Effect of protein binding on high performance liquid chromatography analysis of drugs with an internal-surface reversed-phase silica column

The effect of protein binding on the high performance liquid chromatography (HPLC) elution profile of drugs injected directly onto an internal-surface reversed-phase (ISRP) silica column was investigated. When a relatively large volume (greater than or equal to 100 microliters) of the sample solution containing warfarin and bovine serum albumin (BSA) was applied directly onto the ISRP column and elution was carried out with the mobile phase containing an organic modifier, two distinct peaks, both due to warfarin, appeared separated from the protein peak. The peak splitting was not observed in the case of antipyrine-BSA mixed solution, where the protein binding is weak. It was found that the drug bound at the strong-binding site on the BSA molecule was released slowly during the process of chromatography and was eluted as the first peak with a shorter retention time, while the drug bound at the weak-binding site was released quickly, and was eluted as the second peak together with the free drug. The warfarin-BSA interaction at the strong-binding site was evaluated, under minimum influence from the other binding site, from the warfarin concentration obtained from the first peak and the free warfarin concentration determined by the ultrafiltration method.     

Direct synthesis of Poly(Ԑ-Caprolactone)-block-poly (glycidyl methacrylate) copolymer and its usage as a potential nano micelles carrier for hydrophobic drugs

Ring-opening (ROP) and enzymatic copolymerization (ECP) are among the most widely used approaches for synthesizing copolymers of polycaprolactone (PCL). It involves multiple-step reactions and the utilization of enzymes that make the process a lot more complicated, time consuming, and expensive. Atom transfer radical polymerization (ATRP) has been adopted to synthesize a novel amphiphilic copolymer in our study. The study presents a method to eliminate the ROP/ECP multiple steps in monomer polymerization thus making the process simpler and smoother. The synthesis of cationic polymer micelles copolymer of PCL-PGMA (polycaprolactone grafted poly glycidyl methacrylate) was carried out using direct functionalization of hydroxy group in crude PCL to achieve a higher degree of functionalization, i.e., 12.8% for macroinitiator. FTIR and ¹H-NMR confirmed the successful synthesis of the copolymer with better control over the molecular weight with a PDI (1.84). DSC and XRD results showed the reduction of crystallinity by 86.81%, making copolymer more compatible for drug delivery application. The synthesized copolymer was further converted to nano-micelles drug carrier having an average size of 96.08 ± 21.22 nm. The drug encapsulation efficiency achieved was 60.0 ± 1.7%, and nano-micelles rendered a slow and controlled release of naproxen with long-term storage stability.     

微乳液法制备水溶性双亲丙烯酰胺-苯乙烯嵌段共聚物

分别以十二烷基硫酸钠 (SDS)、壬基酚聚氧乙烯醚 (OP 10 )为表面活性剂 ,丙烯酰胺 (AM)的水溶液为连续相 ,苯乙烯 (St)为分散相 ,构成微乳液共聚合体系 ,合成了水溶性双亲嵌段共聚物 ,并通过荧光探针技术、差示扫描量热 (DSC)测试及流变性能的测定表征了共聚物的嵌段性结构 ,用红外光谱 (FTIR)及紫外光谱 (UV)分析了共聚物的化学组成     

Thermoresponsive N-vinyl caprolactam grafted sodium alginate hydrogel beads for the controlled release of an anticancer drug

A series of thermoresponsive sodium alginate-g-poly(vinyl caprolactam) (NaAlg-g-PNVCL) beads were prepared as drug delivery matrices of 5-flurouracil (5-FU) crosslinked by glutaraldehyde (GA) in the hydrochloric acid catalyst. Graft copolymers of sodium alginate with vinyl caprolactam were synthesized using azobisisobutyronitrile as an initiator, and characterized by Fourier infrared spectroscopy, differential scanning calrimetry and X-ray diffraction for analysis of the amorphous nature drug in the beads, and by scanning electron microscopy for the spherical nature of the beads. Preparation condition of the beads was optimized by considering the percentage of encapsulation efficiency, swelling behavior of beads and their release data. Effects of variables such as GA concentration, drug/polymer ratio and catalyst concentration on the release of 5-FU were carried out at two different temperatures (25 and 37 °C) in simulated intestinal fluid for 12 h. It was observed that, drug release from the beads decreased with increasing drug/polymer (d/p) ratio, extent of crosslinking agent and catalyst concentration. The swelling degree of graft copolymer beads was found to be increased with decreasing of environmental temperature. In vitro release studies were performed at 25 and 37 °C for 12 h, and showed that thermoresponsive graft copolymer beads had higher drug release behavior at 25 °C than that at 37 °C, following Fickian diffusion transport mechanism with slight deviation.     

Graft Copolymerization of Methyl Methacrylate on Poly(phenyl Vinyl Sulfide)

Graft copolymer of poly(phenyl vinyl sulfide) and methyl methacrylate was obtained. The isolation of graft copolymer was carried out by the fractional precipitation method. The isolated polymer was confirmed to be a graft copolymer by IR spectra and T determinations. Graft copolymerizations of poly(phenyl vinyl sulfide) with vinyl acetate, acrylonitrile, acrylamide, and acrylic acid were also carried out, but the separation of graft copolymer in these cases was difficult, and satisfactory results could not be obtained.     

Synthesis and Characterization of Poly[N-Vinyl-2-Pyrrolidone-Polyethylene Glycol Diacrylate] Copolymeric Hydrogels for Drug Delivery

Abstract

Novel polymeric biodegradable and biocompatible copolymeric hydrogels based on N-vinyl-2-pyrrolidone (NVP) and polyethylene glycol diacrylate (PAC) were designed and synthesized. PAC macromonomer was synthesized by a modified procedure and characterized. Poly[N-vinyl-2-pyrrolidone-polyethylene glycol diacrylate] (Poly[NVP-PAC]) hydrogels were synthesized by varying the concentration of PAC. Azobisisobutyronitrile (AIBN) was used as the free radical initiator and N,N¹-methylene bis(acryl-amide) (BIS) was employed as the crosslinking agent. These hydrogels were characterized by various spectroscopic techniques. Fourier transform-infrared spectroscopy (FT-IR) confirms the formation of copolymer. Thermogravimetric analysis (TGA) curves obtained were continuous indicating the formation of copolymer. The glass transition temperature (T_g) of the copolymer was measured using differential scanning calorimetry (DSC). The equilibrium swelling measurements were carried out in simulated gastric and intestinal fluids (SGF & SIF). These swelling studies indicated that these gels had a higher sorption capacity in SIF when compared to that in SGF. 5-Fuorouracil (5-FU), an anti-cancer drug was entrapped in these hydrogels and the in-vitro release profiles were established in a sequential manner in SGF and SIF. About 50–56% of the drug entrapped was released in a period of 10 days.     

双金属氰化络合物催化环氧丙烷和邻苯二甲酸酐共聚

采用双金属氰化络合物 (DMC)催化环氧丙烷 (PO)和邻苯二甲酸酐 (PA)共聚 ,探讨了共聚合特征 ,并用IR、1 H NMR和GPC对共聚物的结构和分子量进行了表征 .发现DMC催化剂对该共聚反应速度快 ,转化率高 ,是该反应的有效催化剂 ,催化剂浓度为 6 0mg kg时 ,90℃下 ,以THF作溶剂共聚反应 3h ,转化率可达94 0 % .聚合速度甚至比DMC催化PO均聚还快 .该共聚反应可在多种溶剂中进行 ,极性溶剂更有利于共聚合 ,溶液聚合温度比本体共聚低 ,合适的溶液共聚温度在 90～ 10 0℃之间 .共聚产物的分子量受催化剂用量、反应温度和体系中水份含量的影响 ,数均分子量在数百至数千之间 .考察该共聚体系的动力学表明 ,该共聚反应速率对单体浓度呈一级关系     

聚(丙烯酰胺-丙烯酸十八酯)的合成及其增稠性能

共聚合;聚(丙烯酰胺-丙烯酸十八酯)的合成及其增稠性能     

Controlled drug release through poly(L-leucine) and its copolymer

The release behavior of a water-soluble drug through membranes made of poly(L-leucine) and its copolymer with different hydrophilic properties was studied. The effect of casting methods on the release rate was also investigated. It was found that the membrane with a higher hydrophilic property resulted in a higher permeation rate. The capsule was prepared as a composite sheet from a poly(L-leucine)-prednisolone 21-sodium succinate sponge and a poly(L-leucine) membrane. Release of the water-soluble drug from the capsule was found to be effectively governed by the hydrophilic character and thickness of the outer membrane. Biocompatibility studies carried out by implanting the poly(L-leucine) sponge subcutaneously in the dorsal surface of the rat showed that the sponge had a good biocompatibility and slow biodegradation. It was concluded from these results that poly(L-leucine) should be a suitable material for preparing a controlledrelease drug device for long-term dosage.     

Thermosensitive copolymer coatings with enhanced wettability switching

Expanded cross-linked copolymers of poly(N-isopropylacrylamide) (PNiPAAm) and poly(acrylic acid) (PAAc) of varying monomer ratios were grafted from a crystalline silicon surface. Surface-tethered polymerization was performed at a slightly basic pH, where electrostatic repulsion among acrylic acid monomer units forces the network into an expanded polymer conformation. The influence of this expanded conformation on switchability between a hydrophilic and a hydrophobic state was investigated. Characterization of the copolymer coating was carried out by means of X-ray photoelectron spectroscopy (XPS) ellipsometry, and diffuse reflectance IR. Lower critical solution temperatures (LCSTs) of the copolymer grafts on the silicon surfaces were determined by spectrophotometry. Temperature-induced wettability changes were studied using sessile drop contact angle measurements. The surface topography was investigated by atomic force microscopy (AFM) in Milli-Q water at 25 and 40 degrees C. The reversible attachment of a fluorescently labeled model protein was studied as a function of temperature using a fluorescence microscope and a fluorescence spectrometer. Maximum switching in terms of the contact angle change around the LCST was observed at a ratio of 36:1 PNiPAAm to PAAc. The enhanced control of biointerfaces achieved by these coatings may find applications in biomaterials, biochips, drug delivery, and microfluidics.     

α-甲基苯乙烯-马来酸酐共聚物的合成及其引发的甲基丙烯酸甲酯的无皂乳液聚合

以α-甲基苯乙烯(AMS)、马来酸酐(MANH)为共聚单体,偶氮二异丁腈(AIBN)为引发剂,采用自稳定沉淀聚合法合成了α-甲基苯乙烯和马来酸酐的共聚物,再将其皂化后得到具有引发和乳化双重作用的共聚物.该共聚物可以作为大分子引发剂再引发甲基丙烯酸甲酯(MMA)进行无皂乳液聚合.采用扫描电镜、红外光谱仪、乌氏黏度计等仪器对AMS-MANH共聚物以及乳液聚合产物进行了表征.结果表明,乳液聚合产物是以PMMA为主长链,AMS和MANH低聚物为短链的嵌段共聚物.单体最高转化率可达到85%,特性黏数在80 mL/g左右.乳胶粒子粒径在150～200 nm之间.聚合速率随着引发剂浓度的增加而增大,聚合物的特性黏数随着转化率的提高基本呈线性增大.     

COPOLYMERIZATION OF ETHYLENE WITH 1-OCTENE USING Et(Ind)2ZrCl2/MAO CATALYST

Copolymerization of ethylene/1-octene was carried out in toluene withvarious concentrations of comonomer in the feed using Et(Ind)_2ZrCl_2/MAO (methyl alu-minoxane) as catalyst. It was found that with the increase of 1-octene concentration in thefeed the content of 1-octene in the copolymer increases, while the density, melting point,crystallinity and intrinsic viscosity of copolymer decrease. A copolymer with very lowdensity, containing 11.5 mol% of 1-octene (VLLDPE) can be produced with this catalystsystem. The effect of temperature and zirconium aluminum mole ratio of the catalyst onthe copolymerization was also investigated. The results of ~(13)C NMR determination of thecopolymer showed that the 1-octene units in the copolymer are principally isolated.     

Studies on monitoring the composition of the copolymer by cyclic voltammetry and in situ spectroelectrochemical analysis

Electrochemical copolymerization of diphenylamine (DPA) with ortho-toluidine (OT) was carried out in 4 M sulphuric acid medium by cyclic voltammetry. Cyclic voltammograms (CVs) of the copolymer films were recorded to deduce the electrochemical characteristics. In situ UV-visible spectroelectrochemical studies on copolymerization were carried out using indium tin oxide (ITO) coated glass plate as working electrode for different feed ratios of DPA and OT. UV-visible spectral characteristics show clear dependencies on the molar feed composition of DPA or OT used in electropolymerization. Derivative cyclic voltabsorptogram (DCVA) was deduced at the wavelength corresponding to the absorption by the intermediate species and used to identify the intermediates generated during the electropolymerization. The molar composition of DPA and OT units in the copolymer for the copolymers synthesized with different molar feed ratios of DPA and OT was determined by UV-visible spectroscopy. Reactivity ratios of DPA and OT were deduced by using Fineman-Ross and Kelen-Tudos methods and the observed differences in the composition of DPA/OT in the copolymers were correlated with CV characteristics and results obtained from in situ spectroelectrochemical studies.     

Separation of <Superscript>125</Superscript>IBZM and <Superscript>125</Superscript>ILIS using polyacrylamide-acrylic acid resin

Radioiodination of both S(−)BZM and LIS was carried out using n-bromosuccimide(NBS) as a mild oxidizing agent. The factors affecting on the radiochemical yield such as pH, reaction time, substrate concentration and oxidizing agent have been studied. The chromatographic separation of both ¹²⁵IBZM and ¹²⁵ILIS was carried out using HPLC and poly(acrylamide-acrylic acid) resin P(AAm-AA). The copolymer was prepared by a template polymerization of AA in aqueous solution on PAAm as a template polymer and in the presence of N,N-methylenebisacrylamide (NMBA) as a crosslinker using gamma rays as initiator. The purifications of tracers were carried out using prepared resin compared with TLC and HPLC. The effects of pH buffer, variable elution volumes, flow rate and temperature on the separation process of the resin efficiency have been studied.     

Synthesis of block copolymer poly (n-butyl acrylate)-b-polystyrene by DPE seeded emulsion polymerization with monodisperse latex particles and morphology of self-assembly film surface

Synthesis of poly (n-butyl acrylate)-b-polystyrene (PnBA-b-PSt) with high molecular weight in an environmentally benign medium was carried out in seeded emulsion polymerization, using a novel chain transfer active DPE (1,1-diphenylethylene) agent. Seed latex containing precursor P(nBA-DPE) was prepared first, and the second monomer styrene was swelled into seed latex particles, yielding block copolymer at high conversion. Structures as well as molecular weight of precursor and block copolymer were characterized by FTIR, (1)H NMR, and SEC, respectively. Furthermore, Transmission Electron Microscopy (TEM) observation and Laser Light Scattering (LLS) manifested that monodisperse latex particles were obtained. Self-assembly morphology of block copolymer membrane surface was examined by atom force microscopy (AFM). Phase separation was observed clearly, which was confirmed by the observation of two glass transitions in DSC curve.     

Synthesis of crosslinked poly(α-amino acids) with various functional groups

The esterification of the carboxyl group in copoly(γ-benzyl-L -glutamyl-L -glutamic acid) was carried out using N-hydroxysuccinimide and dicyclohexylcarbodimide to yield the activated site for the coupling reaction with amino compounds. The α-helix stability of the reactive copolymer thus obtained is remarkably affected in the presence of succinimide ring. This copolymer was proved to react nearly completely with amino alcohols such as 2-aminoethanol, 3-aminopropanol, and diethanolamine. The copoly(N⁵-hydroxyalkyl-L -glutamine) thus prepared is insoluble in water, since the benzyl ester remains in this copolymer. The copoly(α-amino acids) having another functional group were also prepared using aminoalkylsilane. Crosslinked poly(α-amino acids) were prepared by the reaction of the reactive copolymer with a low-molecular-weight polymer of PBLG having one amino group on each end of its main chain which was obtained from the corresponding NCA using p-diaminobenzene as an initiator. Another crosslinked polymer was prepared using an alkyl diamine such as 1,6-diaminohexane or 1,12-diaminododecane as a crosslinking reagent. The crosslinked copoly(α-amino acids) bearing the activated site are able to further react with various compounds having amino groups.     

接枝聚合物PAA—g—PIPA微球的制备及其温控释药研究

采用自由基溶液聚合法合成出Ｎ－异丙基丙烯酰胺齐聚物（Ｐｏｌｙ—Ｎ—Ｉｓｏｐｒｏｐｙｌａｍｉｄｅ，ＰＩＰＡ）．通过缩合将ＰＩＰＡ接枝在聚烯丙胺盐酸盐（Ｐｏｌｙａ－ｌｌｙａｍｉｎｅｈｙｄｒｏｃｈｌｏｒｉｄｅ，ＰＡＡ）上得到接枝聚合物ＰＡＡ—ｇ—ＰＩＰＡ．用化学交联法将ＰＡＡ－ｇ－ＰＩＰＡ制备成１０μｍ左右的微球．所得微球通过物理法吸附阿霉素（Ａｄｒｉａｍｙｃｉｎ，ＡＤ）后，采用动力学透析法测定其体外释药性能．实验数据拟合数学模型得到表征药物微球的释药特性的药物扩散系数Ｋｍ．Ｋｍ在３０℃—４５℃范围内随温度的升高而增大，反映了载药ＰＡＡ—ｇ—ＰＩＰＡ微球具有温控释药性．     

POLYCAPROLACTONE-POLY (ETHYLENE GLYCOL) BLOCK COPOLYMER Ⅲ DRUG RELEASE BEHAVIOR

The drug release behavior of degradable polymer--polycaprolactone-poly (ethyleneglycol)block copolymer(PCE) in vitro was investigated by using 5-Fluoro-uracil (5-Fu) asa model drug under a condition of pH 7. 4 at 37C. It is found that the release rate of 5-Fufrom PCE increased with increasing polyether content of the copolymer. The results showthat the increasing polyether content of the copolymer caused increasing hydrophilicity anddecreasing crystallinity of the PCE copolymer. Thus, the drug release behavior and thedegradable property of the PCE can be controlled by adjusting the composition of thecopolymer.     

原子转移自由基聚合法合成含羟基星状共聚物

以２－溴异丁酸季戊四醇四酯为引发剂在ＣｕＢｒ／ｂｐｙ催化下实施苯乙烯和丙烯酸β－羟丙酯原子转移自由基共聚合,结果表明聚合物的分子量与理论分子量接近,聚合反应具有活性聚合的特征。进一步对聚合产物进行ＧＰＣ,Ｈ－ＮＭＲ,ＩＲ和羟值滴定分析,表明合成的星状共聚合物中同时具有苯乙烯和丙烯酸β－羟丙酯结构单元,而且羟基在聚合物中近似均匀分布。     

Hydrophilic polymer drug from a derivative of salicylic acid: synthesis, controlled release studies and biological behavior

Hydrophilic polymeric drugs bearing "Triflusal" (4-trifluoromethylsalicylic acid), a drug widely used as antithrombogenic agent (Disgren), have been prepared by free radical copolymerization of methacryloyloxyethyl [2-(acetyloxy)-4-(trifluoromethyl)] benzoate (HTRF) and N,N'-dimethylacrylamide (DMA). The reactivity ratios of both monomers have been determined by 1H NMR spectra by applying non-linear least square treatments to the copolymerization equation (terminal model), and the kinetic parameters obtained indicated that the microstructure of copolymer chains is homogeneous, with a random distribution of the active HTRF units along the copolymer chains. That means that for the copolymer system THDMA22 used in this work, HTRF units are mainly isolated in relatively long DMA sequences. Therefore, in this structure the intramolecular interactions between adjacent HTRF units are negligible. Release of Triflusal from THDMA22 has been studied in vitro using buffered solutions at pH = 2, 7.4 and 10 and 37 degrees C. The system showed an interesting pseudo-zero order release profile at pH = 7.4 during several months. It has been also evaluated the pharmacological activity and the behavior of the system in contact with biological media. In this sense, we have carried out some in vitro studies about the antiaggregant properties and biocompatibility of THDMA22. Results demonstrate that this copolymer inhibits platelet aggregation in its macromolecular form and presents a good biocompatibility with Human Osteoblastic Cells (HOS).