ABSTRACT
Aptamers are kinds of single-strand oligonucleotides with high affinity to their targets. Compared to other commonly used target ligands,like antibodies,aptamers are small,non-immunogenic,as well as the undemanding in vitro screening. At pres?ent,the nano-delivery systems modified with aptamers for tumor targeting are often divided into three types:aptamers modifying on the surface of nanocarriers,such as liposomes,nanoparticles,and micelles,to form aptamer-targeted nanocarriers;aptamers conju?gating to molecular drugs or fluorescent agents to form aptamer-drug/fluorescent agent conjugates;and aptamers serving as drug carri?ers for further tumor targeting and drug delivery. In this paper,the advances in nano-delivery system based on aptamer targeting to tu?mor are summarized.
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Objective:To investigate the preparation, optimization and in vitro properties of riboflavin sodium phosphate floating microspheres. Methods: The floating microspheres composed of riboflavin sodium phosphate and calcium alginate were prepared using ion gelatin-oven drying method. Results: The properties of the microspheres were investigated, including the buoyancy, release, appearance and entrapment efficiency. The formulation was optimized by response surface methodology (RSM). Conclusion: The optimized microspheres were round. The entrapment efficiency was 57.49%. All the microspheres could float on the artificial gastric juice over 8 hours. The release of the drug from the microspheres complied with Fick' s diffusion.
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Objective:To develop and study the properties of ion-exchange polyvinyl alcohol-acrylic acid microspheres(PVA-AA-Ms) for embolization.Methods:The PVA-AA-Ms were produced by the method of inverse suspension polymerization.The morphology and particle size were determined by optical microscope;FT-IR was used to investigate the special functional groups of PVA-AA-Ms;the carboxyl content of PVA-AA-Ms was measured by chemical titration;the compression elasticity was examined by texture analyzer(TA-plus).Pingyangmycin(bleomycin A5) was used as model drug to prepare drug-loaded PVA-AA-Ms.Drug loading and entrapment efficiency were measured through UV-spectrophotometer;in vitro drug release characteristic was detected by constant temperature vibration dialysis assay.Results:The PVA-AA-Ms were round and integrated.The average diameter of PVA-AA-Ms was 500 ?m with a range of 150-1 000 ?m.The carboxyl vibration was demonstrated by FT-IR and the content of carboxyl was 8.905 mmol/g.PVA-AA-Ms were mechanically stable with appropriate elasticity.Drug loading and entrapment efficiency were 30 g/L and 99.4%,respectively.The drug release rate was slow in phosphate buffer solution(PBS),88.3% of the drug was released after 24 h and the t50 was 2.19 h.Conclusion:PVA-AA-Ms prepared in this study were supposed to be suitable for clinical embolization according to the physicochemical properties.The high carboxyl content of PVA-AA-Ms which allowed them to load cationic drugs(e.g.,drug with amino group) through ion-exchange mechanism brought broad prospects for combination of embolization and chemotherapy.
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Objective:To develop and characterize the hydrogel microspheres for embolization.Methods:N-[tris(hydroxymethyl)methyl] acrylamide-gelatin microspheres(TGMs)were prepared by an inverse suspension polymerization approach.Effects of materials on size,water absorption rate and elasticity of the microspheres were investigated.The materials which were included consisted of gelatin in the range of 10.0-100.0 g/L,N-[tris(hydroxymethyl)methyl]acrylamide in the range of 33.3-200 g/L,cross-linking agent N,N'-methylene-bis-acrylamide in the range of 3.3-10.0 g/L,surfactant Span 80 in the range of 0.5-1.8 g/L,and initiator ammonium persulfate in the range of 1.0-5.0 g/L.The appearance of TGMs was observed under microscope.TGMs were analyzed by infrared spectrum(IR).Results:The TGMs were round with smooth surface in view of photograph of microscope.The average diameter of TGMs was increased with the increase of gelatin,monomer or cross-linking agent concentrations but decreased with the increase of surfactant or initiator Concentration.The water adsorption rate of the microspheres was decreased with the increase of gelatin or cross-linking agent concentration but not affected by surfactant concentration.The elasticity of TGMs was increased with the increase of monomer or cross-linking agent concentration,decreased with the increase of gelatin concentration,but not affected by surfactant or initiator concentration.All factors above considered,the final prepared TGMs consisted of 10 g/L gelatin,100.0 g/L monomer,6.7 g/L cross-linking agent,0.9 g/L surfactant,and 3.0 g/L initiator.The average diameter of TGMs obtained was about 700.0 ?m.The water adsorption rate and the elasticity in accordance with the maximum diameter of the microspheres passed through a microcatheter of TGMs were 12.4(g/g),and 1 600.0 ?m,respectively.The results of IR spectra confirmed the polymerization of monomer,resulting in N-[tris(hydroxymethyl)methyl]acrylamide-gelatin microspheres.Conclusion:The developed TGMs seemed to be suitable for clinical embolization according to the surface,average diameter,elastic and hydrophilic property of TGMs.
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Objective:To develop lipiodol-containing calcium alginate microspheres (LAMs) for embolization,and study the characterization for emoblization and the radiopacity. Methods:LAMs were prepared by dripping method. The preparation of LAMs was optimized by orthogonal experiment which involved effects of three factors (the volume ratio of lipiodol to the external aqueous solution,airflow rate,and the weight pushing the injector) at three levels on the responses to the size,polydisperse index and entrapment efficiency of LAMs. The morphology of LAMs was observed under microscope. The elasticity of LAMs was investigated by texture analyzer. The capability injected through catheter of LAMs was monitored by video spinning-drop tensionmeter. The radiopacity of LAMs was measured by X-ray imaging system after LAMs were injected into vas of a rat. Results:The optimal condition for preparation of LAMs was:the volume ratio of lipiodol to the external aqueous solution was 3∶ 10,airflow rate was 40 g/mL and the weight pushing the injector was 100 g. According to the optimized condition,LAMs were prepared and characterized. The mean diameter of LAMs was (493.9?42.6) ?m,the polydisperse index was 1.02 and the entrapment efficiency was (88.97?1.09)%. The LAMs were with round shape and smooth surface in view of photograph of microscope. The maximum average load was (1.09?0.18) N when LAMs were compressed to 60%. The LAMs were injected through catheter without much difficulty. The radiopacity of LAMs in rats was demonstrated to be visible under X-ray photography system. Conclusion:The radiopaque LAMs developed are suitable for the arterial embolization,with round shape,proper size,good elasticity,easy handling character and visible property under X-ray imaging. The radiopaque embolic agent is supposed to be useful for emoblization therapy.
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Objective: To investigate the preparation of pulsatile release tablets, the release of the drug in vitro and the pharmacokinetics in vivo . Methods: Dil tiazem hydrochloride（DIL） was used as model drug. The pulsatile release tabl e ts were prepared by dry-coated method with carnauba wax, bee wax and hydrophil i c cellulose as coating materials. The effects of formulation and technology on t he release characteri stic of diltiazem hydrochloride was investigated. The mechanism of pulsatile rel ease of the drug was proved by erosion test. The pharmacokinetic study on four h uman subjects was done by means of HPLC measurement. Results: In vitro ， delayed-release ti me t 10 was 2.1 h, the maximum release time t rm 4.0 h and t he pulsed-releas e time t 10-90 1.7 h. In vivo ， delayed-release time t la g was 5.7 h, the p eak time 8.5 h and the pulsed-release time 2.6 h. Conclusion: The rele ase of drug from pulsatile-released tablets of diltiazem hydrochloride was in a pulsed way both in vitro and in vivo .