PLGA nanoparticles prepared by nanoprecipitation: drug loading and release studies of a water soluble drug

The nanoprecipitation technique for preparation of nanoparticles suffers the drawback of poor incorporation of water soluble drugs. The aim of this study was therefore to assess various formulation parameters to enhance the incorporation of a water soluble drug (procaine hydrochloride) into poly(dl-lactide-co-glycolide) (PLGA) nanoparticles prepared by this technique. Approaches investigated for drug incorporation efficiency enhancement included the influence of aqueous phase pH, replacement of procaine hydrochloride with procaine dihydrate and the inclusion of excipients: poly(dl-lactide) (PLA) oligomers, poly(methyl methacrylate-co-methacrylic acid) (PMMA-MA) or fatty acids into the formulation. The nanoparticles produced were submicron size (<210 nm) and of low polydispersity. It was found that an aqueous phase pH of 9.3, replacement of procaine hydrochloride with procaine dihydrate and the incorporation of PMMA-MA, lauric and caprylic acid into the formulation could enhance drug incorporation efficiency without the size, morphology and nanoparticle recovery being adversely influenced. For instance changing the aqueous phase pH from 5.8 to 9.3 increased nanoparticle recovery from 65.1 to 93.4%, drug content from 0.3 to 1.3% w/w and drug entrapment from 11.0 to 58.2%. However, the presence of high ratios of lauric acid and procaine dihydrate in the formulation adversely affected the morphology and size of the nanoparticles. Also, PLA oligomers were not considered a feasible approach since it decreased drug entrapment from 11.0 to 8.4% and nanoparticle recovery from 65.1 to 19.6%. Drug release from nanoparticles appears to consist of two components with an initial rapid release followed by a slower exponential stage. This study has demonstrated that formulation variables can be exploited in order to enhance the incorporation of a water soluble drug into PLGA nanoparticles by the nanoprecipitation technique.     

Development of a quantitative polyacrylamide gel electrophoresis analysis using a multichannel radioactivity counter for the evaluation of oligonucleotide-bound drug carrier

A quantitative polyacrylamide gel electrophoresis (PAGE) analysis using a multichannel radioactivity counter was designed for the evaluation of 33P-labeled antisense oligonucleotide associated with polymeric drug carrier (nanoparticles). The proposed analytical method was first validated. The criteria of specificity, linearity, reliability, detection and quantification limits, and resolution power were determined. Results were compared to those obtained using liquid scintillation counting of crude samples or after solubilization of gel slices. The proposed method gave a better linearity and reliability than liquid scintillation counting of solubilized gel slices. In comparison with the liquid scintillation counting of crude samples, the method presented the advantage of being able to directly separate oligonucleotides differing by only one nucleotide in length. This method was applied for the separation of free oligonucleotides and oligonucleotides bound onto nanoparticles, allowing quantification of the amount of free and bound oligonucleotides without any further separation steps. Thus, because it is easy and rapid, the quantitative PAGE analysis using a multichannel radioactivity counter offers interesting possibilities for the characterization of oligonucleotide nanoparticles.     

无机纳米载体在靶向药物输送中的应用研究进展

纳米材料在生物领域的渗透形成了纳米生物材料,而纳米药物载体的研究是纳米生物材料的前沿和热点之一.常见的无机纳米药物载体包括磁性纳米粒子、介孔二氧化硅、纳米碳材料、量子点等,这些无机纳米药物载体在实现靶向性给药、控释和缓释药物以及癌症靶向治疗等方面表现出良好的应用前景.而且,集成像、靶向给药和癌症治疗功能于一身的多功能纳米药物载体比常规化疗药物载体具有明显优势.文中综述了近年来上述无机纳米材料尤其是多功能无机纳米载体在靶向药物输送中的应用及其载药释药行为的研究进展.     

某难选含金矿石的载体浮选研究

对某高泥化高氧化铁锰黑土矿中的金进行了试验研究,试验采用黄铁矿作为载体有效回收了黑土矿中的金,并对载体浮选的几个主要条件进行了对比,结果表明用磺化煤油作辅助捕收剂可增加细粒金回收,同时也降低了黄药和２＃油的用量。     

Development of physicochemical foundations for the synthesis of tungsten-based nanopowders with controlled properties

A chemical and metallurgical method for the preparation of alloyed tungsten-based nanopowders has been developed. The synthesis conditions providing the formation of tungsten-based nanopowders with a specified complex of properties are determined. The chemical and phase compositions and the sizes of nanoparticles and agglomerates of the alloyed tungsten-based nanopowders are studied.     

Drug targeting using low density lipoprotein (LDL): physicochemical factors affecting drug loading into LDL particles

Low density lipoprotein (LDL) has been found suitable as a targeting carrier for cytotoxic drugs. However, higher drug loading into LDL particles without disrupting their native integrity remains a major obstacle. The purpose of this study is to investigate the different physicochemical factors that may affect drug loading and to characterize LDL-drug conjugates. Doxorubicin (Dox) and 3', 5'-O-dipalmitoyl-5-iodo-2'-deoxyuridine (dpIUdR) were used as reference cytotoxic drugs. Drugs were loaded into LDL particles using the dry film method with or without surfactants, liposomal and the direct addition method. The effects of incubation temperature, time and stoichiometry of LDL-drug conjugates on drug loading were investigated. The LDL-drug conjugates were evaluated for their stability and characterized by differential scanning calorimetry (DSC), denatured gel (SDS-PAGE), and electron microscopy (EM). We have suitably incorporated 45+/-10 Dox and 150+/-25 dpIUdR molecules/LDL particle. A seven-fold increase in Dox incorporation was achieved with the liposomal preparation compared to the dry film method. A 4- to 6-h incubation at 37 degreesC was suitable to restore the native structure of LDL particles. No apo B fragmentation of LDL particles was noted on denatured gel. DSC studies showed no change in the Tm of the LDL and the LDL-drug conjugates. An increase in particle size of LDL-dpIUdR, not LDL-Dox was observed in EM compared to the native LDL which may be related to higher incorporation of dpIUdR. The results indicate that physicochemical factors significantly affect drug loading efficiency and may need to be considered to optimize drug incorporation into LDL particles.     

The folding of centromeric DNA strands into intercalated structures: a physicochemical and computational study

We have carried out a physicochemical and computational analysis on the stability of the intercalated structures formed by cytosine-rich DNA strands. In the computational study, the electrostatic energy components have been calculated using a Poisson-Boltzmann model, and the non-polar energy components have been computed with a van der Waals function and/or a term dependent on the solvent-accessible surface area of the molecules. The results have been compared with those obtained for Watson-Crick duplexes and with thermodynamic data derived from UV experiments. We have found that intercalated DNA is mainly stabilized by very favorable electrostatic interactions between hydrogen-bonded protonated and neutral cytosines, and by non-polar forces including the hydrophobic effect and enhanced van der Waals contacts. Cytosine protonation electrostatically promotes the association of DNA strands into a tetrameric structure. The electrostatic interactions between stacked C.C+ pairs are strongly attenuated by the reaction field of the solvent, and are modulated by a complex interplay of geometric and protonation factors. The forces stabilizing intercalated DNA must offset an entropic penalty due to the uptake of protons for cytosine protonation, at neutral pH, and also the electrostatic contribution to the solvation free energy. The latter energy component is less favorable for protonated DNA due to the partial neutralization of the negative charge of the molecule, and probably affects other protonated DNA and RNA structures such as C+-containing triplexes.     

Influence of molecular weight on passive tumour accumulation of a soluble macromolecular drug carrier

The molecular weight-dependence of tumour capture of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers (fractions of mw 22,000-778,000) was studied in vivo using subcutaneous (s.c.) Sarcoma 180 or B16F10 melanoma models. At 10 min, all fractions were already detectable in the tumour (1.5-3% of dose administered per gram) and those of molecular weight greater than the renal threshold showed progressive tumour accumulation up to 20% of dose administered per gram after 72 h in the Sarcoma 180 model. Tumour-selective uptake was confirmed for all copolymer fractions in both tumour models and in the sarcoma 180 model, the ratio (accumulation index, AI) of the AUC in tumour to AUC in skeletal muscle (a typical normal tissue) increasing from six to 12 with increasing copolymer molecular weight. The tumour/blood AI was greater (1-3) in the Sarcoma 180 model than the B16F10 melanoma model (0.4-1.0).     

Pharmacognostical study on the Chinese drug biejia

The Chinese drug Biejia is taken from a variety of animals. In this paper, 3 kinds of Biejia from different genera have been studied in their pharmacognostical characteristics and microproperties. A key has been complied based on the experimental results.     

Physico-chemical characterization and application for drug carrier of soybean-derived sterols and their glucosides-containing liposomes

With a rapid demand to decrease the side effect of drug, a variety of drug delivery systems have been developed. This review will focus on the development of liposomes with soybean-derived sterols and their glucosides for drug carriers. Current status and further perspectives in this research field are reviewed mainly based on the results obtained in our laboratory. First we studied the different physicochemical properties of dipalmitoylphos-phatidylcholine (DPPC) liposomes with soybean-derived sterols (SS) and their glucosides (SG). SS rigidifies the liposomal membrane but SG fluidizes it. SS stabilizes liposomes more than cholesterol that is conventionally used as stabilizing agents in liposomes. On the basis of this information, we developed liposomes with SS and SG for a drug carrier. Secondly we studied the stability of liposomes in the blood and biodistribution and found that liposomes with SS were stable as expected in vitro results. In particular, DPPC: SS (7:4, molar ratio) size 0.2 micron showed long circulation. Thirdly successful targeting of the drugs to the liver was achieved by liposomes with SG. Finally, we succeeded in developing liposomal erythropoietin and doxorubicin using liposomes with SS for sustained release of drugs. Liposomal drugs increased the pharmacological effect compared with free drugs, suggesting a decrease of side effect and long circulation. The attempt for oral administration using liposomes of peptide drugs was carried out successfully. We have established that the study of physicochemical properties of liposomes is needed rationally as the distribution of drugs in liposomes and the rigidity of liposomal membrane, prior to the development of the drug carrier of liposomes. SS is useful to stabilize liposomes and SG to targeting to the liver parenchymal cells. This information can be useful and practical for the development of liposomes for drug carriers.     

Disposition characteristics of glycosylated poly(amino acids) as liver cell-specific drug carrier

Alveolar type II pneumocytes (PII) were studied in 12 human donor lungs perfused with modified Euro-Collins solution during single-lung transplantation (SLTx). While one lung was transplanted, the contralateral donor lung (cDL) was fixed at the time of SLTx for examination by electron microscopy, stereology, and microanalysis. Three groups were then formed: group A (n = 7), cDL without contusions, uneventful early postoperative course; group B (n = 3), cDL with conclusions, uneventful early postoperative course; group C (n = 2), cDL without contusions, early postoperative respiratory dysfunction. The major findings were that the presence of contusions had no effect on PII ultrastructure and that intracellular surfactant-storing lamellar bodies of cDL in group C were characterized by a higher volume-to-surface ratio (VsR) and larger area per cell profile than group A. Correlation analysis based on pooled data (groups A and C) showed that ischaemic time had little effect on PII ultrastructure and bore no relationship to postoperative clinical variables. The duration of preoperative donor intubation had a pronounced influence on ultrastructure and postoperative clinical variables. The stereologically estimated amount of intracellular surfactant and mitochondrial VsR were the only ultrastructural parameters that were significantly associated with early postoperative oxygenation. Lamellar bodies were the only ultrastructural components found to have a significant relationship to postoperative intubation time. The ultrastructural integrity of type II pneumocytes of human donor lungs is an important determinant of early respiratory function following clinical lung transplantation.     

Development of drug therapy for children

The National Commission is about to finalize its recommendations with regard to research in children. It is significant that the commission will propose that research in children is necessary and should be supported. Clinical pharmacologic studies in infants and children require encouragement, as well as support, if drugs are to be developed in the future that do not have limited indications for the pediatric-aged patient, due to incomplete pediatric studies. The ethics of conducting pharmacologic investigations in infants and children have been discussed and recommendations have been prepared by the Committee on Drugs of the American Academy of Pediatrics. These discussions and recommendations differ in some significant ways from the most recent draft available from the National Commission.     

An experimental study on the relationship between BMP's activity and its carrier

To find out the relationship between human bone morphogenetic protein's activity and its carrier and to document the clinical application of BMP, we investigated six kinds of BMP carrier's influence upon hBMP's osteogenic activity with small sample size at first. Then three kinds of carriers selected from the six, added with the seventh carrier, were investigated with large sample size. The result showed that the compound of hBMP and hDDBM had best osteogenic ability. The human bone matrix had been formerly demineralized and extracted without hBMP. The hDDBM showed porous structure under SEM, its mean pore's diameter was 127 +/- 34 microns. It was demonstrated that the function of demineralized bone matrix extracted without BMP (i.e. DDBM) was related not only to its pore's diameter, but to the fibrolike matter in it as well. With the method of BMP bioassay, BMP was composited with carrier, then the compound was injected into the calf of mouse. This made BMP's bioassay become simple and reliable.     

Effect of serum proteins and osteoblasts on the surface transformation of a calcium phosphate coating: a physicochemical and ultrastructural study

We describe a practical method for the analysis of multiple analytes in a single sample. The vehicle for each separate measurement consists of a set of microspheres identifiable by characteristic fluorophores embedded in the particles. The use of robust, bench-top flow cytometers (flow microfluorimeters) for the analysis of the multiple sets of microspheres is facilitated by hardware and software, which acquire the data from the cytometer, classify the microspheres according to sets, and collate measurement information from each microsphere set in real time. This measurement system can analyze up to 64 analytes in a single sample. The advantages of multiplexed assays using flow cytometry include robust measurements, because each microsphere set is measured repeatedly. The advantage of the assay's is consistent with simultaneous measurement of many parameters as well as the speed with which the flow microfluorimeter (cytometer) makes measurements (many hundreds per second). Here, we describe the properties of the microspheres, the calibration of the cytometer, and the influence of the properties of the microspheres on the sensitivity of measurements.     

Impact of pharmaceutical underutilization: a study of insurance drug claims data

From 1989 to 1992, a longitudinal study of the relationships between different tick species and domestic ungulates in the transmission and amplification of Crimean-Congo hemorrhagic fever (CCHF) virus was undertaken in the Bandia area in Senegal where the presence of the virus had been reported previously. An epizootic occurred in 1991-1992 and 22 strains of CCHF virus were isolated from Hyalomma marginatum rufipes Koch, Amblyomma variegatum (F.), Rhipicephalus guilhoni Morel & Vassiliades, and R. evertsi evertsi Neumann ticks collected from cattle and goats. No human cases were reported. Transmission of CCHF virus in the area involves a complicated pattern including many tick species and hosts. Amplicons of the S fragment (536 bp) of the CCHF genome of 12 isolates from the study were obtained by polymerase chain reaction and analyzed by restriction-length fragment polymorphism. Three different genotypes of CCHF virus were identified and present during the epizootic. One genotype was recovered from A. variegatum, R. guilhoni, and R. e. evertsi and 2 genotypes were isolated from H. m. rufipes.     

Synthesis of hollow and mesoporous structured NaYF_4:Yb,Er upconversion luminescent nanoparticles for targeted drug delivery

In this paper, we demonstrated a one-step template-free strategy to fabricate a hollow mesoporous structured NaY F4:Yb,Er nanoparticles with excellent upconversion luminescence. Folic acid(FA), a commonly used cancer-targeting agent, was conjugated on the surface of the nanoparticles based on the presence of free amine groups, which were labeled as NaY F4:Yb,Er-FA HMUCNPs. The properties were extensively studied, which indicated the obtained samples showed a typical hollow mesoporous structure and excellent upconversion luminescence that were useful for cell imaging and drug delivery. The L929 cells viability, hemolysis assay and coagulation test demonstrated good biocompatibility of the samples. The anti-cancer drug doxorubicin hydrochloride(DOX) storage/release properties were demonstrated to be pH-responsive, in which, the drug release might be beneficial at the reduced pH for targeted release and controlled therapy. Moreover, it was found that DOX-loaded NaY F4:Yb,Er-FA HMUCNPs exhibited greater cytotoxicity to KB cells than free DOX due to the specific cell uptake by KB cells via folate receptor-mediate endocytosis. Therefore, the multifunctional nanoparticles combining upconversion luminescent property and hollow mesoporous structure have potential for simultaneous targeted anti-cancer drug delivery and cell imaging.     

Prevalence and a drug use development model for the study of adolescent drug use in Japan

The purposes of this study were to estimate the prevalence of drug use, to examine the correlation between drug use and drinking/smoking in Japan, and to test a developmental model of adolescents' drug use based on three basic theories of deviance: Strain, Social control, and Differential association. The survey was conducted from April to May, 1996, in 14 public high schools in Tokyo, using anonymous self-reporting. A total of 4,171 (99.45%) students responded to our questionnaire. It included central concept items in the three deviant theories, beliefs about the ill effects of drugs, sex, grades, etc. The following findings were obtained: 1) Among the subjects, 255 students (6.1%) reported drug use within the past year. Of these drug users, 73.3% used drugs soon after being "tempted" by friends. Responding to "When was it.", as a first year junior high school was the most common first experience, and the next most common was during the sixth year of elementary school. 2) Drinking and smoking appeared to be gateway drugs for adolescents in Japan as has been shown in the United States. 3) Multiple regression and logistic multiple regression analyses suggested that differential association variables were far more powerful predictors of adolescent drinking, smoking and drug use than either the control or strain variables. Results provided modest support for the Differential Association Theory as an explanation of drug use. 4) LISREL's goodness-of-fit statistic indicated a much better fit between the model and the data. (CN: 282, GFI: 0.967, AGFI: 0.941). These findings show two processes by which adolescents become involved in drug use. Strain and Social Control do not directly affect drug use. However, Social Control is important because it works indirectly, through Differential Association resulting in drug use. Second, though weaker, Differential Association appears to lead to dangerous beliefs in drug use followed by actual drug use.