核酸疫苗的药动学与安全性研究进展

核酸疫苗是将编码某种抗原蛋白的外源基因（DNA或RNA）直接导入机体细胞内，通过宿主细胞的转录系统合成抗原蛋白，诱导宿主对该抗原蛋白的免疫应答，从而达到预防和治疗疾病的目的。作为一种新型疫苗，核酸疫苗迄今已有10余种被FDA批准进入非临床和临床试验，但其应用于人体的有效性、安全性、可接受性仍是值得关注的问题。基于对乙肝病毒DNA疫苗药动学的研究基础，结合近几年国内外相关研究，笔者对核酸疫苗的药动学与安全性进行综述。     

Improved effect of 131I-MIBG treatment by predosing with non-radiolabeled MIBG in carcinoid patients, and studies in xenografted mice

Background: ¹³¹I-meta-iodobenzylguanidine (MIBG) hasbeen used with success for the palliation of metastatic carcinoid. To qualifymore patients for this treatment, we evaluated the effect of predosing withnon-radiolabeled MIBG on ¹³¹I-MIBG tumour targeting in carcinoidpatients and in mice with BON human carcinoid xenografts. Patients and methods:Ten carcinoid patients with a faint tumourimaging on a diagnostic ¹³¹I-MIBG scan (1 mCi = 37 MBq, 5 mg MIBG)received non-radiolabeled MIBG prior to a second scintigraphy. In case ofimproved tumour targeting patients were treated with 200 mCi (7.4 GBq)¹³¹I-MIBG following a pharmacological predose of 20–40mg/m² MIBG. Results:In six patients, highly increased tumour/non-tumour ratios were seen due to reduced levels in normal tissues and increased tumouraccumulation. The combined treatment applied in five patients, considerablyimproved symptoms in all (duration 6–12 months), accompanied bybiochemical response in three. In BON carcinoid xenografted mice, MIBG wasinjected intraperitoneally followed by intravenous ¹²⁵I-MIBG withsimilar findings: increased tumour/non-tumour radioactivity ratios by1.5–3-fold. Conclusion:Predosing with non-radiolabeled MIBG resulted inimproved ¹³¹I-MIBG tumour targeting, prolonged palliation andencouragingly often biochemical responses in carcinoid.     

Etoposide-incorporated tripalmitin nanoparticles with different surface charge: Formulation, characterization, radiolabeling, and biodistribution studies

Etoposide-incorporated tripalmitin nanoparticles with negative (ETN) and positive charge (ETP) were prepared by melt emulsification and high-pressure homogenization techniques. Spray drying of nanoparticles led to free flowing powder with excellent redispersibility. The nanoparticles were characterized by size analysis, zeta potential measurements, and scanning electron microscopy. The mean diameter of ETN and ETP nanoparticles was 391 nm and 362 nm, respectively, and the entrapment efficiency was more than 96%. Radiolabeling of etoposide and nanoparticles was performed with Technetium-99m (99mTc) with high labeling efficiency and in vitro stability. The determination of binding affinity of 99mTc-labeled complexes by diethylene triamine penta acetic acid (DTPA) and cysteine challenge test confirmed low transchelation of 99mTc-labeled complexes and high in vitro stability. Pharmacokinetic data of radiolabeled etoposide, ETN, and ETP nanoparticles in rats reveal that positively charged nanoparticles had high blood concentrations and prolonged blood residence time. Biodistribution studies of 99mTc-labeled complexes were performed after intravenous administration in mice. Both ETN and ETP nanoparticles showed significantly lower uptake by organs of the reticuloendothelial system such as liver and spleen (P < .001) compared with etoposide. The ETP nanoparticles showed a relatively high distribution to bone and brain (14-fold higher than etoposide and ETN at 4 hours postinjection) than ETN nanoparticles. The ETP nanoparticles with long circulating property could be a beneficial delivery system for targeting to tumors by Enhanced Permeability and Retention effect and to brain.     

Technetium-99m-Labeled N-(2-Hydroxypropyl) Methacrylamide Copolymers: Synthesis,Characterization, and in Vivo Biodistribution

PURPOSE: To synthesize novel technetium-99m (99mTc)-labeled N-(2-hydroxypropyl) methacrylamide (HPMA) copolymers and characterize the effect of charge and molecular weight on their biodistribution in SCID mice. METHODS: Electronegative and neutral 7-kDa, 21-kDa, and 70-kDa HPMA copolymers containing a 99mTc chelating comonomer, bearing N-omega-bis(2-pyridylmethyl)-L-lysine (DPK), were synthesized by free-radical precipitation copolymerization. The copolymers were labeled via 99mTc tricarbonyl chelation to DPK-bearing comonomer. They were characterized by side-chain content, molecular weight, molecular weight distribution, radiochemical purity, and labeling stability. Scintigraphic images were obtained during the first 90 min and at 24 h postintravenous injection in SCID mice. At 24 h, organ radioactivity was determined from necropsy tissue counting. RESULTS: 99mTc-labeled HPMA copolymers showed greater than 90% stability over a 24-h challenge with cysteine and histidine. Scintigraphic images and the necropsy data showed that the negatively charged copolymers were eliminated from the body significantly faster than the neutral copolymers in a size-dependent manner. CONCLUSIONS: To facilitate clinical scintigraphic imaging, stable chelation of 99mTc may be achieved by incorporation of a DPK-bearing comonomer into the HPMA backbone. Electronegative and neutral 99mTc-labeled HPMA copolymers of 7, 21, and 70 kDa show significant variation in organ biodistribution in SCID mice. 99mTc-labeled HPMA copolymers could be used as diagnostic agents and to study pharmacokinetics of delivery systems based on these copolymers.     

Computer Simulation of Convective and Diffusive Transport of Controlled-Release Drugs in the Vitreous Humor

Purpose. Biodistribution of drugs in the eye is central to the efficacy of pharmaceutical ocular therapies. Of particular interest to us is the effect of intravitreal transport on distribution of controlled-released drugs within the vitreous. Methods. A computer model was developed to describe the three-dimensional convective-diffusive transport of drug released from an intravitreal controlled release source. Unlike previous studies, this work includes flow of aqueous from the anterior to the posterior of the vitreous. The release profile was based on in vitro release of gentamicin from poly(L-lactic acid) microspheres into vitreous. Results. For small drugs, convection plays a small role, but for large (slower diffusing) drugs, convection becomes more important. For the cases studied, the predicted ratio of drug reaching the retina to drug cleared by the aqueous humor was 2.4 for a small molecule but 13 for a large molecule. Transport in neonatal mouse eye, in contrast, was dominated by diffusion, and the ratio decreased to 0.39. Conclusions. The interaction among convection, diffusion, and geometry causes significant differences in biodistribution between large and small molecules or across species. These differences should be considered in the design of delivery strategies or animal studies.     

Modified lipoproteins as contrast agents for imaging of atherosclerosis

The ability to detect and characterize atherosclerosis with targeted contrast agents may enable initiation of therapy for atherosclerotic lesions prior to becoming symptomatic. Since lipoproteins such as high‐density lipoprotein (HDL) and low‐density lipoprotein (LDL) play a critical role in the regulation of plaque biology through the transport of lipids into and out of atherosclerotic lesions, modifying HDL and LDL with radioisotopes for nuclear imaging, chelates for magnetic resonance imaging (MRI) or other possible contrast agents for computed tomography imaging techniques may aid in the detection and characterization of atherosclerosis. This review focuses on the literature employing lipoproteins as contrast agents for imaging atherosclerosis and the feasibility of this approach. Copyright © 2007 John Wiley & Sons, Ltd.     

荧光定量PCR技术在基因治疗药物组织分布研究中的应用

介绍应用荧光定量PCR技术对基因治疗药物组织分布研究的实验方法。从以下几个方面,即定量PCR技术原理、实验设计思路、各种检测方法的比较来说明这一问题。其中,可以使用的检测方法包括紫外定量法和引入内参基因法,后者又可以分为外标法和内标法。充分对比了这些方法的优缺点,并结合本实验室的研究现状,介绍了本监测中心在选用外标法进行研究时所取得的一些成果和实验经验。     

HSV-1基因转移载体在荷瘤裸鼠体内的生物分布研究

目的 研究HSV-1基因转移栽体在BALB/c荷瘤裸鼠体内的生物分布.方法 BALB/c裸鼠注射人乳腺癌MCF-7细胞制备肿瘤模型,瘤体内注射1×107pfu HSV-1,每2天给药1次,共给药3次.分别于给药后24h、5d和17d采集组织脏器,采用Taqman实时荧光定量PCR法,检测不同组织脏器中HSV-1基因拷贝数.结果 成功制备裸鼠肿瘤模型.在不同时间点,肿瘤中检测到的病毒载体最多,且随着时间延长不断增加;淋巴结、背根神经节和性腺中也有较高水平的病毒载体;其他组织器官中病毒载体量较少.结论 HSV-1能为基因转移提供有效、安全的载体平台,并能用于构建溶瘤基因治疗产品.     

In vitro biodistribution of silver nanoparticles in isolated perfused porcine skin flaps

Nanomaterials increasingly are playing a role in society for uses ranging from biomedicine to microelectronics; however, pharmacokinetic studies, which will be necessary for human health risk assessments, are limited. Currently the most widely used nanoparticle in consumer products is silver (Ag). The objective of the present study was to quantify the local biodistribution of two types of Ag nanoparticles, Ag‐citrate and Ag‐silica, in the isolated perfused porcine skin flap (IPPSF). IPPSFs were perfused for 4 h with 0.84 µg ml^–1 Ag‐citrate or 0.48 µg ml^–1 Ag‐silica followed by a 4‐h perfusion with media only during a washout phase. Arterial and venous concentrations of Ag were measured in the media by inductively coupled plasma optical emission spectrometry (ICP‐OES). Venous concentrations of Ag for both types of nanoparticles were best fit with a two compartment model. The normalized volumes of distribution estimated from the noncompartmental analysis of the venous concentrations indicated distribution of Ag greater than the vascular space; however, because total Ag was measured, the extravascular distribution could be attributed to diffusion of Ag ions. The estimated clearance for both types of Ag nanoparticles was 1 ml min^–1, which was equal to the flap perfusion rate, indicating no detectable elimination of Ag from the system. Four hours after infusion of the Ag nanoparticles, the recovery of Ag in the venous effluent was 90 ± 5.0% and 87 ± 22 % of the infused Ag for Ag‐citrate and Ag‐silica, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and biological evaluation of a series of 99mTc‐labeled diphosphonates as novel radiotracers with improved bone imaging

Three radiolabeled diphosphonates, ^99mTc‐labeled 1‐hydroxy‐3‐(2‐propyl‐1H‐imidazol‐1‐yl)propane‐1,1‐diyldiphosphonic acid (PIPrDP), 1‐hydroxy‐4‐(2‐propyl‐1H‐imidazol‐1‐yl)butane‐1,1‐diyldiphosphonic acid (PIBDP), and 1‐hydroxy‐5‐(2‐propyl‐1H‐imidazol‐1‐yl)pentane‐1,1‐diyldiphosphonic acid (PIPeDP), have been designed and synthesized with good chemical yields and high radiochemical purity. Their in vitro and in vivo biological properties were investigated and compared. All radiotracers evaluated in mice showed substantial retention in bone (8.42 ± 0.53, 9.08 ± 0.65, and 10.3 ± 0.61 ID%/g, respectively) at 1 h post‐injection and had rapid clearance in blood (1.9484, 1.3666, and 0.7704 ID%/g/min, respectively). ^99mTc‐PIBDP has the highest uptake ratio of bone‐to‐soft tissue at 1 h post‐injection among the three radiotracers. The results indicate that ^99mTc‐PIBDP is the most promising bone imaging agent. Copyright © 2012 John Wiley & Sons, Ltd.