Self-assembled hydrogels from poly[N-(2-hydroxypropyl)methacrylamide] grafted with beta-sheet peptides.

A new hybrid hydrogel based on poly[N-(2-hydroxypropyl)methacrylamide] grafted with a beta-sheet peptide, Beta11, was designed. Circular dichroism spectroscopy indicated that the folding ability of beta-sheet peptide was retained in the hybrid system, whereas the sensitivity of the peptide toward temperature and pH variations was hindered. The polymer backbone also prevented the twisting of the fibrils that resulted from the antiparallel arrangement of the beta-strands, as proved by Fourier transform infrared spectroscopy. Thioflavin T binding experiments and transmission electron microscopy showed fibril formation with minimal lateral aggregation. As a consequence, the graft copolymer self-assembled into a hydrogel in aqueous environment. This process was mediated by association of beta-sheet domains. Scanning electron microscopy revealed a particular morphology of the network characterized by long-range order and uniformly aligned lamellae. Microrheology results confirmed that concentration-dependent gelation occurred.

Dynamic light scattering study of self-assembly of HPMA hybrid graft copolymers.

The time course of self-assembly of a hybrid hydrogel system was investigated using dynamic light scattering (DLS) techniques. The self-assembling system consisted of a hydrophilic synthetic N-(2-hydroxypropyl)methacrylamide (HPMA) polymer backbone and a pair of oppositely charged peptide grafts (CCE and CCK). These two distinct pentaheptad peptides were anticipated to act as physical cross-linkers by the formation of antiparallel coiled-coil heterodimers. Equimolar mixture of HPMA graft copolymers CCE-P and CCK-P solutions (where P is the HPMA copolymer backbone) with total concentration from 1.25 to 10 mg/mL were measured at a scattering angle 90 degrees and room temperature. A critical extension of average relaxation time was observed with increasing concentration and incubation time. To reveal the role of coiled-coil grafts in the self-assembly process, a pair of modified random coil peptides, CCEw and CCKy, was designed. The DLS evaluation of HPMA copolymer conjugates (CCEw-P and CCKy-P) at total concentration of 10 mg/mL demonstrated that no association occurred after 28 h of incubation. Moreover, addition of a competing peptide (CCK) or a denaturant (guanidium chloride, GndHCl) to the self-assembled CCE-P/CCK-P hydrogels resulted in partial disassembly or collapse of the hydrogel clusters. These results correlated to changes in the secondary structure of peptides (grafts) as measured by circular dichroism spectroscopy (CD). These investigations supported the hypothesis that the self-assembly of CCE-P/CCK-P into hybrid hydrogels is mediated by the formation of coiled-coil heterodimers.

[Preparation of magnetoliposomes and its in vivo behavior on ICR mice].

AIM: To prepare magnetoliposome (MLP) containing dextran-encapsulated magnetite (Fe3O4), and to examine its physicochemical properties and its in vivo behavior on ICR mice. METHODS: Reverse phase evaporation method was used to formulate MLP and the Fe2+ concentration was measured by o-phenanthroline method. Then the basic properties of MLP and in vivo distribution were studied with the aid of 3H isotope as biomarker. RESULTS: The mean diameter of MLP was 602.5 nm and the final concentration of encapsulated Fe3O4 was 88.1 mg x L(-1). Under natural conditions most of the MLP was taken up by spleen after the administration via tail vain, but its uptake was reduced under the magnetic field. There was a great difference in vivo distribution between the left and right lobes of the liver and the left and right kidneys in magnetic fields. CONCLUSION: Reverse phase evaporation method was utilized to prepare magnetoliposomes. The formulation was stable and encapsulated high amount of magnetite. The delivery system could be oriented to certain tissues under magnetic field and satisfying magnetic responsiveness was observed.

[Development of sustained release tablet of tamoxifen citrate and its in vitro release profile].

OBJECTIVE: To reduce the frequency of administration of tamoxifen citrate so as to improve its bioavailability and patients' compliance. METHODS: HPMC(K4M) was employed as major retarded-release controller. The wetting granulation and directly compressing method was used to produce the sustained release tablet. Then the in vitro release profile was applied as main criteria to evaluate six formulations according to the variation of HPMC(K4M) amount. The concentration of tamoxifen citrate was measured by UV spectrometry. Finally the releasing characteristics of sustained release and conventional tablets were compared to clarify the sustained effect of the former. RESULT: At 278 nm there was no interaction between tamoxifen citrate and the recipients so that it was adopted as the wavelength of determination. The recovery efficiency of this method ranged from 95%-105%. The final formulation could release 86.40% of its loading amount in 12 h and its releasing profile fitted the Zero-order equation well. The percentages of accumulative release in 1 h were 76.81% and 7.08% for sustained release tablet and conventional tablet respectively. CONCLUSION: The sustained release tablet of tamoxifen citrate could demonstrate a continuous and stable releasing profile and last for over 12 h. It has significant retarded effect in comparison with the conventional one and could be a new choice of regimen in its clinical application.

Coiled-coil based drug-free macromolecular therapeutics: in vivo efficacy.

We evaluated a new concept in cancer therapy, coiled-coil mediated induction of apoptosis in Raji B cells, for treatment of human B-cell lymphoma in a preclinical animal model. The system is composed of a pair of complementary coiled-coil peptides, CCE and CCK, forming antiparallel heterodimers; Fab' fragment of the 1F5 anti-CD20 antibody; and N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer. One peptide is conjugated to the Fab' fragment (Fab'-CCE), the other is conjugated in multiple grafts to polyHPMA (CCK-P; P is the HPMA copolymer backbone). Intravenous administration of Fab'-CCE conjugate, followed by the administration of CCK-P produced long-term survivors in SCID (C.B.-17) mice bearing human B-lymphoma xenografts. The rationale of the design is the absence of low molecular weight drugs and the fact that crosslinking of CD20 at B-cell surface results in apoptosis. This approach creates a new paradigm for manipulating molecular recognition principles in the design of improved cancer treatment.

Biodistribution and pharmacokinetic studies of bone-targeting N-(2-hydroxypropyl)methacrylamide copolymer-alendronate conjugates.

The biodistribution and pharmacokinetics of bone-targeting N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-alendronate conjugates were evaluated following intravenous administration of radioiodinated conjugates to young healthy BALB/c mice. The synthesis of a polymerizable and cathepsin K cleavable alendronate derivative, N-methacryloylglycylglycylprolylnorleucylalendronate, enabled the preparation of HPMA copolymer-alendronate conjugates with varying composition. Using the RAFT (reversible addition-fragmentation chain transfer) polymerization technique, four conjugates with different molecular weight and alendronate content and two control HPMA copolymers (without alendronate) with different molecular weight were prepared. The results of biodistribution studies in mice demonstrated a strong binding capacity of alendronate-targeted HPMA copolymer conjugates to bone. Conjugates with low (1.5 mol%) alendronate content exhibited a similar bone deposition capacity as conjugates containing 8.5 mol % of alendronate. The molecular weight was an important factor in the biodistribution of the HPMA copolymer conjugates. More conjugate structures need to be evaluated, but the data suggest that medium molecular weights (50-100 kDa) might be effective drug carriers for bone delivery.

[Survey on the situation of antenatal care in different regions of China, in 1971 - 2003].

OBJECTIVE: To comprehensively understand the situation of antenatal care in the last thirty years and to identify the existing problems and challenges. METHODS: PPS method was used to select those women under study and face to face interview was carried out at the house. RESULTS: The quality and coverage rate of antenatal care as well as the rate of hospital delivery had been continuously increasing over time and the coverage rate of antenatal checkup had increased from 38.7% in 1970s to 95.9%, while the institutional delivery rose from 20.1% to 87.4% in the last three years. However, problems and challenges were found refering to the of delay first antenatal care, inadequate timing and with incomplete contents. Only 71.7% of the pregnant women had received first checkup during the first three months. 64.1% of the women received 5 times or more of the checkups while only 29.1% of the women had received all the 7 basic checkup items. Rate of hospital delivery was unsatisfactory that most (79.5%) of the women had the delivery not in the hospitals when under the assistance of midwife/village doctors. Indicators showed that the worst was in the western regions. CONCLUSION: Great progress had been made in the field of antenatal care in last thirty yeats in China. The coverage rate of antenatal checkup and institutional delivery had been improved. But the quality of antenatal care should be further improved, especially in the western regions.