Co-delivery of LETM1 and CTMP synergistically inhibits tumor growth in H-ras12V liver cancer model mice

As hepatocellular carcinoma (HCC) is one of the most common tumors worldwide, development of novel therapeutic approaches for HCC is urgently needed. Two different genes, LETM1 and CTMP, which target mitochondrial functions, were chosen and linked using 2A-peptide sequence. Successful self-cleavage of 2A-peptide induced synergistic antitumor effect in the liver of H-ras12V, the HCC model mice, by simultaneous activation of LETM1 (Leucine zipper/EF hand-containing transmembrane-1) and CTMP (carboxyl-terminal modulator protein). Overexpression of LETM1 and CTMP significantly reduced the incidence of tumorigenesis, which were confirmed by gross and microscopic observations. Morphological changes in mitochondria, such as swelling and loss of cristae, were significant, and the prolonged activation of defects in mitochondrial function led to mitochondria-mediated apoptosis. Furthermore, with CTMP as a direct binding partner of Akt1, and LETM1 as a binding partner of CTMP, LETM1-2A-CTMP downregulated the Akt1 pathway at both Ser473 and Thr308 sites of phosphorylation. Proliferation and angiogenesis, which are important in cancer prognosis, were reduced in tumor sites after introduction of LETM1-2A-CTMP. Taken together, the results indicate that introduction of the mitochondria-targeting genes, LETM1 and CTMP, and self-processing capacity of 2A-peptide sequence exerts an antitumor effect in liver of H-ras12V mice, suggesting its potential as a tool for gene therapy.

Suppression of tumor growth in xenograft model mice by programmed cell death 4 gene delivery using folate-PEG-baculovirus

Cancer gene therapy using tumor suppressor genes is considered to be an attractive approach for arresting cell growth and inducing apoptosis. Programmed cell death 4 (Pdcd4) is a tumor suppressor gene, which prevents tumorigenesis and tumor progression. To address the issue of whether expression of PDCD4 protein induces apoptosis in cancerous cells, the Pdcd4 gene was delivered using folate-PEG-baculovirus. Folate-PEG-baculovirus containing Pdcd4 gene (F-P-Bac-Pdcd4) was constructed by attachment of F-PEG to the baculovirus surface using chemical modification. The F-P-Bac-Pdcd4 showed enhanced transduction efficiency, efficiently expressed PDCD4 protein, and induced apoptosis in human epidermal carcinoma (KB) cells as compared with an unmodified baculovirus. In a tumor xenograft study, injection of F-P-Bac-Pdcd4 into tumors established from the KB cell line by subcutaneous implantation significantly suppressed tumor growth and induced apoptosis. Thus, this study shows a new baculovirus-mediated tumor suppressor gene delivery system for cancer therapy.

Degradable polyethylenimines as DNA and small interfering RNA carriers

Gene therapy is a powerful approach in the treatment of a wide range of both inherited and acquired diseases. Nonviral delivery systems have been proposed as safer alternatives to viral vectors because they avoid the inherent immunogenicity and production problems that are seen when viral systems are used. Many cationic polymers, including high-molecular-weight polyethylenimine (PEI) have been widely studied as gene-delivery carriers, both, in vitro and in vivo. However, interest has recently developed in degradable polymeric systems. The advantage of degradable polymer is its low in-vivo cytotoxicity, which is a result of its easy elimination from the cells and body. Degradable polymer also enhances transfection of DNA or small interfering RNA (siRNA) for efficient gene expression or silencing, respectively. This review paper summarizes and discusses the recent advances with degradable PEIs, such as cross-linked and grafted PEIs for DNA and siRNA delivery.

Bioadhesive Fluorescent Microspheres as Visible Carriers for Local Delivery of Drugs. II: Uptake of Insulin-Loaded PCEFB/PLGA Microspheres by the Gastrointestinal Tract

Uptake of novel inherently fluorescent microspheres composed of a luminescent polyanhydride, poly[p-(carboxyethylformamido)-benzoic anhydride] (PCEFB), and poly(lactide-co-glycolide) (PLGA) (2:1, weight ratio) by the gastrointestinal tract was evaluated by fluorescent microscopy. Oral efficiency of the incorporated insulin also was determined by measuring reduction of plasma glucose levels after feeding diabetic rats with a single dose of the microspheres. We found that PCEFB/PLGA microspheres could adhere to the intestinal epithelium and traverse the absorptive cells. A large number of the spheres were observed in spleen, whereas few were detected in liver within the evaluated period of time. Apparent reduction of the plasma glucose levels was observed over a span of 6 h postfeeding. The unique properties of the delivery system such as biodegradability, bioadhesivity, and inherently luminescent characteristics render it an ideal "visible" tracer for monitoring oral fate of polymeric microspheres.

Preparation, characterization andin vitrorelease properties of ibuprofen-loaded microspheres based on polylactide, poly(϶-caprolactone) and their copolymers

In this paper, ibuprofen was encapsulated into microspheres by oil-in-water (o/w) emulsion solvent evaporation method. Biodegradable polymers with certain compositions and characteristics such as polylactide (PLA), poly(epsilon-caprolactone) (PCL) and their block copolymer were used to prepare the microspheres. The results indicate that, under the same processing conditions, the drug entrapment efficiency was similar (approximately 80%) for microspheres prepared with PLA and P(LA-b-CL) (78.7/21.3 by mole), but it was only 25.4% for PCL microspheres. The in vitro drug release rate decreased in the order of PCL, P(LA-b-CL) (78.7/21.3 by mole) and PLA microspheres. PCL microspheres showed more serious burst release during the first day (almost 80%) than P(LA-b-CL) (50%) and PLA microspheres (18%). The complete ibuprofen release duration from the last two kinds of microspheres exceeded 1 month. Characterization of the microspheres by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and polarized optical microscope (POM) revealed that ibuprofen was amorphous in PCL microspheres and partially crystalline in P(LA-b-CL) and PLA microspheres. The different release behaviour of ibuprofen from the three kinds of microspheres could be attributed to the different crystallinity of the studied polymers and drug dispersion state in polymer matrices. All the above results suggest that the copolymer with a certain ratio of lactide to -caprolactone could have potential applications for long-term ibuprofen release.

Improvement of protein loading and modulation of protein release from poly(lactide-co-glycolide) microspheres by complexation of proteins with polyanions

A novel method was proposed to incorporate and modulate protein release from poly(lactide-co-glycolide) (PLGA) microspheres by a modified w/o/w emulsion solvent evaporation technique with poly(methacrylic acid) (PMAA)/insulin complex suspension as the inner aqueous phase instead of the neat protein solution. It was found that a reversible, water-insoluble complex could be formed between PMAA and insulin by electrostatic interactions. A great increase in insulin entrapment efficiency was observed as the PMAA/insulin complex was adopted to prepare PLGA microspheres. A large number of the complex particles adsorbed at the surface of the microspheres, resulting in the more rapid insulin release. The complexation and microencapsulation processes have little effect on insulin bioactivity, which was revealed by examination of the plasma glucose levels of the diabetic rats administrated with the microspheres.

Receptor-mediated gene delivery using chemically modified chitosan

Chitosan has been investigated as a non-viral vector because it has several advantages such as biocompatibility, biodegradability and low toxicity with high cationic potential. However, the low specificity and low transfection efficiency of chitosan need to be solved prior to clinical application. In this paper, we focused on the galactose or mannose ligand modification of chitosan for enhancement of cell specificity and transfection efficiency via receptor-mediated endocytosis in vitro and in vivo.

Galactosylated chitosan-graft-polyethylenimine as a gene carrier for hepatocyte targeting

Chitosans have been proposed as alternative, biocompatible cationic polymers for nonviral gene delivery. However, the low transfection efficiency and low specificity of chitosan need to be addressed before clinical application. We prepared galactosylated chitosan-graft-polyethylenimine (GC-g-PEI) copolymer by an imine reaction between periodate-oxidized GC and low-molecular-weight PEI. The molecular weight and composition were characterized using gel permeation chromatography column with multi-angle laser scattering and (1)H nuclear magnetic resonance, respectively. The copolymer was complexed with plasmid DNA in various copolymer/DNA (N/P) charge ratios, and the complexes were characterized. GC-g-PEI showed good DNA-binding ability and superior protection of DNA from nuclease attack and had low cytotoxicity compared to PEI 25K. GC-g-PEI/DNA complexes showed higher transfection efficiency than PEI 25K in both HepG2 and HeLa cell lines. Transfection efficiency into HepG2, which has asialoglycoprotein receptors, was higher than that into HeLa, which does not. GC-g-PEI/DNA complexes also transfected liver cells in vivo after intraperitoneal (i.p.) administration more effectively than PEI 25K. These results suggest that GC-g-PEI can be used in gene therapy to improve transfection efficiency and hepatocyte specificity in vitro and in vivo.

Regulation of adipocyte differentiation by PEGylated all-trans retinoic acid: reduced cytotoxicity and attenuated lipid accumulation

Obesity is major risk factor for many disorders, including diabetes, hypertension and heart disease. Unfortunately, there is a dearth of therapeutic agents available to clinicians for the treatment of obesity. The principal aim of this study was to investigate whether PEGylated all-trans retinoic acid (PRA) can have favorable stability and biological activity in 3T3-L1 preadipocytes as an antiobesity drug. Here, we found that PRA inhibits the process of adipogenesis, including survival of adipocytes and differentiation to mature adipocytes. The results showed that RA nanoparticles (NPs) were prepared by PEGylation; below 200 nm, PRA-NPs were obtained. Moreover, PRA decreased glycerol-3-phosphate dehydrogenase activity in 3T3-L1 preadipocytes by acting with major adipocyte marker proteins such as PPARgamma2, C/EBPalpha and aP2 modulators. Apoptosis, in addition, increased as the level of RA increased from 10 to 20 microM, whereas PRA reduced apoptosis with increasing concentrations. Our data suggest that PRA-NP has potential as an antiobesity drug carrier due to its small particle size and PEGylated core-shell structure. In addition, our results suggest that PRA inhibits the process of adipogenesis and may be developed to treat obesity. Based on these results, PRA is suitable for adipocyte studies, and an enhanced effect of PRA with adipocyte differentiation offers a challenging approach for pharmaceutical applications.

Preparation, characterization and nasal delivery of alpha-cobrotoxin-loaded poly(lactide-co-glycolide)/polyanhydride microspheres

In this study, alpha-cobrotoxin was incorporated into the microspheres composed of poly(lactide-co-glycolide) (PLGA) and poly[1,3-bis(p-carboxy-phenoxy) propane-co-p-(carboxyethylformamido) benzoic anhydride] (P(CPP:CEFB)) and intranasally delivered to model rats in order to improve its analgesic activity. The microspheres with high entrapment efficiency (>80%) and average diameter of about 25 microm could be prepared by a modified water-in-oil-in-oil (w/o/o) emulsion solvent evaporation method. Scanning electron micrograph (SEM) study indicated that P(CPP:CEFB) content played a considerable role on the morphology and degradation of the microspheres. The presence of P(CPP:CEFB) in the microspheres increased their residence time at the surface of the nasal rat mucosa. The toxicity of the composite microspheres to nasal mucosa was proved to be mild and reversible. A tail flick assay was used to evaluate the antinociceptive activity of the microspheres after nasal administration. Compared with the free alpha-cobrotoxin and PLGA microspheres, PLGA/P(CPP:CEFB) microspheres showed an apparent increase in the strength and duration of the antinociceptive effect at the same dose of alpha-cobrotoxin (80 microg/kg body weight).

In vitro and in vivo studies of cyclosporin A-loaded microspheres based on copolymers of lactide and ɛ-caprolactone: Comparison with conventional PLGA microspheres

A hydrophobic peptide, cyclosporin A (CyA), was incorporated in microspheres based on poly(lactide-b-epsilon-caprolactone) (P(LA-b-CL), LA/CL (in molar ratio): 78.7/21.3 and 48.1/51.9) and poly(lactide-co-glycolide) (PLGA, LA/GA: 80/20) using oil-in-water (O/W) emulsion solvent evaporation method. The microspheres were characterized by SEM, DSC and X-ray diffraction, and CyA release rate was determined by HPLC. It was revealed that CyA can be efficiently loaded into all the microspheres (exceed 96%). Compared to PLGA microspheres, P(LA-b-CL) microspheres liberated CyA more rapidly. Within the first day, about 75, 50 and 12% of CyA released from P(LA-b-CL) (48.1/51.9), P(LA-b-CL) (78.7/21.3) and PLGA microspheres, respectively, which can be attributed to the partial crystallization occurring in P(LA-b-CL) microspheres. CyA levels in whole blood were also tested. In comparison with PLGA microspheres, P(LA-b-CL) microspheres provided a higher blood level of CyA. The maximum CyA concentration in whole blood (approximately 520, 450 and 400 ng ml(-1) for P(LA-b-CL) (48.1/51.9) P(LA-b-CL) (78.7/21.3) and PLGA microspheres, respectively) was reached at the second day post administration. And then P(LA-b-CL) microspheres showed a constant CyA level (about 100-200 ng ml(-1)) for extended periods of time (several weeks). Such CyA-loaded P(LA-b-CL) microspheres displaying higher CyA concentration during the first few days and similar constant blood CyA level thereafter showed more advantages than those prepared with PLGA and could meet clinical needs more efficiently.

Changes in structure, activity and metabolism of aerobic granules as a microbial response to high phenol loading

Four column-type sequential aerobic sludge blanket reactors were fed with phenol as the sole carbon and energy source and operated at loading rates of 1.0, 1.5, 2.0 and 2.5 kg phenol m(-3) day(-1). The results indicated that phenol loading exerted a profound influence on the structure, activity and metabolism of the aerobic granules. Compact granules with good settling ability were maintained at loadings up to 2.0 kg phenol m(-3) day(-1), and structurally weakened granules with enhanced production of extracellular polymers and proteins and significantly lower hydrophobicities were observed at the highest loading of 2.5 kg phenol m(-3) day(-1). Specific oxygen uptake rate, catechol 2,3-dioxygenase (C23O) and catechol 1,2-dioxygenase (C12O) activities peaked at a loading of 2.0 kg phenol m(-3) day(-1), and declined thereafter. Granules degraded phenol completely in all four reactors, mainly through the meta cleavage pathway as C23O activities were significantly higher than C12O activities. At the highest loading applied, the anabolism and catabolism of microorganisms were regulated such that phenol degradation proceeded exclusively via the meta pathway, apparently to produce more energy for overstimulation of protein production against phenol toxicity. This work contributes to a better understanding of the ability of aerobic granules to handle high-strength industrial wastewaters containing chemicals that are normally inhibitory to microbial growth.

Functional analysis of microbial community in phenol-degrading aerobic granules cultivated in SBR

Phenol-degrading aerobic granules were cultivated in a sequencing batch reactor with an influent phenol concentration of 500 mg l(-1). Eight strains were isolated from aerobic granules to characterize the functional redundancy of the microbial community in the granules. The specific oxygen utilization kinetics show the eight strains possessed different phenol-degrading activities, with half-saturation constants (Ks) ranging from 0.4 to 70.5 mg phenol l(-1). Two isolates belonging to dominant populations expressed differing functions. The first strain was linked to the function of phenol degradation as this strain has the highest phenol-degrading ability among all isolates, while the second strain was linked to the maintenance of the granule structure because of its strong self-flocculation activity. This study could be used to exploit the granule-based system for treating high-strength wastewaters.

Removal of micro-particles by microbial granules used for aerobic wastewater treatment

Microbial granules with a diameter from 0.4 mm to 3.0 mm have been produced by fast sedimentation and retention of microbial aggregates in sequencing batch airlift reactors used for model wastewater treatment. The wastewater was with or without addition of calcium salt. The granules were able not only to degrade organic matter but to remove nano- and micro-particles from wastewater due to microchannels and pores in the matrix of the granules. To detect the removal of 0.1 microm, 0.6 pm, 4.2 microm fluorescent microspheres, and cells of Escherichia coli, stained by permeable nucleic acid stain SYTO9, the granules were incubated with these particles. The rate of particle removal and their accumulation in the granules was measured by a Fluoview300 confocal laser scanning microscope (CLSM) (Olympus, Japan); a FACSCalibur flow cytometer (Becton Dickinson, CA, USA), and a fluorescence spectrometer LS-50B (Perkin-Elmer, UK). The release or removal of biological and non-biological particles was analyzed by a flow cytometer after DNA staining. Total number of the particles bigger than 0.1 microm in the reactors was approximately 4 x 10(7) per ml, and 23% of these particles were bacterial cells. The 0.1 microm and 4.2. microm microbeads were accumulated within 250 microm in the upper layer of the microbial granule but externally added cells of Escherichia coli penetrated to the depth of approximately 800 microm in the granules without calcium addition. Microbial granules contained also attached ciliates but accumulation of the particles in protozoan cells was smaller than in the granule matrix. Kinetics of particle sorption was revealed by flow cytometry and fluorescence spectrometry. Almost half of the stained cells of E. coli can be removed by the granules for one hour. The ability of the microbial granules to remove the particles can enhance their function in aerobic treatment of wastewater.

In vivo degradation and biocompatibility of a new class of alternate poly(ester-anhydrides) based on aliphatic and aromatic diacids

The degradation, tissue compatibility, and toxicology of a novel class of alternate poly(ester-anhydrides) were assessed in rats. It was observed that the degradation rate of the polymers in vivo was slower than that in vitro. In addition, erosion and intact zone were observed for all the polymers. IR and SEM analysis of the outer erosion and inner intact zone revealed that the outer zone degraded more rapidly than the inner zone. Such results were similar to that in vitro. All the studied poly(ester-anhydrides) produced mild inflammatory reactions and tissue encapsulation by layers of fibroblastic cells in vivo. Observation of liver and kidney tissue by light microscopy suggested the hydrolytic products of the studied poly(ester-anhydrides) had no harmful effects on the normal tissue/organs. In addition, the polymer and the breakdown products were found to be non-mutagenic by examination of micronucleus in bone marrow.

Biomass and porosity profiles in microbial granules used for aerobic wastewater treatment

AIMS

To obtain biomass and porosity profiles for aerobically grown granules of different diameters and to determine a suitable range of granule diameters for application in wastewater treatment.

METHODS AND RESULTS

Microbial granules were cultivated in an aerobic granulated sludge reactor with model wastewaters containing acetate, or ethanol plus acetate, or glucose as the main carbon source. Granules were formed by retaining microbial aggregates using a settling time of 2 min. Sampled granules had diameters ranging from 0.45 to 3 mm. Microbial biomass in the granules was detected with the nucleic acid stain SYTO 9 and confocal laser scanning microscopy. The thickness of the microbial biomass layer was proportional to the granule diameter, and had a maximum value of 0.8 mm. The thickness of the microbial biomass layer correlated with the penetration depth of 0.1 microm fluorescent beads into the granule.

CONCLUSIONS

The microbial biomass and porosity studies suggest that aerobically grown microbial granules should have diameters less than a critical diameter of 0.5 mm, if deployed for wastewater treatment applications. This critical diameter is based on the assumption that whole granules should have a porous biomass-filled matrix.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work could contribute to the development of aerobic granulation technology for effective biological wastewater treatment.

Aggregation of immobilized activated sludge cells into aerobically grown microbial granules for the aerobic biodegradation of phenol

AIMS

The aim of this study is to evaluate the utility of aerobically grown microbial granules for the biological treatment of phenol-containing wastewater.

METHODS AND RESULTS

A column-type sequential aerobic sludge blanket reactor was inoculated with activated sludge and fed with phenol as the sole carbon source, at a rate of 1.5 g phenol l-1 d-1. Aerobically grown microbial granules first appeared on day 9 of reactor operation and quickly grew to displace the seed flocs as the dominant form of biomass in the reactor. These granules were compact and regular in appearance, and consisted of bacterial rods and cocci and fungi embedded in an extracellular polymeric matrix. The granules had a mean size of 0.52 mm, a sludge volume index of 40 ml g-1 and a specific oxygen utilization rate of 110 mg oxygen g VSS-1 h-1 (VSS stands for volatile suspended solids). Specific phenol degradation rates increased with phenol concentration from 0 to 500 mg phenol l-1, peaked at 1.4 g phenol g VSS-1 d-1, and declined with further increases in phenol concentration as substrate inhibition effects became important.

CONCLUSIONS

Aerobically grown microbial granules were successfully cultivated in a reactor maintained at a loading rate of 1.5 g phenol l-1 d-1. The granules exhibited a high tolerance towards phenol. Significant rates of phenol degradation were attained at phenol concentrations as high as 2 g l-1.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study to demonstrate the ability of aerobically grown microbial granules to degrade phenol. These granules appear to represent an excellent immobilization strategy for microorganisms to biologically remove phenol and other toxic chemicals in high-strength industrial wastewaters.

X-ray structures of Torpedo californica acetylcholinesterase complexed with (+)-huperzine A and (-)-huperzine B: structural evidence for an active site rearrangement

Kinetic and structural data are presented on the interaction with Torpedo californica acetylcholinesterase (TcAChE) of (+)-huperzine A, a synthetic enantiomer of the anti-Alzheimer drug, (-)-huperzine A, and of its natural homologue (-)-huperzine B. (+)-Huperzine A and (-)-huperzine B bind to the enzyme with dissociation constants of 4.30 and 0.33 microM, respectively, compared to 0.18 microM for (-)-huperzine A. The X-ray structures of the complexes of (+)-huperzine A and (-)-huperzine B with TcAChE were determined to 2.1 and 2.35 A resolution, respectively, and compared to the previously determined structure of the (-)-huperzine A complex. All three interact with the "anionic" subsite of the active site, primarily through pi-pi stacking and through van der Waals or C-H.pi interactions with Trp84 and Phe330. Since their alpha-pyridone moieties are responsible for their key interactions with the active site via hydrogen bonding, and possibly via C-H.pi interactions, all three maintain similar positions and orientations with respect to it. The carbonyl oxygens of all three appear to repel the carbonyl oxygen of Gly117, thus causing the peptide bond between Gly117 and Gly118 to undergo a peptide flip. As a consequence, the position of the main chain nitrogen of Gly118 in the "oxyanion" hole in the native enzyme becomes occupied by the carbonyl of Gly117. Furthermore, the flipped conformation is stabilized by hydrogen bonding of Gly117O to Gly119N and Ala201N, the other two functional elements of the three-pronged "oxyanion hole" characteristic of cholinesterases. All three inhibitors thus would be expected to abolish hydrolysis of all ester substrates, whether charged or neutral.

Bioadhesive fluorescent microspheres as visible carriers for local delivery of drugs. I: preparation and characterization of insulin-loaded PCEFB/PLGA microspheres

Inherently fluorescent microspheres composed of a fluorescent polyanhydride, poly(p-(carboxyethylformamido) benzoic anhydride) (PCEFB), and poly(lactide-co-glycolide) (PLGA) were prepared using the water-in-oil-in-water (w/o/w) emulsion solvent evaporation technique. The effect of the PCEFB/PLGA feed ratio and composition of the oil phase on insulin entrapment and microsphere diameter was evaluated. It was found that the insulin entrapment efficiency increased with PCEFB content and acetone per cent in the oil phase. Microsphere diameter decreased as acetone was added into the oil phase. The blend of microspheres were further characterized by GPC, IR, fluorometry and SEM. Although slight degradation of PCEFB during the fabrication process was revealed by GPC and IR, PCEFB/PLGA microspheres could still be clearly visualized by either CLSM or fluorescent microscopy, which makes it possible to directly detect the microspheres by fluorometry in vivo without the need of labelling with fluorescent dyes. The surface of PCEFB/PLGA (1:2) microspheres was smooth, while PCEFB/PLGA (2:1) microspheres were observed with rough and uneven surfaces. Sustained release of insulin from the microspheres could be achieved for approximately 4 days.

Novel fluorescent copolyanhydrides as potential visible matrices for drug delivery

Two classes of fluorescent copolyanhydrides were synthesized by melt copolycondensation of the fluorophoric diacid, p-(carboxyethylformamido)benzoic acid (CEFB), with sebacic acid (SA) or N-trimellitylimidoglycine (TMA-gly). Alternate copolyanhydride based on SA and CEFB was also prepared by solution polycondensation of CEFB and sebacoyl chloride. 'H NMR spectra of the copolymers confirm their structures. Fluorescence was observed for all the copolymers, the intensity of which increases with the CEFB fraction. Either blue (ca. 429 nm) or green (ca. 520 nm) light can be emitted from the copolymers with the excitation of UV (356 nm) and visible (470 nm) light, respectively. The polymers were further fabricated to microsphere formulation, which can be clearly visualized by fluorescent microscopy.

Preparation and release characteristics of protein-loaded polyanion/gelatin complex

PURPOSE

This paper describes preparation of polymethacrylic acid/gelatin complex and Myoglobin release characteristics in order to evaluate the polyanion/gelatin complexes as matrices that can release proteins at a near zero-order kinetics over a long period of time.

METHODS

Mb-loaded PMAA/gelatin complex was prepared by two different titration methods. Mb entrapment efficiency and PMAA/gelatin ratio in the complex were determined by HPLC. The release of Mb and gelatin from the complex was followed by HPLC. Mb conformation was detected by UV-vis spectrophotometer and capillary electrophoresis apparatus.

RESULTS

Polyanion/gelatin feed ratio of the polyanion/gelatin/Mb mixed solution has great effects on complex yield and protein entrapment efficiency when "Type I" titration method is adopted, while for the colloid titration method the complex yield and protein entrapment efficiency are hardly influenced by preparative conditions (ca. 100%). Mb release rate could be adjusted by the complex composition (e.g., PMAA MW, hydrophobilization of PMAA, Mb loading and PMAA/gelatin ratio, etc.). Moreover, by coating of high MW PMAA/gelatin complex cylinder in a hydrophobic membrane with one open-end left, the period of protein release can extend to ca. 20 days and the release displays a near zero-order pattern. The protein release profiles can be described by the dissociation/erosion mechanism. The entrapment process has little effect on Mb conformation.

CONCLUSIONS

The studied polyanion/gelatin complex is promising to be used as protein carriers to release proteins at a near zero-order kinetics over a long period of time by selecting suitable polyanions and designing the device structure.

Preparation and characterization of hCG-loaded polylactide or poly(lactide-co-glycolide) microspheres using a modified water-in-oil-in-water (w/o/w) emulsion solvent evaporation technique

A modified w/o/w emulsion solvent evaporation technique was adopted to prepare human Chorionic Gonadotropin (hCG)-loaded polylactide (PLA) or poly(lactide-co-glycolide) (PLGA) microspheres. The effects of preparative parameters, such as stirring rate, polymer MW and concentration, and the composition of both the inner aqueous phase and oil phase etc., on hCG entrapment efficiency and microsphere characteristics were investigated. It was found that by adding 20% glycerol into the inner aqueous phase and 40% acetone into the oil phase, smooth microspheres approximately 1 microm in diameter could be produced with high hCG entrapment efficiency (>90%). In vitro release test showed a burst release of hCG from PLGA (75:25) microspheres, followed by sustained release of 55% hCG over 2 months. The initial hCG burst from PLGA microspheres increased with the glycerol concentration in the inner aqueous phase, but decreased to a low value (ca. 20%) with the addition of acetone into the oil phase, which could be attributed to the associated changes in surface morphology of the microspheres. In vivo experiments demonstrated that a single shot of hCG-loaded PLGA microspheres could produce a comparable antibody response with the inoculation of free hCG four times.

Synthesis, characterization and in vitro degradation of a new family of alternate poly(ester-anhydrides) based on aliphatic and aromatic diacids

A new family of alternate poly(ester-anhydrides) containing aliphatic and aromatic diacids were synthesized. The dicarboxylic acids were obtained by derivatization of p-hydroxy benzoic acid at the hydroxy terminus with cyclic anhydride (adipic anhydride and succinic anhydride) and subsequently polymerized via the corresponding mixed anhydrides by melt polycondensation. DSC traces revealed that the polymers had low Tg (< 40 degrees C) and no crystallinity. The static contact angle measurements indicated that the poly(ester-anhydrides) were more hydrophobic than poly(D,L-lactide) and poly(adipic anhydride). In vitro degradation of the polymers was also investigated in pH 7.4 PBS at 37 degrees C. It was found that degradation rate of the poly(ester-anhydrides) increased with p-carboxy phenyl adipic monoester (CPA) content in the polymers and the degradation duration could be adjusted from ca. 20 days to ca. 2 months. Erosion curve of poly(p-carboxy phenyl adipic monoester anhydride) (PCPA) was characterized by a linear region of weight loss at nearly constant rate in the first 7 days (ca. 80% of weight loss) followed by a gradual decrease region. IR and SEM analysis showed that significant erosion of PCPA occurred in the outer layer and no apparent erosion could be seen in the inner layer of the degrading sample after 7-day degradation. The poly(ester-anhydrides) may be used as either anti-infective polymeric prodrugs or matrices for drug delivery.

A 3D structural model of memapsin 2 protease generated from theoretical study

AIM

To build a 3D structural model of memapsin 2 (M2) protease for theoretical study and drug design.

METHODS

Structural alignment was performed based on multiple and pairwise sequence alignment of three templates. After the initial model was generated, energy minimization was completed by applying molecular mechanics method. Molecular dynamics (MD) technique was used to do further structural optimization.

RESULTS

The 3D structural model of memapsin 2 was constructed. The model is reasonable according to several validation criteria. The active-site motifs of M2 are structurally supported by a beta-sheet rich domain and linked together with this domain through alpha helices. Tyr132 contained in beta-hairpin is a general characteristic of aspartic protease. The Calpha atom superimposing result is a direct verification that M2 is structurally unique but still belongs to the aspartic protease superfamily.

CONCLUSION

The 3D-structure model from our study is informative to guide future molecular biology study about M2 and drug design based on database searching.

Structural characterization of the catalytic active site in the latent and active natural gelatinase B from human neutrophils

Matrix metalloproteinases are endopeptidases that have a leading role in the catabolism of the macromolecular components of the extracellular matrix in a variety of normal and pathological processes. Human gelatinase B is a zinc-dependent proteinase and a member of the matrix metalloproteinase family that is involved in inflammation, tissue remodeling, and cancer. We have conducted x-ray absorption spectroscopy, atomic emission, and quantum mechanics studies of natural and activated human gelatinase B. Our results show that the natural enzyme contains one catalytic zinc ion that is central to catalysis. In addition, upon enzyme activation, the catalytic zinc site exhibits a conformation change that results in the expansion of the bond distances around the zinc ion and the replacement of one sulfur with oxygen. Interestingly, quantum mechanics calculations show that oxygen ligation at the catalytic zinc ion exhibits a greater affinity to the binding of an oxygen from an amino acid residue rather than from an external water molecule. These results suggest that the catalytic zinc ion plays a key role in both substrate binding and catalysis.