Ionically crosslinked cellulose nanocrystals by metal nitrates for the preparation of stable emulsions with tunable interface properties.

Biologically extracted cellulose nanocrystals (CNCs) are rod-like and amphiphilic materials with surface-exposed (hydrophilic sites) and hidden (hydrophobic sites) hydroxyl groups. These physicochemical characteristics make CNCs suitable for use as emulsifying agents to stabilize emulsions. Stable oil-in-water emulsions, using sulfated (i.e., -[Formula: see text]) CNCs that were ionically crosslinked with alkaline-earth (i.e., [Formula: see text]) or transition-d-block (i.e., [Formula: see text]) metal cations, were developed without the use of any synthetic surfactants or prior functionalization of pure CNCs with hydrophobic molecules. Various emulsion surface properties such as interfacial tension, surface charge, surface chemistry, as well as rheology were characterized. Ionically crosslinked CNCs (iCNCs) adsorbed at the interface of an oil and water and fortified the emulsion droplets (5-30 µm) against coalescence by lowering the interfacial tension from 65 mN/m (i.e., pure CNC mixture with oil) to 25 mN/m (i.e., iCNC mixture with oil) and reducing zeta potential with surface charge values (-30 mV to -10 mV), ideal to maintain droplet layer assembly at the water-oil interface. This study provided an alternative approach to achieve particle-stabilized and surfactant-free emulsions by using divalent metal nitrates to develop "clean" emulsion-based technologies for applications in many industries from agriculture to food to pharmaceuticals.

Guar-Based Injectable Hydrogel for Drug Delivery and In Vitro Bone Cell Growth.

Injectable hydrogels offer numerous advantages in various areas, which include tissue engineering and drug delivery because of their unique properties such as tunability, excellent carrier properties, and biocompatibility. These hydrogels can be administered with minimal invasiveness. In this study, we synthesized an injectable hydrogel by rehydrating lyophilized mixtures of guar adamantane (Guar-ADI) and poly-ß-cyclodextrin (p-ßCD) in a solution of phosphate-buffered saline (PBS) maintained at pH 7.4. The hydrogel was formed via host-guest interaction between modified guar (Guar-ADI), obtained by reacting guar gum with 1-adamantyl isocyanate (ADI) and p-ßCD. Comprehensive characterization of all synthesized materials, including the hydrogel, was performed using nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and rheology. The in vitro drug release study demonstrated the hydrogel's efficacy in controlled drug delivery, exemplified by the release of bovine serum albumin (BSA) and anastrozole, both of which followed first-order kinetics. Furthermore, the hydrogel displayed excellent biocompatibility and served as an ideal scaffold for promoting the growth of mouse osteoblastic MC3T3 cells as evidenced by the in vitro biocompatibility study.

Covalent Crosslinking of Colloidal Cellulose Nanocrystals for Multifunctional Nanostructured Hydrogels with Tunable Physicochemical Properties.

Cellulose nanocrystals (CNCs) have shown promise for the development of multifunctional materials for many research communities, ranging from bioresource engineering and biomedical engineering to materials science and engineering. However, accessible hydroxyl (OH) groups on the surface of colloidal CNCs at the (11̅0)ß/(100)α and (110)ß/(010)α facets and the intermolecular hydrogen bonding (H-bonds) between these OH groups account for the instability of self-assembled CNC structures in moist environments, limiting their practical uses to dry media. In this work, accessible OH groups of CNCs were crosslinked using two crosslinkers, that is, glutaraldehyde (GA) and epichlorohydrin (EC), to form nanoparticle-based hydrogels with tunable physicochemical properties. The intensity of the intermolecular H-bonds was controlled by the type and concentration of crosslinkers as well as the CNC concentration. Rheological analyses through the loss tangent were used to determine the degree of crosslinking with maximal values beyond 90%. Fourier-transform infrared spectroscopy demonstrated that H-bond intensity was inversely proportional to the degree of crosslinking for both GA and EC, indicating a dissimilar crosslinking mechanism for GA and EC in acidic and alkaline pH conditions, respectively. Atomic force microscopy and wettability analyses showed a significant increase in the surface roughness from 3.2 ± 0.41 nm (pure CNC) to 31.5 ± 1.08 nm (CNCs crosslinked by GA) and 23.8 ± 0.14 nm (CNCs crosslinked by EC) and water contact angle from 13° (pure CNC) to 108° (CNCs crosslinked by GA) and 104° (CNCs crosslinked by EC). Moreover, optimum water absorption values were found at 157.67 ± 2.01 g and 173.59 ± 1.26 g of water for 1 g of freeze-dried hydrogels for 10% GA and 1% EC, respectively. The results aligned with reaction conditions that led to maximal degrees of crosslinking and indicated the transformation of surface chemistry from a hydrophilic to a hydrophobic network as well as tunable topology and aqueous stability of self-assembled structures made from crosslinked CNCs. This technology demonstrated the potential of crosslinked CNCs with tunable physicochemical properties for use as advanced building blocks to produce 2D and 3D structures for their related functions.

A Bio-Conjugated Chlorin-Based Metal-Organic Framework for Targeted Photodynamic Therapy of Triple Negative Breast and Pancreatic Cancers.

The field of photodynamic therapy (PDT) has continued to show promise as a potential method for treating tumors. In this work a photosensitizer (PS) has been delivered to cancer cell lines for PDT by incorporation into the metal-organic framework (MOF) as an organic linker. By functionalizing the surface of MOF nanoparticles with maltotriose the PS can efficiently target cancer cells with preferential uptake into pancreatic and breast cancer cell lines. Effective targeting overcomes some current problems with PDT including long-term photosensitivity and tumor specificity. Developing a PS with optimal absorption and stability is one of the foremost challenges in PDT and the synthesis of a chlorin which is activated by long-wavelength light and is resistant to photo-bleaching is described. This chlorin-based MOF shows anti-cancer ability several times higher than that of porphyrin-based MOFs with little toxicity to normal cell lines and no dark toxicity.

Maltotriose Conjugated Metal-Organic Frameworks for Selective Targeting and Photodynamic Therapy of Triple Negative Breast Cancer Cells and Tumor Associated Macrophages.

Herein, we report a nano-MOF conjugated to maltotriose as a new DDS. MA-PCN-224-0.1Mn/0.9Zn showed its ability to target cancer and TAM. This novel MOF is an effective PDT agent and shows little dark toxicity, MA-PCN-224-0.1Mn/0.9Zn uptakes selectively into cancer cells. A well-suited size control methodology was used so that the nano-scaled MOFs may take advantage of the EPR effect. This development of a nano-scale MOF for PDT that is conjugated to a cancer targeting ligand represents a meaningful development for the use of MOFs as drug delivery systems.