Research on injectable in situ-forming hydrogels has been conducted in diverse biomedical applications for a long period. These hydrogels exhibit sol-to-gel phase transition in accordance with the ...external stimuli such as temperature change. Also, unlike the traditional surgical procedures the hydrogels have the distinct properties of easy management and minimal invasiveness via simple aqueous state injections at target sites. Currently, numerous polymer materials have been reported as potential stimulus-induced in situ-forming hydrogels. In this review, a comprehensive overview of the state-of-the-art of these rapidly developing materials has been outlined. In situ-forming hydrogels formed by electrostatic and hydrophobic interactions as well as their mechanistic characteristics and biomedical applications in regenerative medicine have also been discussed. The review concludes with perspectives on the future of stimulus-induced in situ-forming hydrogels.
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•Highly negatively charged ultrathin (∼15 nm) InVO4 NRs were synthesized.•The as-obtained materials exhibited maximum RhB adsorption capacity 780 mg/g.•The InVO4 NRs showed superior ...selective adsorption capability towards cationic micropollutants in presence of impurities.•The adsorbents showed robust resilience in a wide pH range and could be effectively recovered by ethanol solution.•The electrostatic attraction was confirmed as the predominant adsorption mechanism.
Seeking adsorbents with high adsorption capacity and ease of regeneration is imperative for environmental remediation. Herein, strongly negatively charged two-dimensional (2D) ultrathin InVO4 nanoribbons (NRs) were synthesized. The material exhibited impressive selective adsorption capabilities towards cationic dyes, and the fitted Langmuir maximum adsorption capacity is 789.7 mg/g when using RhB as a model signal pollutant. The adsorption curve towards Rhodamine B (RhB) fits well with the pseudo-second-order (PSO) reaction. The corresponding adsorption isotherm is confirmed in accordance with the Freundlich model, indicating the adsorption is likely a multi-layer adsorption process. Through examining its adsorption activities with positively charged upconversion nanoparticles (UCNPs) and dyes with different surface charges, the strong electrostatic attraction is found to be the predominant adsorption mechanism. Furthermore, the new adsorbents showed remarkable resilience to even large pH variation (from 3 to 12), and could be rapidly and efficiently regenerated using a mixture of water and ethanol (volume ratio 1:1) in 30 min. These advantages are highly favorable for the application of efficient adsorbents for wastewater treatment and resource recovery.
The widespread utilization of plastic products ineluctably leads to the ubiquity of nanoplastics (NPs), causing potential risks for aquatic environments. Interactions of NPs with mineral surfaces may ...affect NPs transport, fate and ecotoxicity. This study aims to investigate systematically the deposition and aggregation behaviors of carboxylated polystyrene nanoplastics (COOH-PSNPs) by four types of clay minerals (illite, kaolinite, Na-montmorillonite, and Ca-montmorillonite) under various solution chemistry conditions (pH, temperature, ionic strength and type). Results demonstrate that the deposition process was dominated by electrostatic interactions. Divalent cations (i.e., Ca2+, Mg2+, Cd2+, or Pb2+) were more efficient for screening surface negative charges and compressing the electrical double layer (EDL). Hence, there were significant increases in deposition rates of COOH-PSNPs with clay minerals in suspension containing divalent cations, whereas only slight increases in deposition rates of COOH-PSNPs were observed in monovalent cations (Na+, K+). Negligible deposition occurred in the presence of anions (F−, Cl−, NO3−, CO32−, SO42−, or PO43−). Divalent Ca2+ could incrementally facilitate the deposition of COOH-PSNPs through Ca2+-assisted bridging with increasing CaCl2 concentrations (0–100 mM). The weakened deposition of COOH-PSNPs with increasing pH (2.0–10.0) was primarily attributed to the reduce in positive charge density at the edges of clay minerals. In suspensions containing 2 mM CaCl2, increased Na+ ionic strength (0–100 mM) and temperature (15–55 ◦C) also favored the deposition of COOH-PSNPs. The ability of COOH-PSNPs deposited by four types of clay minerals followed the sequence of kaolinite > Na-montmorillonite > Ca-montmorillonite > illite, which was related to their structural and surface charge properties. This study revealed the deposition behaviors and mechanisms between NPs and clay minerals under environmentally representative conditions, which provided novel insights into the transport and fate of NPs in natural aquatic environments.
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•Divalent cations contribute more to the deposition of COOH-PSNPs than monovalent.•Ca2+-assisted bridging facilitates the deposition of COOH-PSNPs with clay minerals.•Deposition capacity of clay minerals for COOH-PSNPs was weakened as pH increased.•Increasing ionic strength and temperature promotes the occurrence of deposition.•COOH-PSNPs deposition rates follow the order of kaolinite > montmorillonite > illite.
Hydrogen bonding and electrostatic interactions play an important role in the microstructure of soy hull polysaccharide (SHPA) and the stability of corresponding emulsions. In this study, urea and ...NaCl were added in the preparation of samples, which could destroy these two noncovalent interactions, and they were labeled as SHPA-U and SHPA-N, respectively. The results show that more hydrogen bonding was generated along with the electrostatic shielding effect, which led to longer and branched polysaccharide chains of SHPA-N. However, the chain of SHPA-U was rough and fragmentary, which may be attributed to hydrogen bonding and protein regions destroyed by urea. Furthermore, the addition of NaCl and urea led to lower interfacial pressure, and the adsorption kinetics at the oil/water interface were significantly changed. In addition, all emulsions had a liquid-like structure, and both SHPA-N and SHPA-U emulsions had a bimodal size distribution. The relaxation time and line width of the 1H NMR analysis decreased with the addition of NaCl and urea, indicating the decreasing interaction between SHPA-N/SHPA-U and oil molecules. These phenomena were related to the coalescence and flocculation in these two emulsions. After 24 h of storage, the stability of the SHPA-N emulsion was superior to the others; this may be due to its higher viscosity. This study laid the foundation for further research on the mechanism of polysaccharide O/W emulsions stabilized by SHPA and other polysaccharides.
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•The effect of NaCl and urea on soy hull polysaccharide (SHPA) and emulsions were investigated.•The length and thermal stability of SHPA chains was increased with the hydrogen bonding increasing.•NaCl and urea increased the penetration and reorganization rate of SHPA at the oil-water interface.•Emulsion stabilized by SHPA-N has higher viscosity and better stability for 24 h storage.
•DPPT-R exhibits a strong affinity for PF6− through strong electrostatic interactions and hydrophobicity.•Solid fluorescence was enhanced through anion-π+ interactions, with a fluorescence quantum ...yield of up to 10.46 %.•DPPT-R@PF6 complex enhances its solid-state fluorescence, intensity of bacterial fluorescence imaging, and antibacterial activity through anion-π+ interactions.
The contamination of anions and the overuse of antibiotics pose significant hazards to human health. Excess anions can cause serious damage to organisms and the natural environment, while the misuse of antibiotics has led to the emergence of multi-drug resistant bacteria. Therefore, it is important to develop multifunctional fluorescent sensing devices that integrate the rapid and sensitive detection of specific anions and that exhibit excellent antimicrobial activity against multi-resistant bacteria. This study describes the synthesis of three water-soluble cationic fluorescent molecules, DPPT-R (R = 5C, 6C, 7C). Their structures were characterized using 1H NMR spectroscopy, HRMS, and single crystal X-ray diffraction. Spectroscopic properties of the probes were recorded using UV–visible absorption and fluorescence spectroscopy. The recognition mode and mechanism of the fluorescent probes towards PF6− were investigated. Under aqueous solution conditions involves the PF6− induced aggregation of the probe via strong electrostatic interactions, leading to fluorescence quenching. Adjusting the alkyl chain length of the probe can enhance the sensitivity for the detection of the target anions. The detection limits are 0.892 μM, 0.786 μM and 0.444 μM for R = 5C, 6C, 7C, respectively. In addition, DPPT-R and DPPT-R@PF6 exhibit good inhibitory activity and fluorescence imaging capability against methicillin-resistant Staphylococcus aureus and multidrug-resistant Escherichia coli. Among them, the side chain of DPPT-R@PF6 with an almost 90° bend may be more advantageous for membrane insertion, thus enhancing its antimicrobial activity. In particular, after DPPT-R and PF6− form the DPPT-R@PF6 complex, the complex enhances its solid-state fluorescence, intensity of bacterial fluorescence imaging, and antibacterial activity through anion-π+ interactions. Therefore, this study can provide a new strategy and theoretical basis for the design and application of multifunctional fluorescent sensing materials and antibacterial molecules based on electrostatic interactions and anion-π+ interactions.
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Soybean and peanut oil bodies (OBs) receive considerable interest in the food, cosmetic, and pharmaceutical industries. However, they aggregate easily because of their low ζ-potentials and weak ...electrostatic repulsion. Therefore, this study aimed to improve their stabilities using apple pectin (AP) under acidic conditions (pH 3.0, 5.0, and 7.0). The combined influences of pH and AP concentration on the interfacial proteins and rheological and physical properties were assessed. An AP concentration of 0.05% significantly reduced the storage stability of OBs at pH 3.0 (P < 0.05). The storage and oxidative stabilities of the emulsions with AP concentration ≥ 0.15% were improved by increasing the ζ-potential and apparent viscosity and decreasing the mean particle diameter. When the AP concentration was between 0.3% and 0.5%, the influence of AP on the stability of emulsion was steady. AP decreased the content of extrinsic proteins and increased the apparent viscosity. The emulsion showed superior stability at pH 5.0. Our findings indicate that AP exhibits potential as an OB stabilizer and may be used in yogurt-like foods and acidic dressings.
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The term “hydrogen bond” has been used in the literature for nearly a century now. While its importance has been realized by physicists, chemists, biologists, and material scientists, there has been ...a continual debate about what this term means. This debate has intensified following some important experimental results, especially in the last decade, which questioned the basis of the traditional view on hydrogen bonding. Most important among them are the direct experimental evidence for a partial covalent nature and the observation of a blue-shift in stretching frequency following X
H···Y hydrogen bond formation (XH being the hydrogen bond donor and Y being the hydrogen bond acceptor). Considering the recent experimental and theoretical advances, we have proposed a new definition of the hydrogen bond, which emphasizes the need for evidence. A list of criteria has been provided, and these can be used as evidence for the hydrogen bond formation. This list is followed by some characteristics that are observed in typical hydrogen-bonding environments.
A series of amphiphilic ionic peptoid block copolymers where the total number (1 or 3) and position of ionic monomers along the polymer chain are precisely controlled have been synthesized by the ...submonomer method. Upon dissolution in water at pH = 9, the amphiphilic peptoids self-assemble into small spherical micelles having hydrodynamic radius in ∼5–10 nm range and critical micellar concentration (CMC) in the 0.034–0.094 mg/mL range. Small-angle neutron scattering (SANS) analysis of the micellar solutions revealed unprecedented dependence of the micellar structure on the number and position of ionic monomers along the chain. It was found that the micellar aggregation number (N agg) and the micellar radius (R m) both increase as the ionic monomer is positioned progressively away from the junction of the hydrophilic and hydrophobic segments along the polymer chain. By defining an ionic monomer position number (n) as the number of monomers between the junction and the ionic monomer, N agg exhibited a power law dependence on n with an exponent of ∼1/3 and ∼3/10 for the respective singly and triply charged series. By contrast, R m exhibited a weaker dependence on the ionic monomer position by a power law relationship with an exponent of ∼1/10 and ∼1/20 for the respective singly and triply charged series. Furthermore, R m was found to scale with N agg in a power-law relationship with an exponent of 0.32 for the singly charged series, consistent with a weakly charged ionic star-like polymer model in the unscreened regime. This study demonstrated a unique method to precisely tailor the structure of small spherical micelles based on ionic block copolymers by controlling the sequence and position of the ionic monomer.
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•pH-stimulated PDMAEMA microgels were synthesized for selective PFOA recovery.•PDMAEMA microgels showed a maximum PFOA adsorption capacity of ∼ 2632 mg g−1.•The PDMAEMA showed high ...selectivity for PFOA adsorption in presence of impurities.•PFOA can be easily released and recycled by adjusting the solution pH.•The adsorption mechanism includes electrostatic and hydrophobic interactions.
Perfluorooctanoic acid (PFOA) is a high-value chemical which has been widely used in the semiconductor industry. There is currently a lot of work focusing on the removal of low concentration of PFOA due to its potential toxicity, whereas the recovery of high concentration of PFOA from semiconductor wastewater via adsorption could be more valuable. This work reported a novel pH-stimulated poly (dimethyl amino) ethyl methacrylate (PDMAEMA) microgel for selective PFOA recovery. The results showed that the calculated maximum adsorption capacity for PFOA on PDMAEMA microgel is as high as 2632 mg g−1 in the presence of 5% (v/v) isopropyl alcohol (IPA). Electrostatic interaction was considered as the main adsorption mechanism combined with hydrophobic interactions. The strong interactions made the adsorption highly selective; therefore, the components in the water matrix, including acids, metal ions, and organic solvents, would not affect the adsorption performance. Meanwhile, due to the pH responsiveness of PDMAEMA microgels, PFOA could be released easily when the solution pH was adjusted to higher values. Finally, the application mode was investigated by incorporating PDMAEMA microgels into a dense membrane, in which the separation of the microgels in a water system could be effectively achieved.
Environment friendly methods for the synthesis of copper nanoparticles have become a valuable trend in the current scenario. The utilization of phytochemicals from plant extracts has become a unique ...technology for the synthesis of nanoparticles, as they possess dual nature of reducing and capping agents to the nanoparticles. In the present investigation we have synthesized copper nanoparticles (CuNPs) using a rare medicinal plant Cissus arnotiana and evaluated their antibacterial activity against gram negative and gram positive bacteria. The morphology and characterization of the synthesized CuNPs were studied and done using UV-Visible spectroscopy at a wavelength range of 350–380 nm. XRD studies were performed for analyzing the crystalline nature; SEM and TEM for evaluating the spherical shape within the size range of 60–90 nm and AFM was performed to check the surface roughness. The biosynthesized CuNPs showed better antibacterial activity against the gram-negative bacteria, E. coli with an inhibition zone of 22.20 ± 0.16 mm at 75 μg/ml. The antioxidant property observed was comparatively equal with the standard antioxidant agent ascorbic acid at a maximum concentration of 40 μg/ ml. This is the first study reported on C. arnotiana mediated biosynthesis of copper nanoparticles, where we believe that the findings can pave way for a new direction in the field of nanotechnology and nanomedicine where there is a significant potential for antibacterial and antioxidant activities. We predict that, these could lead to an exponential increase in the field of biomedical applications, with the utilization of green synthesized CuNPs, due to its remarkable properties. The highest antibacterial property was observed with gram-negative strains mainly, E. coli, due to its thin peptidoglycan layer and electrostatic interactions between the bacterial cell wall and CuNPs surfaces. Hence, CuNPs can be potent therapeutic agents in several biomedical applications, which are yet to be explored in the near future.
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•To prepare the copper nanoparticles using novel medicinal plant Cissus arnotiana•Characterization of CuNPs by different microscopic techniques•To evaluate the antioxidant and antibacterial activity
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