Formation Of Intermolecular Hydrogen Bonds Research Articles

Spectroscopic characterization and quantum chemical calculations on Favipiravir-Guanine biomolecular complex

Favipiravir, a medication, has drawn a lot of interest recently as a possible therapeutic option for viral illnesses such as the COVID-19 pandemic. In the current work, Favipiravir + Guanine combination is being spectroscopically characterized using Fourier Transformed Infrared Spectroscopy, Raman, and Surface-Enhanced Raman Spectroscopy tools. Density functional theory along with the Becke 3-Parameter, Lee-Yang-Parr method and the basis set 6-311++ G(d,p) is used to explore the molecular interactions between the monomers of Guanine and Favipiravir. The stability of the complex resulting from the charge delocalization is thoroughly examined by natural bond orbital analysis that demonstrates the C=O∙∙∙H intermolecular hydrogen bond formation. The nature of the intermolecular hydrogen bond is described using atoms in molecules analysis. Molecular electrostatic potential mapping depicts various regions of electrostatic potential for the molecules, characterizing their reactive nature. The complex’s frontier molecular orbital gap of 2.39 eV indicates a higher possibility of electronic charge transfer, which in turn enhances the chemical reactivity of the complex. An analysis of the complex’s hyperpolarizability reveals a good non-linear optical response. The antiviral activity of the Favipiravir + Guanine complex is demonstrated by its molecular docking against the 6LU7 receptor (−5.61 kcal/mol).

Lysine-Triggered Polymeric Hydrogels with Self-Adhesion, Stretchability, and Supportive Properties.

Hydrogels, recognized for their flexibility and diverse characteristics, are extensively used in medical fields such as wearable sensors and soft robotics. However, many hydrogel sensors derived from biomaterials lack mechanical strength and fatigue resistance, emphasizing the necessity for enhanced formulations. In this work, we utilized acrylamide and polyacrylamide as the primary polymer network, incorporated chemically modified poly(ethylene glycol) (DF-PEG) as a physical crosslinker, and introduced varying amounts of methacrylated lysine (LysMA) to prepare a series of hydrogels. This formulation was labeled as poly(acrylamide)-DF-PEG-LysMA, abbreviated as pADLx, with x denoting the weight/volume percentage of LysMA. We observed that when the hydrogel contained 2.5% w/v LysMA (pADL2.5), compared to hydrogels without LysMA (pADL0), its stress increased by 642 ± 76%, strain increased by 1790 ± 95%, and toughness increased by 2037 ± 320%. Our speculation regarding the enhanced mechanical performance of the pADL2.5 hydrogel revolves around the synergistic effects arising from the co-polymerization of LysMA with acrylamide and the formation of multiple intermolecular hydrogen bonds within the network structures. Moreover, the acid, amine, and amide groups present in the LysMA molecules have proven to be instrumental contributors to the self-adhesion capability of the hydrogel. The validation of the pADL2.5 hydrogel's exceptional mechanical properties through rigorous tensile tests further underscores its suitability for use in strain sensors. The outstanding stretchability, adhesive strength, and fatigue resistance demonstrated by this hydrogel affirm its potential as a key component in the development of robust and reliable strain sensors that fulfill practical requirements.

Effect of Hydrogen Bonding and Chirality in Star-Shaped Molecules with Peripheral Triphenylamines: Liquid Crystal Semiconductors and Gels.

Organic semiconductors with well-defined architectures pose a suitable alternative to amorphous silicon-based inorganic semiconductors. Encouraged by the development of organic semiconductors based on columnar liquid crystals, herein, we report on a family of C3-symmetric star-shaped mesogens based on triphenylamine (TPA), a functional unit with strong electron donor character. Highly stable columnar phases with high hole mobility values were obtained out of this nonplanar functional unit, and this was achieved by using flexible amide spacers to join the TPA units to a tris(triazolyl)triazine (T) star-shaped core, allowing the formation of intermolecular hydrogen bonds. The presence of hydrogen bonds results in a stabilization of the columnar architectures either in bulk or in the presence of solvents by reinforcing π-stacking and van der Waals interactions, as deduced by Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) studies. Furthermore, the introduction of a stereogenic center in the flexible spacer prompts the formation of chiral aggregates in the liquid crystal state and in the organogel formed in 1-octanol, as demonstrated by circular dichroism spectroscopy.

Guest-induced supramolecular helices and its application in L-Arg detection and L-Arg controlled reversible morphology modulation

A novel AIE supramolecular polymer (BPK) was synthesized by bis(2-hydroxy-1-naphthaldehyde) terephthalo hydrazone functionalized pillar [5]arene and cross-linked using a bis(4.4-dipyridinium salt)cross-linker via host-guest complexation. BPK exhibited strong aggregation-induced emission (AIE) in binary solutions of DMSO/H2O. BPK could be an AIE-based sensor with specific fluorescence sensing ability for L-Arg in water. The detection limit of BPK for L-Arg was 3.95 × 10−7 M, and other amino acids did not interfere with the sensing process. Moreover, in a pure DMSO solvent, BPK can self-assemble into a fibrous structure of the right-hand spiral by guest-induced supramolecular helices. At 80 % water content, BPK undergoes a morphological transformation into supramolecular polymer. Intriguingly, BPK exhibits a reversible transformation from a polymer to a nanosphere through the alternating addition of trifluoroacetic acid and arginine. Additionally, the fluorescence of BPK demonstrates an "on-off" switch. This phenomenon is attributed to the formation and disruption of intermolecular hydrogen bonds. The reversible manipulation of polymer materials' morphology and optical properties holds significant potential in biomedicine and smart materials.

In silico study of therapeutic deep eutectic solvent for tetracaine liquid delivery

The development of a drug delivery liquid formulation of ester – based tetracaine local anaesthetic is synthesised in silico via the formation of a therapeutic deep eutectic solvent in combination with citral, a natural monoterpenoid. The properties of the obtained liquid system, studied at the nanoscopic level, are derived from a combination of quantum chemistry and classical molecular dynamics simulations. The intermolecular forces (hydrogen bonding) were analysed and their relationship with liquid phase properties were established. Water effect on the liquid phase properties were also considered in terms of competing for hydrogen bonding sites in the components of the developed fluid. The systems proposed in this work were studied using CIT (HBA) 1:1 TET (HBD) molar ratio at temperatures ranging from 288 K to 318 K and 1 bar. The hydrogen bond network developed between the oxygen atom in citral molecules and the –NH group in tetracaine molecules under those conditions, confirmed via minimal cluster analysis, is maintained during the addition of water up to 1.3 wt% as the water molecules do not disrupt the intermolecular hydrogen bond but develop new interactions (hydrogen bonds) with citral and tetracaine monomers presented in the fluid. The reported results probed the suitability of the considered system as an alternative drug delivery method as well as the possibility of developing deep eutectic-based formulation of anaesthetics using natural compounds due to the formation of effective and strong intermolecular hydrogen bonds.

Development, characterization and application of colorimetric active packaging based on soy protein isolate, trehalose and Oxalis triangularis extract

Colorimetric active packaging based on soy protein isolate (SPI)/trehalose (TRE) and Oxalis triangularis extract (OTE) was developed for monitoring pork spoilage and preserving Actinidia arguta. The formation of intermolecular hydrogen bonds among TRE, OTE, and the SPI matrix resulted in a more compact film structure and improved mechanical, barrier and water resistance properties. The addition of OTE greatly increased the antibacterial and antioxidant activities of the films. The stability of the films improved due to their dense network structure and good barrier and antioxidant capacity. Among all samples, SPI films containing both TRE and OTE (ST-OTE) exhibited the best barrier and mechanical properties after 45 days of storage and maintained a high level of antioxidant activity after heating and UV irradiation. SPI-OTE and ST-OTE films showed good pH sensitivity and responsiveness and exhibited visible color changes during the monitoring of pork spoilage. Compared to the control group, ST-OTE effectively prolonged the storage period of A. arguta.

Efficient selective leaching of ytterbium and lutetium oxides by new hydrophobic deep eutectic solvents

This research reports the first study of selective leaching of ytterbium-lutetium oxides mixture with hydrophobic deep eutectic solvents (DESs), and high-efficiency and simple-prepared were used to separate and beneficiate lutetium. With hydrophobic DESs, which were formed with hydrophobic salicylic acid (SA) or 3,5-dinitrosalicylic acid (DNS) as the hydrogen bond donor (HBD) and hydrophobic tri-n-octyl phosphine oxide (TOPO) as the hydrogen bond acceptor (HBA), powdered eutectic mixtures of ytterbium-lutetium oxides were leached. The separation factor of ytterbium-lutetium was concluded to reached 2.11 with a solid-liquid (S/L) ratio of 1/50 g/ml, a temperature of 90 °C and a 4 h leaching time, and the experimental conditions, such as the S/L ratio, temperature and reaction time, were explored. The formation of intermolecular hydrogen bonds between the HBD and HBA was revealed through multiple methods, such as IR (disappearance of OH characteristic peaks), 1H NMR (formation of sharp peaks not present for intramolecular hydrogen bonds) and 31P NMR (shift of P = O peaks to higher fields). The lattice energies of the intermolecular hydrogen bonds and the solid oxide lattice energies, which were calculated with Gaussian 16 software (0.87 eV for SA/TOPO = 1:1 and 0.94 eV for DNA/TOPO = 1:1) and the Born–Haber cycle (12957.56 kJ/Mol for Yb2O3 and 12993.59 kJ/Mol for Lu2O3), provided a theoretical illustration of preferential Yb/Lu dissolution leading to separation. The stripping, regeneration and recycling capabilities of the DESs were investigated with stripping and recirculation experiments. Based on these results, the new DES as the leaching agent to separation of ytterbium lutetium oxide is identified as a new efficient mothed with industrialization potential.

CHARACTERISATION, EVALUATION AND DENSITY FUNCTIONAL ANALYSIS OF CILNIDIPINE-NICOTINAMIDE COCRYSTALS DEVELOPED BY LIQUID ASSISTED GRINDING TECHNIQUE: A SUSTAINABLE APPROACH FOR ENHANCED SOLUBILITY

Objective: Improving the solubility of poorly water-soluble drugs has always been a challenge in drug development. This study aimed to enhance the aqueous solubility of a poorly water-soluble drug, Cilnidipine, by cocrystallisation method using liquid-assisted grinding (LAG) technique with Nicotinamide as the coformer. The study also aimed to understand the mechanism of cocrystal formation by quantum mechanical calculations. Methods: The Cilnidipine-Nicotinamide cocrystals were prepared in various stoichiometric ratios using the liquid-assisted grinding (LAG) technique. The cocrystals obtained were characterised by vibrational spectroscopy, thermal methods such as differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and surface morphology by field emission scanning electron microscopy (FE-SEM). The cocrystals were evaluated for saturation solubility, and the mechanistic study of cocrystal formation was performed using the Gaussian 09 software package. Results: FT-IR spectra of the formulated cocrystal indicated the intermolecular hydrogen bond formation between-N-H of Nicotinamide and the nitro group of Cilnidipine. DSC analysis showed a single endotherm at 96.76 °C, PXRD patterns were different from that of the reactants, and FE-SEM analysis revealed the changes in the surface morphology of the obtained cocrystal. The prepared cocrystal showed a 26.36-fold enhancement in the aqueous solubility of Cilnidipine. The DFT study demonstrated the formation of a strong intermolecular hydrogen bonding between the nitro-oxygen atom of Cilnidipine and the amide hydrogen atom of Nicotinamide in cocrystal formed. Conclusion: This study highlights the potential of the liquid-assisted grinding method for preparing cocrystals as a sustainable and reliable approach to address the challenges posed by poorly water-soluble drugs.

Robust polyvinyl alcohol with broad thermoplastic window enabled by controlled citrate-plasticizing adding ways

Given that the decomposition temperature is close to the melting point, polyvinyl alcohol (PVA) fails thermoplastic processing. Developing a suitable plasticizer-enhancing system to reduce melting point or increase the decomposition temperature, resulting in generating a temperature window of thermoplastic processing is an urgent research topic in practical processing applications. In this work, triethyl citrate (TEC) (or tributyl citrate (TBC)), as a green plasticizer, was successfully introduced in the PVA matrix by rational and scientific means. To systematically explore the effects of plasticizers on melting point and mechanical properties of the PVA, distinguishing from traditional plasticizer-adding means, the optimized plasticizer was added to the PVA precursor (i.e., polyvinyl acetate (PVAc)), generating a highly effective blend at upon molecular level, which can achieve a uniform phase mixture of plasticizer molecules in PVA after alcoholysis. In this case, small molecular plasticizers participate in the formation of intermolecular hydrogen bonds between PVA molecules, thus forming abundant effective energy dissipation sites. As a result, thus-obtained A-PVA/TEC10 exhibited an elongation at break of 385.3% and toughness of 154.4 MPa, which are 2.87 times and 1.75 times than those of unplasticized PVA, respectively. Also, the elongation at break and toughness of A-PVA/TEC10 are far superior to those of PVA that are prepared by directly blending way. Most importantly, along with the augmentation of the TEC plasticizer in the PVA system, the melting temperature of plasticized PVA achieved after the alcoholysis reaction of PVAc/TEC10 decreased significantly, and slightly increased in decomposition temperature. This work offers a valuable and justified plasticizing strategy for the processability of PVA materials.

Revealing Pathway Complexity and Helical Inversion in Supramolecular Assemblies Through Solvent-Induced Radical Disparities.

New insights are raised to interpret pathway complexity in the supramolecular assembly of chiral triarylamine tris-amide (TATA) monomer. In cosolvent systems, the monomer undergoes entirely different assembly processes depending on the chemical feature of the two solvents. Specifically, 1,2-dichloroethane (DCE) and methylcyclohexane (MCH) cosolvent trigger the cooperative growth of monomers with M helical arrangement, and hierarchical thin nanobelts are further formed. But in DCE and hexane (HE) combination, a different pathway occurs where monomers go through isodesmic growth to generate twisted nanofibers with P helical arrangement. Moreover, the two distinct assemblies exhibit opposite excited-state chirality. The driving force for both assemblies is the formation of intermolecular hydrogen bonds between amide moieties. However, the mechanistic investigation indicates that radical and neutral triarylamine species go through distinct assembly phases by changing solvent structures. The neutralization of radicals in MCH plays a critical role in pathway complexity, which significantly impacts the overall supramolecular assembly process, giving rise to inversed supramolecular helicity and distinct morphologies. This differentiation in pathways affected by radicals provides a new approach to manipulate chiral supramolecular assembly process by facile solvent-solute interactions.

Effect of Applied Pressure on the Performance of Biodegradable Fiber Insulation Board Manufactured from Camphor Branches (Cinnamomum camphora)

Currently, the predominant thermal insulation materials in the construction industry are primarily derived from inorganic sources. While these materials demonstrate commendable thermal insulation capabilities, their widespread use raises significant environmental concerns. The utilization of wood fiber materials presents a promising solution to mitigate these drawbacks. This study focuses on the fabrication of biodegradable fiber insulation board (BFIB) using camphor branches. The manufacturing process avoids the use of chemical additives, employing a physical method that utilizes hot pressing and relies on the formation of intermolecular hydrogen and hydroxide bonds between the fibers. The study evaluates the influence of applied pressure on the properties of BFIB. SEM images reveal that, with an increase in applied pressure, the fibers exhibit a more regular pattern, subsequently enhancing the mechanical properties, hygric behavior, and fire resistance properties of BFIB. As an environmentally friendly and renewable material, BFIB holds the potential to substitute conventional insulation materials. It is particularly intriguing for energy-saving purposes when applied as building insulation for walls or ceilings.

Water detection in organic solvents using a copolymer membrane immobilised with a fluorescent intramolecular charge transfer-type dye: effects of intramolecular hydrogen bonds.

Numerous fluorescent dye-based optical sensors have been developed to detect water in organic solvents. However, only a few such sensors can detect water in polar solvents such as methanol or dimethyl sulfoxide, and their detection range is generally narrow. Therefore, in this study, a copolymer membrane incorporated with a pyridinium betaine dye (denoted PB1), which exhibited intramolecular charge transfer (ICT) characteristics, was developed to realise simple water detection in organic solvents. The pyridinium betaine structure, comprising intramolecular hydrogen bonds between the oxygen in the maleimide moiety and the hydrogen in the pyridinium, was vital for achieving efficient fluorescence emission. The membrane was prepared by copolymerising PB1 with the N,N-dimethyl acrylamide/acrylamide monomer on a glass plate, and the fluorescence in water-mixed organic solvents was investigated (λabs = 490 nm, λfl = 630 nm). The fluorescence intensity of the dye-immobilised membrane decreased with increasing water content of the organic solvents. The detection ranges in tetrahydrofuran, ethanol, methanol, and dimethyl sulfoxide were approximately <40, <40, <40, and <60 vol% water, respectively. In contrast, membranes based on a quaternary pyridinium dye (without intramolecular hydrogen bonds) did not detect water in methanol and dimethyl sulfoxide, although it was more sensitive than PB1 in the narrow region of low water concentration in THF. Theoretical calculations corroborated the importance of the pyridinium betaine structure in detecting water in organic solvents, with the increase in polarity and the formation of intermolecular hydrogen bonds between PB1 and water found to induce molecular rotation and fluorescence quenching.

Theoretical insight of reactive oxygen species scavenging mechanism in lignin waste depolymerization products.

Apart from natural products and synthesis, phenolic compounds can be produced from the depolymerization of lignin, a major waste in biofuel and paper production. This process yields a plethora of aryl propanoid phenolic derivatives with broad biological activities, especially antioxidant properties. Due to its versatility, our study focuses on investigating the antioxidant mechanisms of several phenolic compounds obtained from renewable and abundant resources, namely, syringol (Hs), 4-allylsyringol (HAs), 4-propenylsyringol (HPns), and 4-propylsyringol (HPs). Employing the density functional theory (DFT) approach in conjunction with the QM-ORSA protocol, we aim to explore the reactivity of these compounds in neutralizing hydroperoxyl radicals in physiological and non-polar media. Kinetic and thermodynamic parameter calculations on the antioxidant activity of these compounds were also included in this study. Additionally, our research utilizes the activation strain model (ASM) for the first time to explain the reactivity of the HT and RAF mechanisms in the peroxyl radical scavenging process. It is predicted that HPs has the best rate constant in both media (1.13 × 108 M-1 s-1 and 1.75 × 108 M-1 s-1, respectively). Through ASM analysis, it is observed that the increase in the interaction energy due to the formation of intermolecular hydrogen bonds during the reaction is an important feature for accelerating the hydrogen transfer process. Furthermore, by examining the physicochemical and toxicity parameters, only Hs is not suitable for further investigation as a therapeutic agent because of potential toxicity and mutagenicity. However, overall, all compounds are considered potent HOO˙ scavengers in lipid-rich environments compared to previously studied antioxidants.

The dawn of hydrogen and halogen bonds and their crucial role in collisional processes probing long-range intermolecular interactions.

This perspective review focuses on the results of an internally consistent study developed in the Perugia laboratory, centered on the fundamental interaction components that, at large intermolecular distances, determine the formation of weak intermolecular hydrogen (HB) and halogen (XB) bonds. This investigation exploits old and novel molecular beam scattering experiments involving several gaseous prototypical systems. In particular, we focus on the kinetic energy dependence of the total (elastic + inelastic) integral cross-sections. Of particular interest is the measure of quantum interference patterns in the energy dependence of cross-sections of targeted systems and their shift compared to that of known reference systems. We interpreted these findings as interaction energy stabilization components, such as charge transfer, σ-hole, and polar flattening, that emerge at intermediate separation distance ranges and selectively manifest for specific geometries of collision complexes. Another significant observable we discuss is the absolute value of the cross-section and its dependence on permanent multipole moments of the collisional partners. Specifically, we show how the spontaneous orientation of rotationally cold and polar molecules, due to the electric field gradient associated with the interaction between permanent multipole moments, can significantly modify the magnitude of the total cross-section, even at high values of the impact parameter. We are confident that the present results can help extend the force field formulation to various interacting systems and carry out molecular dynamics simulations under conditions of application interest.

A near-infrared spectroscopic study of the conformational equilibria of lidocaine molecules in a highly concentrated lidocaine solution in supercritical CO2

In this work, we studied conformational equilibria of molecules of lidocaine in its highly concentrated solutions in scCO2 at the CO2 density values ranging from ∼1.5 to ∼2.0 of the critical value along the isotherm of 35 °C. The study was based on analyzing the spectral band related to the first overtone of the stretching vibrations of the lidocaine molecule N–H fragment. To determine the key factor affecting the formation of intermolecular hydrogen bonds between the lidocaine molecules in the solution we divided our experiment into two stages. First, in the pressure range of 100–180 bar we analyzed the spectra evolution associated with an increase in the concentration of the saturated solution. Then, in the pressure range of 180–300 bar we analyzed the spectra evolution for a solution, where the lidocaine concentration, which was reached at 180 bar, remained constant.We found that the probability of intermolecular hydrogen bond formation considerably increased with lidocaine concentration growth, which, in turn, led to a rise in the population of lidocaine molecules without an intramolecular hydrogen bond. We concluded that the formation of intermolecular hydrogen bonds caused redistribution of the conformer fractions with and without an intramolecular hydrogen bond. Finally, we showed that the key factor affecting the formation of intermolecular hydrogen bonds between the molecules of lidocaine in its solution in scCO2 is the solute concentration rather than the pressure.

Insight into Organization of Gliadin and Glutenin Extracted from Gluten Modified by Phenolic Acids

The changes in the secondary structure of individual gluten protein fractions (gliadin and glutenin) caused by the supplementation of model dough with eight phenolic acids were analysed. Gliadins and glutenins were extracted from gluten samples obtained from overmixed dough. The changes in the gliadin secondary structure depended on the amount of phenolic acid added to the dough. Higher acid concentrations (0.1% and 0.2%) led to a significant reduction in the amount of α-helices and to the formation of aggregates, non-ordered secondary structures, and antiparallel β-sheets. After the addition of acids at a lower concentration (0.05%), the disaggregation of pseudo-β-sheet structures and the formation of β-turns, hydrogen-bonded β-turns, and antiparallel β-sheets were detected. In the case of glutenin, most of the phenolic acids induced the formation of intermolecular hydrogen bonds between the polypeptide chains, leading to glutenin aggregation. When phenolic acids were added at a concentration of 0.05%, the process of protein folding and regular secondary structure formation was also observed. In this system, antiparallel β-sheets and β-turns were created at the expense of pseudo-β-sheets.

Hydrophilic Surface Modification of Poly(methyl methacrylate)/Poly(methyl methacrylate‐co‐acrylic acid) Composite Film by Surface Activation

AbstractFocusing on hydrophilic surface modification of poly(methyl methacrylate)/poly(methyl methacrylate‐co‐acrylic acid) (PMMA/PMMA‐co‐PAA) composite film, a copolymer is synthesized to improve the hydrophilicity and compatibility with PMMA matrix, and the composite film is subjected to surface activation using a sodium hydroxide solution. The infrared absorption peaks corresponding to –OH and –C═O functional groups become progressively weaker with the increase of copolymer content, indicating the formation of intermolecular hydrogen bonds. The hydroxyl absorption peak is significant and two new absorption peaks corresponding to the symmetric contraction and antisymmetric contraction of –COO– appear, indicating that sodium hydroxide solution can disrupt the intermolecular hydrogen bond and react with acrylic acid to form sodium acrylate to make the surface contain sodium elements. The elemental sodium content on the composite film can reach 1.9% and the nanostructures contain 20 times more sodium than the smooth parts, indicating the sodium acrylate can induce surface segregation of PMMA and form nanoparticle‐like structures to improve surface roughness. The hydrophilic component combined with the surface structure makes the contact angle less than 10°. Furthermore, thermostability can be slightly promoted by introducing the copolymer which is closely related to the intermolecular hydrogen bonding formed directly between the copolymer and the PMMA matrix.

Turn-Mimic Hydantoin-Based Loops Constructed by a Sequential Multicomponent Reaction.

A collection of peptidomimetics characterized by having an aspartic acid motif embedded in a rigid hydantoin heterocycle are synthesized through a sequential multicomponent domino process followed by standard regioselective deprotection/coupling reactions based on acid-base liquid/liquid purification protocols. 1H nuclear magnetic resonance experiments, molecular modeling, and X-ray analysis showed that the resulting hydantoin-based loops I (in particular) and II (to a lesser extent) can be considered novel β-turn inducer motifs being able to project two peptide-like strands in a U-shaped conformation driven by the formation of intermolecular hydrogen bonds.

A Novel Indicator Based on Polyacrylamide Hydrogel and Bromocresol Green for Monitoring the Total Volatile Basic Nitrogen of Fish.

An intelligent indicator was developed by immobilizing bromocresol green (BCG) within the polyacrylamide (PAAm) hydrogel matrix to monitor the total volatile basic nitrogen (TVB-N) content of fish. The FTIR analysis indicated that BCG was effectively incorporated into the PAAm through the formation of intermolecular hydrogen bonds. A thermogravimetric analysis (TGA) showed that the PAAm/BCG indicator had a mere 0.0074% acrylamide monomer residue, meanwhile, the addition of BCG improved the thermal stability of the indicator. In vapor tests with various concentrations of trimethylamine, the indicator performed similarly at both 4 °C and 25 °C. The total color difference values (ΔE) exhibited a significant linear response to TVB-N levels ranging from 4.29 to 30.80 mg/100 g at 4 °C (R2 = 0.98). Therefore, the PAAm/BCG indicator demonstrated stable and sensitive color changes based on pH variations and could be employed in smart packaging for real-time assessment of fish freshness.

Effects of starch–fatty acid complexes with different fatty acid chain lengths and degrees of saturation on the rheological and 3D printing properties of corn starch

The effect of corn starch-fatty (CS-FA) complexes from varying carbon chain length and degree of unsaturation on the rheological and 3D printing properties of corn CS–FA complex gels. The CS-FA complexes with longer carbon chain lengths and lower saturation enhanced the ability of gels to bind water, promoting the formation of intermolecular hydrogen bonds. The CS-FA complexes inhibit retrogradation and increase the amount of bound water, thereby reducing the structural integrity and transforming the original skeleton structure into a flake-like structure. These changes in gel structure led to lower flow stress and storage modulus for CS-FA gels containing FAs with shorter carbon chain lengths and lower saturation, resulting in reduced “extrusion swelling” of the material and facilitating its extrusion. The decreased “extrusion swelling” of gel improved print line width and printing performance. The CS-FA complex gel-printed product with a 12-carbon chain FA has the greatest printing accuracy, thanks to its moderate G', flow stress, and viscosity. This study provides important information for the CS-FA complexes for the preparation of starch-based 3D printing materials.