Synthesis and cellular uptake of p-[(123)I]-phenyl-amino-thiazole ((123)I-PAT) as a potential agent for targeting tubulin polymerization in tumors.

The phenyl-amino-thiazole (PAT) templates of methoxylbenzoyl-aryl-thiazole are potent agents against cancer by inhibiting tubulin polymerization in the nanomolar range. Herein, a radioiodinated PAT, [(123)I]-PAT 1, was prepared via a tributylstannyl precursor and [(123)I]iodide through electrophilic aromatic radioiodination. Radiolabelling of [(123)I]-PAT 1 was achieved in less than 15 min, with a radiochemical purity of over 99%. The accumulated radioactivity in tumor cellular uptake experiments suggested that [(123) I]-PAT could serve as a potential radioprobe for targeting tumor cells.

Polymeric micelles comprising stearic acid-grafted polyethyleneimine as nonviral gene carriers.

Non-viral vectors composed of biodegradable polymers or lipids have been considered as a safer alternative for gene carriers over viral vectors. Among some of the cationic polymers, polyethyleneimine (PEI) possess high pH-buffering capacity that can provide protection to nucleotides from acidic degradation and promotes endosomal and lysosomal release. However, it has been reported that cytotoxicity of PEI depends on the molecular weight of the polymer. Hence modifications of PEI structure for clinical application have been developed in order to reduce the cytotoxicity, or improve the insufficient transfection efficiency of lower molecular weight PEI. In this study, 10 k PEI was modified by grafting stearic acid (SA) and formulated to polymer micelles with positive surface charge and evaluated for pDNA delivery. The amine group on PEI was crosslinked with the carboxylic group of stearic acid by 1-ethyl-3-(3-dimethylamino-propyl) carbodiimide (EDC) as linker. PEI-SA micelles were then prepared using oil in water (o/w) solvent evaporation method. The success of PEI-SA conjugation structure was confirmed with 1H NMR. The average diameter and zeta potential determined by photon correlation spectroscopy was 149.6 +/- 1.2 nm and 64.1 +/- 1.5 mV, respectively. These self-assemble positive charge micelles showed effective binding to pDNA for transfection. PEI-SA micelles exhibited lower cytotoxicity compared to that of PEI only, while flow cytometry analysis revealed PEI-SA/pEGFP complex provided 62% high EGFP expression. Luciferase activity also showed high transfection efficiency of PEI-SA micelles for weight ratio above 4.5 that was comparable to PEI only. These results demonstrated that stearic acid grafted PEI micelles can provide high transfection efficiency comparable to unmodified PEI, and exhibit low cytotoxicity. Stearic acid grafted PEI micelles can be promising polymer carriers in genetic therapy.

Cell uptake and intracellular visualization using quantum dots or nuclear localization signal-modified quantum dots with gold nanoparticles as quenchers.

Understanding and controlling the interactions between nanoscale objects and living cells is of great importance for diagnostic imaging and therapeutic applications. Quantum dots (QDs) have remarkable optical characteristics, such as uniquely feature bright, photostable, tunable and narrow fluorescence emissions, as well as broad absorption spectra. Here we report a platform of using quantum dots to investigate the cell uptake and the interactions between nanoscale objects and cells. QDs are uptaken by BHK cells easily through endocytosis. We could clearly differentiate the QDs outside the cell or inside the cell by quenching the QDs with similar sized gold nanoparticles and reduce the noise of fluorescent image. Microscopic images show that QDs are homogeneously distributed within the whole cell except the nucleus. However, unmodified QDs could not penetrate the nuclear membrane and move into the nucleus. Coupling QDs with Nuclear Localization Signal (NLS, CGGGPKKKRKVGG) can significantly enhance the translocation amount of QDs into the cell and cell nucleus. This method combined with microscopy imaging system can visualize the particle delivery routes and provide valuable information in the drug/gene delivery and tumor diagnosis.

Evaluation of (131/123)I-5-iodo-2'-deoxycytidine as a novel proliferation probe in a tumor mouse model.

This study evaluated a radioiodinated deoxycytidine analog, (131)I-5-iodo-2'-deoxycytidine ([(131)I]ICdR), as a novel proliferation probe and compared it with (131)I-5-iodo-2'-deoxyuridine ([(131)I]IUdR) in a NG4TL4 sarcoma-bearing mouse model. As an imaging agent, the biological characteristics of [(123)I]IUdR is not satisfactory due to its metabolic instability and short biological half-life in vivo. With [(123)I]ICdR/SPECT it was possible to clearly delineate the tumor lesion at 1h post-injection (tumor-to-muscle ratio 7.74) in tumor-bearing mice. The results of biodistribution were consistent with those observed in scintigraphic imaging. This study demonstrated that [(131)I]ICdR is a more promising SPECT probe than [(131)I]IUdR for imaging proliferation.

Co-delivery of anti-vascular endothelial growth factor siRNA and doxorubicin by multifunctional polymeric micelle for tumor growth suppression.

Nonviral gene carriers composed of biodegradable polymers or lipids have been considered as a safer alternative for gene carriers over viral vectors. We have developed multifunctional nanomicelles for both drug and gene delivery application. Polyethylenimine (PEI) was modified by grafting stearic acid (SA) and further formulated to polymeric micelles (PEI-SA) with positive surface charge for gene delivery evaluation. Our results showed that PEI-SA micelles provided high siRNA binding efficiency and exhibited low cytotoxicity compared with unmodified PEI. siRNA delivered by PEI-SA carriers also demonstrated significantly higher cellular uptake efficiency and stability even in the presence of serum proteins when compared with free siRNA. The post-transcriptional gene silencing efficiency was greatly improved by the polyplex formulated by 10k PEI-SA/siRNA. In the animal intratumoral model study, the combination of co-delivering doxorubicin and vascular endothelial growth factor (VEGF) siRNA delivered by PEI-SA micelles showed a promising effect on anti-tumor growth. The amphiphilic structure of PEI-SA micelles provides advantages for multifunctional tasks; such that hydrophilic shell modified with cationic charges can electrostatically interact with DNA or siRNA, and hydrophobic core can serve as a payload for hydrophobic drugs, making it truly a promising multifunctional vehicle for both genetic and chemotherapy application.

High-efficiency cell seeding method by relatively hydrophobic culture strategy.

Cell adhesion efficiency is one of the key factors affecting the results of manufacturing tissue engineering constructs. High efficiency is required for seeding low proliferation cells onto scaffolds. In this study, we designed a strategy to improve the efficiency of cell adhesion using hydrophobic cell culture environment to enhance cells adhering to a scaffold. Cells have lower affinity to the surface of polydimethylsiloxane (PDMS) than tissue culture polystyrene (TCPS) plates. When cells were cultured with gelatin microspheres or chitosan films in a PDMS-coated plate instead of a normal TCPS plate, there was a significant increase in cell attachment efficiency. Cells cultured in the PDMS-coated system tended to selectively attach onto the gelatin microspheres or chitosan films, which are relatively more hydrophilic than the PDMS surface. However, minimal cell attachment on gelatin microspheres or chitosan films was observed when gelatin microspheres or chitosan films were placed in normal TCPS plate. Cell counting experiments with gelatin microspheres in the PDMS-coated system resulted in a cell attachment efficiency of 89.8% after 1 day of cultivation, whereas the cell attachment efficiency was less than 1% in normal TCPS plate. The results demonstrate that the method is easy to use and could be useful for fast cultivation of cell-scaffold constructs.

Intracellular trafficking, metabolism and toxicity of current gene carriers.

Gene delivery remains to be a very challenging field to efficiently transport the therapeutic gene and to modulate proteins with the desired function at the target site. The physiochemical and biological barriers are the major hurdles that need to be considered, particularly when administered systematically, in order to optimize the therapeutic efficacy. Numerous modifications have been extensively investigated aiming to provide protection from the plasma degradation, enhancement of transfection, target specificity, and most importantly, minimizing the side effects such as cellular toxicity and immune response. This article provides a review with respect to the in vitro and in vivo toxicity, as well as cellular and physiological interactions with the gene delivery system composed from viral vectors, cationic lipids and polymers. Recent progress and development are also addressed, with promising results that may be further adopted for clinical use.