Design of liposome to improve encapsulation efficiency of gelonin and its effect on immunoreactivity and ribosome inactivating property

Investigation on the Preparation, Characteristics, and Controlled Release Model of Paeonol-Loaded Liposome in Carbomer Hydrogel

OBJECTIVE

Paeonol is a phenolic compounce that is volatile. In order to decrease its volatility and achieve controlled release, paeonol-loaded liposome in carbomer hydrogel was prepared by coating with soybean phospholipid via ethanol injection method and then added into the carbomer hydrogel.

METHODS

The quality of paeonol-loaded liposome in carbomer hydrogel was evaluated by the degree of roundness, particle size distribution, zeta potential, entrapment efficiency (filtration method and chitosan neutralization method), viscosity, infrared spectrum, etc. Furthermore, the diffusion from paeonolloaded liposome in hydrogel was studied in vitro.

RESULTS

The results showed that the average particle size of paeonol-loaded liposome was about 401 nm, the potential was -17.8 mV, and the entrapment efficiency was above 45%. The viscosity of paeonol- loaded liposome in hydrogel was 23.972×10-3 Pa*s, and the diffusion rate from paeonol-loaded liposome in hydrogel in vitro was obviously slower than that from the other paeonol preparations.

CONCLUSION

The conclusions could be drawn that paeonol-loaded liposome in hydrogel was a kind of novel preparation, and its diffusion in vitro had obvious controlled-release characteristics, which further proved that it might improve the bioavailability of paeonol.

Nasal delivery of donepezil HCl-loaded hydrogels for the treatment of Alzheimer's disease

This study aims to prepare, characterize and evaluate the pharmacokinetics of liposomal donepezil HCl (LDH) dispersed into thiolated chitosan hydrogel (TCH) in rabbits. Various hydrogels including TCH were prepared, and after characterization, TCH was selected for subsequent evaluations, due to the promising results. TCH was then incorporated with LDH prepared by reverse phase evaporation method. The hydrogel was characterized using scanning electron microscope, dialysis membrane technique, and ultra-performance liquid chromatography methods. The optimized resultant was then evaluated in terms of pharmacokinetics in an in vivo environment. The mean size of LDH and drug entrapment efficiency were 438.7 ± 28.3 nm and 62.5% ± 0.6, respectively. The controlled drug release pattern results showed that the half-life of the loaded drug was approximately 3.5 h. Liposomal hydrogel and free liposomes were more stable at 4 °C compared to those in 20 °C. The pharmacokinetics study in the rabbit showed that the optimized hydrogel increased the mean peak drug concentration and area under the curve by 46% and 39%, respectively, through nasal route compared to the oral tablets of DH. Moreover, intranasal delivery of DH through liposomal hydrogel increased the mean brain content of the drug by 107% compared to the oral DH tablets. The results suggested that liposomes dispersed into TCH is a promising device for the nasal delivery of DH and can be considered for the treatment of Alzheimer's disease.

Synergistic antitumor activity from two-stage delivery of targeted toxins and endosome-disrupting nanoparticles

Plant-derived Type I toxins are candidate anticancer therapeutics requiring cytosolic delivery into tumor cells. We tested a concept for two-stage delivery, whereby tumor cells precoated with an antibody-targeted gelonin toxin were killed by exposure to endosome-disrupting polymer nanoparticles. Co-internalization of particles and tumor cell-bound gelonin led to cytosolic delivery and >50-fold enhancement of toxin efficacy. This approach allows the extreme potency of gelonin to be focused on tumors with significantly reduced potential for off-target toxicity.

Carcinogenesis response modulation induced by gelonin encapsulated in liposome

The effectiveness of gelonin to arrest protein synthesis, thereby limiting the growth of cancer cells was studied by encapsulating it into liposomes. The protein was extracted from the seeds of Indian plant Gelonium multiflorum by ammonium sulfate precipitation and purified using cation-exchange and gel-filtration chromatography. Biological activity of purified gelonin was determined using a rabbit reticulocyte lysate assay in the cell-free translational experiments. Gelonin was encapsulated in conventional liposomes prepared by the dry film method in order to retain biological activity of the entrapped protein. Carcinogenesis was induced in Swiss albino mice by intravenous administration of DBN (10 mg kg(-1) body weight) at weekly intervals. Marker enzyme assays (GGT, AChE, and GST), GSH levels, cell proliferation assay, hepatocyte DNA analysis, histological examination of micro sections of liver tissues were parameters used to monitor carcinogenesis induction, and regression in mice. From the in vitro experiments conducted, it was observed that gelonin upon its encapsulation into liposome, resulted in significant destruction of the transformed liver cells by its cytotoxic effects that arrest protein synthesis. Various parameters studied to monitor regression also suggested mass cell destruction to liver upon administration of liposomal gelonin in mice exposed to DBN.

Radiomodulatory effect of liposome encapsulated AK-2123 on tumor in mice exposed to hepatocarcinogen

An attempt was made to evaluate the whole body gamma-radiation effect on tumor in the presence of free and liposome encapsulated AK-2123, a hypoxic cell radiosensitizer that has widely been used in combination with a number of cancer therapies such as thermotherapy, chemotherapy and radiotherapy. Entrapment efficiency of AK-2123 into liposome was determined by LASER Raman spectroscopy. Cancer induction in mice was carried out by repeated exposure of N-nitrosodiethylamine (DEN) in combination with partial hepatectomy. Parameters such as marker enzymes activities (GGT and AChE), rates of nucleic acid synthesis, viability modification factor and the histology of liver tissues monitored, supported the induction of cancer in liver. In addition, the effect of free as well as liposome encapsulated AK-2123 on haemopoietic parameters were also studied. It was observed that AK-2123 after incorporation into liposome afforded more efficient radiomodulatory effects than that of free AK-2123 as determined by the above-mentioned parameters. Neither free AK-2123 nor liposome encapsulated AK-2123 showed any detectable toxic effects on the mice. Thus, it is seen that treatment of cancer with a combination of radiation, a radiomodifier and a drug delivery system, opens a wide scope for exploitation for the improvement of existing cancer therapies.

Tumor cell killing enabled by listeriolysin O-liposome-mediated delivery of the protein toxin gelonin

Gelonin is a type I plant toxin that has potential as an effective anti-tumor agent by virtue of its enzymatic capacity to inactivate ribosomes and arrest protein synthesis, thereby effectively limiting the growth of cancer cells. Being a hydrophilic macromolecule, however, gelonin has limited access to its target subcellular compartment, the cytosol; it is effectively plasma membrane-impermeant and subject to rapid degradation within endosomes and lysosomes upon cellular uptake as it lacks the membrane-translocating capability that is typically provided by a disulfide-linked B polypeptide found in the type II toxins (e.g. ricin). These inherent characteristics generate the need for the development of a specialized cytosolic delivery strategy for gelonin as an effective anti-tumor therapeutic agent. Here we describe an efficient means of delivering gelonin to the cytosol of B16 melanoma cells. Gelonin was co-encapsulated inside pH-sensitive liposomes with listeriolysin O, the pore-forming protein that mediates escape of the intracellular pathogen Listeria monocytogenes from the endosome into the cytosol. In in vitro experiments, co-encapsulated listeriolysin O enabled liposomal gelonin-mediated B16 cell killing with a gelonin IC50 of approximately 0.1 nM with an extreme efficiency requiring an incubation time of only 1 h. By contrast, cells treated with equivalent concentrations of unencapsulated gelonin or gelonin encapsulated alone in pH-sensitive liposomes exhibited no detectable cytotoxicity. Moreover, treatment by direct intratumor injection into subcutaneous solid tumors of B16 melanoma in a mouse model showed that pH-sensitive liposomes containing both listeriolysin O and gelonin were more effective than control formulations in curtailing tumor growth rates.

Direct evidence for the deoxyribonuclease activity of the plant ribosome inactivating protein gelonin

Several plant ribotoxins, including gelonin, were reported to have additional weak nuclease activities on supercoiled DNA. The potential contribution of this activity to their cytotoxicity has not been given serious consideration due to concerns about contaminating nucleases in the protein preparations. We now report the degradation of single-stranded DNA by preparations of native plant gelonin and recombinant gelonin produced in E. coli. The DNase activity of both preparations is similarly modulated by zinc. An SDS-PAGE DNase assay identifies gelonin as the polypeptide responsible for deoxyribonuclease activity.