Protein complexed with chondroitin sulfate in poly(lactide-co-glycolide) microspheres

Engineering microenvironment of biodegradable polyester systems for drug stability and release control

Polymeric systems made of poly(lactic acid) or poly(lactic-co-glycolic acid) are widely used for long-term delivery of small and large molecules. The advantages of poly(lactic acid)/poly(lactic-co-glycolic acid) systems include biodegradability, safety and a long history of use in US FDA-approved products. However, as drugs delivered by the polymeric systems and their applications become more diverse, the significance of microenvironment change of degrading systems on long-term drug stability and release kinetics has gained renewed attention. In this review, we discuss various issues experienced with acidifying microenvironment of biodegradable polymer systems and approaches to overcome the detrimental effects of polymer degradation on drug stability and release control.

Inhalable Spray-Dried Chondroitin Sulphate Microparticles: Effect of Different Solvents on Particle Properties and Drug Activity

Spray-drying stands as one of the most used techniques to produce inhalable microparticles, but several parameters from both the process and the used materials affect the properties of the resulting microparticles. In this work, we describe the production of drug-loaded chondroitin sulphate microparticles by spray-drying, testing the effect of using different solvents during the process. Full characterisation of the polymer and of the aerodynamic properties of the obtained microparticles are provided envisaging an application in inhalable tuberculosis therapy. The spray-dried microparticles successfully associated two first-line antitubercular drugs (isoniazid and rifabutin) with satisfactory production yield (up to 85%) and drug association efficiency (60%–95%). Ethanol and HCl were tested as co-solvents to aid the solubilisation of rifabutin and microparticles produced with the former generally revealed the best features, presenting a better ability to sustainably release rifabutin. Moreover, these presented aerodynamic properties compatible with deep lung deposition, with an aerodynamic diameter around 4 μm and fine particle fraction of approximately 44%. Finally, it was further demonstrated that the antitubercular activity of the drugs remained unchanged after encapsulation independently of the used solvent.

Protein-polysaccharide nanohybrids: Hybridization techniques and drug delivery applications

Complex nanosystems fabricated by hybridization of different types of materials such as lipids, proteins, or polysaccharides are usually superior to simple ones in terms of features and applications. Proteins and polysaccharides hold great potential for development of nanocarriers for drug delivery purposes based on their unique biocompatibility, biodegradability, ease of functionalization, improved biodistribution and minimal toxicity profiles. Protein-polysaccharide nanohybrids have gained a lot of attention in the past few years particularly for drug delivery applications. In this review, different hybridization techniques utilized in the fabrication of such nanohybrids including electrostatic complexation, Maillard conjugation, chemical coupling and electrospinning were thoroughly reviewed. Moreover, various formulation factors affecting the characteristics of the formed nanohybrids were discussed. We also reviewed in depth the outcomes of such hybridization ranging from stability enhancement, to toxicity reduction, improved biocompatibility, and drug release modulation. We also gave an insight on their limitations and what hinders their clinical translation and market introduction.

Soybean Lecithin-Mediated Nanoporous PLGA Microspheres with Highly Entrapped and Controlled Released BMP-2 as a Stem Cell Platform

Injectable polymer microsphere-based stem cell delivery systems have a severe problem that they do not offer a desirable environment for stem cell adhesion, proliferation, and differentiation because it is difficult to entrap a large number of hydrophilic functional protein molecules into the core of hydrophobic polymer microspheres. In this work, soybean lecithin (SL) is applied to entrap hydrophilic bone morphogenic protein-2 (BMP-2) into nanoporous poly(lactide-co-glycolide) (PLGA)-based microspheres by a two-step method: SL/BMP-2 complexes preparation and PLGA/SL/BMP-2 microsphere preparation. The measurements of their physicochemical properties show that PLGA/SL/BMP-2 microspheres had significantly higher BMP-2 entrapment efficiency and controlled triphasic BMP-2 release behavior compared with PLGA/BMP-2 microspheres. Furthermore, the in vitro and in vivo stem cell behaviors on PLGA/SL/BMP-2 microspheres are analyzed. Compared with PLGA/BMP-2 microspheres, PLGA/SL/BMP-2 microspheres have significantly higher in vitro and in vivo stem cell attachment, proliferation, differentiation, and matrix mineralization abilities. Therefore, injectable nanoporous PLGA/SL/BMP-2 microspheres can be potentially used as a stem cell platform for bone tissue regeneration. In addition, SL can be potentially used to prepare hydrophilic protein-loaded hydrophobic polymer microspheres with highly entrapped and controlled release of proteins.

An Inhalable Powder Formulation Based on Micro- and Nanoparticles Containing 5-Fluorouracil for the Treatment of Metastatic Melanoma

Melanoma is the most aggressive and lethal type of skin cancer, with a poor prognosis because of the potential for metastatic spread. The aim was to develop innovative powder formulations for the treatment of metastatic melanoma based on micro- and nanocarriers containing 5-fluorouracil (5FU) for pulmonary administration, aiming at local and systemic action. Therefore, two innovative inhalable powder formulations were produced by spray-drying using chondroitin sulfate as a structuring polymer: (a) 5FU nanoparticles obtained by piezoelectric atomization (5FU-NS) and (b) 5FU microparticles of the mucoadhesive agent Methocel™ F4M for sustained release produced by conventional spray drying (5FU-MS). The physicochemical and aerodynamic were evaluated in vitro for both systems, proving to be attractive for pulmonary delivery. The theoretical aerodynamic diameters obtained were 0.322 ± 0.07 µm (5FU-NS) and 1.138 ± 0.54 µm (5FU-MS). The fraction of respirable particles (FR%) were 76.84 ± 0.07% (5FU-NS) and 55.01 ± 2.91% (5FU-MS). The in vitro mucoadhesive properties exhibited significant adhesion efficiency in the presence of Methocel™ F4M. 5FU-MS and 5FU-NS were tested for their cytotoxic action on melanoma cancer cells (A2058 and A375) and both showed a cytotoxic effect similar to 5FU pure at concentrations of 4.3 and 1.7-fold lower, respectively.

γ-Cyclodextrin-phenylacetic acid mesh as a drug trap

In this study, we developed a nanoporous biodegradable mesh, bioinspired by the spider web, which is prepared via electrospinning using γ-cyclodextrin (γ-CD) conjugated with phenylacetic acid (PA), named γ-CDP. The resulting γ-CDP has a microfibrous or microspherical shape and contains drug trap meshlike γ-CD pores. These γ-CDP micromeshes (microspheres or microfibers) enable efficient drug capture and drug transport into deep γ-CDP nanocompartments or out of the γ-CDP web, resulting in a driving domain for a 4-week drug release. When used to deliver chemotherapeutic agents to xenografted tumors, the γ-CDP implants caused nearly complete tumor regression for 4 weeks after single administration. This strategy of a drug trap biodegradable mesh (with low density) will make drug containers uniquely attractive for the development of therapeutic implants and functional biomedical devices.

Chondroitin sulfate-capped super-paramagnetic iron oxide nanoparticles as potential carriers of doxorubicin hydrochloride

Chondroitin-4-sulfate (CS), a glycosaminoglycan, was used to prepare CS-capped super-paramagnetic iron oxide nanoparticles, which were further employed for loading a water-soluble chemotherapeutic agent (doxorubicin hydrochloride, DOX). CS-capped SPIONs have potential biomedical application in cancer targeting. The optimized formulation had a hydrodynamic size of 91.2±0.8nm (PDI; 0.228±0.004) and zeta potential of -49.1±1.66mV. DOX was loaded onto the formulation up to 2% (w/w) by physical interaction with CS. TEM showed nano-sized particles having a core-shell structure. XRD confirmed crystal phase of iron oxide. FT-IR conceived the interaction of iron oxide with CS as bidentate chelation and also confirmed DOX loading. Vibration sample magnetometry confirmed super-paramagnetic nature of nanoparticles, with saturation magnetization of 0.238emug(-1). In vitro release profile at pH 7.4 showed that 96.67% of DOX was released within 24h (first order kinetics). MTT assay in MCF7 cells showed significantly higher (p<0.0001) cytotoxicity for DOX in SPIONs than DOX solution (IC50 values 6.294±0.4169 and 11.316±0.1102μgmL(-1), respectively).

Positive Charge of "Sticky" Peptides and Proteins Impedes Release From Negatively Charged PLGA Matrices

The influence of electrostatic interactions and/or acylation on release of charged ("sticky") agents from biodegradable polymer matrices was systematically characterized. We hypothesized that release of peptides with positive charge would be hindered from negatively charged poly(lactic-co-glycolic acid) (PLGA) microparticles. Thus, we investigated release of peptides with different degrees of positive charge from several PLGA microparticle formulations, with different molecular weights and/or end groups (acid- or ester-terminated). Indeed, release studies revealed distinct inverse correlations between the amount of positive charge on peptides and their release rates from each PLGA microparticle formulation. Furthermore, we examined the case of peptides with net charge that changes from negative to positive within the pH range observed in degrading microparticles. These charge changing peptides displayed counterintuitive release kinetics, initially releasing faster from slower degrading (less acidic) microparticles, and releasing slower from the faster degrading (more acidic) microparticles. Importantly, trends between agent charge and release rates for model peptides also translated to larger, therapeutically relevant proteins and oligonucleotides. The results of these studies may improve future design of controlled release systems for numerous therapeutic biomolecules exhibiting positive charge, ultimately reducing time-consuming and costly trial and error iterations of such formulations.

Preparation of polymeric particles in CO2 medium using non-toxic solvents: discussions on the mechanism of particle formation

Development of a novel and effective process for protein encapsulation into PLGA microparticles by the emulsification–extraction method in CO₂ medium using non-toxic solvents.

Solid-state protein formulations

When formulated as liquid dosage forms, therapeutic proteins and peptides often show instability during handling as a result of chemical degradation. Solid formulations are frequently required to maintain protein stability during storage, transport and upon administration. Herein we highlight current strategies used to formulate pharmaceutical proteins in the solid form. An overview of the physical instabilities which can arise with proteins is first described. The key solidification techniques of crystallization, freeze-drying and particle forming technologies are then discussed. Examples of current commercial products that are formulated in the solid state are provided and include neutral protamine Hagedorn – insulin crystal suspensions, freeze-dried monoclonal antibodies and leuproride polylactide-co-glycolide microparticles. Finally, future perspectives in solid-state protein formulation are described.

Pharmaceutical and biomedical applications of lipid-based nanocarriers

Increasing attention is being given to lipid nanocarriers (LNs) as drug delivery systems, due to the advantages offered of a higher biocompatibility and lower toxicity compared with polymeric nanoparticles. Many administration routes are being investigated for LNs, including topical, oral and parenteral ones. LNs are also proposed for specific applications such as cancer treatment, gene therapy, diagnosis and medical devices production. However, the high number of published research articles does not match an equal amount of patents. A recent Review of ours, published in Pharmaceutical Patent Analyst, reported the patents proposing novel methods for the production of LNs. This review work discusses recent patents, filed in 2007-2013 and dealing with the industrial applications of lipid-based nanocarriers for the vectorization of therapeutically relevant molecules, as well as biotech products such as proteins, gene material and vaccines, in the pharmaceutical, diagnostic and biomedical areas.

Preparation and properties of BSA-loaded microspheres based on multi-(amino acid) copolymer for protein delivery

A multi-(amino acid) copolymer (MAC) based on ω-aminocaproic acid, γ-aminobutyric acid, L-alanine, L-lysine, L-glutamate, and hydroxyproline was synthetized, and MAC microspheres encapsulating bovine serum albumin (BSA) were prepared by a double-emulsion solvent extraction method. The experimental results show that various preparation parameters including surfactant ratio of Tween 80 to Span 80, surfactant concentration, benzyl alcohol in the external water phase, and polymer concentration had obvious effects on the particle size, morphology, and encapsulation efficiency of the BSA-loaded microspheres. The sizes of BSA-loaded microspheres ranged from 60.2 μm to 79.7 μm, showing different degrees of porous structure. The encapsulation efficiency of BSA-loaded microspheres also ranged from 38.8% to 50.8%. BSA release from microspheres showed the classic biphasic profile, which was governed by diffusion and polymer erosion. The initial burst release of BSA from microspheres at the first week followed by constant slow release for the next 7 weeks were observed. BSA-loaded microspheres could degrade gradually in phosphate buffered saline buffer with pH value maintained at around 7.1 during 8 weeks incubation, suggesting that microsphere degradation did not cause a dramatic pH drop in phosphate buffered saline buffer because no acidic degradation products were released from the microspheres. Therefore, the MAC microspheres might have great potential as carriers for protein delivery.

Succinylated polysaccharide-based thermosensitive polyelectrostatic complex for protein drug delivery

The objective of this study was to develop a thermosensitive polyelectrostatic complex, based on polysaccharides, as carriers for long-term protein delivery. We developed a thermosensitive polyelectrostatic complex formed through combined electrostatic and hydrophobic interactions. The copolymer (succinylated pullulan -poly(l-lactide)) showed thermosensitivity in aqueous solution and complexed with protein (lysozyme) via electrostatic attractions and hydrophobic interactions at physiological temperature which formed a thermosensitive polyelectrostatic complex. The particle size of the thermosensitive polyelectrostatic complex was decreased from ~520 nm at 4°C to ~190 nm at 37.5°C. These thermosensitive polyelectrostatic complexes were stable in serum and salt conditions, and maintained the bioactivity of encapsulated protein for 36 days. The thermosensitive polyelectrostatic complex had prolonged in vivo stability that was greater than the polyelectrostatic complex. Based on stability and bioactivity tests for the lysozyme-loaded thermosensitive polyelectrostatic complexes, the potential of the long-term protein delivery carrier in physiological conditions was confirmed.

A sulfate polysaccharide/TNF-related apoptosis-inducing ligand (TRAIL) complex for the long-term delivery of TRAIL in poly(lactic-co-glycolic acid) (PLGA) microspheres

OBJECTIVES

The aim was to develop a long-term delivery system for Apo2 ligand/tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) without chemical modification (such as pegylation).

METHODS

A nanocomplex system between the positively charged TRAIL and the negatively charged chondroitin sulfate (CS) (CS/TRAIL) was designed and applied in poly(lactide-co-glycolide) (PLGA) microspheres (MSs).

KEY FINDINGS

A nanocomplex of approximately 200 nm was easily formed in a weight ratio of 2 TRAIL to CS (TC2) at pH 5.0. The cytotoxicity of CS/TRAIL against HeLa cells was similar to that of native TRAIL. The complex also had higher loading efficiency (above 95%) in PLGA MSs prepared by the multi-emulsion method than that of native TRAIL. The release behaviour of TRAIL from the PLGA MSs was monitored. Although the release of TRAIL from native TRAIL-loaded PLGA MSs (TMS0) was almost complete after 3 days, TC2-loaded PLGA MSs (TMS2) showed sustained TRAIL release without an initial burst for 10 days. The released TRAIL from TMS2 led to cytotoxicity accompanied by massive apoptosis of cancer cells. TMS2 significantly inhibited tumour growth in an in-vivo xenograft model in mice, without any loss of body weight after treatment.

CONCLUSIONS

From the results, we concluded that TC-loaded PLGA MSs have the potential for long-term delivery of TRAIL without side effects.

Controlled release of bone morphogenetic protein (BMP)-2 from nanocomplex incorporated on hydroxyapatite-formed titanium surface

Both osteoconductivity and osteoinductivity are equally very important aspects in a new bone formation and ultimately for bone regeneration. The purpose of this study was to create an environment, not only osteoconductive but also osteoinductive on titanium (Ti) surface. To do this bone morphogenetic protein-2 (BMP-2) nanocomplex (NC) was fabricated by using an ionic interaction between BMP-2 and chondroitin sulfate (CS). Meanwhile, Ti was chemically treated, then subjected to soaking in simulated body fluid (SBF), naming the sample Ti(C)-hydroxyapatite (HA). Once the BMP-2 NC was precipitated on the Ti(C)-HA surface, along with the addition of calcium/phosphate solution, the final product was formed as Ti(C)-HA-BMP-2. The size of NC was ranged from 150 to 250nm and the amount of CS was influential in determining both NC size and zeta potential. From the SEM observation, Ti surface was found nicely covered with the crystallized apatite layer that was identified using FTIR and NMR. The immobilized BMP-2 was released in a moderate rate for 4 weeks, without an initial burst of BMP-2. When mouse osteoblast cells were seeded on different Ti substrates, cell proliferation was faster in the Ti(C)-HA-BMP-2 group, as compared to other groups. The gene expression of bone-specific markers, osteocalcin and type I collagen, was significantly upregulated with the use of BMP-2 NC. The same result was witnessed in the measurement of alkaline phosphatase activity, in which the difference was statistically significant. This study demonstrated that the delivery system of BMP-2 NC was effective in holding BMP-2 on the apatite-coated Ti surface and that the Ti surface could be modified into the environment osteoinductive as well as osteoconductive.

Dual delivery for stem cell differentiation using dexamethasone and bFGF in/on polymeric microspheres as a cell carrier for nucleus pulposus regeneration

This study aimed to investigate the feasibility of the nanostructured 3D poly(lactide-co-glycolide) (PLGA) constructs, which are loaded with dexamethasone (DEX) and growth factor embedded heparin/poly(L-lysine) nanoparticles via a layer-by-layer system, to serve as an effective scaffold for nucleus pulposus (NP) tissue engineering. Our results demonstrated that the microsphere constructs were capable of simultaneously releasing basic fibroblast growth factor and DEX with approximately zero order kinetics. The dual bead microspheres showed no cytotoxicity, and promoted the proliferation of the rat mesenchymal stem cells (rMSCs) by lactate dehydrogenase assay and CCK-8 assay. After 4 weeks of cultivation in vitro, the rMSCs-scaffold hybrids contained significantly higher levels of sulfated GAG/DNA and collagen type II than the control samples. Moreover, quantitative real time PCR analysis revealed that the expression of disc-matrix proteins including collagen type II, aggrecan, and versican in the rMSCs-scaffold hybrids was significantly higher than that in the control group, whereas the expression of osteogenic differentiation marker (collagen type I) was decreased. Taken together, these data indicate that Dex/bFGF PLGA microspheres could be used as a scaffold to improve the rMSCs growth and differentiating into NP like cells, and reduce the inflammatory response for IVD tissue engineering.

The controlled photoactivity of nanoparticles derived from ionic interactions between a water soluble polymeric photosensitizer and polysaccharide quencher

In order to design a water soluble polymeric photosensitizer (WPS) with controllable photoactivity, a nano-photosensitizer (NPS) was prepared from a polyelectrolyte complex between polyethylene glycol-polyethylenimine-chlorine e6 conjugate (PEG-PEI-Ce6) and Black Hole Quencher-3 chondroitin sulfate conjugate (BHQ-3-CS). NPSs have a unimodal size distribution below 100 nm. Photoquenching of the NPS was dependent on the weight ratio of BHQ-3-CS/WPS. This phenomenon was maintained in a salt condition up to 300 mm, indicating that the photoactivity of the NPS disappears in the normal blood stream of the body. The quenched photoactivity was restored by the enzyme degradation of BHQ-3-CS after esterase treatment. In a HCT-116 (human colon cancer) cell test, the rapid cellular internalization of the NPS without any other ligands was observed by confocal imaging. Upon light irradiation after internalization, phototoxicity was detected via MTT colorimetric assay. Also, when the NPS was subcutaneously injected in both tumoral and normal regions of HCT-116 tumor-bearing mice, the fluorescence signal in the tumors rapidly increased compared to the normal region due to the enzymatic-triggered dissociation of the NPS in vivo. These results suggest that the NPS can provide both tumor diagnosis and therapy simultaneously, and has great potential for biological studies and clinical treatments of various tumors.

Development of chondroitin sulfate encapsulated PLGA microsphere delivery systems with controllable multiple burst releases for treating osteoarthritis

The purpose of the study was to design and develop unique drug delivery systems with controllable multiple burst releases of drugs for treating osteoarthritis. Chondroitin sulfate (CS) was encapsulated into four types of PLGA materials, that is, PLGA 50:50, PLGA 65:35, PLGA 75:25, and PLGA 85:15. The effects of microsphere size and various combinations of blend PLGA microspheres on CS release were investigated. The cytotoxicity of the CS-encapsulated microspheres was investigated according to the ISO 10993 guideline. Our study showed that the encapsulation efficiency of CS into PLGA 50:50 microspheres varied with the size of microspheres; however, the encapsulation efficiencies of CS into PLGA microspheres were independent of the types of PLGA materials. The size of PLGA microspheres was shown to affect the rate of CS release. With the increase of microsphere size from 75-150 μm to 300-355 μm, the initial CS release decreased. Further increase in microsphere size led to an increase in the initial CS release. In addition, combination of different types of PLGA microspheres was shown to be capable of achieving multiple burst CS releases. Moreover, the CS encapsulated PLGA microspheres were shown to be non-cytotoxic. This study proved the concept of multiple burst drug releases that were achieved by encapsulating CS into different types of PLGA microspheres and delivering CS from systems consisting of mixed types of PLGA microspheres, which may be applied to treat osteoarthritis by mimicking multiple intra-joint injection of therapeutic agents.

Development of nano- and microscale chondroitin sulfate particles for controlled growth factor delivery

Size scale plays an important role in the release properties and cellular presentation of drug delivery vehicles. Because negatively charged chondroitin sulfate (CS) is capable of electrostatically sequestering positively charged growth factors, CS-derived nanoscale micelles and microscale spheroids were synthesized as potential growth factor carriers to enhance differentiation of stem cells. Particles were characterized for morphology, size distribution, surface charge and cytocompatibility, as well as release of transforming growth factor-β1 (TGF-β1) and tumor necrosis factor-α (TNF-α). CS micelles were spherical and negatively charged with a bimodal distribution of 324.1±8.5 and 73.2±4.4 nm diameters, and CS microspheres possessed a rounded morphology and a diameter of 4.3±0.93 μm. Positively charged TGF-β1 demonstrated minimal release after loading in CS microspheres, while negatively charged TNF-α exhibited substantial release over the first 15 h, suggesting that TGF-β1 electrostatically complexed with CS. The micelles and microparticles were found to be cytocompatible at moderate concentrations with marrow stromal cell monolayers and within embryonic stem cell embryoid bodies. These synthesis techniques, which allow the formation of CS-based carriers over a variety of nano- and microscale sizes, offer versatility for tailored release of positively charged growth factors and controlled CS presentation for a variety of stem cell-based applications in tissue engineering and regenerative medicine.

Magnetic levitating polymeric nano/microparticular substrates for three-dimensional tumor cell culture

Herein, we describe magnetic cell levitation models using conventional polymeric microparticles or nanoparticles as a substrate for the three-dimensional tumor cell culture. When the magnetic force originating from the ring-shaped magnets overcame the gravitational force, the magnetic field-levitated KB tumor cells adhered to the surface area of magnetic iron oxide (Fe(3)O(4))-encapsulated nano/microparticles and concentrated clusters of levitated cells, ultimately developing tumor cells to tumor spheroids. These simple cell culture models may prove useful for the screening of anticancer drugs and their formulations.

Ionic complex systems based on hyaluronic acid and PEGylated TNF-related apoptosis-inducing ligand for treatment of rheumatoid arthritis

The clinical applications of tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL), an emerging therapeutic protein for cancer and rheumatoid arthritis (RA), are limited by its instability and short biological half-life. In this study, efficient therapeutic modalities for RA treatment were developed in the form of nano-sized complexes (nanocomplexes) based on hyaluronic acid (HA) and polyethylene glycol (PEG)-derivatized TRAIL (PEG-TRAIL) formed by N-terminal specific PEGylation. The nanocomplexes were prepared by simply mixing the positively charged PEG-TRAIL and negatively charged HA, and showed negligible loss of bioactivity compared with the PEG-TRAIL. The in vivo biodistribution and diffusion kinetics of Cy5.5-labeled PEG-TRAIL in mice were observed using a near-infrared optical imaging system after subcutaneous injection of three different formulations: PEG-TRAIL in phosphate-buffered saline (PBS, pH 7.4), nanocomplex in PBS, or nanocomplex in 1% HA solution. The results suggested that PEG-TRAIL is released slowly in vivo from the nanocomplex in 1% HA. Experiments in a collagen-induced arthritis mouse model demonstrated that the magnitudes of therapeutic effects, as judged by clinical scores and histology, were significantly enhanced by the sustained delivery of PEG-TRAIL, with the order of nanocomplex in 1% HA>nanocomplex in PBS>PEG-TRAIL in PBS. In addition, sustained delivery of PEG-TRAIL from the nanocomplex in 1% HA resulted in significant reduction of serum inflammatory cytokines and collagen-specific antibodies that are responsible for the pathogenesis of RA. These results imply that HA/PEG-TRAIL nanocomplex formulations are promising therapeutic modalities for the treatment of RA.

The antimicrobial efficacy of sustained release silver-carbene complex-loaded L-tyrosine polyphosphate nanoparticles: characterization, in vitro and in vivo studies

The pressing need to treat multi-drug resistant bacteria in the chronically infected lungs of cystic fibrosis (CF) patients has given rise to novel nebulized antimicrobials. We have synthesized a silver-carbene complex (SCC10) active against a variety of bacterial strains associated with CF and chronic lung infections. Our studies have demonstrated that SCC10-loaded into L-tyrosine polyphosphate nanoparticles (LTP NPs) exhibits excellent antimicrobial activity in vitro and in vivo against the CF relevant bacteria Pseudomonas aeruginosa. Encapsulation of SCC10 in LTP NPs provides sustained release of the antimicrobial over the course of several days translating into efficacious results in vivo with only two administered doses over a 72 h period.

Polyelectrolyte complex of chondroitin sulfate and peptide with lower pI value in poly(lactide-co-glycolide) microsphere for stability and controlled release

A polyelectrolyte complex between a therapeutic peptide and chargeable polymer was applied to prevent peptide denaturation in poly(lactide-co-glycolide) (PLGA) microspheres. Chondroitin sulfate A (CsA) was employed as a polymeric additive for the formation of an ionic complex with insulin (InS). The complex prepared at pH 3.0 evidenced a nano-size in the range of 100-400 nm with a mono distribution. The stability of InS in the complex in an organic/water (O/W) interface was verified via RP-HPLC. The insulin in the complex evidenced a retention time almost identical to native InS, whereas free insulin did not evidence such a retention time. On the basis of these studies, PLGA microspheres including a complex with various CsA/InS ratios were prepared via a double-emulsion method (PLGA/CsA MS). InS loading efficiency in the system is higher than that of the microspheres without CsA. The system evidenced a lower initial burst and, following the initial burst, continuous release kinetics for 30 days. Circular dichroism (CD) spectra demonstrated that the insulin in PLGA/CsA MS is more stable than the PLGA-only microspheres (PLGA/only MS) for 20 days. These results indicate that the complex system with CsA is useful for the long-term delivery of peptides with lower pI values.

Poly(ethylene glycol)-modified proteins: implications for poly(lactide-co-glycolide)-based microsphere delivery

The reduced injection frequency and more nearly constant serum concentrations afforded by sustained release devices have been exploited for the chronic delivery of several therapeutic peptides via poly(lactide-co-glycolide) (PLG) microspheres. The clinical success of these formulations has motivated the exploration of similar depot systems for chronic protein delivery; however, this application has not been fully realized in practice. Problems with the delivery of unmodified proteins in PLG depot systems include high initial "burst" release and irreversible adsorption of protein to the biodegradable polymer. Further, protein activity may be lost due to the damaging effects of protein-interface and protein-surface interactions that occur during both microsphere formation and release. Several techniques are discussed in this review that may improve the performance of PLG depot delivery systems for proteins. One promising approach is the covalent attachment of poly(ethylene glycol) (PEG) to the protein prior to encapsulation in the PLG microspheres. The combination of the extended circulation time of PEGylated proteins and the shielding and potential stabilizing effects of the attached PEG may lead to improved release kinetics from PLG microsphere system and more complete release of the active conjugate.