PEGylation of G-CSF using cleavable oligo-lactic acid linkage

Smart pH-sensitive nanoassemblies with cleavable PEGylation for tumor targeted drug delivery

A new acidly sensitive PEGylated polyethylenimine linked by Schiff base (PEG-s-PEI) was designed to render pH-sensitive PEGylation nanoassemblies through multiple interactions with indomethacin and docetaxel (DTX). DTX nanoassemblies driven by PEG-s-PEI thus formulated exhibited an excellent pH-sensitivity PEGylation cleavage performance at extracellular pH of tumor microenvironment, compared to normal tissues, thereby long circulated in blood but were highly phagocytosed by tumor cells. Consequently, this smart pH-sensitive PEGylation cleavage provided an efficient strategy to target tumor microenvironment, in turn afforded superior therapeutic outcome in anti-tumor activity.

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

Background

The main treatments for cancers are still chemotherapy and radiotherapy for intermediate-stage cancer and terminal cancer. However, the therapeutic methods often result in a decreased neutrophilic granulocyte count and other side effects. In this study, in order to improve the neutrophilic granulocyte levels in the blood after radiotherapy and chemotherapy, we developed a sustained-release granulocyte colony–stimulating factor (G-CSF) microsphere formulation using a novel solid-in-oil-in-oil-in-water (S/O/O/W) emulsification method.

Methods

G-CSF was loaded into dextran nanoparticles by freezing-induced phase separation, and then the G-CSF–loaded nanoparticles were encapsulated into sustained-release poly(lactic-co- glycolic acid) microspheres using S/O/O/W emulsification. The control microspheres were also prepared through W/O/W emulsification. The performance of the two microsphere formulations was investigated both in vitro and in vivo.

Results

The microspheres for the controlled release of G-CSF in a zero-order or near-zero-order pattern were provided for 2 weeks. The in vitro cumulative G-CSF release kept over 90% of its bioactivity, which was proved by a NFS-60 cell line growth assay. The microspheres of the control group fabricated by W/O/W emulsification maintained less then half of its bioactivity. The in vivo efficacy of microspheres made using the S/O/O/W method was higher than those using the W/O/W method.

Conclusion

These results suggested that the microspheres prepared by the S/O/O/W method had increased neutrophil activity compared to those prepared by W/O/W.

Surgical wound healing using hemostatic gauze scaffold loaded with nanoparticles containing sustained-release granulocyte colony-stimulating factor

Background

The therapeutic strategies for malignant melanoma are still cancer chemotherapy, radiotherapy, and tumor resection. However, these therapeutic strategies often lead to a reduced neutrophilic granulocyte count or loss of more blood after surgical tumor resection. In this study, we developed a formulation of hemostatic gauze impregnated with sustained-release granulocyte colony-stimulating factor (G-CSF) with increasing of the neutrophilic granulocyte count in the blood following chemotherapy and decreasing blood loss after surgical tumor resection.

Methods

We designed a formulation with both hemostatic properties and increased neutrophil content to be used in cancer chemotherapy, radiotherapy, and tumor resection, comprising a hemostatic gauze as a scaffold and (G-CSF)-loaded dextran nanoparticles coated with polylactic-co- glycolic acid (PLGA) solution fabricated by direct spray-painting onto the scaffold and then vacuum-dried at room temperature. The performance of this system was evaluated in vitro and in vivo.

Results

Nearly zero-order release of G-CSF was recorded for 12–14 days, and the cumulative release of G-CSF retained over 90% of its bioactivity in a NFS-60 cell line proliferation assay when the scaffold was incubated in phosphate-buffered saline (pH 7.4) at 37°C. The in vivo hemostatic efficacy of this formulation was greater than that of native G-CSF, the scaffold directly spray-painted with G-CSF solution or PLGA organic solution as a coating, or when a blank scaffold was covered with the coating.

Conclusion

Our results suggest that this formulation has both hemostatic properties and increased neutrophil activity.

Releasable PEGylation of proteins with customized linkers

Releasable PEGylation employs customized linkers that reversibly tether a therapeutic moiety with polyethylene glycol polymers. The choice of releasable PEG linkers may have numerous applications that are insufficiently addressed by stable polymer attachment. Releasable PEGylation provides regeneration of authentic and fully active drug and allows tailored design of critical pharmacological parameters such as the maximal drug concentration and total drug exposure. This provides a prodrug format that combines beneficial attributes of PEGylation with controlled release. The linker release mechanisms are shown to be kinetically controlled by the design of a hydrolytically labile center and side chains for the steric modulation of the intramolecular elimination reactions and linker self-immolation. Recent reports have described both aromatic and aliphatic based customized linkers that release the unaltered original drug under physiological conditions and at therapeutically useful release rates. These studies have examined bioconjugates of cytokines, peptide hormones, immunotoxins, enzymes, and reporter proteins.

G-CSF loaded biodegradable PLGA nanoparticles prepared by a single oil-in-water emulsion method

A new formulation method was developed for preparing poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles loaded with recombinant human granulocyte colony-stimulating factor (rhG-CSF). Lyophilized rhG-CSF powder and PLGA polymer were directly co-dissolved in a single organic phase, and the resulting solution was dispersed into an aqueous solution. PLGA nanoparticles encapsulating rhG-CSF were produced by a spontaneous emulsion/solvent diffusion method. In this manner, rhG-CSF was molecularly dissolved in the polymer phase. Release profile of rhG-CSF from PLGA nanoparticles was compared with those from two kinds of PLGA microparticles which were separately prepared by either single oil-in-water (O/W) or double water-in-oil-in-water (W/O/W) emulsion technique. The sizes of rhG-CSF loaded nanoparticles, O/W microparticles, and W/O/W microparticles were about 257 nm, 4.7 microm, and 4.3 microm, respectively. For rhG-CSF nanoparticles, about 90% of encapsulated rhG-CSF was released out in a sustained manner from PLGA nanoparticles over a 1 week period, but for rhG-CSF microparticles, only about 20% of rhG-CSF could be released out during the same period. Reversed phase and size exclusion chromatograms revealed that the structural integrity of released rhG-CSF from nanoparticles was nearly intact, compared to that of native rhG-CSF.

Folate receptor mediated intracellular protein delivery using PLL–PEG–FOL conjugate

To develop a receptor-mediated intracellular delivery system that can transport therapeutic proteins or other bioactive macromolecules into a specific cell, a di-block copolymer conjugate, poly(L-lysine)-poly(ethylene glycol)-folate (PLL-PEG-FOL), was synthesized. The PLL-PEG-FOL conjugate was physically complexed with fluorescein isothiocyanate conjugated bovine serum albumin (FITC-BSA) in an aqueous phase by ionic interactions. Cellular uptake of PLL-PEG-FOL/FITC-BSA complexes was greatly enhanced against a folate receptor over-expressing cell line (KB cells) compared to a folate receptor deficient cell line (A549 cells). The presence of an excess amount of free folate (1 mM) in the medium inhibited the intracellular delivery of PLL-PEG-FOL/FITC-BSA complexes. This suggests that the enhanced cellular uptake of FITC-BSA by KB cells in a specific manner was attributed to folate receptor-mediated endocytosis of the complexes having folate moieties on the surface. The PLL-PEG-FOL di-block copolymer could be potentially applied for intracellular delivery of a wide range of other biological active agents that have negative charges on the surface.