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Thixotropic data of the NaOH responsive hydrogel contained 1.0% (w/v) gelator, obtained by step-strain measurements at 20 °C at a constant frequency (0.1 rad s −1 ).
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Ordered self-assembly of small organic molecules may induce novel properties in a supramolecular arrangement and can act as advance functional materials. This paper discusses the development of a new stimuli-responsive dipeptide hydrogelator containing l-phenylalanine and α-aminoisobutyric acid (Aib). The dipeptide Boc-Phe-Aib-OH, on addition with...
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... figure out the thixotropic property of the NaOH-responsive hydrogel, rheological step-strain experiments 52,53 have been done at 20 °C under varying strain. At first, gels were placed at a constant strain of 0.1%, which shows that G′ is higher than G″ (step 1, Figure 5). Finally, the strain increased from 0.1 to 50% and was continued for few minutes. ...
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... the strain increased from 0.1 to 50% and was continued for few minutes. This shows the complete inversion of G′ and G″, indicating the complete break of the hydrogel (step 2, Figure 5). Again the strain was decreased from 50 to 0.1% and continued for few minutes and gel restoration kinetics were observed (step 3, Figure 5). ...
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... shows the complete inversion of G′ and G″, indicating the complete break of the hydrogel (step 2, Figure 5). Again the strain was decreased from 50 to 0.1% and continued for few minutes and gel restoration kinetics were observed (step 3, Figure 5). This was continued for several cycles and confirmed the self-healing behavior of the NaOH-responsive hydrogel. ...
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... cylindrical electrodes which are separated by 1 cm were used. The NaOH-responsive hydrogel block formed by peptide 1 is highly conducting (Supporting Information, Figure S5). Conductance of NaOH added water = 253.60 ...
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... of the gel = 194.20 μS/cm. Therefore, the conductivity decreased from Figure S5c to S5d, but the decrease is quite small. As the gels were formed, the mobility of the ions decreased and as a result of that conductivity decreased. ...
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... thixotropic behavior of the hydrogel was confirmed by rheological measurement. Under external stimuli, a thixotropic gel can disintegrate to solution or a quasiliquid state and can regain its original shape after the removal of the applied force. To figure out the thixotropic property of the NaOH-responsive hydrogel, rheological step-strain experiments 52,53 have been done at 20 °C under varying strain. At first, gels were placed at a constant strain of 0.1%, which shows that G′ is higher than G″ (step 1, Figure 5). Finally, the strain increased from 0.1 to 50% and was continued for few minutes. This shows the complete inversion of G′ and G″, indicating the complete break of the hydrogel (step 2, Figure 5). Again the strain was decreased from 50 to 0.1% and continued for few minutes and gel restoration kinetics were observed (step 3, Figure 5). This was continued for several cycles and confirmed the self-healing behavior of the NaOH-responsive ...
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... thixotropic behavior of the hydrogel was confirmed by rheological measurement. Under external stimuli, a thixotropic gel can disintegrate to solution or a quasiliquid state and can regain its original shape after the removal of the applied force. To figure out the thixotropic property of the NaOH-responsive hydrogel, rheological step-strain experiments 52,53 have been done at 20 °C under varying strain. At first, gels were placed at a constant strain of 0.1%, which shows that G′ is higher than G″ (step 1, Figure 5). Finally, the strain increased from 0.1 to 50% and was continued for few minutes. This shows the complete inversion of G′ and G″, indicating the complete break of the hydrogel (step 2, Figure 5). Again the strain was decreased from 50 to 0.1% and continued for few minutes and gel restoration kinetics were observed (step 3, Figure 5). This was continued for several cycles and confirmed the self-healing behavior of the NaOH-responsive ...
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... thixotropic behavior of the hydrogel was confirmed by rheological measurement. Under external stimuli, a thixotropic gel can disintegrate to solution or a quasiliquid state and can regain its original shape after the removal of the applied force. To figure out the thixotropic property of the NaOH-responsive hydrogel, rheological step-strain experiments 52,53 have been done at 20 °C under varying strain. At first, gels were placed at a constant strain of 0.1%, which shows that G′ is higher than G″ (step 1, Figure 5). Finally, the strain increased from 0.1 to 50% and was continued for few minutes. This shows the complete inversion of G′ and G″, indicating the complete break of the hydrogel (step 2, Figure 5). Again the strain was decreased from 50 to 0.1% and continued for few minutes and gel restoration kinetics were observed (step 3, Figure 5). This was continued for several cycles and confirmed the self-healing behavior of the NaOH-responsive ...
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... NaOH-responsive hydrogel formed by peptide 1 at low concentration (4 wt %) is very stable. Different self-supporting geometrical shape can be crafted from the gel. 55 By holding, one side a gel bar can be suspended in air (Figure 9a). The NaOH-responsive hydrogels formed by peptide 1 low concentration (4 wt %) are strong enough to tolerate several grams of weight (Figure 9b,c). Even, one can slice a big gel block into several small pieces (Figure 9d). 56 The hydrogel is very dynamic in nature. The dye rhodamine 6G can disperse through the gel block. Moreover, the hydrogels have significant self-healing properties. When a block of gel was cut into two pieces and then placed together, the pieces merged. 56 Also, several small pieces of hydrogels could be merged into a continuous stable self-supporting bar. These fused bars could be suspended in air by holding one side. Inside the hydrogel, there exists a dynamic equilibrium showing the formation of new self-assembled fibers as well as dissociation of mature fibers. This dynamic equilibrium allows the regeneration of new fibers at the fusion interface, which is important for the self- healing and repairing process. The fusion of a rhodamine 6G- doped hydrogel bar with an undoped hydrogel bar shows the diffusion of rhodamine 6G through an undoped hydrogel bar. This exhibits the dynamic exchange of dissolved molecules at the interface (Figure 9d−f). This is further established by electric conductivity experiments. 57 The conductivity of a hydrogel was measured by an ONKTON PC-2700 conductivity meter. The cylindrical electrodes which are separated by 1 cm were used. The NaOH-responsive hydrogel block formed by peptide 1 is highly conducting (Supporting Information, Figure S5). Conductance of NaOH added water = 253.60 μS/cm. Conductance of the gel = 194.20 μS/cm. Therefore, the conductivity decreased from Figure S5c to S5d, but the decrease is quite small. As the gels were formed, the mobility of the ions decreased and as a result of that conductivity decreased. Connection of the battery, LED, and gel block complete the circuit and shows the flow of electricity. However, chopping the gel block into two pieces disrupts the electric circuit and exhibits no flow of electricity. However, when joining the pieces together, because of self-healing, the gel pieces merged into a continuous gel block and conductivity of the circuit is regained (Figure ...
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... NaOH-responsive hydrogel formed by peptide 1 at low concentration (4 wt %) is very stable. Different self-supporting geometrical shape can be crafted from the gel. 55 By holding, one side a gel bar can be suspended in air (Figure 9a). The NaOH-responsive hydrogels formed by peptide 1 low concentration (4 wt %) are strong enough to tolerate several grams of weight (Figure 9b,c). Even, one can slice a big gel block into several small pieces (Figure 9d). 56 The hydrogel is very dynamic in nature. The dye rhodamine 6G can disperse through the gel block. Moreover, the hydrogels have significant self-healing properties. When a block of gel was cut into two pieces and then placed together, the pieces merged. 56 Also, several small pieces of hydrogels could be merged into a continuous stable self-supporting bar. These fused bars could be suspended in air by holding one side. Inside the hydrogel, there exists a dynamic equilibrium showing the formation of new self-assembled fibers as well as dissociation of mature fibers. This dynamic equilibrium allows the regeneration of new fibers at the fusion interface, which is important for the self- healing and repairing process. The fusion of a rhodamine 6G- doped hydrogel bar with an undoped hydrogel bar shows the diffusion of rhodamine 6G through an undoped hydrogel bar. This exhibits the dynamic exchange of dissolved molecules at the interface (Figure 9d−f). This is further established by electric conductivity experiments. 57 The conductivity of a hydrogel was measured by an ONKTON PC-2700 conductivity meter. The cylindrical electrodes which are separated by 1 cm were used. The NaOH-responsive hydrogel block formed by peptide 1 is highly conducting (Supporting Information, Figure S5). Conductance of NaOH added water = 253.60 μS/cm. Conductance of the gel = 194.20 μS/cm. Therefore, the conductivity decreased from Figure S5c to S5d, but the decrease is quite small. As the gels were formed, the mobility of the ions decreased and as a result of that conductivity decreased. Connection of the battery, LED, and gel block complete the circuit and shows the flow of electricity. However, chopping the gel block into two pieces disrupts the electric circuit and exhibits no flow of electricity. However, when joining the pieces together, because of self-healing, the gel pieces merged into a continuous gel block and conductivity of the circuit is regained (Figure ...
Citations
... Therefore, the characteristic and unique features of Boc-Phe-Aib-OH injectable hydrogel makes it an interesting candidate for HCl sensors and conductive materials. 148 A study conducted by Wu and associates presented a new opportunity for the peptides into carbohydrate-based gel matrices furnished with applications in the fields of food industry, tissue engineering and drug delivery. They fabricated Ala-Lys dipeptide (AK) (16) and the iota-carrageenan (ι-C)based hydrogel and evaluated that addition of AK to ι-C promoted the gel strength of ι-C, leading to a sol−gel transition. ...
Owing to their properties such as biocompatibility, tunable mechanical properties, permeability toward oxygen, nutrients, and the ability to hold a significant amount of water, hydrogels have wide applications in biomedical research. They have been engaged in drug delivery systems, 3D cell culture, imaging, and extracellular matrix (ECM) mimetics. Injectable hydrogels represent a major subset of hydrogels possessing advantages of site-specific conformation with minimal invasive techniques. It preserves the inherent properties of drug/biomolecules and is devoid of any side effects associated with surgery. Various polymeric materials utilized in developing injectable hydrogels are associated with the limitations of toxicity, immunogenicity, tedious manufacturing processes, and lack of easy synthetic tunability. Peptides are an important class of biomaterials that have interesting properties such as biocompatibility, stimuli responsiveness, shear thinning, self-healing, and biosignaling. They lack immunogenicity and toxicity. Therefore, numerous peptide-based injectable hydrogels have been explored in the past, and a few of them have reached the market. In recent years, minimalistic dipeptides have shown their ability to form stable hydrogels through cooperative noncovalent interactions. In addition to inherent properties of lengthy peptide-based injectable hydrogels, dipeptides have the unique advantages of low production cost, high synthetic accessibility, and higher stability. Given the instances of expanding significance of injectable peptide hydrogels in biomedical research and an emerging recent trend of dipeptide-based injectable hydrogels, a timely review on dipeptide-based injectable hydrogels shall highlight various aspects of this interesting class of biomaterials. This concise review that focuses on the dipeptide injectable hydrogel may stimulate the current trends of research on this class of biomaterial to translate its significance as interesting products for biomedical applications.
... This can be attributed to the profound van der Waals interactions within the D2P5 peptides in their gel state. reproduced with permission from Ref. [73]. Copyright (2018) American Chemical Society. ...
... Copyright (2018) American Chemical Society. Based on the outstanding self-assembly ability of Phe, Haldar et al. demonstrated a dipeptide (D2P6) composed of Phe and a non-natural amino acid, α-aminoisobutyric acid (Aib), which undergoes self-assembly into freshly prepared NaOH solution through noncovalent interactions to form a transparent hydrogel ( Figure 3C) [73]. The gel is thixotropic in nature, as confirmed by the rheological loop test ( Table 2). ...
Thixotropy is a fascinating feature present in many gel systems that has garnered a lot of attention in the medical field in recent decades. When shear stress is applied, the gel transforms into sol and immediately returns to its original state when resting. The thixotropic nature of the hydrogel has inspired scientists to entrap and release enzymes, therapeutics, and other substances inside the human body, where the gel acts as a drug reservoir and can sustainably release therapeutics. Furthermore, thixotropic hydrogels have been widely used in various therapeutic applications, including drug delivery, cornea regeneration and osteogenesis, to name a few. Because of their inherent biocompatibility and structural diversity, peptides are at the forefront of cutting-edge research in this context. This review will discuss the rational design and self-assembly of peptide-based thixotropic hydrogels with some representative examples, followed by their biomedical applications.
... 21 We have also shown that a selfhealing hydrogel from a dipeptide can act as a HCl sensor. 22 Recently, we have reported a robust tripeptide for in-field selective naked eye ultratrace detection of 2,4,6-trinitrophenol. 23 Herein, we have reported the effect of isomerism on the structure, self-assembly and properties of two peptide mimetics. From X-ray crystallography, it is observed that the p-isomer adopted a kink-like conformation stabilized by C-HÁ Á Áp interactions and formed a supramolecular anti-parallel duplex and layer by layer sheet-like structure in higher order assembly. ...
The effect of isomerism on the structure, self-assembly and properties of two peptide mimetics has been investigated. These peptide mimetics contain m-aminobenzoic acid, p-aminobenzoic acid and N,N′-dicyclohexylurea. From X-ray crystallography, it is observed that the p-isomer adopted a kink-like conformation stabilized by C–H⋯π interactions and formed a supramolecular anti-parallel duplex and layer by layer sheet-like structure in higher order assembly. However, only the m-isomer formed sonication responsive gels in different hydrocarbons such as hexane–EtOAc (19 : 1), diesel, kerosene, body oil and coconut oil. From rheology experiments, the gel was found to have physical cross-links and is elastic in nature. The FE-SEM images depicted that the m-isomer exhibited nanofiber network morphology, whereas the p-isomer exhibited polydisperse microsphere morphology. The gel was found to be highly sensitive to alcohol vapours, although the kinetics become much slower from methanol to ethanol to isopropanol. The gel is also very responsive to acid vapours like HCl.
... Naproxen-capped dipeptide Nap-Phe-Phe only showed biocompatibility at low concentrations and the IC 50 value is lower than the minimum gel concentration, which suggested that the molecule was not suitable for biomedical applications (Li et al., 2013). Haldar et al. have reported a N-(tert-butoxycarbonyl) (N-Boc)-modified dipeptide Boc-Phe-Aib (Nandi et al., 2018), which transformed into a robust hydrogel upon addition with three equivalents of sodium hydroxide and water (Figure 7). The other similar analogs of dipeptides, such as Boc-Tyr-Aib, Boc-Trp-Aib, Boc-Phe-Ala (Sangeetha and Maitra, 2005), Boc-Phe-Gly (O'Leary et al., 2011), and Boc-Aib-Phe, have all failed to form such a hydrogel under the same condition. ...
... The structures of dipeptide Boc-Phe-Aib analogs and their gelation studies(Nandi et al., 2018).Frontiers in Chemistry | www.frontiersin.org September 2021 | Volume 9 | Article 739791FIGURE 8 | (A) APs scoring distribution of all 400 C13-dipeptides after 50ns CG-MD simulations. ...
Self-assembly peptide-based hydrogels are well known and popular in biomedical applications due to the fact that they are readily controllable and have biocompatibility properties. A dipeptide is the shortest self-assembling motif of peptides. Due to its small size and simple synthesis method, dipeptide can provide a simple and easy-to-use method to study the mechanism of peptides’ self-assembly. This review describes the design and structures of self-assembly linear dipeptide hydrogels. The strategies for preparing the new generation of linear dipeptide hydrogels can be divided into three categories based on the modification site of dipeptide: 1) COOH-terminal and N-terminal modified dipeptide, 2) C-terminal modified dipeptide, and 3) uncapped dipeptide. With a deeper understanding of the relationship between the structures and properties of dipeptides, we believe that dipeptide hydrogels have great potential application in preparing minimal biocompatible materials.
... Previously, we have reported NaOH-responsive hydrogel that exhibits blue emission under excitation at 366 nm. 52 Here also, we have examined the emission property of NaOH-responsive hydrogel, but that type of blue emission is absent, and the hydrogel is also nontransparent. Surprisingly, peptide 2b gel in toluene shows blue emission under excitation at 366 nm, although in solution, such kind of blue emission was not observed ( Figure 7a). ...
... 30 The mixture undergoes removal of the dyes. 31 The process was repeated three times, and the removal (visually) of dyes occurred in each case. ...
... Compound concentrations were in the 1−10 mM range in DMSO-d 6 and CDCl 3 solution. 31 FT-IR Experiments. FT-IR spectroscopy in the solid state was performed with a Perkin Elmer Spectrum RX1 spectrophotometer using KBr disk method. ...
... The storage modulus (G′) and loss modulus (G″) of the gel were then recorded by using the setup. 31 X-ray Crystallography. Diffraction quality light yellow color crystals of peptide 1 were obtained from methanol− water solution by slow evaporation. ...
The effect of geometrically rigid trans α,β-unsaturated ε-amino acids on the structure, folding, and assembly of α,ε-hybrid peptide foldamers has been reported. From single-crystal diffraction analysis, the unsaturated tetrapeptide 1 has stapler-pin-like structure but without intramolecular hydrogen bond. The asymmetric unit has two molecules that are stabilized by multiple intermolecular hydrogen bonding interactions as well as π–π stacking interactions between the aromatic rings of 3-aminocinnamic acid. Peptide 1 does not form organogel. But on hydrogenation, peptide 1 provides the saturated α,ε-hybrid peptide foldamer 2, which forms instant gel in most of the aromatic solvents. The gel exhibits high stability. The unsaturated peptide 1 has porous microsphere morphology, but saturated analogue 2 has ribbonlike morphology. The gel has been used efficiently for removal of cationic organic pollutants from waste water.
Short designer self-assembling peptide (dSAP) biomaterials are a new addition to hemostat group. It may provide diverse and robust toolboxes for surgeon to integrate wound microenvironment with much safer and stronger hemostatic capacity than conventional materials and hemostatic agents. Especially in noncompressible torso hemorrhage (NCTH), diffuse mucosal surface bleeding, and internal medical bleeding (IMB), et al., with respect to the optimal hemostatic formulation, dSAP biomaterials are the ingenious nanofiber alternatives to make bioactive neural scaffold, nasal packing, large mucosal surface coverage in gastrointestinal surgery (esophagus, gastric lesion, duodenum, and lower digestive tract), epicardiac cell delivery carrier, transparent matrix barrier, et al. Herein, in multiple surgical specialties, dSAP biomaterials-based nano hemostats achieve safe, effective and immediate hemostasis, facile wound healing, and potentially reduce the risks in delayed bleeding, rebleeding, postoperative bleeding or related complications. The biosafety in vivo, bleeding indications, tissue-sealing quality, surgical feasibility, and local usability are addressed comprehensively and sequentially and pursued to develop useful surgical techniques with better hemostatic performance. This article provides the state of art and all-round advancements of nano hemostatic approaches in surgery. Relevant critical insights will inspire exciting investigations on peptide nanotechnology, next-generation biomaterials, and better promising prospects in clinics. This article is protected by copyright. All rights reserved.
Dipeptides are minimalistic peptide building blocks that form well ordered structures through molecular self-assembly. The driving forces involved are cooperative noncovalent interactions such as π-π stacking, hydrogen bonding, and ionic as well as hydrophobic interactions. One of the most intriguing self-assembled motifs that has been extensively explored as a low molecular weight hydrogel for drug delivery, tissue engineering, imaging and techtonics, etc. is Phe-Phe (FF). The backbone of the dipeptide is very crucial for extending secondary structures in self-assembly, and any subtle change in the backbone drastically affect the molecular recognitions. The squaramide (SQ) motif has the unique advantage of hydrogen bonding which can promote the self-assembly process. In this work we have integrated the SQ unit into the dipeptide FF backbone to achieve molecular self-assembly. The resulting carbamate protected backbone modified dipeptide (BocFSAF-OH, 10) has exhibited molecular self-assembly with a fibrilar network. It formed a stable hydrogel (with CAC of 0.024 ± 0.0098 wt %) via the solvent switch method and was found to possess excellent enzymatic stability. The dipeptide and the resulting hydrogel were found to be cytocompatible. When integrated with a polysaccharide based biopolymer, e.g. sodium alginate, the resulting matrix exhibited strong hydrogel character. Therefore, the dipeptide hydrogel of 10 may find its applications in a variety of fields including drug delivery and tissue engineering.
Modern technologies surround future of human races. Therefore, constantly development of materials and devices as well as creation of intelligent and hybrid materials are being prioritized. This chapter aims to cover a new type of hybrid materials of which self-healing ability and analyte-responsive sensitivity are synergized into a hydrogel matrix. Synthesis of these materials is approached by two relatively independent tasks. The first task is designing self-healing chemistry for hydrogel, while the second task is inclusion of sensing and transduction elements into the self-healing hydrogels. Important, some proof-of-concept sensors using the self-healing hydrogels are communicated in this chapter.
