Sustained-release G-CSF microspheres using a novel solid-in-oil-in-oil-in-water emulsion method

Recent Advances in the Preparation of Protein/peptide Microspheres by Solvent Evaporation Method

Protein/peptide drugs are extensively used to treat various chronic and serious diseases. The short half-life in vivo of protein and peptide as therapeutics drug limit the realization of complete effects. Encapsulating drugs in microspheres can slow the speed of drug release and prolong the efficacy of drugs. The solvent evaporation method is widely used to prepare protein/ peptide microspheres because of its facile operation and minimal equipment requirements. This method has several challenges in the lower encapsulation efficiency, fluctuant release profiles and the stabilization of protein/peptides, which researchers believe may be solved by adjusting the preparation parameter or formulation of microspheres. The article discusses the formulation parameters that govern the preparation of protein/peptide-loaded microspheres by the solvent evaporation method, which provides an overview of the current promising strategies for solvent evaporation for protein/peptide microspheres. The article takes parameter evaluation as the framework, facilitating subsequent researchers to quickly find possible solutions when encountering problems.

A Poly-ADP-Ribose Polymer-GCSF Conjugate

Poly-ADP-ribose (PAR) is a naturally occurring form of polymers synthesized through enzymatic reactions catalyzed by poly(ADP-ribose) polymerases (PARPs). It is known for regulating various important cellular signaling pathways and processes. As a water soluble and biocompatible type of polymer, PAR may hold promise for safe and efficient delivery of therapeutics. To explore the therapeutic potential of PAR polymers, we herein generate PAR polymers conjugated with human granulocyte colony-stimulating factor (GCSF) protein by harnessing human PARP1-catalyzed auto-poly-ADP-ribosylation and a clickable analogue of nicotinamide adenine dinucleotide (NAD⁺). The resulting PAR polymer-based conjugate with multivalent GCSF ligands exhibits a potent cell proliferative activity. Notably, mice treated with a single dose of the PAR polymer-GCSF conjugate show sustained high levels of neutrophil in blood for 11 days, demonstrating excellent in vivo efficacy. Functionalized PAR polymers may provide new scaffolds for conjugating with therapeutic proteins or peptides toward improved pharmacological activities.

Novel G-CSF conjugated anionic globular dendrimer: Preparation and biological activity assessment

The most crucial role of granulocyte colony-stimulating factor (G-CSF) in the body is to increase the strength of immune system. In recent years, research on the use of nanoparticles in pharmaceuticals has been considered, most of which have been for drug-loading purposes. In this study, a novel G-CSF conjugated dendrimer was synthesized and characterized using different techniques. In vitro cytotoxicity was assessed on A549 and L929 cells, while abnormal toxicity was studied in mice. In vitro and in vivo biological activities were assessed in NFS60 cells and rats, respectively. In addition, in vivo distribution, plasma half-life, and histopathological effect were studied in rat. The characterization tests confirmed the successful conjugation. There was no difference between G-CSF cytotoxicity before and after conjugation, and no difference with the control group. No mice showed abnormal toxicity. Although in vitro biological activity revealed both conjugated and free G-CSF promote proliferation cells, biological activity decreased significantly after conjugation about one-third of the unconjugated form. Nonetheless, in vivo biological activity of conjugated G-CSF increased by more than 2.5-fold relative to the unconjugated form, totally. Fortunately, no histopathologic adverse effect was observed in vital rat tissues. Also, in vivo distribution of the conjugate was similar to the native protein with an enhanced terminal half-life. Our data revealed that G-CSF conjugated dendrimer could be considered as a candidate to improve the in vivo biological activity of G-CSF. Moreover, multivalent capability of the dendrimer may be used for other new potentials of G-CSF in future perspectives.

Sorafenib and 2,3,5-triiodobenzoic acid-loaded imageable microspheres for transarterial embolization of a liver tumor

Sorafenib (SOF; an angiogenesis inhibitor) and 2,3,5-triiodobenzoic acid (TIBA; a contrast agent for computed tomography imaging)-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres (MSs) were fabricated. Embolization, drug delivery, and tracing the distribution of MSs for liver cancer therapy were accomplished with the developed MSs after their intra-arterial (IA) administration. SOF/TIBA/PLGA MSs with 24.8–28.5 µm mean diameters were prepared, and the sustained release of SOF from MSs was observed. Lower systemic exposure (represented as the area under the curve [AUC]) and maximum drug concentration in plasma (C_max) values of the SOF/TIBA/PLGA MSs group (IA administration, 1 mg/kg) in the results of the pharmacokinetic study imply alleviated unwanted systemic effects (e.g., hand and foot syndrome), compared to the SOF solution group (oral administration, 10 mg/kg). In a rat hepatoma model, the increase of microvessel density (MVD) following arterial embolization (i.e., reactive angiogenesis) was partially limited by SOF/TIBA/PLGA MSs. This resulted in the SOF/TIBA/PLGA MSs group (IA administration, single dosing, 1 mg/kg) showing a smaller tumor size increase and viable tumor portion compared to the TIBA/PLGA MSs group. These findings suggest that a developed SOF/TIBA/PLGA MS can be a promising therapeutic system for liver cancer using a transarterial embolization strategy.

Synchrotron radiation-based Fourier-transform infrared spectromicroscopy for characterization of the protein/peptide distribution in single microspheres

The present study establishes a visualization method for the measurement of the distribution and localization of protein/peptide constituents within a single poly-lactide-co-glycolide (PLGA) microsphere using synchrotron radiation–based Fourier-transform infrared spectromicroscopy (SR-FTIR). The representative infrared wavenumbers specific for protein/peptide (Exenatide) and excipient (PLGA) were identified and chemical maps at the single microsphere level were generated by measuring and plotting the intensity of these specific bands. For quantitative analysis of the distribution within microspheres, Matlab software was used to transform the map file into a 3D matrix and the matrix values specific for the drug and excipient were extracted. Comparison of the normalized SR-FTIR maps of PLGA and Exenatide indicated that PLGA was uniformly distributed, while Exenatide was relatively non-uniformly distributed in the microspheres. In conclusion, SR-FTIR is a rapid, nondestructive and sensitive detection technology to provide the distribution of chemical constituents and functional groups in microparticles and microspheres.

pH-sensitive degradable nanoparticles for highly efficient intracellular delivery of exogenous protein

BACKGROUND

Encapsulating exogenous proteins into a nanosized particulate system for delivery into cells is a great challenge. To address this issue, we developed a novel nanoparticle delivery method that differs from the nanoparticles reported to date because its core was composed of cross-linked dextran glassy nanoparticles which had pH in endosome-responsive environment and the protein was loaded in the core of cross-linked dextran glassy nanoparticles.

METHODS

In this study, dextran in a poly(ethylene glycol) aqueous two-phase system created a different chemical environment in which proteins were encapsulated very efficiently (84.3% and 89.6% for enhanced green fluorescent protein and bovine serum albumin, respectively) by thermodynamically favored partition. The structures of the nanoparticles were confirmed by confocal laser scanning microscopy and scanning electron microscopy.

RESULTS

The nanoparticles had a normal size distribution and a mean diameter of 186 nm. MTT assays showed that the nanoparticles were nontoxic up to a concentration of 2000 μg/mL in human hepatocarcinoma cell line SMMC-7721, HeLa, and BRL-3A cells. Of note, confocal laser scanning microscopy studies showed that nanoparticles loaded with fluorescein isothiocyanate-bovine serum albumin were efficiently delivered and released proteins into the cytoplasm of HeLa cells. Flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling assays showed that nanoparticles with a functional protein (apoptin) efficiently induced significant tumor cell apoptosis, which was confirmed by DAPI staining.

CONCLUSION

Our findings indicate that these nanoparticles meet the high demands for delivering protein medicines and have great potential in protein therapy.

Novel preparation method for sustained-release PLGA microspheres using water-in-oil-in-hydrophilic-oil-in-water emulsion

An increasing number of drugs are needing improved formulations to optimize patient compliance because of their short half-lives in blood. Sustained-release formulations of drugs are often required for long-term efficacy, and microspheres are among the most popular ones. When drugs are encapsulated into microsphere formulations, different methods of preparation need to be used according to specific clinical requirements and the differing physicochemical characteristics of individual drugs. In this work, we developed a novel method for sustained-release drug delivery using a water-in-oil-in-hydrophilic oil-in-water (w/o/oh/w) emulsion to encapsulate a drug into poly(lactic-co-glycolic acid) (PLGA) microspheres. Different effects were achieved by varying the proportions and concentrations of hydrophilic oil and PLGA. Scanning electron and optical microscopic images showed the surfaces of the microspheres to be smooth and that their morphology was spherical. Microspheres prepared using the w/o/oh/w emulsion were able to load protein efficiently and had sustained-release properties. These results indicate that the above-mentioned method might be useful for developing sustained-release microsphere formulations in the future.