Shixian Huang

Plasmid pORF-hTRAIL and doxorubicin co-delivery targeting to tumor using peptide-conjugated polyamidoamine dendrimer

A combination cancer therapy was investigated via co-delivery of therapeutic gene encoding human tumor necrosis factor-related apoptosis-inducing ligand (pORF-hTRAIL) and doxorubicin (DOX) using a tumor-targeting carrier, peptide HAIYPRH (T7)-conjugated polyethylene glycol-modified polyamidoamine dendrimer (PAMAM-PEG-T7). T7, a transferrin receptor-specific peptide, was chosen as the ligand to target the co-delivery system to the tumor cells expressing transferrin receptors. The result of fluorescence scanning showed that about 375 DOX molecules were bound to one pORF-hTRAIL molecule. The co-delivery system was constructed based on the electrostatic interactions between pORF-hTRAIL-DOX complex and cationic PAMAM-PEG-T7. T7-modified co-delivery system showed higher efficiency in cellular uptake and gene expression than unmodified co-delivery system in human liver cancer Bel-7402 cells, and accumulated in tumor more efficiently in vivo. In comparison with single DOX or pORF-hTRAIL delivery system, co-delivery system induced apoptosis of tumor cells in vitro and inhibited tumor growth in vivo more efficiently. In mice bearing Bel-7402 xenografts, lower doses of co-delivery system (4 μg DOX/mouse, about 0.16 mg/kg) effectively inhibited tumor growth comparable to high doses (5 mg/kg) of free doxorubicin (77% versus 69%). These results suggested that T7-mediated co-delivery system of DOX and pORF-hTRAIL was a simply prepared, combined delivery platform which can significantly improve the anti-tumor effect. This co-delivery system might widen the therapeutic window and allow for the selective destruction of cancer cells.

Gene and doxorubicin co-delivery system for targeting therapy of glioma

The combination of gene therapy and chemotherapy is a promising treatment strategy for brain gliomas. In this paper, we designed a co-delivery system (DGDPT/pORF-hTRAIL) loading chemotherapeutic drug doxorubicin and gene agent pORF-hTRAIL, and with functions of pH-trigger and cancer targeting. Peptide HAIYPRH (T7), a transferrin receptor-specific peptide, was chosen as the ligand to target the co-delivery system to the tumor cells expressing transferrin receptors. T7-modified co-delivery system showed higher efficiency in cellular uptake and gene expression than unmodified co-delivery system in U87 MG cells, and accumulated in tumor more efficiently in vivo. DOX was covalently conjugated to carrier though pH-trigged hydrazone bond. In vitro incubation of the conjugates in buffers led to a fast DOX release at pH 5.0 (intracellular environment) while at pH 7.4 (blood) the conjugates are relatively stable. The combination treatment resulted in a synergistic growth inhibition (combination index, CI < 1) in U87 MG cells. The synergism effect of DGDPT/pORF-hTRAIL was verified in vitro and in vivo. In vivo anti-glioma efficacy study confirmed that DGDPT/pORF-hTRAIL displayed anti-glioma activity but was less toxic.

Peptide-Conjugated PAMAM for Targeted Doxorubicin Delivery to Transferrin Receptor Overexpressed Tumors

The purpose of this work was to evaluate the potential of HAIYPRH (T7) peptide as a ligand for constructing tumor-targeting drug delivery systems. T7 could target to transferrin-receptor (TfR) through a cavity on the surface of TfR and then transport into cells via endocytosis with the help of transferrin (Tf). In this study, T7-conjugated poly(ethylene glycol) (PEG)-modified polyamidoamine dendrimer (PAMAM) (PAMAM-PEG-T7) was successfully synthesized and further loaded with doxorubicin (DOX), formulating PAMAM-PEG-T7/DOX nanoparticles (NPs). In vitro, almost 100% of DOX was released during 2 h in pH 5.5, while only 55% of DOX was released over 48 h in pH 7.4. The cellular uptake of DOX could be significantly enhanced when treated with T7-modified NPs in the presence of Tf. Also, the in vitro antitumor effect was enhanced markedly. The IC(50) of PAMAM-PEG-T7/DOX NPs with Tf was 231.5 nM, while that of NPs without Tf was 676.7 nM. T7-modified NPs could significantly enhance DOX accumulation in the tumor by approximately 1.7-fold compared to that of unmodified ones and by approximately 5.3-fold compared to that of free DOX. For in vivo antitumor studies, tumor growth of mice treated with PAMAM-PEG-T7/DOX NPs was significantly inhibited compared to that of mice treated with PAMAM-PEG/DOX NPs and saline. The study provides evidence that PAMAM-PEG-T7 can be applied as a potential tumor-targeting drug delivery system. T7 may be a promising ligand for targeted drug delivery to the tumor.

Peptide-conjugated polyamidoamine dendrimer as a nanoscale tumor-targeted T1 magnetic resonance imaging contrast agent

A tumor-targeting carrier, peptide HAIYPRH (T7)-conjugated polyethylene glycol-modified polyamidoamine dendrimer (PAMAM-PEG-T7) was explored to deliver magnetic resonance imaging (MRI) contrast agents targeting to the tumor cells specifically. Two different types of tumors, liver cancer and early brain glioma model (involved with the blood-brain barrier), were chosen to evaluate the imaging capacity of this contrast agent. PAMAM-PEG-T7 was synthesized, conjugated with diethylene triamine pentaacetic acid (DTPA) and further chelated gadolinium (Gd), yielding GdDTPA-PAMAM-PEG-T7. The result of ICP-AES showed that about 92 Gd ions could be loaded per PAMAM molecule. The calculated longitudinal relaxivity R1 of the GdDTPA-PAMAM-PEG-T7 was 10.7 mm(-1) S(-1) per Gd (984.4 mm(-1) S(-1) per PAMAM), while that of GdDTPA was only 4.8 mm(-1) S(-1). PAMAM-PEG-T7 had better targeting capacity to the liver cancer cells in vitro and in vivo, compared with PAMAM-PEG. The accumulation of PAMAM-PEG-T7 was 162.5% times that of PAMAM-PEG. But for glioma cells, PAMAM-PEG-T7 did not show its specificity. Furthermore, GdDTPA-PAMAM-PEG-T7 could improve the diagnostic efficiency of liver cancer with the enhanced signal (187%), compared to 130% for PAMAM-PEG and 121% for GdDTPA. GdDTPA-PAMAM-PEG-T7 could selectively identify liver cancer but not early glioma. This nanoscaled MRI contrast agent GdDTPA-PAMAM-PEG-T7 might allow for selective and efficient diagnosis of tumors without the natural barrier including liver cancer.

T7 peptide-functionalized nanoparticles utilizing RNA interference for glioma dual targeting

Among all the malignant brain tumors, glioma is the deadliest and most common form with poor prognosis. Gene therapy is regarded as a promising way to halt the progress of the disease or even cure the tumor and RNA interference (RNAi) stands out. However, the existence of the blood-brain barrier (BBB) and blood tumor barrier (BTB) limits the delivery of these therapeutic genes. In this work, the delivery system targeting to the transferrin (Tf) receptor highly expressed on both BBB and glioma was successfully synthesized and would not compete with endogenous Tf. U87 cells stably express luciferase were employed here to simulate tumor and the RNAi experiments in vitro and in vivo validated that the gene silencing activity was 2.17-fold higher with the targeting ligand modification. The dual-targeting gene delivery system exhibits a series of advantages, such as high efficiency, low toxicity, stability and high transaction efficiency, which may provide new opportunities in RNAi therapeutics and nanomedicine of brain tumors.

Evaluation and mechanism studies of PEGylated dendrigraft poly-L-lysines as novel gene delivery vectors

Dendrimers have attracted great interest in the field of gene delivery due to their synthetic controllability and excellent gene transfection efficiency. In this work, dendrigraft poly-L-lysines (DGLs) were evaluated as a novel gene vector for the first time. Derivatives of DGLs (generation 2 and 3) with different extents of PEGylation were successfully synthesized and used to compact pDNA as complexes. The result of gel retardation assay showed that pDNA could be effectively packed by all the vectors at a DGLs to pDNA weight ratio greater than 2. An increase in the PEGylation extent of vectors resulted in a decrease in the incorporation efficiency and cytotoxicity of complexes in 293 cells, which also decreased the zeta potential a little but did not affect the mean diameter of complexes. Higher generation of DGLs could mediate higher gene transfection in vitro. Confocal microscopy and cellular uptake inhibition studies demonstrated that caveolae-mediated process and macropinocytosis were involved in the cellular uptake of DGLs-based complexes. Also the results indicate that proper PEGylated DGLs could mediate efficient gene transfection, showing their potential as an alternate biodegradable vector in the field of nonviral gene delivery.

Choline‐Derivate‐Modified Nanoparticles for Brain‐Targeting Gene Delivery

The major obstacle for drug delivery to the central nervous system (CNS) is the blood–brain barrier (BBB), which protects the CNS from potentially harmful xenobiotics and endogenous molecules to ensure an optimal environment for brain function. [ 1 ] Despite this natural barricade, small molecules and macromolecules including peptides and proteins could be transported into the CNS to maintain its normal physiological function via the endogenous BBB transporters. There are three families of endogenous BBB transporters: carrier-mediated transporters (CMT), active effl ux transporters (AET), and receptor-mediated transporters (RMT). The CMT and AET systems are mainly responsible for the transport of small molecules, while the RMT systems are responsible for endogenous large molecules. [ 2 , 3 ]

A brain-vectored angiopep-2 based polymeric micelles for the treatment of intracranial fungal infection

One of the most common life-threatening infections in immunosuppressive patients, like AIDs patients, is cryptococcal meningitis or meningoencephalitis. Current therapeutic options are mostly ineffective and mortality rates remain high. Hydrophobic antifungal drug Amphotericin B (AmB), has become a golden standard in severe systemic fungal infection therapy. However, most AmB commercial formulations, including deoxycholate AmB and lipid formulations of AmB, show poor penetration into the CNS and difficulty to reach the therapeutic levels. To improve the CNS permeability of AmB, we have successfully developed an effective brain-targeting polymeric micellar system with angiopep-2 modified, named Angiopep-PEG-PE/AmB polymeric micelles. An immunosuppressive murine model with Cryptococcus neoformans meningoencephalitis (CNME) was established to evaluate the CNS penetration efficiency and antifungal treatment efficacy of the AmB-incorporated brain-vectored polymeric micellar formulation, compared with the AmB commercial formulations. After three consecutive days of i.v. administration, the results showed that the group treated with Angiopep-PEG-PE/AmB achieved the greatest treatment efficacy, which reached the highest AmB level in brain, reduced the brain fungal burden significantly, decreased histopathological severity and prolonged the median survival time. The increased treatment efficacy could be attributed to the brain-targeting delivery system promoted AmB crossing the BBB and penetrating into the brain to reach the therapeutic concentration. The underlying mechanism was also explored in this work. Therefore, the brain-targeting delivery system could have potential and promising implications for treatment of intracerebral fungal infection.

A choline derivate-modified nanoprobe for glioma diagnosis using MRI

Gadolinium (Gd) chelate contrast-enhanced magnetic resonance imaging (MRI) is a preferred method of glioma detection and preoperative localisation because it offers high spatial resolution and non-invasive deep tissue penetration. Gd-based contrast agents, such as Gd-diethyltriaminepentaacetic acid (DTPA-Gd, Magnevist), are widely used clinically for tumor diagnosis. However, the Gd-based MRI approach is limited for patients with glioma who have an uncompromised blood-brain barrier (BBB). Moreover, the rapid renal clearance and non-specificity of such contrast agents further hinders their prevalence. We present a choline derivate (CD)-modified nanoprobe with BBB permeability, glioma specificity and a long blood half-life. Specific accumulation of the nanoprobe in gliomas and subsequent MRI contrast enhancement are demonstrated in vitro in U87 MG cells and in vivo in a xenograft nude model. BBB and glioma dual targeting by this nanoprobe may facilitate precise detection of gliomas with an uncompromised BBB and may offer better preoperative and intraoperative tumor localization.

Optical characteristics of laser-crystallized Si1 −xGex nanocrystals

Si1−xGex nanocrystals were obtained by means of laser-induced crystallization of a-SiGe films deposited by plasma-enhanced chemical vapour deposition. The crystallization was confirmed by x-ray diffraction spectroscopy, Fourier transmission infrared spectroscopy and atomic force microscopy; the average diameter of the nanocrystals was about 4.1 nm. The Ge fraction component was estimated to be 0.3 from the Raman spectra. In the near-infrared photoluminescence (PL) a peak located at 1.357 eV was observed. For Si1−xGex nanocrystals about 4.1 nm in diameter, the PL is considered to originate from the recombination of electron–hole pairs confined in Si1−xGex nanocrystals, and direct recombination and indirect recombination both occur in the recombination process. Another possible cause of near-infrared PL is the presence of defects at the interface between Si1−xGex nanocrystals and the surrounding matrix and/or in the matrix region itself.