Enzyme-sensitive cytotoxic peptide-dendrimer conjugates enhance cell apoptosis and deep tumor penetration.

Peptide nanodrugs have been developed as promising antitumor chemotherapeutics because they partially overcome the drawbacks of free peptide drugs, but insufficient tumor penetration and interference of peptide function limit their further application. In this work, we have developed multifunctional peptide conjugated dendrimers for improving tumor penetration, cancer cell-specific peptide delivery and anticancer ability. The cytotoxic peptide KLAK, cell-penetrating peptide TAT and matrix metalloproteinase 2 (MMP2)-sensitive peptide-poly(ethylene glycol) (PEG) were conjugated onto dendrimers by one-pot synthesis to gain PKT-S-PEG. The enzyme-sensitive properties and incubation stability of the dendrimers were investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Moreover, the cell viability, internalization pathway, mitochondria-regulated apoptosis and tumor penetration ability were measured by CCK-8 assay, lysosome colocalization, JC-1 assay and multicellular spheroid (MCS) experiments, respectively, in human primary glioblastoma (U87) cells. PKT-S-PEG showed significantly enhanced intracellular delivery performance, antitumor efficacy and deep tumor penetration capacity compared to a control non-MMP2 sensitive dendrimer PKT-C-PEG. The MMP2-overexpressing tumor microenvironment caused deprotection by removal of PEG, resulting in the decrease of particle size and exposure of KLAK and TAT, which enhanced tumor penetration, the entry of bioactive peptides into cells and subsequently the effective disruption of mitochondria. We believe that the peptide-dendrimer conjugate has potential for specific and effective delivery of peptide-based therapeutics into tumors.

A General Strategy for Facile Synthesis and In Situ Screening of Self-Assembled Polymer-Peptide Nanomaterials.

A universal strategy for efficient, mild, and purification-free synthesis and in situ screening of functional polymer-peptide nanomaterials is described. More than 1000 polymer-peptide conjugates (PPCs) with various chemical structures, compositions, and therapeutic efficacy are created. According to this strategy, the structure-function relationship of the PPCs is revealed, and the antitumor efficacies of the top performing PPCs are evaluated in vivo.

Self-assembled NIR nanovesicles for long-term photoacoustic imaging in vivo.

We report a supramolecular approach for the preparation of photostable NIR nanovesicles based on a cyanine dye derivative as a photoacoustic (PA) contrast agent for high-performance nano-imaging.

Synthesis of self-reporting polymeric nanoparticles for in situ monitoring of endocytic microenvironmental pH.

The bis(pyrene) conjugated pH-sensitive polymers () were synthesized and self-assembled into nanoparticles through hydrophobic interactions. The Nile red (NR) loaded nanoparticles showed red emission due to the FRET effect. The nanoparticles entered cells via endocytosis, and the microenvironmental pH in the endocytosis process was monitored in situ by the simultaneous dual-wavelength fluorescence changes.

A pH-responsive natural cyclopeptide RA-V drug formulation for improved breast cancer therapy.

The natural plant cyclopeptide RA-V, which was isolated from the roots of Rubia yunnanensis, was discovered to be a novel anti-cancer candidate. However, the cyclic hexapeptide exhibited poor solubility in physiological conditions, limiting its application for cancer therapy in vivo. To solve this problem, pH-sensitive polymers were developed for targeted RA-V delivery into tumor sites and for acid-triggered drug release. The poly(ß-amino ester)s (PAE) copolymers self-assembled into micelle-like nanoparticles in an aqueous solution at pH 7.4, and the solubility of RA-V was enhanced by loading the drug into the hydrophobic cores of micelles. The near-infrared (NIR) fluorescent probe squaraine (SQ) dye, as an imaging probe, could also be encapsulated into polymer micelles simultaneously. The diameters of the RA-V/SQ loaded micelles were measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM), which proved that the micelles with sizes of 35-60 nm were suitable as anti-cancer drug nano-vehicles. The drug-loading capacity and drug release profiles of RA-V-loaded micelles were calculated and monitored by high performance liquid chromatography (HPLC) measurements. The RA-V/SQ loaded micelles were stable at a neutral pH, and drug release could be greatly accelerated by the acid-triggered ionization of copolymer chains. Similarly, with free RA-V cyclopeptide, the RA-V/SQ loaded micelles exhibited high anti-cancer efficiency toward MCF-7 cells and Hela cells, while the intact polymer micelles and SQ-loaded micelles are non-toxic. Moreover, the endocytosis pathway and mitochondria-regulated apoptosis of RA-V/SQ loaded micelles were proved by lysosome colocalization and JC-1 assay, respectively. Finally, biodistribution and tumor growth inhibition were evaluated in MCF-7 cell-xenografted nude mice, demonstrating that RA-V/SQ loaded micelles could realize tumor imaging and effectively and simultaneously inhibit tumor growth. Therefore, the RA-V/SQ loaded micelles may find use as potential nano-scaled cancer therapeutics and imaging agents.

Self-assembly of cytotoxic peptide conjugated poly(ß-amino ester)s for synergistic cancer chemotherapy.

Nanotechnology has played an important role in cancer therapy due to the potential advantages of nano-drugs including enhanced accumulation in the tumor sites, improved pharmacokinetics and minimized systemic toxicity in vivo. Self-assembled peptides can improve the cellular internalization of peptides effectively through the endocytosis pathway for enhanced bioavailability. Herein, cytotoxic peptide (KLAKLAK)2 (named KLAK) conjugated poly(ß-amino ester)s (PAE-KLAK) were synthesized by Michael-type addition. The copolymers could self-assemble into micelle-like nanoparticles with pH-sensitive properties, which were measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The endocytosis pathway, mitochondria-regulated apoptosis and enhanced cytotoxicity of P2-KLAK micelles were proved by lysosome colocalization, JC-1 assay and CCK-8 assay in human breast cancer cells (MCF-7 cells), respectively. The cancer cell killing effect of P2-KLAK micelles was higher than that of free KLAK, which could be attributed to the efficient internalization into cells via an endocytosis pathway and a subsequent disruption of mitochondria in cells. Encapsulation of anti-cancer drug doxorubicin (DOX) into P2-KLAK micelles realized the co-delivery of the chemotherapeutic drug and the peptide drug with acid-triggered release in cells. The treatment efficacy of DOX-loaded P2-KLAK micelles was higher than that of DOX-loaded P2 micelles and blank P2-KLAK micelles, indicating their synergistic ability to kill MCF-7 cells. Finally, In vivo tumor imaging and growth inhibition were evaluated in MCF-7 cell-xenografted nude mice, demonstrating that DOX-loaded P2-KLAK micelles could inhibit tumor growth effectively with a one order magnitude lower injection amount of DOX, which was attributed to the specific accumulation in tumor sites, efficient cellular entry and controlled intracellular release of therapeutic drugs.

DFT study of intermolecular [4 + 2] versus [3 + 2] cycloadditions in the dimerization of 2,4,6-trinitrotoluene (TNT): regioselectivity and stereoselectivity.

Two novel types of intermolecular hetero cycloadditions in the participation of the nitro group are put forward in the dimerization of TNT, in comparison with Diels-Alder cross-linking of benzene ring skeletons. Possible transition states and products; for example, their geometrical details, vibrational frequencies, and energies are verified at the B3LYP/6-31+G(d,p) level. Contrary to the hetero Diels-Alder reaction, the folding of the benzene ring side endo is slightly selective specific in 1,3-dipolar cycloaddition. The substituent pattern on reactivity indicates that the methyl group at the bridged sites significantly retards the reaction. Two new sigma bonds are formed kinetically and thermodynamically through the single state; however, the first sigma bond is more easily generated by the triplet state. The shock-wave-produced chemically bound dimer of TNT is most likely to be the oxygen-carbon linkage product. The initial chemical events in TNT under high pressure can be extended to interpret the shock insensitivity of other unsaturated nitro-explosives. The calculated results agree well with some experimental observations.

A study of the hydrogen abstraction reactions of C2H radical with CH3CN, C2H5CN, and C3H7CN by dual-level generalized transition state theory.

The hydrogen abstraction reactions C2H + CH3CN --> products (R1), C2H + CH3CH2CN --> products (R2), and C2H + CH3CH2CH2CN --> products (R3) have been investigated by dual-level generalized transition state theory. Optimized geometries and frequencies of all the stationary points and extra points along the minimum-energy path (MEP) are performed at the BH&H-LYP and MP2 methods with the 6-311G(d, p) basis set, and the energy profiles are further refined at the MC-QCISD level of theory. The rate constants are evaluated using canonical variational transition state theory (CVT) with a small-curvature tunneling correction (SCT) over a wide temperature range 104-2000 K. The calculated CVT/SCT rate constants are in good agreement with the available experimental values. Our calculations show that for reaction R2, the alpha-hydrogen abstraction channel and beta-hydrogen abstraction channel are competitive over the whole temperature range. For reaction R3, the gamma-hydrogen abstraction channel is preferred at lower temperatures, while the contribution of beta-hydrogen abstraction will become more significant with a temperature increase. The branching ratio to the alpha-hydrogen abstraction channel is found negligible over the whole temperature range.

Ab initio study of the spectroscopy of (CH3)(3)CN and (CH3)(2)CHN.

Using the complete active space self-consistent field (CASSCF) method with 6-311++g(3df,3pd) basis sets, a few electronic states of nitrenes (CH3)3CN and (CH3)2CHN and their positive ions are calculated. All calculated states are valence states, and their characteristics are discussed in detail. In order to investigate the Jahn-Teller effect on (CH3)3CN radical, Cs symmetry was used for (CH3)3CN and (CH3)2CHN in the calculations. The results of our calculations (CASPT2 adiabatic excitation energies and RASSI oscillator strengths) suggest that the calculated transitions of (CH3)3CN at 27,710 cm(-1) and (CH3)2CHN at 28,110 cm(-1) are attributed to 23A'' --> 13A'', while those of (CH3)3CN at 28,916 cm(-1) and (CH3)2CHN at 29,316 cm(-1) are attributed to 13A' --> 13A''. The vertical and adiabatic ionization energies were obtained to compare with the photoelectron spectroscopic data. These results are in agreement with previous experimental data. Also, we present a comprehensive review on the CAS calculation results for (CH3)nCH(3-n)N (n = 0-3) presented in our previous and present papers.

Ab initio study of the spectroscopy of CH3N and CH3CH2N.

Complete active space (CAS) calculations with 6-311++g(3df,3pd) basis sets were performed for a large number of electronic states of the nitrate free radical (CH3N/CH3CH2N) and their positive and negative ions. All calculated states are valence states, and their characters are discussed in detail. To investigate the Jahn-Teller effect on the CH3N radical, Cs symmetry was used for both CH3N and CH3CH2N in calculations. The results (CASPT2 adiabatic excitation energies and CASSI oscillator strengths) suggest that the calculated transitions of CH3N at 32172 and 32139 cm(-1) are attributed to the 2(3)A' ' --> 1(3)A' ' and 1(3)A' --> 1(3)A' ', respectively, which is in accordance with the A3E --> X3A2 emission spectrum at T0 = 31 817 cm(-1). The calculated transitions of CH3CH2N at 334 nm are attributed to the 1(3)A' ' --> 2(3)A' ' and 1(3)A' ' --> 1(3)A', respectively, which is in accordance with the UV absorption spectrum of a series of 11 bands beginning at 335 nm. The vertical and adiabatic ionization energies were obtained to compare with the PES data. These results are in agreement with previous experimental data, which is discussed in detail.