Tiehong Yang

Dual-pH Sensitive Charge-reversal Nanocomplex for Tumor-targeted Drug Delivery with Enhanced Anticancer Activity

Poly(β-L-malic acid) (PMLA), a natural aliphatic polyester, has been proven to be a promising carrier for anti-cancer drugs. In spite of excellent bio-compatibility, the application of PMLA as the drug carrier for cancer therapy is limited by its low cellular uptake efficiency. The strong negative charge of PMLA impedes its uptake by cancer cells because of the electrostatic repulsion. In this study, a dual pH-sensitive charge-reversal PMLA-based nanocomplex (PMLA-PEI-DOX-TAT@PEG-DMMA) was developed for effective tumor-targeted drug delivery, enhanced cellular uptake, and intracellular drug release. The prepared nanocomplex showed a negative surface charge at the physiological pH, which could protect the nanocomplex from the attack of plasma proteins and recognition by the reticuloendothelial system, so as to prolong its circulation time. While at the tumor extracellular pH 6.8, the DMMA was hydrolyzed, leading to the charge reversal and exposure of the TAT on the polymeric micelles, thus enhancing the cellular internalization. Then, the polymeric micelles underwent dissociation and drug release in response to the acidic pH in the lyso/endosomal compartments of the tumor cell. Both in vitro and in vivo efficacy studies indicated that the nanocomplex significantly inhibited the tumor growth while the treatment showed negligible systemic toxicity, suggesting that the developed dual pH-sensitive PMLA-based nanocomplex would be a promising drug delivery system for tumor-targeted drug delivery with enhanced anticancer activity.

Multifunctional pH-sensitive micelles for tumor-specific uptake and cellular delivery

The distinct ability of cell-penetrating peptides (CPPs) has led to the development of novel drug delivery methods in human cells for therapeutic purposes. The lack of specific selectivity is a main obstacle to the widespread use of CPPs. A novel delivery method based on acid-sensitive micelles used for the introduction and protection of TAT was developed. Doxorubicin-TAT conjugate (Dox-TAT) was loaded in the luteinizing hormone-releasing hormone modified poly (ethylene glycol)-poly (L-histidine)-doxorubicin (LHRH-PEG-PHIS-Dox) micelle. Dox was chemically conjugated to the polymer backbone not only to improve the stability of micelles, but also to increase the drug loading efficiency of the micelle. These micelles could dissociate the responding tumor extracellular pHe and release Dox-TAT to pass directly through the cell membrane to the cytosol of the multidrug resistant cancer cells. The undissociated micelles could also be actively internalized into the cells by receptor-mediated endocytosis, resulting in high cytotoxicity. LHRH-PEG-PHIS-Dox/Dox-TAT showed the highest antitumor effects among the four treatment groups in vitro and vivo and showed no remarkable effect on the body weight compared to the control. This skillfully designed system combined the double functions of targeted delivery and TAT-mediated efficient entry, which could increase the antitumor activity, even in drug resistant tumor cells.

Characterization of Compounds in Psoralea corylifolia Using High-Performance Liquid Chromatography Diode Array Detection, Time-of-Flight Mass Spectrometry and Quadrupole Ion Trap Mass Spectrometry.

High-performance liquid chromatography with diode array detection (HPLC-DAD), time-of-flight mass spectrometry (HPLC-TOFMS) and quadrupole ion trap mass spectrometry (HPLC-QITMS) were used for separation and identification of multi-components in Psoralea corylifolia. Benefiting from combining the accurate mass measurement of HPLC-TOFMS to generate elemental compositions, the complementary multilevel structural information provided by HPLC-QITMS and the characteristic UV spectra obtained from HPLC-DAD, 24 components in P. corylifolia were identified. The five groups of isomers were differentiated based on the fragmentation behaviors in QITMS and UV spectra. It can be concluded that an effective method based on the combination of HPLC-DAD, HPLC-TOFMS and HPLC-QITMS for identification of chemical components in P. corylifolia was established. The results provide essential data for further pharmacological and clinical studies of P. corylifolia and facilitate the rapid quality control of the crude drug.

Preparation of poly(β-L-malic acid)-based charge-conversional nanoconjugates for tumor-specific uptake and cellular delivery

In this study, a multifunctional poly(β-L-malic acid)-based nanoconjugate with a pH-dependent charge conversional characteristic was developed for tumor-specific drug delivery. The short branched polyethylenimine-modified poly(β-L-malic acid) (PEPM) was first synthesized. Then, the fragment HAb18 F(ab′)2 and 2,3-dimethylmaleic anhydride were covalently attached to the PEPM to form the nanoconjugate, HDPEPM. In this nanoconjugate, the 2,3-dimethylmaleic anhydride, the shielding group, could shield the positive charge of the conjugate at pH 7.4, while it was selectively hydrolyzed in the tumor extracellular space (pH 6.8) to expose the previously-shielded positive charge. To study the anticancer activity, the anticancer drug, doxorubicin, was covalently attached to the nanoconjugate. The doxorubicin-loaded HDPEPM nanoconjugate was able to efficiently undergo a quick charge conversion from −11.62 mV to 9.04 mV in response to the tumor extracellular pH. The electrostatic interaction between the positively charged HDPEPM nanoconjugates and the negatively charged cell membrane significantly enhanced their cellular uptake, resulting in the enhanced anticancer activity. Also, the tumor targetability of the nanoconjugates could be further improved via the fragment HAb18 F(ab′)2 ligand–receptor-mediated tumor cell-specific endocytosis.

Stimuli-responsive polymeric micelles for drug delivery and cancer therapy

Polymeric micelles (PMs) have been widely investigated as nanocarriers for drug delivery and cancer treatments due to their excellent physicochemical properties, drug loading and release capacities, facile preparation methods, biocompatibility, and tumor targetability. They can be easily engineered with various functional moieties to further improve their performance in terms of bioavailability, circulation time, tumor specificity, and anticancer activity. The stimuli-sensitive PMs capable of responding to various extra- and intracellular biological stimuli (eg, acidic pH, altered redox potential, and upregulated enzyme), as well as external artificial stimuli (eg, magnetic field, light, temperature, and ultrasound), are considered as “smart” nanocarriers for delivery of anticancer drugs and/or imaging agents for various therapeutic and diagnostic applications. In this article, the recent advances in the development of stimuli-responsive PMs for drug delivery, imaging, and cancer therapy are reviewed. The article covers the generalities of stimuli-responsive PMs with a focus on their major delivery strategies and newly emerging technologies/nanomaterials, discusses their drawbacks and limitations, and provides their future perspectives.

Preparation of Two Types of Polymeric Micelles Based on Poly(β-L-Malic Acid) for Antitumor Drug Delivery.

Polymeric micelles represent an effective delivery system for poorly water-soluble anticancer drugs. In this work, two types of CPT-conjugated polymers were synthesized based on poly(β-L-malic acid) (PMLA) derivatives. Folic acid (FA) was introduced into the polymers as tumor targeting group. The micellization behaviors of these polymers and antitumor activity of different self-assembled micelles were investigated. Results indicate that poly(ethylene glycol)-poly(β-L-malic acid)-campotothecin-I (PEG-PMLA-CPT-I, P1) is a grafted copolymer, and could form star micelles in aqueous solution with a diameter of about 97 nm, also that PEG-PMLA-CPT-II (P2) is an amphiphilic block copolymer, and could form crew cut micelles with a diameter of about 76 nm. Both P1 and P2 micelles could improve the cellular uptake of CPT, especially the FA-modified micelles, while P2 micelles showed higher stability, higher drug loading efficiency, smaller size, and slower drug release rate than that of P1 micelles. These results suggested that the P2 (crew cut) micelles possess better stability than that of the P1 (star) micelles and might be a potential drug delivery system for cancer therapy.

Optimal Design of Novel Functionalized Nanoconjugates Based on Polymalic Acid for Efficient Tumor Endocytosis with Enhanced Anticancer Activity

To overcome the strong negative charge and improve the endocytosis of poly-β-malic acid (PMLA) as a drug carrier, a pH-sensitive nanoconjugate of PMLA/hyd-PEG5000/PEG2000-TAT/DOX (PHPTD) was developed. The trans activator of transcription (TAT) modified with polyethylene glycol2000(PEG2000) was conjugated with the PMLA backbone which improved the endocytosis of PMLA. PEG5000 was utilized to shield TAT by a pH-sensitive hydrazone (Hyd) bond. In order to decrease the potential risk of accelerated blood clearance (ABC) phenomenon by anti-PEG IgM, the minimal content of TAT for penetrating tumor cells and the optimal protecting layer density of PEG5000 were screened. The result showed that 0.3 mol% TAT was enough to efficiently improve cellular uptake of PMLA (30 kda). The cytotoxicity and the 1H-NMR results indicated that 3.6 mol% PEG5000-modified nanoconjugates could shield 0.3 mol% TAT. The antitumor effect in breast cancer cells (MDA-MB-231) in tumor-bearing BALB/C mice demonstrated that this nanoconjugates exhibits high therapeutic efficiency in artificial solid tumors and low toxicity to normal tissues. It is indicated that TAT could be hidden in the long chain of PEG5000 at a neutral pH, when arrival to the tumor extracellular microenvironment, PEG5000 was cleaved from the nanoconjugates through the hydrazone bond due to the acidic tumor environment. Then, TAT was exposed, allowing the nanoconjugates to be transported into tumor cells. Our findings provide important and detailed information regarding the optimal content of TAT and the shielded density of PEG5000 and reveal their abilities of tumor penetration and potential for the efficient drug carrier.

Construction and Biological Evaluation of Nanoparticle-Based Tumor Targeting Drug Delivery Systems

Nanoparticle-based drug delivery systems have gained immense popularity due to their ability to overcome biological barriers, effectively deliver drugs, and preferentially target tissue. In this chapter, the current progresses and challenges, especially evaluation methods for nanodrugs in antitumor drug delivery systems, are summar‐ ized, citing our works targeted at cancer therapy. It includes four parts. First, the principle, advantages, and significance of nanoparticle-based tumor targeting drug delivery system are presented. Recent developments in nanoparticle-based tumor targeting drug delivery system including passive targeting, active targeting, and stimuli-responsive systems/triggered release are introduced. Second, current formula‐ tions of nanoparticle-based drug delivery systems are described, including lipid-based, polymeric and branched polymeric, metal-based, magnetic, and mesoporous silica. Third, analytical techniques used for evaluating nanodrugs in vitro and in vivo are emphatically described. Finally, disadvantages and challenges of nanodrug are also discussed.