A new technique to efficiently entrap leuprolide acetate into microcapsules of polylactic acid or copoly(lactic/glycolic) acid

Polymeric nanoparticles and microparticles for the delivery of peptides, biologics, and soluble therapeutics

Biologically derived therapeutics, or biologics, are the most rapidly growing segment of the pharmaceutical marketplace. However, there are still unmet needs in improving the delivery of biologics. Injectable polymeric nanoparticles and microparticles capable of releasing proteins and peptides over time periods as long as weeks or months have been a major focus in the effort to decrease the frequency of administration. These particle systems fit broadly into two categories: those composed of hydrophilic and those composed of hydrophobic polymeric scaffolds. Here we review the factors that contribute to the slow and controlled release from each class of particle, as well as the effects of synthesis parameters and product design on the loading, encapsulation efficiency, biologic integrity, and release profile. Generally, hydrophilic scaffolds are ideal for large proteins while hydrophobic scaffolds are more appropriate for smaller biologics without secondary structure. Here we also introduce a Flash NanoPrecipitation method that has been adopted for encapsulating biologics in nanoparticles (40-200nm) at high loadings (50-75wt.%) and high encapsulation efficiencies. The hydrophilic gel interior and hydrophobic shell provide an opportunity to combine the best of both classes of injectable polymeric depots.

Preformulation Studies of Bee Venom for the Preparation of Bee Venom-Loaded PLGA Particles

It is known that allergic people was potentially vulnerable to bee venom (BV), which can induce an anaphylactic shock, eventually leading to death. Up until recently, this kind of allergy was treated only by venom immunotherapy (VIT) and its efficacy has been recognized worldwide. This treatment is practiced by subcutaneous injections that gradually increase the doses of the allergen. This is inconvenient for patients due to frequent injections. Poly (D,L-lactide-co-glycolide) (PLGA) has been broadly studied as a carrier for drug delivery systems (DDS) of proteins and peptides. PLGA particles usually induce a sustained release. In this study, the physicochemical properties of BV were examined prior to the preparation of BV-loaded PLGA nanoparticles NPs). The content of melittin, the main component of BV, was 53.3%. When protected from the light BV was stable at 4 °C in distilled water, during 8 weeks. BV-loaded PLGA particles were prepared using dichloromethane as the most suitable organic solvent and two min of ultrasonic emulsification time. This study has characterized the physicochemical properties of BV for the preparation BV-loaded PLGA NPs in order to design and optimize a suitable sustained release system in the future.

Preparation of 4-arm star PELA and its encapsulation of rotavirus for drug delivery

A relatively high molecular weight of 4-arm star PELA was obtained by ring-opening polymerization of l-lactic acid O-carboxyanhydride with 4-arm-PEG in the presence of DMAP as an initiator. The results via(1)H NMR and (13)C NMR show that the end of the star PELA chain is a hydroxyl group and the central core is a PEG group. Rotavirus (strain SA11) was incorporated into 4-arm star PELA microspheres formulated by the water in oil in water emulsification solvent extraction method. The microspheres produced were spherical, and the mean diameter was 1.34 μm with a narrow size distribution. The drug release profile displayed a low burst release effect of 1.8% on the first day and a sustained release of antigen over 100 days. After the immunization of mice, the microsphere-entrapped RV elicited improved and long-lasting IgA and IgG antibody response in serum detected by ELISA in comparison to the free RV antigen. This study shows that 4-arm-PEG is an effective initiator for the ring-opening polymerization of Lac-OCA by DMAP as an initiator and that the resulting polymer is useful as a delivery system for the rotavirus vaccine.

PLGA microspheres encapsulating siRNA

The therapeutic use of small interfering RNA (siRNA) represents a new and powerful approach to suppress the expression of pathologically genes. However, biopharmaceutical drawbacks, such as short half-life, poor cellular uptake, and unspecific distribution into the body, hamper the development of siRNA-based therapeutics. Poly(lactide-co-glycolide), (PLGA) microspheres can be a useful tool to overcome these issues. siRNA can be encapsulated into the PLGA microspheres, which protects the loaded nucleic acid against the enzymatic degradation. Moreover, PLGA microspheres can be injected directly into the action site, where the siRNA can be released in controlled manner, thus avoiding the need of frequent invasive administrations. The complete biodegradability of PLGA to monomers easily metabolized by the body, and its approval by FDA and EMA for parenteral administration, assure the safety of this copolymer and do not require the removal of the device after the complete drug release. In chapter, a basic protocol for the preparation of PLGA microspheres encapsulating siRNA is described. This protocol is based on a double emulsion/solvent evaporation technique, a well known and easy to reproduce method. This specific protocol has been developed to encapsulate a siRNA anti-TNFα in PLGA microspheres, and it has been designed and optimized to achieve high siRNA encapsulation efficiency and slow siRNA release in vitro. However, it can be extended also to other siRNA as well as other RNA or DNA-based oligonucleotides (miRNA, antisense, decoy, etc.). Depending on the applications, chemical modifications of the backbone and site-specific modification within the siRNA sequences could be required.

PLGA/alginate composite microspheres for hydrophilic protein delivery

Poly(lactic-co-glycolic acid) (PLGA) microspheres and PLGA/alginate composite microspheres were prepared by a novel double emulsion and solvent evaporation technique and loaded with bovine serum albumin (BSA) or rabbit anti-laminin antibody protein. The addition of alginate and the use of a surfactant during microsphere preparation increased the encapsulation efficiency and reduced the initial burst release of hydrophilic BSA. Confocal laser scanning microcopy (CLSM) of BSA-loaded PLGA/alginate composite microspheres showed that PLGA, alginate, and BSA were distributed throughout the depths of microspheres; no core/shell structure was observed. Scanning electron microscopy revealed that PLGA microspheres erode and degrade more quickly than PLGA/alginate composite microspheres. When loaded with anti-laminin antibody, the function of released antibody was well preserved in both PLGA and PLGA/alginate composite microspheres. The biocompatibility of PLGA and PLGA/alginate microspheres were examined using four types of cultured cell lines, representing different tissue types. Cell survival was variably affected by the inclusion of alginate in composite microspheres, possibly due to the sensitivity of different cell types to excess calcium that may be released from the calcium cross-linked alginate.

Preparation, characterization, in vitro release and degradation of cathelicidin-BF-30-PLGA microspheres

Cathelicidin-BF-30 (BF-30), a water-soluble peptide isolated from the snake venom of Bungarus fasciatus containing 30 amino acid residues, was incorporated in poly(D,L-lactide-co-glycolide) (PLGA) 75∶25 microspheres (MS) prepared by a water in oil in water W/O/W emulsification solvent extraction method. The aim of this work was to investigate the stability of BF-30 after encapsulation. D-trehalose was used as an excipient to stabilize the peptide. The MS obtained were mostly under 2 µm in size and the encapsulation efficiency was 88.50±1.29%. The secondary structure of the peptide released in vitro was determined to be nearly the same as the native peptide using Circular Dichroism (CD). The ability of BF-30 to inhibit the growth of Escherichia coli was also maintained. The cellular relative growth and hemolysis rates were 92.16±3.55% and 3.52±0.45% respectively.

Drug carriers in osteoporosis: preparation, drug encapsulation and applications

Carriers are largely used to enhance therapy efficiency via the encapsulation of active molecules. The encapsulation enhances the stability of drug molecules, improves the targeting properties and prolongs pharmacological activity via continuous local release of active molecules. The aim of this review is to report the carrier systems used in osteoporosis therapy. This state of the art research has mainly focused on describing all types of carriers used in this area, their elaboration and properties, the drug characteristics used in such specific application, and drug release and efficiency. In this field, various processes have been used in order to obtain well-defined capsules, spheres and more complex carriers. In this exhaustive review, each process is described, illustrated and discussed.

Suppression of cell attachment and protein adsorption onto amphiphilic polylactide-grafted dextran films

To develop novel biodegradable biomedical materials, polylactide-grafted dextrans (Dex-g-PLA)s having various lengths, numbers of graft chains and sugar units were synthesized using the trimethylsilyl (TMS) protection method. To explore the possibility of using Dex-g-PLA as a biomedical soft-material, the contact angle, cell attachment and protein adsorption properties of the films prepared from these biodegradable and amphiphilic graft co-polymers were investigated. The poly-L-lactide (PLLA) film did not absorb water at all because of its high hydrophobicity, while the graft co-polymer films started immediately to swell after immersion in PBS. The percentage of water absorption at equilibrium increased with increasing sugar unit content. The receding contact angle of the Dex-g-PLA films against water was smaller than that of the PLLA film. The receding contact angle of Dex-g-PLA films against water decreased with increasing the sugar unit content. The top surface of the Dex-g-PLA film was suggested to be covered with hydrophilic Dex segments by means of annealing in water and to afford the wettable surface. Such a wettable surface led to the suppression of cell attachment and protein adsorption onto the film.

Drug discovery by formulation design and innovative drug delivery systems (DDS)

This review describes studies on drug discovery using a rational formulation design and innovative, drug delivery systems (DDS) for biomaterials such as therapeutic peptides and nucleotides. The microcapsules of the LH-RH superagonist leuprorelin acetate prepared using the new in-water drying method and biodegradable polymers, such as PLGA and PLA, could achieve a long-term sustained release for 1-6 months thereby facilitating easily treatment of hormone-dependent diseases, prostate cancer, endometriosis, and precocious puberty. This DDS technology showed an improvement in patient QOL and highly promoted the clinical value of the agonist. Moreover, PLGA microcapsules of siRNAs against VEGF, cFLIP, Raf-1, and Int6 have also been developed to treat various cancers and arteriosclerosis obliterans. To develop therapeutic nucleotides, a particle design is created using functional peptides, such as cell penetrating peptides (CPP), nuclear localizing signals (NLS), tight junction reversible openers (AT1002), bombesin, and dynein light chain-associated sequences. siRNA use should lead to a paradigm shift in drug discovery against various diseases. Tat analog with NLS could enhance the potency of a vaginal DNA vaccine. The artificial Tat CPP of STR-CH(2)R(4)H(2)C synthesized in our laboratory could efficiently deliver siRNAs into many types of cells and enhance the therapeutic effects for treating sarcoma, atopic dermatitis, allergic rhinitis, and asthma by intratumor injection and inhalation of the nanoparticles. Tat and AT1002 analogs used to treat atopic dermatitis in mice increased cell membrane permeability to siRelA, a siRNA against a subclass of NF-κB, and exhibited striking therapeutic and preventive effects.

Controlled release of insulin from self-assembling nanofiber hydrogel, PuraMatrix™: application for the subcutaneous injection in rats

The concept of this research is, using the acetyl-(Arg-Ala-Asp-Ala)₄-CONH₂ peptide hydrosol (PuraMatrix™, PM), to develop an new injectable formula of controlled insulin delivery for subcutaneous injection. PM has sol-gel phase transition behavior, and was developed as a scaffold in the field of tissue engineering. The aqueous media of the PM including insulin changed from a sol to a gel phase with increasing ion strength of phosphate ion and pH in working environments in vitro and in vivo. In this study, we examined the in vitro insulin dissolution behavior and the in vivo pharmacokinetics and pharmacodynamics after subcutaneous administration of PM-insulin sol (PM-Isol). In the in vitro release study, after PM-Isol was converted to a gel phase (PM-Igel), PM concentration-dependent and controlled release of insulin were observed at the final concentrations of PM between 0.1% and 2.0% (w/v). The PM-Isol is changed to gel form in vivo, and exhibited a sustained-release pharmacokinetics of insulin, where PM concentration-dependent prolongation of efficacy was found. The plasma glucose level markedly decreased, and the lowest plasma glucose level was maintained up to 24h when 2.0% (w/v) PM-Isol was administered subcutaneously to rats. The PM-Isol, we developed here, is applicable for the wild-type of insulin, and increased the bioavailability and hypoglycemic efficacy of insulin after subcutaneous injection. Hence, the PM is a useful inactive ingredient to produce various types of control-released system of insulin by making just a few changes in PM content of the formulation.

Formulation design considerations for oral vaccines

Whilst oral vaccination is a potentially preferred route in terms of patient adherence and mass vaccination, the ability to formulate effective oral vaccines remains a challenge. The primary barrier to oral vaccination is effective delivery of the vaccine through the GI tract owing to the many obstacles it presents, including low pH, enzyme degradation and bile-salt solubilization, which can result in breakdown/deactivation of a vaccine. For effective immune responses after oral administration, particulates need to be taken up by the M cells however, these are few in number. To enhance M-cell uptake, particle characteristics can be optimized with particle size, surface charge, targeting groups and bioadhesive properties all being considerations. Yet improved uptake may not translate into enhanced immune responses and formulating particulates with inherent adjuvant properties can offer advantages. Within this article, we establish the options available for consideration when building effective oral particulate vaccines.

Mapping Uncertainties in the Upstream: The Case of PLGA Nanoparticles in Salmon Vaccines

The diversity of nanotechnologies and of the governance challenges that their applications raise calls for exploration and learning across different cases. We present an Upstream Oversight Assessment (UOA) of expected benefits and potential harms of nanoparticles made of a synthetic polymer (PLGA) to improve vaccines for farmed salmon. Suggested by Jennifer Kuzma and colleagues, an UOA may help identify and prioritise research needs, and it may support evaluations of the adequacy of relevant existing regulatory frameworks. In this work, the UOA approach is modified and supported with elements from the uncertainty analysis framework developed by Warren Walker and colleagues. Empirically, we draw on relevant available published literature and insights generated in an ongoing nanoparticle salmon vaccine project, in which one of the authors participates. Nanotechnologies have not previously been encountered in the regulatory context of fish vaccines, which in part raises unique challenges due to prospective large scale vaccine use in semi-open aquatic systems. Strengthened through cooperation between ELSA and technology researchers we found the UOA useful for an early mapping of benefits and concerns, and for identifying areas in need of further research prior to a nanoparticle based salmon vaccine is developed and taken into use. We consider our approach to represent one among several complementing initiatives that seek to contribute to early stage evaluations of possible negative side effects, broadly conceived, in order to facilitate a more robust nanotechnology development.

Elastic-contractile model proteins: Physical chemistry, protein function and drug design and delivery

This review presents the structure and physico-chemical properties of ECMPs, elastic-contractile model proteins using sparse design modifications of elastic (GVGVP)(n); it describes the capacity of ECMP to perform the energy conversions that sustain living organisms; it arrives at the hydration thermodynamics of ECMP in terms of the change in Gibbs free energy of hydrophobic association, ΔG(HA), and the apolar-polar repulsive free energy of hydration, ΔG(ap); it applies ΔG(HA), ΔG(ap), and the nature of elasticity to describe the function of basic diverse proteins, namely - the F₁-motor of ATP synthase, Complex III of mitochondria, the KscA potassium-channel, and the molecular chaperonin, GroEL/ES; it applies ΔG(HA) and ΔG(ap) to describe the function of ABC exporter proteins that confer multi-drug resistance (MDR) on micro-organisms and human carcinomas and suggests drug modifications with which to overcome MDR. Using ECMP, means are demonstrated, for quantifying drug hydrophobicity with which to combat MDR and for preparing ECMP drug delivery nanoparticles, ECMPddnp, decorated with synthetic antigen-binding fragments, Fab1 and Fab2, with which to target specific up-regulated receptors, characteristic of human carcinoma cells, for binding and localized drug release.

Control of encapsulation efficiency in polymeric microparticle system of tolmetin

Ethylcellulose microparticles containing tolmetin sodium, an anti-inflammatory drug, were prepared by a solvent diffusion method based on the formation of multiple W/O(1)/O(2)-emulsion. The drug used was TOL, which is water-soluble and n-hexane was used as the non-solvent. Important parameters in the evaluation of a microencapsulation technique are actual drug loading, the encapsulation efficiency, the yield, solvent systems, dispersed phase to continuous phase ratio (DP/CP ratio), composition of continuous phase, drug distribution in microparticles and stability of primary emulsion. A small volume of internal aqueous phase and volume of organic solvent were favorable to achieve high drug encapsulation efficiencies. Since drug release during the initial stages depends mostly on the diffusion escape of the drug, major approaches to prevent the initial burst have focused on efficient encapsulation of the drug within the microparticles. For this reason, control of efficiency and the extent of initial burst are based on common formulation parameters. Most parameters affect encapsulation efficiency and initial burst by modifying solidification rate of dispersed phase. In order to prevent many unfavorable events such as pore formation, drug loss, and drug migration that occur while the dispersed phase is in the semi-solid state, it is important to understand and optimize these variables.

Control of drug loading efficiency and drug release behavior in preparation of hydrophilic-drug-containing monodisperse PLGA microspheres

We prepared monodisperse poly(lactide-co-glycolide) (PLGA) microspheres containing blue dextran (BLD)--a hydrophilic drug--by membrane emulsification technique. The effects of electrolyte addition to the w(2) phase and significance of the droplet size ratio between primary (w(1)/o) and secondary (w(1)/o/w(2)) emulsions during the preparation of these microspheres was examined. The droplet size ratio was evaluated from the effect of stirring rate of the homogenizer when preparing the primary emulsion. The drug loading efficiency of BLD in these microspheres increased with stirring rate. It increased to approximately 90% when 2.0% NaCl was added to the w(2) phase. Drug release from these microspheres was slower than that when they were prepared without electrolyte addition. Despite the very high efficiency drug release was gradual because BLD was distributed at the microspheres core. Relatively monodisperse hydrophilic-drug-containing PLGA microspheres with controlled drug loading efficiency and drug release behavior were prepared.