Weighted Mean Squared Deviation Feature Screening for Binary Features.

In this study, we propose a novel model-free feature screening method for ultrahigh dimensional binary features of binary classification, called weighted mean squared deviation (WMSD). Compared to Chi-square statistic and mutual information, WMSD provides more opportunities to the binary features with probabilities near 0.5. In addition, the asymptotic properties of the proposed method are theoretically investigated under the assumption log p = o ( n ) . The number of features is practically selected by a Pearson correlation coefficient method according to the property of power-law distribution. Lastly, an empirical study of Chinese text classification illustrates that the proposed method performs well when the dimension of selected features is relatively small.

Formulation and evaluation of poly(lactic-co-glycolic acid) microspheres loaded with an altered collagen type II peptide for the treatment of rheumatoid arthritis.

The aim of this research was to evaluate the potential of water-in-oil-in-water (w/o/w) and solid-in-oil-in-water (s/o/w) emulsification techniques to prepare the altered collagen type II peptide AP268-270 (ACTP)-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres to make ACTP more convenient as an rheumatoid arthritis treatment. Microspheres produced by the s/o/w method had higher drug encapsulation efficiency (69.7-79.8%) than those prepared by the w/o/w method (21.8-39.3%). In vitro drug release was influenced by the microencapsulation technique, molecular weight, and composition of the polymer. After intramuscular injection of the optimal formulation to Lewis rats, the concentration of ACTP peptide in serum reached its maximum level on day 3 and then remained nearly stable for approximately 4 weeks. In a collagen-induced arthritis rat model, a single intramuscular injection of ACTP-loaded PLGA microspheres had comparable efficacy to the intravenous injection of ACTP peptide solution once every other day.

Effect of site-specific PEGylation on the fibrinolytic activity, immunogenicity, and pharmacokinetics of staphylokinase.

The bacterial plasminogen-activator staphylokinase (Sak) is a promising thrombolytic agent for treating acute myocardial infarction. To effectively reduce the immunogenicity of Sak while maintaining its fibrinolytic activity, site-specific PEGylation was performed in the present study. The chemoselective cysteine PEGylation site was selected within an immunodominant region (amino acid residues 71-87) using an in silico approach. The PEGylated Sak variants prepared in this study showed a purity of >97.0%. PEGylation at Position 80 resulted in a Sak variant Sak(E80C-PEG) which has similar fibrinolytic activity and thermostability compared with the native recombinant staphylokinase (r-Sak). The immunogenicity of Sak(E80C-PEG) in guinea pigs was greatly reduced compared with the native r-Sak. Furthermore, preliminary pharmacokinetic results suggested that the plasma clearance of Sak(E80C-PEG) from the blood stream of rabbit was significantly decreased compared with that of r-Sak, resulting in a 2.8-fold increase of initial half-life and a 3.8-fold increase of systemic availability. In summary, these results demonstrated that site-specific PEGylation yielded a novel Sak variant Sak(E80C-PEG) with remarkable advantages over the unmodified Sak.

Chitosan-based thermosensitive hydrogel for nasal delivery of exenatide: Effect of magnesium chloride.

The aim of this research was to evaluate the potential of two chitosan (CS)-based hydrogel systems for nasal delivery of exenatide (EXT) in rats. Both of the EXT-loaded CS/glycerophosphate (GP)/CaCl2 (EXT/CS/GP/CaCl2) and EXT/CS/GP/MgCl2 hydrogel systems had similar in vitro release profiles. However, a difference in metal salt surprisingly resulted in multifaceted differences between the two hydrogel systems, such as EXT stability, gelation time, transepithelial transport, biodistribution and pharmacokinetics. The gelation time of the EXT/CS/GP/MgCl2 hydrogel (more than 110 min) at 37 °C was much longer than that of the EXT/CS/GP/CaCl2 hydrogel (8.0-20.4 min). Transepithelial transport analysis showed that the CS/GP/MgCl2 hydrogel enhanced EXT transport across the Calu-3 cell monolayers more than the CS/GP/CaCl2 hydrogel (P < 0.05). After nasal administration in the rats, the EXT/CS/GP/MgCl2 hydrogel increased the distribution of EXT in the targeting organs and the relative bioavailability of EXT in the rats more than the EXT/CS/GP/CaCl2 hydrogel. Moreover, both EXT/CS/GP/salt hydrogel formulation treatments in high-fat-fed rats significantly decreased food intake and body weight relative to the EXT solution within ten days (P < 0.05). The aforementioned results suggest that the EXT/CS/GP/MgCl2 hydrogel formulation is more suitable to be used as a nasally delivered EXT formulation for the treatment of weight loss.

[FTIR characterization of the secondary structure of a staphylokinase variant (K35R) encapsulated within PLGA microspheres].

The secondary structure of a staphylokinase variant (K35R, DGR) encapsulated in poly (lactic-co-glycolic acid) (PLGA) microspheres was quantitatively examined by Fourier transform infrared (FTIR) spectroscopy. Resolution enhancement technique and Fourier deconvolution were combined with band with curve-fitting procedures to quantitate the spectral information from the amide I bands. Nine component bands were found under the broad, nearly featureless amide I bands and assigned to alpha-helix, beta-sheet, turn and irregular (random) structures. The changes of bands at 1 651 and 1 623 cm(-1) after encapsulation were discussed.

Surface-functionalized, pH-responsive poly(lactic-co-glycolic acid)-based microparticles for intranasal vaccine delivery: Effect of surface modification with chitosan and mannan.

In the present study, surface-functionalized, pH-responsive poly(lactic-co-glycolic acid) (PLGA) microparticles were investigated for nasal delivery of hepatitis B surface Antigen (HBsAg). pH-responsive PLGA, chitosan modified PLGA (CS-PLGA), mannan modified PLGA (MN-PLGA), mannan and chitosan co-modified PLGA (MN-CS-PLGA) microparticles were prepared utilizing a double-emulsion method. Antigen was released rapidly from four types of microparticles at pH5.0 and pH 6.0, but slowly released at pH 7.4. Mannan and chitosan surface modification enhanced intracellular microparticle uptake by macrophages. Following intracellular macrophage antigen uptake, antigen release occurred in three different patterns: fast release from PLGA and MN-PLGA microparticles in endosomes/lysosomes, slow release from CS-PLGA microparticles in cytoplasm and a combination of fast release and slow release patterns from MN-CS-PLGA microparticles. Furthermore, chitosan coating modification increased the residence time of CS-PLGA and MN-CS-PLGA microparticles in the nasal cavity. In vivo immunogenicity studies indicated that MN-CS-PLGA microparticles induced stronger humoral and cell-mediated immune responses compared with PLGA, MN-PLGA and CS-PLGA microparticles. These results suggest that surface modification of pH-responsive PLGA microparticles with mannan and chitosan is a promising tool for nasal delivery of HBsAg.

Stabilization and immune response of HBsAg encapsulated within poly(lactic-co-glycolic acid) microspheres using HSA as a stabilizer.

The aim of this study was to prepare poly(lactic-co-glycolic acid) (PLGA) microspheres containing hepatitis B virus surface antigen (HBsAg) using human serum albumin (HSA) as a stabilizer. Lyophilization and emulsification of HBsAg solution with dichloromethane caused a considerable loss of HBsAg antigenicity. Thus, the effects of HSA and trehalose on HBsAg recovery during lyophilization and emulsification were investigated. Adding HSA to HBsAg solutions significantly improved antigen recovery to >90% during lyophilization and emulsification. The effects of co-encapsulated HSA on the characteristics of the PLGA microspheres and stability of HBsAg released from the microspheres were also investigated. The in vitro release test showed that HBsAg was released from the PLGA microspheres continuously over seventy days. A large amount of released HBsAg was inactive without co-encapsulation of HSA. On the contrary, with HSA co-encapsulation, the released HBsAg retained approximately 90% of its antigenicity. The single injection of the HBsAg-HSA-loaded PLGA microspheres in rats resulted in higher anti-HBsAg IgG and Th1 cytokine levels than the single injection of the HBsAg-loaded microspheres or two injections of the conventional aluminum-adjuvanted HBsAg vaccine. Based on these findings, the HBsAg-HSA-loaded PLGA microspheres could be an effective carrier for HBsAg and form a promising depot system.

Reversed flow injection spectrophotometric determination of low residuals of chlorine dioxide in water using chlorophenol red.

A novel, simple, rapid, sensitive and highly selective flow injection procedure for the spectrophotometric determination of chlorine dioxide in the presence of other chlorine species, viz, free chlorine, chlorite, chlorate and hypochlorite, is developed. The method is based on the discoloration reaction between chlorine dioxide and chlorophenol red and can overcome the shortcomings existed in direct spectrophotometric determination for chlorine dioxide owing to the serious interference of free and combined chlorine. The procedure gave a linear calibration graph over the range 0-0.71 mg/L of chlorine dioxide. With a detection limit of 0.024 mg/L and a sample throughput of 60 samples/h.

Refolding of a staphylokinase variant y1-Sak by reverse dilution.

To develop more potent thrombolytic agents with fibrinolytic and antiplatelet aggregation activity, staphylokinase (Sak) variant Y1-Sak, a recombinant mutant of the Staphylococcus aureus protein Sak, was constructed. Y1-Sak formed an insoluble inclusion body when overexpressed in Escherichia coli strain JF1125. To obtain an optimized refolding process, dilution refolding was used to optimize refolding conditions. The results revealed that additive L: -arginine and refolding temperature played critical roles in the refolding of Y1-Sak. Subsequently, two refolding methods, gel filtration and reverse dilution, were investigated to refold Y1-Sak. The results indicated that the fibrinolytic activity and recovery of Y1-Sak from gel filtration were lower than those from reverse dilution. Reverse dilution refolding successfully reduced the side reaction of refolding with the help of L: -arginine, and the fibrinolytic activity and recovery of Y1-Sak were significantly improved. Functional analysis revealed that refolded Y1-Sak by reverse dilution possessed fibrinolytic and antiplatelet aggregation activities. Moreover, the immunogenicity of Y1-Sak was significantly reduced.

Purification and characterization of a staphylokinase variant, K35R.

DGR [staphylokinase (Sak) variant K35R, in which lysine (K) at position 35 is replaced by arginine (R)], a recombinant mutant of the Staphylococcus aureus enzyme, is a promising drug for thrombotic disorders. In the present work, DGR was successfully overexpressed by the plasmid JF1125[pST-DGR] as a soluble cytoplasmic protein in a 30-litre fermentor that accounted for more than 50% of the total cellular protein. The expressed DGR was subsequently purified by using a simple three-step chromatographic purification process developed at a pilot scale. The clearance of host-cell-protein contaminants in the protein purification process was confirmed by SDS/PAGE and Western blotting, using rabbit antisera raised against Escherichia coli JF1125 cell proteins. SDS/PAGE, isoelectric focusing and HPLC-MS analysis indicated that the purified DGR is almost completely homogeneous. The purification process resulted in greater-than-98% pure DGR and yielded up to 25.0 mg/g wet weight of cells. The effect of pH and temperature on the stability of DGR was investigated further. The results showed that DGR was highly stable at neutral pH and more stable than two other wild-type Saks, SakSTAR and Sak42D, when submitted to high temperatures.