Design of Cationic Lipids with Acetal Linkers: Conformational Preferences, Hydrolytic Stability, and High Drug-Loading Abilities.

Lipids are key constituents of numerous biomedical drug delivery technologies. Here, we present the design, synthesis and biophysical characterizations of a library of cationic lipids containing an acetal residue in their linker region. These cationic acetal lipids (CALs) were conveniently prepared through a trans-acetalization protocol from commercially available precursors. NMR studies highlighted the conformational rigidity at the acetal residue and the high hydrolytic stability of these CALs. Fluorescence anisotropy studies revealed that the CAL with a pyridinium headgroup (CAL1) formed highly cohesive vesicular aggregates in water. These structural and self-assembly features of the CAL1 allowed up to 196 % w/w loading of curcumin (Cur) as a representative hydrophobic drug. A reconstitutable formulation of Cur was obtained as a result, which could deliver the drug inside mammalian cells with very high efficiency. The hemocompatibility and cytocompatibility of CAL1 was significantly enhanced by creating a coating of polydopamine (PDA) onto its vesicular assemblies to produce hybrid lipid-polymer nanocapsules. This work demonstrates rapid access to the useful synthetic lipid formulations with high potential in drug and gene delivery applications.

Chirally Twisted Ultrathin Polydopamine Nanoribbons: Synthesis and Spontaneous Assembly of Silver Nanoparticles on Them.

Polydopamine (PDA) is a synthetic polymeric material with immense potential in biomedical and surface functionalization applications. Herein, we have screened self-assemblies formed by Phenylalanine-based amphiphiles (Phe-AMPs) as soft templates for preparing chiral PDA nanostructures. Our study revealed that the amphiphile 2 endowed with a primary amine residue afforded chirally-twisted ultrathin nanoribbons of PDA under optimized conditions. The chirality at the Phe residue of 2 modulated the twist-chirality of the PDA nanoribbons; the l-2 resulted in nanoribbons with right-handed twist, whereas the d-2 induced a left-handed twist to the ribbons. The racemic mixture of these two amphiphiles produced flat, achiral tapes. The PDA ribbon thickness was ≈5.86±0.40 nm, whereas its width and length were ≈133.5±3.2 nm and >5000 nm, respectively. Upon dialysis, hollow PDA nanotubes were obtained due to curling of the PDA nanoribbons. These PDA-nanoarchitectures were employed to spontaneously form and assemble Ag-nanoparticles along the edges of the PDA nanoribbons. In this work we are reporting chirality controlled synthesis of PDA nanostructures for the first time.

Dietary-phytochemical mediated reversion of cancer-specific splicing inhibits Warburg effect in head and neck cancer.

BACKGROUND: The deregulated alternative splicing of key glycolytic enzyme, Pyruvate Kinase muscle isoenzyme (PKM) is implicated in metabolic adaptation of cancer cells. The splicing switch from normal PKM1 to cancer-specific PKM2 isoform allows the cancer cells to meet their energy and biosynthetic demands, thereby facilitating the cancer cells growth. We have investigated the largely unexplored epigenetic mechanism of PKM splicing switch in head and neck cancer (HNC) cells. Considering the reversible nature of epigenetic marks, we have also examined the utility of dietary-phytochemical in reverting the splicing switch from PKM2 to PKM1 isoform and thereby inhibition of HNC tumorigenesis. METHODS: We present HNC-patients samples, showing the splicing-switch from PKM1-isoform to PKM2-isoform analyzed via immunoblotting and qRT-PCR. We performed methylated-DNA-immunoprecipitation to examine the DNA methylation level and chromatin-immunoprecipitation to assess the BORIS (Brother of Regulator of Imprinted Sites) recruitment and polII enrichment. The effect of dietary-phytochemical on the activity of denovo-DNA-methyltransferase-3b (DNMT3B) was detected by DNA-methyltransferase-activity assay. We also analyzed the Warburg effect and growth inhibition using lactate, glucose uptake assay, invasion assay, cell proliferation, and apoptosis assay. The global change in transcriptome upon dietary-phytochemical treatment was assayed using Human Transcriptome Array 2.0 (HTA2.0). RESULTS: Here, we report the role of DNA-methylation mediated recruitment of the BORIS at exon-10 of PKM-gene regulating the alternative-splicing to generate the PKM2-splice-isoform in HNC. Notably, the reversal of Warburg effect was achieved by employing a dietary-phytochemical, which inhibits the DNMT3B, resulting in the reduced DNA-methylation at exon-10 and hence, PKM-splicing switch from cancer-specific PKM2 to normal PKM1. Global-transcriptome-analysis of dietary-phytochemical-treated cells revealed its effect on alternative splicing of various genes involved in HNC. CONCLUSION: This study identifies the epigenetic mechanism of PKM-splicing switch in HNC and reports the role of dietary-phytochemical in reverting the splicing switch from cancer-specific PKM2 to normal PKM1-isoform and hence the reduced Warburg effect and growth inhibition of HNC. We envisage that this approach can provide an effective way to modulate cancer-specific-splicing and thereby aid in the treatment of HNC.

Cell Permeating Nano-Complexes of Amphiphilic Polyelectrolytes Enhance Solubility, Stability, and Anti-Cancer Efficacy of Curcumin.

Many hydrophobic drugs encounter severe bioavailability issues owing to their low aqueous solubility and limited cellular uptake. We have designed a series of amphiphilic polyaspartamide polyelectrolytes (PEs) that solubilize such hydrophobic drugs in aqueous medium and enhance their cellular uptake. These PEs were synthesized through controlled (∼20 mol %) derivatization of polysuccinimide (PSI) precursor polymer with hydrophobic amines (of varying alkyl chain lengths, viz. hexyl, octyl, dodecyl, and oleyl), while the remaining succinimide residues of PSI were opened using a protonable and hydrophilic amine, 2-(2-amino-ethyl amino) ethanol (AE). Curcumin (Cur) was employed as a representative hydrophobic drug to explore the drug-delivery potential of the resulting PEs. Unprecedented enhancement in the aqueous solubility of Cur was achieved by employing these PEs through a rather simple protocol. In the case of PEs containing oleyl/dodecyl residues, up to >65000× increment in the solubility of Cur in aqueous medium could be achieved without requiring any organic solvent at all. The resulting suspensions were physically and chemically stable for at least 2 weeks. Stable nanosized polyelectrolyte complexes (PECs) with average hydrodynamic diameters (DH) of 150-170 nm (without Cur) and 220-270 nm (after Cur loading) were obtained by using submolar sodium polyaspartate (SPA) counter polyelectrolyte. The zeta potential of these PECs ranged from +36 to +43 mV. The PEC-formation significantly improved the cytocompatibility of the PEs while affording reconstitutable nanoformulations having up to 40 wt % drug-loading. The Cur-loaded PECs were readily internalized by mammalian cells (HEK-293T, MDA-MB-231, and U2OS), majorly through clathrin-mediated endocytosis (CME). Cellular uptake of Cur was directly correlated with the length of the alkyl chain present in the PECs. Further, the PECs significantly improved nuclear transport of Cur in cancer cells, resulting in their death by apoptosis. Noncancerous cells were completely unaffected under this treatment.

An Endogenous Reactive Oxygen Species (ROS)-Activated Histone Deacetylase Inhibitor Prodrug for Cancer Chemotherapy.

Suberoylanilide hydroxamic acid (SAHA, vorinostat) is a potent small-molecule pan-inhibitor of histone deacetylases (HDACs) approved for treatment of cutaneous T-cell lymphoma (CTCL). However, SAHA exhibits poor selectivity for cancer cells over noncancer cells. With an aim to improving its selectivity for cancer cells, we generated a novel SAHA prodrug (SAHA-OBP) that is activated in the presence of hydrogen peroxide, a reactive oxygen species (ROS) known to be overexpressed in cancer cells. The high endogenous ROS content in cancer cells triggers rapid removal of the 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl carbonyl (OBP) cap to release active SAHA. The SAHA-OBP prodrug demonstrates selective activity against multiple cancer cell lines such as HeLa, MCF-7, MDA-MB-231, and B16-F10, while remaining benign toward noncancer cells. The downstream effects of SAHA released from SAHA-OBP in cancer cells is the induction of apoptosis. SAHA-OBP was also found to be effective on multicellular tumor spheroids (MCTS). The SAHA prodrug designed in this study undergoes rapid ROS-dependent activation and imparts much-needed selectivity to SAHA for cancer cells.