Harnessing the Noncovalent Interactions of DNA Backbone with 2D Silicate Nanodisks To Fabricate Injectable Therapeutic Hydrogels

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Nano, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://doi.org/10.1021/acsnano.8b02434.Injectable hydrogels present several advantages over prefabricated scaffolds including ease of delivery, shear-thinning property, and broad applicability in the fields of drug delivery and tissue engineering. Here, we report an approach to develop injectable hydrogels with sustained drug release properties, exploiting the chemical nature of the DNA backbone and silicate nanodisks. A two-step gelation method is implemented for generating a combination of noncovalent network points, leading to a physically cross-linked hydrogel. The first step initiates the development of an interconnected structure by utilizing DNA denaturation and rehybridization mechanism to form hydrogen bonds between complementary base pairs of neighboring DNA strands. The anisotropic charge distribution of two-dimensional silicate nanodisks (nSi) makes them an active center in the second step of the gelation process. Silicate nanodisks create additional network points via attractive electrostatic interactions with the DNA backbone, thereby enhancing the mechanical resilience of the formulated hydrogel. The thermally stable hydrogels displayed an increase in elasticity and yield stress as a function of nSi concentration. They were able to form self-supporting structures post injection due to their rapid recovery after removal of cyclic stress. Moreover, the presence of nanosilicate was shown to modulate the release of a model osteogenic drug dexamethasone (Dex). The bioactivity of released Dex was confirmed from in vitro osteogenic differentiation of human adipose stem cells and in vivo bone formation in a rat cranial bone defect model. Overall, our DNA-based nanocomposite hydrogel obtained from a combination of noncovalent network points can serve as an injectable material for bone regeneration and carrier for sustained release of therapeutics

Controlling Adult Stem Cell Behavior Using Nanodiamond-Reinforced Hydrogel: Implication in Bone Regeneration Therapy

Nanodiamonds (NDs) have attracted considerable attention as drug delivery nanocarriers due to their low cytotoxicity and facile surface functionalization. Given these features, NDs have been recently investigated for the fabrication of nanocomposite hydrogels for tissue engineering. Here we report the synthesis of a hydrogel using photocrosslinkable gelatin methacrylamide (GelMA) and NDs as a three-dimensional scaffold for drug delivery and stem cell-guided bone regeneration. We investigated the effect of different concentration of NDs on the physical and mechanical properties of the GelMA hydrogel network. The inclusion of NDs increased the network stiffness, which in turn augmented the traction forces generated by human adipose stem cells (hASCs). We also tested the ability of NDs to adsorb and modulate the release of a model drug dexamethasone (Dex) to promote the osteogenic differentiation of hASCs. The ND-Dex complexes modulated gene expression, cell area, and focal adhesion number in hASCs. Moreover, the integration of the ND-Dex complex within GelMA hydrogels allowed a higher retention of Dex over time, resulting in significantly increased alkaline phosphatase activity and calcium deposition of encapsulated hASCs. These results suggest that conventional GelMA hydrogels can be coupled with conjugated NDs to develop a novel platform for bone tissue engineering

A Novel Copper Chelate Modulates Tumor Associated Macrophages to Promote Anti-Tumor Response of T Cells

At the early stages of carcinogenesis, the induction of tumor specific T cell mediated immunity seems to block the tumor growth and give protective anti-tumor immune response. However, tumor associated macrophages (TAMs) might play an immunosuppressive role and subvert this anti tumor immunity leading to tumor progression and metastasis.The Cu (II) complex, (chelate), copper N-(2-hydroxy acetophenone) glycinate (CuNG), synthesized by us, has previously been shown to have a potential usefulness in immunotherapy of multiple drug resistant cancers. The current study demonstrates that CuNG treatment of TAMs modulates their status from immunosuppressive to proimmunogenic nature. Interestingly, these activated TAMs produced high levels of IL-12 along with low levels of IL-10 that not only allowed strong Th1 response marked by generation of high levels of IFN-gamma but also reduced activation induced T cell death. Similarly, CuNG treatment of peripheral blood monocytes from chemotherapy and/or radiotherapy refractory cancer patients also modulated their cytokine status. Most intriguingly, CuNG treated TAMs could influence reprogramming of TGF-beta producing CD4(+)CD25(+) T cells toward IFN-gamma producing T cells.Our results show the potential usefulness of CuNG in immunotherapy of drug-resistant cancers through reprogramming of TAMs that in turn reprogram the T cells and reeducate the T helper function to elicit proper anti-tumorogenic Th1 response leading to effective reduction in tumor growth

Characterisation of Trehalase Enzymes from Yeast

Trehalose is a non reducing disaccharide, in which two glucose units are linked through an α,α-1,1-glycosidic linkage. Except in mammals, this sugar is found in a wide variety of organisms including bacteria, yeast, fungi, insects, plants etc1. Trehalose acts as a source of energy and carbon in the organisms. In some organisms, like yeast and plants, it may also serve as a signaling molecule to direct or control certain metabolic pathways or even to affect growth2. Nowadays trehalose accumulation by different organisms is being recognized as a crucial defense mechanism that stabilizes proteins and biological membranes under a variety of stress conditions, including increased temperature, hydrostatic pressure, desiccation, nutrient starvation, oxidative stress, and even exposure to toxic chemicals3. It has also been reported that trehalose is important for the control of glucose influx during the cellular response to adverse condition. Trehalose also stabilizes small molecules like S-adenosyl-L-methionine4

Modelling of shale rock pore structure based on gas adsorption

Shale rock consists of a complex matrix structure due to presence of nano-scale pores. Owing to such complexity determination and/or prediction of the mineralogical, mechanical, and petrophysical properties (e.g., permeability, porosity, pore size distribution, etc.) of shale is a challenging task. A preliminary estimation of these properties is essential before shale gas exploration. In this study, experimental and numerical analyses are conducted to estimate the permeability, porosity, and pore size distribution of a typical shale sample. Gas adsorption experiments were conducted to characterize the pore spaces of the shale via analysing the isotherms. Using conventional theories, such as BET and BJH methods, surface area, pore volume, and pore size distributions were estimated. On the other hand, gross porosity of the shale samples was measured by conducting gas pycnometry experiment. Finally based on the obtained results an equivalent pore network model is constructed which accounts for the pore size distributions and low pore connectivity in the shale matrix. We have simulated gas flow through the network to estimate permeability of the shale. This model considers Knudsen diffusion and the effects of gas slippage on permeability. Further parametric study shows that the apparent permeability primarily depends on the reservoir pressure, pore coordination number and porosity

Self-healing DNA-based injectable hydrogels with reversible covalent linkages for controlled drug delivery

Injectable hydrogels represent a valuable tool for the delivery of therapeutic molecules aimed to restore the functionality of damaged tissues. In this study, we report the design of a nanocomposite DNA-based hydrogel crosslinked with oxidized alginate (OA) via the formation of reversible imine linkages. The formulated hydrogel functioned as an injectable carrier for the sustained delivery of a small molecule drug, simvastatin. The degree of oxidation of alginate and the concentration of silicate-based nanoparticles (nSi) were varied to modulate the rheological properties of the hydrogels. Specifically, the formulations consisting of OA with higher degree of oxidation displayed the highest value of storage moduli, yield stress, yield strain, and rapid recovery after removal of cyclic stress. The hydrogel formulations exhibited self-healing and shear-thinning properties due to the reversible nature of the covalent imine bonds formed between the aldehyde groups of OA and the amine groups present in the DNA nucleotides. Moreover, the incorporation of charged nSi further enhanced the shear strength of the formulated hydrogels by establishing electrostatic interactions with the phosphate groups of the DNA network. The optimized hydrogel was able to promote the sustained release of simvastatin for more than a week. The bioactivity of the released drug was confirmed by testing its ability to induce osteogenic differentiation and migration of human adipose-derived stem cells in vitro. Overall, the results obtained from this study demonstrate that DNA could be used as a natural biopolymer to fabricate self-healing injectable hydrogels with sustained release properties for minimally invasive therapeutic approaches.Statement of significanceDynamic covalent chemistry, especially Schiff base reactions have emerged as a promising route for the formation of injectable hydrogels. Our study demonstrated the development of a DNA-based self-healing hydrogel formed via Schiff base reaction occurring at physiological conditions. The hydrogels functioned as sustained delivery vehicles for the hydrophobic drug simvastatin, which requires a polymeric carrier for controlled delivery of therapeutic concentrations of the drug without exhibiting cytotoxic effects. Presently available hydrogel-based drug delivery systems encounter major challenges for the delivery of hydrophobic drugs due to the hydrophilic nature of the base matrix. Our strategy presents a platform technology for the design of minimally invasive approaches for the sustained delivery of hydrophobic drugs similar to simvastatin. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

A <i>C</i>_3<i>v</i>-Symmetric Tripodal Urea Receptor for Anions and Ion Pairs: Formation of Dimeric Capsular Assemblies of the Receptor during Anion and Ion Pair Coordination

A new <i>C</i>_3<i>v</i>-symmetric urea-based heteroditopic tripodal receptor capable of recognizing both anions and ion pairs was designed, synthesized, and characterized. The protonated receptor forms a sulfate complex which encapsulates a single DMF in the tripodal cavity of the receptor. However, the SO₄^2– anion is located outside the tripodal cavity and is stabilized by N–H···O hydrogen bonds from the urea functions of four receptor cations. With TBAHSO₄ the receptor forms a contact ion pair complex, where both the TBA⁺ and SO₄^2– groups are pseudoencapsulated in the tripodal cavity of the protonated receptor. Significantly, the receptor forms a charge-separated polymeric ion pair complex with K⁺ and HPO₄^2– via formation of a dimeric capsular assembly of the receptor, in which three K⁺ encapsulated dimeric capsular assemblies interdigitate to form a precise cavity that further encapsulates HPO₄^2–. The receptor also forms an anion complex with CO₃^2– via formation of dimeric capsular self-assembly of the receptor. Solution-state binding studies of the receptor with oxyanions have also been carried out by ¹H NMR titration experiments, which show the oxyanion binding trend HCO₃^– > H₂PO₄^– > HSO₄^–, whereas no binding with NO₃^– and ClO₄^– anions is observed

Neutral Acyclic Anion Receptor with Thiadiazole Spacer: Halide Binding Study and Halide-Directed Self-Assembly in the Solid State

A halide binding study of a newly synthesized neutral acyclic receptor <b>LH</b>_<b>2</b> with a thiadiazole spacer has been methodically performed both in solution and in the solid state. Crystal structure analysis of the halide complexes elucidate the fact that fluoride forms an unusual 1:1 hyrogen-bonded complex with monodeprotonated receptor, whereas in the case of other congeners, such as chloride and bromide, the receptor binds two halide anions along with formation of a halide-bridged 1D polymeric chain network by participation of N–H···X^– and aromatic C–H···X^– hydrogen-bonding (where X = Cl and Br) interactions. The presence of a rigid thiadiazole spacer presumably opens up enough space for capturing two halide anions by a single receptor molecule, where the coordinated −NH protons are pointed in the same direction with respect to the spacer and eventually favor formation of halide (Cl^– and Br^–) induced polymeric architecture, although no obvious chloride- or bromide-directed polymeric assembly is found in solution. A significant red shift of 243 nm in the absorption spectra of <b>LH</b>_<b>2</b> was solely observed in the presence of excess fluoride anion, which enables <b>LH</b>_<b>2</b> as an efficient colorimetric sensor for optical detection of fluoride anion (yellow to blue). Furthermore, spectroscopic titration experiments with increasing equivalents of fluoride anion suggest formation of a H-bonded complex with subsequent stepwise deprotonation of two N–H groups, which can be visually monitored by a change in color from yellow to blue via pink