Gel scaffolds and emerging applications in biomedicine

Nowadays, gels are formed by small molecules self-assembling under the influence of various non-covalent interactions. They can be easily perturbed, which allows for the careful tweaking of their properties. They are kinetically confined, and following production, they usually do not demonstrate time-variable changes in material properties. When exposed to external stimuli such as temperature, pH, light, enzymes, redox, and chemical analytes, such materials may become switchable, leading to the reconfiguration of the gel matrix into a different type of network. The transformations allow gel-to-gel transitions, while the changes in the molecular aggregation result in the alteration of the physical and chemical properties of the gel with time. Here, we discuss various methods used to achieve gel-to-gel transitions by modifying a pre-formed gel material through external perturbation. The dynamic modification of gels allows the construction of an array of gels with various properties from a single material, which eventually extends the limit of application of the gels.

Effect of Substitution at Amine Functionality of 2,6-Diaminopyridine-Coupled Rhodamine on Metal-Ion Interaction and Self-Assembly

2,6-Diaminopyridine-coupled rhodamines 1 and 2 have been synthesized, and the effect of substitution on amine functionality toward metal-ion interactions and self-assembly is thoroughly investigated. Both the compounds effectively recognize different metal ions of biological significance fluorimetrically and colorimetrically with a high degree of selectivity and sensitivities. While compound 1 is sensitive to Fe³⁺ ions, compound 2 is responsive to both Fe³⁺ and Al³⁺ ions in aqueous CH₃CN (4/1, v/v; 10 mM tris HCl buffer, pH 6.8). The sensing mechanism involves the metal-ion chelation-induced spirolactam ring opening of the rhodamine scaffold that results in both color and fluorescence changes, while the extent of interactions with the metal ions is truly governed by the chemical structure of the compounds. Both 1 and 2 are proficient in detecting Fe³⁺ and Al³⁺ ions in human lung cancer cells (A549). As new findings, unlike 1, compound 2 formed a faint pink gel in the toluene-hexane mixture solvent (1:1, v/v), and the gel state of 2 selectively recognizes Ag⁺ ions by exhibiting a phase change from gel to purple sol. Experimental findings establish the role of the formamide moiety in forming the self-assembly.

Fluorescent glycoconjugates and their applications

Fluorescent glycoconjugates are discussed for their applications in biology in vitro, in cell assays and in animal models. Advantages and limitations are presented for each design using a fluorescent core conjugated with glycosides, or vice versa.

A reversible rhodamine 6G-based fluorescence turn-on probe for Fe3+ in water and its application in living cell imaging

A reversible fluorescent probe L based on rhodamine 6G was synthesized for the optical detection of Fe³⁺ in water.

One-pot synthesis of fluorescein based β-aminoglycosylketones and their biological and material applications

Facile one-pot synthesis of fluorescein based β-aminoglycosylketones was carried out using 4,6-O-protected-C-glycoside, fluorescein-monoaldehyde and aromatic amines in the presence of potassium carbonate as a catalyst.