Method for large-scale isolation and purification of R-phycoerythrin from red alga Polysiphonia urceolata Grev

Preparation of the phycoerythrin subunit liposome in a photodynamic experiment on liver cancer cells

AIM

Efforts are underway to establish a preparation method for the phycoerythrin subunit (PE-sub) liposome, and enhance the cellular uptake and photodynamic therapy (PDT) effect on cancer cells.

METHODS

A film dispersion method was used to prepare the PE-sub liposome, an orthogonal analysis was conducted to optimize the PE-sub liposome preparation condition and determine the effects of liposomes as carriers on cell uptake in vitro. Under a fluorescence microscope, the cell survival rate of normal liver cell line HL7702 and liver cancer cell line HepG2 was assessed by 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide assay. Cell apoptosis was determined with flow cytometry and acridine orange staining after PDT treatment.

RESULTS

The optimum preparation conditions of the PE-sub liposome were found: a phosphatidylcholine-to-cholesterin ratio of 1:2, a PE-sub-to-lipid ratio of 1:30, 20 mL buffer volume, 10 min sonication time, and an average encapsulation rate of up to 47.2%. The particle size ranged from 80 to 200 nm, and the average particle diameter was 136 nm. At a concentration of 100 microg/mL, the transfection rate of the PE-sub liposome reached 18% at 2 h and 24% at 4 h, and remained steady at 5-6 h. The half lethal dose of PDT on HepG2 was 75 microg/mL, whereas the cell survival rate of HL7702 reached 80% at the same dosage. The PDT-treated cells showed characteristics of apoptosis.

CONCLUSION

The film dispersion method was found to maintain the biological characteristics of the PE-sub. The use of the liposome carrier increased the PE-sub accumulation in the cells and enhanced its PDT effect on HepG2 compared to the PE-sub. HL7702 cell toxicity on had less apparent change after PDT treatment. The PE-sub liposome demonstrated good tumor-targeting characteristics in the in vitro experiment.

Isolation, purification and characteristics of R-phycoerythrin from a marine macroalga Heterosiphonia japonica

R-phycoerythrin is one of the three phycobiliproteins which are extensively employed as fluorescent probes, and it is prepared from red macroalgae. Phycobiliproteins in the marine red macroalga Heterosiphonia japonica were extracted in 50 mM phosphate buffer (pH 7.0) and precipitated by salting-out. The R-phycoerythrin was isolated by gel filtration with Sepharose CL-4B and Sephadex G-200. Then it was purified by ion exchange chromatography on DEAE Sepharose Fast Flow which was developed by linear ionic strength gradients. The purified R-phycoerythrin gave a ratio of A(565) to A(280) of 4.89. It showed a single band and a pI of 4.8 on the examination by polyacrylamide gel electrophoresis (PAGE) and isoelectric focusing. The polypeptide analysis of the purified R-phycoerythrin by SDS-PAGE demonstrated that it contains four chromophore-carrying subunits and no colorless polypeptide and has two hexameric aggregates. The preparative procedures of the R-phycoerythrin purification established based on the experiments exhibit advantages and can offer a reference for R-phycoerythrin preparation from other marine red macroalga.

A novel method of single step hydrophobic interaction chromatography for the purification of phycocyanin from Phormidium fragile and its characterization for antioxidant property

Phycocyanin--a major phycobiliprotein constitutively produced by many cyanobacteria--holds several promising applications in diagnostics, biomedical research, and therapeutics. This paper discusses a novel rapid method for the purification of cyanobacterial phycocyanin (C-PC) from Phormidium fragile using hydrophobic interaction chromatography. The protein was extracted and concentrated by grinding under liquid nitrogen and ammonium sulfate fractionation. C-PC was purified by single step hydrophobic interaction chromatography. Purified phycocyanin showed absorbance maximum (lambda(max)) at 624 nm. The criterion of purity (R) achieved was 4.52. Phycocyanin to phycoerythrin and phycocyanin to allophycocyanin purity ratio were 3.85 and 7.49, respectively. The purified protein showed a pI of 5.2 and has two subunits with molecular mass of 19 and 20 kDa each, corresponding to its highly reported alpha and beta subunits. The subunits of phycocyanin were confirmed by their bilin fluorescence using zinc assisted fluorescence enhancement technique. Intact C-PC was of 125 kDa as determined by HPLC, suggested the (alphabeta)(3) subunit assembly. Results obtained by this method in terms of purity, recovery, process time, simplicity, and efficacy are much better than previous methodologies. Purified phycocyanin was further scrutinized for its antioxidant capacity and judged against five non-enzymatic antioxidants by FRAP assay.

Large-scale recovery of C-phycocyanin from Spirulina platensis using expanded bed adsorption chromatography

C-phycocyanin was purified on a large scale by a combination of expanded bed adsorption, anion-exchange chromatography and hydroxyapatite chromatography from inferior Spirulina platensis that cannot be used for human consumption. First, phycobiliproteins were extracted by a simple, scaleable method and then were recovered by Phenyl-Sepharose chromatography in an expanded bed column. The purity (the A(620)/A(280) ratio) of C-phycocyanin isolated with STREAMLINE column was up to 2.87, and the yield was as high as 31 mg/g of dried S. platensis. After the first step, we used conventional anion-exchange chromatography for the purification steps, with a yield of 7.7 mg/g of dried S. platensis at a purity greater than 3.2 and with an A(620)/A(650) index higher than 5.0. The fractions from anion-exchange chromatography with a level of purity that did not conform to the above standard were subjected to hydroxyapatite chromatography, with a C-PC yield of 4.45 mg/g of dried S. platensis with a purity greater than 3.2. The protein from both purification methods showed one absolute absorption peak at 620 nm and a fluorescence maximum at 650 nm, which is consistent with the typical spectrum of C-phycocyanin. SDS-PAGE gave two bands corresponding to 21 and 18 kDa. In-gel digestion and LC-ESI-MS showed that the protein is C-phycocyanin.

Expanded-bed adsorption immobilized-metal affinity chromatography

The protocol describes a method for capture of secreted hexahistidine-tagged proteins using expanded-bed adsorption immobilized-metal affinity chromatography. The starting material for the procedure is any crude feedstock that contains a histidine (His)-tagged target protein. The protocol is exemplified using unclarified broth from Pichia pastoris fermentation as feedstock. The protocol can be used for laboratory studies or as part of a process for production of recombinant biotherapeutics to standards of good manufacturing practice. It takes approximately 5 h to purify proteins from 10 liters of feedstock and a further 5-6 h to sterilize and regenerate the column.