A thixotropic supramolecular hydrogel of adenine and riboflavin-5'-phosphate sodium salt showing enhanced fluorescence properties

Carboxymethyl cellulose-based supramolecular hydrogel with thermo-responsive gel-sol transition for temporary plugging of oil pipeline in hot work

Temporary plugging of the pipeline is necessary for safety in the hot work process of a flame-cutting pipeline. Chemical hydrogel plugging materials may block valves or sensors in the pipeline due to incomplete breakage. Herein, we prepared a carboxymethyl cellulose-based supramolecular hydrogel with thermo-responsive gel-sol transition, crosslinked by hydrogen bonding and π-π stacking between melamine (MEL) and 6-aminouracil modified carboxymethyl cellulose (AUCMC). The supramolecular hydrogel exhibits tunable mechanical properties and good self-recovery. Furthermore, the result of rheo-kinetics suggests a rapid gel-sol transition of the hydrogel with thermal stimulus due to the hydrogen bonding. The pressure resistance test indicates that the hydrogel has a good plugging effect in the simulated pipeline, and the great flame retardancy of the hydrogel can ensure the safety of operation. The residual hydrogel was completely broken and the simulated pipeline with the plugging length of 10 cm was dredged within 21 min by flushing hot water above 70 °C. The supramolecular hydrogel, as the plugging materials for hot work of oil pipeline, exhibits obvious advantages such as ensuring the safety of hot work, simplifying the operation process, and avoiding secondary damage to the pipeline, which further widens the application field of CMC.

Construction of high internal phase Pickering emulsions using cold plasma modified soy protein isolate-proanthocyanidin complex

Protein-based high internal phase Pickering emulsions (HIPPEs) feature numerous multi-functionalities and widespread applications. However, the direct use of native proteins for the constructions of HIPPEs is limited since it is fragile under various conditions. Here, cold plasma was used to modify soy protein isolates (SPI) to improve their surficial properties. Meanwhile, proanthocyanidins (PA) were applied to interact with cold plasma-treated SPI to form complex. Furthermore, the well-prepared SPI-PA complex was used to construct novel HIPPEs. Results showed cold plasma treatment significantly improved the functionalities of SPI, which were confirmed by surface hydrophobicity (H₀ ＜ 500), sulfhydryl (SH) groups and spectral analysis. Further, the emulsification and oxidation resistance of cold plasma treated SPI were enhanced after forming complex with PA. Soybean oils can be stabilized by SPI-PA complexes to form HIPPEs with a lipid oxidation inhibition rate of ＞ 65%, creaming index (CI) ＞ 80%, excellent rheological properties and better stability compared with conventional emulsion systems. Overall, this SPI-PA complexes provides a unique approach to improve the emulsification and oxidation resistance to engineer HIPPEs with versatile applications.

Adenine selected hydrogelation of vitamin B2 with amplified circularly polarized luminescence

Although the individual VB2 cannot form gels in water, it could form a two-component hydrogel with adenine (A) through the intermolecular π-π stacking and hydrogen bonding between VB2 and A, while other nucleobases, including thymine (T), guanine (G), cytosine (C) and uracil (U), could not. The chiral information of VB2 was amplified in the co-assembly of VB2 and A, which was revealed by the enhanced circular dichroism (CD) and circularly polarized luminescence (CPL). Moreover, due to the different interaction modes between VB2 and A in 1 : 1 and 1 : 2 molar ratio, a reversion of the CPL signal was observed. This work demonstrated how biological molecules could be fabricated into functional materials using the specific interactions within the biological molecules.

Injectable chitosan-based self-healing supramolecular hydrogels with temperature and pH dual-responsivenesses

In this study, a supramolecular hydrogel was fabricated with orotic acid (OA) modified chitosan (OACS) and 2,6-diaminopurine (DAP). The obtained OACS-DAP supramolecular hydrogels have dual responsiveness to temperature and pH. Phase transition experiments indicate this is a temperature-dependent thermoreversible supramolecular hydrogel. Rheological experiments proved the formation of the supramolecular hydrogel and its thixotropic properties. FTIR spectra confirmed that hydrogen bonds and π-π interactions are the main driving forces for OACS and DAP to form hydrogels through intermolecular self-assembly. XRD pattern confirmed the amorphous morphology of OACS-DAP hydrogels. The hydrogel has excellent electrical conductivity with a conductivity of 9.48 μ S·cm^-1. And can achieve the precise release of gastrointestinal drugs. OACS-DAP hydrogel is expected to have better applications in the field of gastrointestinal drug release.

Nucleoside-Based Supramolecular Hydrogels: From Synthesis and Structural Properties to Biomedical and Tissue Engineering Applications

Supramolecular hydrogels are of great interest in tissue scaffolding, diagnostics, and drug delivery due to their biocompatibility and stimuli-responsive properties. In particular, nucleosides are promising candidates as building blocks due to their manifold noncovalent interactions and ease of chemical modification. Significant progress in the field has been made over recent years to allow the use of nucleoside-based supramolecular hydrogels in the biomedical field, namely drug delivery and 3D bioprinting. For example, their long-term stability, printability, functionality, and bioactivity have been greatly improved by employing more than one gelator, incorporating different cations, including silver for antibacterial activity, or using additives such as boric acid or even biomolecules. This now permits their use as bioinks for 3D printing to produce cell-laden scaffolds with specified geometries and pore sizes as well as a homogeneous distribution of living cells and bioactive molecules. We have summarized the latest advances in nucleoside-based supramolecular hydrogels. Additionally, we discuss their synthesis, structural properties, and potential applications in tissue engineering and provide an outlook and future perspective on ongoing developments in the field.

Antimicrobial capacity and physico-chemical characteristics of adhesive resin containing riboflavin after photodynamic therapy

PURPOSE

To assess the micro-tensile bond strength (μ-TBS), degree of conversion, and antimicrobial capacity of modified dentin adhesive using riboflavin photoinitiators.

MATERIALS AND METHODS

Three groups of adhesives (control; 0.1 % riboflavin-PDT and 0.5 % riboflavin PDT) were prepared and tested on 70 sound molar teeth. Fourier-transformed infrared spectroscopy (FTIR) was performed for riboflavin and riboflavin-modified adhesives to calculate the degree of conversion. Contact angle measurement was performed by dropping a 5 μL droplet of the adhesives onto polished dentin disk. For μ-TBS testing, the dentin beams were fixed on a micro-tensile tester and were loaded in tension at a cross-head speed of 1 mm per min until fracture. The viability of Streptococcus mutans biofilm was tested using MTT assay.

RESULTS

The spectrum at 1728 cm-1 indicates CO stretching frequency of riboflavin. The groups control and 0.1 % riboflavin PDT showed the highest degree of conversion followed by lowest degree of conversion of 0.5 % riboflavin adhesive after PDT. The control adhesive exhibited the highest contact angle over the dentin surface compared to the riboflavin-modified adhesive groups (p < 0.05). The lowest contact angle was observed for 0.1 % riboflavin that showed increased permeability of the adhesive onto the dentin surface (p < 0.05). The variables of immediate bonding (F = 12.328, p = 0.000) and ageing in artificial saliva (F = 41.559, p = 0.000) significantly affected the bond strength. For aged μ-TBS testing, the scores for 0.1 % riboflavin PDT was significantly higher as compared to the 0.5 % riboflavin PDT samples. The MTT resulted in a lower S. mutans viability for 0.5 % riboflavin PDT compared to 0.1 % riboflavin PDT and control adhesive (p < 0.05), irrespective of any time point, that is, after 24 h and 30 days ageing.

CONCLUSIONS

The addition of riboflavin as photosensitizer in dentin adhesive demonstrated higher bond strength, excellent antimicrobial capability, and degree of conversion following PDT. The addition of riboflavin in dentin adhesive for PDT could be used as a potential restorative material in adhesive dentistry.

A robust stimuli responsive Eu3+ - Metalo organic hydrogel and xerogel emitting white light

Recently, there is incredible growth on optoelectronic properties of new supramolecular gels and white-light-emitting (WLE) metalo-organic gel comprised with single lanthanide metal ion having stimuli-responsive property is not yet reported. Here, we report a mandelic acid (MA)-triethylene tetraamine (TETA)-Eu-acetate conjugate (4.5:1:0.4 mol ratio), producing stimuli-sensitive WLE hydrogel exhibiting thermoreversible, thixotropic, pH-switchable, self-standing and self-healing properties. Energy minimized structure suggests complexation between MA-TETA conjugate and Eu³⁺ ion. Fluorescence intensity of MA-TETA conjugate decreases with increasing Eu³⁺ concentration indicating energy transfer from MA-TETA to Eu³⁺. Decay of donor fluorescence intensity follows Stern-Volmer equation and energy transfer efficiency is 42%. WLE gel has Quantum yield 11.4% and Förster distance 1.7 Å. Hydrogel and xerogel show WLE on excitation at 330 and 350 nm having CIE coordinates (0.34, 0.33) and (0.28, 0.32), respectively. WLE gel has Correlated colour temperature 5148 K, appropriate for cool day light emission and on coating over UV-LED bulb it emits bright white light.

Self-Lubricating Supramolecular Hydrogel for In-Depth Profile Control in Fractured Reservoirs

In-depth profile control is a great challenge for high-efficiency oil displacement by water flooding. In this work, a shear-responsive self-lubricating hydrogel FPP-0.5, by combining the thixotropic FT (N-fluorenylmethoxycarbonyl-l-tryptophan) supramolecular network with high-strength PAM-PAANa (PAM: polyacrylamide, PAANa: sodium polyacrylate) polymer network, was synthesized and applied for in-depth profile control in water flooding. The disassembly of the FT supramolecular network induced by shear force, accompanied by the formation of a lubricating layer on the gel surface, gives FPP-0.5 gel self-lubricating function. Meanwhile, the PAM-PAANa polymer network, as a protective scaffold for the FT network, endows FPP-0.5 with high strength, making it difficult to be broken by water flow. Moreover, the shear responsiveness enables FPP-0.5 to adjust its own strength and self-lubricating performance according to the different stages of the profile control process, so as to realize dynamic profile control. From oil displacement results, in comparison to the PAM-PAANa gel, the plugging rate, water flooding volume sweep efficiency, and oil recovery of FPP-0.5 were improved by 83.1, 155.4, and 34.0%, respectively, up to 86.6, 83.5, and 71.3%, indicating its better in-depth profile control ability.

Excited-State Intramolecular Proton Transfer-Based Multifunctional Solid-State Emitter: A Fluorescent Platform with "Write-Erase-Write" Function

The excited-state intramolecular proton transfer (ESIPT)-based molecular probes have drawn significant attention owing to their environment-sensitive fluorescence properties, large Stokes shift, and emerged as building blocks for the development of molecular sensors and switches. However, most of the ESIPT-based fluorophores exhibit weak emission in the solid state limiting the scope of real-time applications. Addressing such issues, herein, we presented a C₃ symmetric-like molecular architecture employing a simple one-step Schiff base condensation between triaminoguanidinium chloride and 3,5-di- tert-butyl-2-hydroxybenzaldehyde (TGHB). The temperature-dependent fluorescence studies including at 77 K indicated the strong emission from the keto tautomer compared to that of the enol tautomer. The facile ESIPT in TGHB in the solid-state led to a remarkable enhancement of fluorescence quantum yield of 1600 times compared to that of the solution (λ_em = 545 nm) by restricting the intramolecular rotation and subsequently suppressing the nonradiative deactivation. The excited-state processes were further elucidated through time-resolved fluorescence measurements. TGHB exhibited turn on-off fluorescence upon exposure to acid/base vapor in the form of a powder as well as a transparent, free-standing thin film. A rewritable and erasable fluorescent platform was demonstrated using TGHB as molecular ink, which offers a potential testbed for performing "write-erase-write" cycles multiple times. In addition, TGHB, possessing multiple binding sites (O and N donors) involving the central core of the triaminoguanidinium cation displayed selective turn-on fluorescence with Zn²⁺. The structure-property relationship revealed in the present study provides insight into the development of novel cost-effective multifunctional materials, which are promising for stimuli-responsive molecular switches.

Branched polyrotaxane hydrogels consisting of alpha-cyclodextrin and low-molecular-weight four-arm polyethylene glycol and the utility of their thixotropic property for controlled drug release

In this work, we developed a new class of branched polyrotaxane hydrogel made of 4-arm polyethylene glycol (4-PEG) and α-cyclodextrin (α-CD) using supramolecular host-guest interactions as a cross-linking strategy. Because of the dynamic nature of the non-covalent host-guest cross-linking, the resulting supramolecular α-CD/4-PEG hydrogels show thixotropic behavior and undergo a reversible gel-sol transition in response to shear stress change. We loaded the antiglaucoma drug brimonidine into the α-CD/4-PEG gel and found the drug release kinetics was controlled by shear stress. This thixotropic shear thinning property makes the supramolecular hydrogels highly attractive in drug delivery applications and suitable for preparation of injectable drug formulations.

Flexible and highly transparent two-component organogels with enhanced viscoelasticity for self-healing materials and room-temperature phase-selective gelation

A novel two-component organogel system based on acid-base interaction showed flexibility, high-transparency and self-healing properties with enhanced viscoelasticity. Meanwhile, the two-component gelator displayed room-temperature phase selective gelation of aromatic solvents from aromatic solvents/water mixtures in powder form and excellent dye removal ability.

Supramolecular gels made from nucleobase, nucleoside and nucleotide analogs

Supramolecular or molecular gels are attractive for various applications, including diagnostics, tissue scaffolding and targeted drug release. Gelators derived from natural products are of particular interest for biomedical purposes, as they are generally biocompatible and stimuli-responsive. The building blocks of nucleic acids (i.e. nucleobases, nucleosides, and nucleotides) are desirable candidates for supramolecular gelation as they readily engage in reversible, noncovalent interactions. In this review, we describe a number of organo- and hydrogels formed through the assembly of nucleosides, nucleotides, and their derivatives. While natural nucleosides and nucleotides generally require derivatization to induce gelation, guanosine and its corresponding nucleotides are well known gelators. This unique gelating ability is due to propensity of the guanine nucleobase to self-associate into stable higher-order assemblies, such as G-ribbons, G4-quartets, and G-quadruplexes.

Polyisobutylene-Based pH-Responsive Self-Healing Polymeric Gels

This work demonstrates the successful application of dynamic covalent chemistry for the construction of self-healing gels from side-chain primary amine leucine pendant diblock copolymers of polyisobutylene (PIB) ((P(H2N-Leu-HEMA)-b-PIB)) in the presence of PIB based dialdehyde functionalized cross-linker (HOC-PIB-CHO) through imine (-HC═N-) bond formation without aiding any external stimuli. Gels were synthesized in 1,4-dioxane at room temperature at varied wt % of gelator concentration, [H2N]/[CHO] ratios and molecular weight of the block segments. The mechanical property of gels was examined by rheological measurements. We observed higher value of storage modulus (G') than the loss modulus (G″) within the linearity limits of deformation, indicating the rheological behavior in the gel is dominated by an elastic property rather than a viscous property. The G' values significantly depend upon the extent of cross-linking in the gel network. To establish self-healing property of the gels, rheology analysis through step-strain measurements (strain = 0.1 to 200%) at 25 °C was performed. The polymeric gel network shows reversible sol-gel transition for several cycles by adjusting the pH of the medium with the help of hydrochloric acid (HCl) and triethylamine (Et3N) triggers. FT-IR spectroscopy established formation of imine bonds in the gel network and these gels showed poor swelling behavior in various organic solvents because of the small interstitial porosity, confirmed by field emission-scanning electron microscopy (FE-SEM).

Sol–gel transition accelerated by the co-assembly of two components in supramolecular hydrogels

N-Palmitoyl-Gly-His (PalGH) and glycerol monopalmitate (GMP) in water co-assembled into fibrils with twisted ribbon structures and formed a homogeneous network, resulting in gel formation. The mixture exhibits sol–gel transition while a gel made from only PalGH does not.

Long-chain alkylamide-derived oil gels: mixing induced onset of thixotropy and application in sustained drug release

Oil gels composed of long-chain alkylamides exhibited thixotropic properties, although the same property was absent in each alkylamide.

Supramolecular three-component amino acid-based hydrogels with superior mechanical strength for controllably promoting nonpathogenic E. coli growth

Novel three-component hybrid hydrogels have been constructed by amino acid derivatives, riboflavin and melamine through self-assembly, which demonstrate excellent mechanical strength (>10⁴ Pa) and low cell toxicity.