs) provides an unprecedented opportunity to improve the outcomes of transplantation and immune-mediated diseases. The high endothelial venule is a specialized segment of LN vasculature that uniquely expresses peripheral node addressin (PNAd) molecules. PNAd is recognized by MECA79 mAb. We previously generated a MECA79 mAb-coated microparticle (MP) that carries tacrolimus. Although this MP trafficked to LNs, it demonstrated limited therapeutic efficacy in our transplant model. Here, we have synthesized a nanoparticle (NP) as a carrier of anti-CD3, and optimized the conjugation strategy to coat the NP surface with MECA79 mAb (MECA79-anti-CD3-NP) to enhance LN accumulation. As compared with nonconjugated NPs, a significantly higher quantity of MECA79-NPs accumulated in the draining lymph node (DLN). Many MECA79-NPs underwent internalization by T cells and dendritic cells within the LNs. Short-term treatment of murine cardiac allograft recipients with MECA79-anti-CD3-NP resulted in significantly prolonged allograft survival in comparison with the control groups. Prolonged graft survival following treatment with MECA79-anti-CD3-NP was characterized by a significant increase in intragraft and DLN Treg populations. Treg depletion abrogated the prolongation of heart allograft survival. We believe this targeted approach of drug delivery could redefine the methods of administering immune therapeutics in transplantation.

Tuning the Size of Poly(lactic-co-glycolic Acid) (PLGA) Nanoparticles Fabricated by Nanoprecipitation

Polymeric nanoparticles (PNPs) are promising drug carriers in cancer treatment. Size of the particles has a significant impact on drug loading, in vivo distribution, extravasation, intratumor diffusion and cell uptake, and thus is critical for the successful development of a drug delivery regime. However, methods for manufacturing PNPs of defined size are yet to be established. The goal of this study is to establish a method that can be used to fabricate PNPs with controlled size. The factors that could impact the size of PNPs fabricated by nano-precipitation are systematically investigated. The factors studied include polymer concentration, organic solvent, temperature, aqueous phase ionic strength, organic phase injection rate, aqueous phase agitation rate, gauge of the needles, and final polymer concentration. Polymer concentration, the choice of organic solvent, temperature, and the ionic strength of the aqueous phase are shown to have a significant impact on the size of PNPs, and the effect of these factors can be attributed to a single parameter, the diffusion coefficient of the solvent in water, D_pw . It is possible that by tightly control these four parameters, nanoparticles with highly predictable and desirable size with narrow size distribution can be fabricated.

Development, Optimization, and Characterization of PEGylated Nanoemulsion of Prostaglandin E1 for Long Circulation

Lipo-PGE1 is the most widely used formulation of PGE1 in clinic. However, PGE1 is easier to leak out from lipo-PGE1 and this will lead to the phlebophlogosis when intravenous injection. The stability of lipo-PGE1 in storage and in vivo is also discounted. The aim of this study is to develop a long-circulating prostaglandin E1-loaded nanoemulsion modified with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG) to improve the stability and pharmacokinetics profiles of lipo-PGE1. PEGylated PGE1 nanoemulsion was prepared using a dispersing-homogenized method. The stability of nanoemulsion in 1 month was investigated. Pharmacokinetic studies were employed to evaluate the in vivo profile of the optimized nanoemulsion. The optimized nanoemulsion PGE1-PEG2000(1%)-NE showed an oil droplet size <100 nm with a surface charge of -14 mV. Approximately, 97% of the PGE1 was encapsulated in the nanoemulsion. The particle size, zeta potential, and drug loading of PGE1-PEG2000(1%)-NE were stable in 1 month. After PGE1-PEG2000(1%)-NE was intravenously administered to rats, the area under curve (AUC) and half-life of PGE1 were, respectively, 1.47-fold and 5.98-fold higher than those of lipo-PGE1 (commercial formulation). PGE1-PEG2000(1%)-NE was an ideal formulation for prolonging the elimination time of PGE1. This novel parenteral colloidal delivery system of PGE1 has a promising potential in clinic use.

Manufacturing Techniques and Surface Engineering of Polymer Based Nanoparticles for Targeted Drug Delivery to Cancer

The evolution of polymer based nanoparticles as a drug delivery carrier via pharmaceutical nano/microencapsulation has greatly promoted the development of nano- and micro-medicine in the past few decades. Poly(lactide-co-glycolide) (PLGA) and chitosan, which are biodegradable and biocompatible polymers, have been approved by both the Food & Drug Administration (FDA) and European Medicine Agency (EMA), making them ideal biomaterials that can be advanced from laboratory development to clinical oral and parental administrations. PLGA and chitosan encapsulated nanoparticles (NPs) have successfully been developed as new oral drug delivery systems with demonstrated high efficacy. This review aims to provide a comprehensive overview of the fabrication of PLGA and chitosan particulate systems using nano/microencapsulation methods, the current progress and the future outlooks of the nanoparticulate drug delivery systems. Especially, we focus on the formulations and nano/micro-encapsulation techniques using top-down techniques. It also addresses how the different phases including the organic and aqueous ones in the emulsion system interact with each other and subsequently influence the properties of the drug delivery system. Besides, surface modification strategies which can effectively engineer intrinsic physicochemical properties are summarised. Finally, future perspectives and potential directions of PLGA and chitosan nano/microencapsulated drug systems are outlined.

Charge-controlled nanoprecipitation as a modular approach to ultrasmall polymer nanocarriers: making bright and stable nanoparticles

Ultrasmall polymer nanoparticles are rapidly gaining importance as nanocarriers for drugs and contrast agents. Here, a straightforward modular approach to efficiently loaded and stable sub-20-nm polymer particles is developed. In order to obtain ultrasmall polymer nanoparticles, we investigated the influence of one to two charged groups per polymer chain on the size of particles obtained by nanoprecipitation. Negatively charged carboxylate and sulfonate or positively charged trimethylammonium groups were introduced into the polymers poly(d,l-lactide-co-glycolide) (PLGA), polycaprolactone (PCL), and poly(methyl methacrylate) (PMMA). According to dynamic light scattering, atomic force and electron microscopy, the presence of one to two charged groups per polymer chain can strongly reduce the size of polymer nanoparticles made by nanoprecipitation. The particle size can be further decreased to less than 15 nm by decreasing the concentration of polymer in the solvent used for nanoprecipitation. We then show that even very small nanocarriers of 15 nm size preserve the capacity to encapsulate large amounts of ionic dyes with bulky counterions at efficiencies >90%, which generates polymer nanoparticles 10-fold brighter than quantum dots of the same size. Postmodification of their surface with the PEG containing amphiphiles Tween 80 and pluronic F-127 led to particles that were stable under physiological conditions and in the presence of 10% fetal bovine serum. This modular route could become a general method for the preparation of ultrasmall polymer nanoparticles as nanocarriers of contrast agents and drugs.

Development of PLGA-based itraconazole injectable nanospheres for sustained release

Purpose

Itraconazole (ITZ) is a synthetic triazole antifungal agent, which is widely used for treatment and prevention of fungal infections. The purpose of this study is to develop ITZ-loaded poly(lactic-co-glycolic acid) (PLGA) nanospheres (PLGA-ITZ-NS) as a new sustained-release formulation for intravenous ITZ administration.

Materials and methods

PLGA-ITZ-NS were prepared by a nanoprecipitation method and optimized by modifying the surfactant poloxamer 188 concentration and PLGA:ITZ ratio. Their physicochemical properties, including size, zeta potential, external morphology and encapsulation efficiency, were characterized by dynamic light scattering (DLS), scanning electron microscopy (SEM) and high performance liquid chromatography (HPLC). The effect of the different selected lyoprotectants with various concentrations on NS particles size and surface charge were also assessed. Rapid and sensitive HPLC and liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods were developed to determine ITZ concentrations in formulation and in rat plasma, respectively. Pharmacokinetics of the optimum PLGA-ITZ-NS formulation was compared with the former commercial Sporanox® injection formulation using rats as the animal model. Noncompartmental pharmacokinetic parameters were obtained by WinNonlin® software.

Results

Optimal PLGA-ITZ-NS had a mean particle size of about 200 nm with a high homogeneity (polydispersity index ≈0.2), favorable zeta potential (approximately −20 to −30 mV) and encapsulation efficiency (72%). In addition, 2% w/v sucrose was selected as a lyoprotectant for NS freeze-drying. The newly developed LC-MS/MS assay was validated and found to be accurate and precise. The in vivo study showed that the NS formulation has a similar systemic bioavailability to Sporanox® while providing a sustained plasma level (> 100 ng/mL) for up to 24 hours after intravenous administration.

Conclusion

Our newly developed PLGA-ITZ-NS has shown great sustained release and comparable bioavailability with Sporanox®, therefore having the potential to be an alternative injectable formulation of ITZ.

Development and characterization of PLGA nanoparticles as delivery systems of a prodrug of zidovudine obtained by its conjugation with ursodeoxycholic acid

CONTEXT

Zidovudine (AZT) is employed against AIDS and hepatitis; its use is limited by active efflux transporters (AETs) that induce multidrug resistance for intracellular therapies and hamper AZT to reach the brain. Ursodeoxycholic acid (UDCA) conjugation with AZT (prodrug UDCA-AZT) allows to elude the AET systems.

OBJECTIVE

To investigate the effect of the Pluronic F68 coating on the loading, release and stability of poly(D,L lactide-co-glicolide) nanoparticles (NPs) embedded with UDCA-AZT.

MATERIALS AND METHODS

The mean diameter of the NP prepared by nanoprecipitation or emulsion/solvent evaporation methods was determined using both photon correlation spectroscopy and sedimentation field-flow fractionation; particle morphology was detected by scanning electron microscope. The stability of the free and encapsulated UDCA-AZT was evaluated in rat liver homogenates by high-performance liquid chromatography analysis.

RESULTS AND DISCUSSION

The mean diameter of the NPs was found to be ∼ 600 nm with a relatively high polydispersity. The NPs obtained by emulsion/solvent evaporation were not able to control the prodrug release, differently from NPs obtained by nanoprecipitation. The presence of the Pluronic coating did not substantially modify the kinetics of the drug release, or the extent of the burst effect that were instead only influenced by the preparation parameters. UDCA-AZT incorporated in the NPs was more stable in the rat liver homogenates than the free prodrug and no influence of the Pluronic coating was observed.

CONCLUSIONS

Considering the different potential applications of nanoparticles coated and uncoated with Pluronic (brain and macrophage targeting, respectively), both of these nanoparticle systems could be useful in the therapies against HIV.

Chitosan-modified PLGA nanoparticles with versatile surface for improved drug delivery

Shortage of functional groups on surface of poly(lactide-co-glycolide) (PLGA)-based drug delivery carriers always hampers its wide applications such as passive targeting and conjugation with targeting molecules. In this research, PLGA nanoparticles were modified with chitosan through physical adsorption and chemical binding methods. The surface charges were regulated by altering pH value in chitosan solutions. After the introduction of chitosan, zeta potential of the PLGA nanoparticle surface changed from negative charge to positive one, making the drug carriers more affinity to cancer cells. Functional groups were compared between PLGA nanoparticles and chitosan-modified PLGA nanoparticles. Amine groups were exhibited on PLGA nanoparticle surface after the chitosan modification as confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The modified nanoparticles showed an initial burst release followed by a moderate and sustained release profile. Higher percentage of drugs from cumulative release can be achieved in the same prolonged time range. Therefore, PLGA nanoparticles modified by chitosan showed versatility of surface and a possible improvement in the efficacy of current PLGA-based drug delivery system.