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1.
ACS Polym Au ; 4(3): 255-265, 2024 Jun 12.
Artículo en Inglés | MEDLINE | ID: mdl-38882035

RESUMEN

The precise sequence of a protein's primary structure is essential in determining its folding pathways. To emulate the complexity of these biomolecules, functional block copolymers consisting of segmented triblocks with distinct functionalities positioned in a sequence-specific manner are designed to control the polymer chain compaction. Triblock polymers P- b -C- b -F and P- b -F- b -C and random diblock copolymer P- b -C- r -F consist of a hydrophilic poly(ethylene oxide) (PEO) block and a hydrophobic block with coumarin (C) and ferrocene (F) moieties that are grafted in a sequence-specific or random manner onto the hydrophilic block. External stimuli such as UVB light, redox, and chemical cues influence the functional hydrophobic block to alter the packing parameters that are monitored with spectroscopic and scattering techniques. Interestingly, the positioning of the stimuli-responsive moiety within the hydrophobic block of P- b -C- b -F, P- b -F- b -C, and P- b -C- r -F affects the extent of the hydrophobic-hydrophilic balance in block copolymers that renders orthogonal control in stimuli-responsive transformation of self-assembled vesicles to micelles.

2.
Methods Enzymol ; 697: 473-498, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38816133

RESUMEN

Development of biomolecular enzyme mimics to efficiently catalyse biochemical reactions are of prime relevance for the bulk scale production of industrially relevant biocatalyst. In this regard, amyloidogenic peptides act as suitable self-assembling scaffolds, providing stable nanostructures with high surface area facilitating biocatalysis. Herein, we rationally design two positional amyloidogenic peptide isomers, "Fmoc-VYYAHH (1)" and "Fmoc-VHHAYY (2)" considering catalytic and metal binding affinity of histidine and tyrosine when placed in periphery vs. inner core of the peptide sequence. With an ultimate objective of designing metalloenzyme mimic, we choose Co2+ and Cu2+ as divalent transition metal cations for peptide complexation to aid in catalysis. After optimizing self-assembly of innate peptides, we investigate metal-peptide binding ratio and co-ordination, finally selecting 1:1 peptide metal complex suitable for biocatalysis. Metallopeptides act as better catalysts than the innate peptides as acyl esterase when tyrosines were present at the periphery. Kinetic parameters for assessing hydrolysis rate were calculated by fitting data into Michaelis-Menten and Lineweaver Burk plots. Catalytic activity is altered depending on the stability of peptide metal complexes. 2-Cu acting as the best biocatalyst with a kcat/KM = 0.08 M/s. The protocols mentioned in this chapter meticulously cover the design, synthesis, self-assembly and enzyme kinetics.


Asunto(s)
Biocatálisis , Cobre , Cobre/química , Cinética , Priones/química , Priones/metabolismo , Cobalto/química , Péptidos/química , Péptidos/metabolismo , Secuencia de Aminoácidos , Catálisis , Hidrólisis
3.
Mol Biol Rep ; 51(1): 482, 2024 Apr 05.
Artículo en Inglés | MEDLINE | ID: mdl-38578512

RESUMEN

BACKGROUND: Natural bone grafts are the highly preferred materials for restoring the lost bone, while being constrained of donor availability and risk of disease transmission. As a result, tissue engineering is emerging as an efficacious and competitive technique for bone repair. Bone tissue engineering (TE) scaffolds to support bone regeneration and devoid of aforesaid limitations are being vastly explored and among these the avian eggshell membrane has drawn attention for TE owing to its low immunogenicity, similarity with the extracellular matrix, and easy availability. METHODOLOGY AND RESULTS: In this study, the development of bone ingrowth support system from avian eggshell membrane derived collagen hydrolysates (Col-h) is reported. The hydrolysate, cross-linked with glutaraldehyde, was developed into hydrogels with poly-(vinyl alcohol) (PVA) by freeze-thawing and further characterized with ATR-FTIR, XRD, FESEM. The biodegradability, swelling, mechanical, anti-microbial, and biocompatibility evaluation were performed further for the suitability in bone regeneration. The presence of amide I, amide III, and -OH functional groups at 1639 cm- 1,1264 cm- 1, and 3308 cm- 1 respectively and broad peak between 16°-21° (2θ) in XRD data reinstated the composition and form. CONCLUSIONS: The maximum ratio of Col-h/PVA that produced well defined hydrogels was 50:50. Though all the hydrogel matrices alluded towards their competitive attributes and applicability towards restorative bone repair, the hydrogel with 40:60 ratios showed better mechanical strength and cell proliferation than its counterparts. The prominent E. coli growth inhibition by the hydrogel matrices was also observed, along with excellent biocompatibility with MG-63 osteoblasts. The findings indicate strongly the promising application of avian eggshell-derived Col-h in supporting bone regeneration.


Asunto(s)
Cáscara de Huevo , Escherichia coli , Animales , Colágeno/farmacología , Andamios del Tejido , Ingeniería de Tejidos/métodos , Hidrogeles , Regeneración Ósea , Amidas
4.
Mol Biol Rep ; 51(1): 391, 2024 Mar 06.
Artículo en Inglés | MEDLINE | ID: mdl-38446253

RESUMEN

BACKGROUND: Corneal disease is a major cause of blindness. Transplantation of cadaver-derived corneas (keratoplasty) is still the current therapy of choice; however, the global shortage of donor corneas continues to drive a search for alternatives. To this end, biosynthetic corneal substitutes have recently begun to gain importance. Here, we present a novel method for the generation of a cornea-like tissue (CLT), using corneo-scleral rims discarded after keratoplasty. METHODS AND RESULTS: Type I collagen was polymerized within the corneo-scleral rim, which functioned as a 'host' mould, directing the 'guest' collagen to polymerize into disc-shaped cornea-like material (CLM), displaying the shape, curvature, thickness, and transparency of normal cornea. This polymerization of collagen appears to derive from some morphogenetic influence exerted by the corneo-scleral rim. Once the CLM had formed naturally, we used collagen crosslinking to fortify it, and then introduced cells to generate a stratified epithelial layer to create cornea-like tissue (CLT) displaying characteristics of native cornea. Through the excision and reuse of rims, each rim turned out to be useful for the generation of multiple cornea-shaped CLTs. CONCLUSIONS: The approach effectively helps to shorten the gap between demand and supply of CLMs/CLTs for transplantation. We are exploring the surgical transplantation of this CLT into animal eyes, as keratoprostheses, as a precursor to future applications involving human eyes. It is possible to use either the CLM or CLT, for patients with varying corneal blinding diseases.


Asunto(s)
Colágeno Tipo I , Córnea , Animales , Humanos , Morfogénesis , Polimerizacion
5.
Nanoscale ; 16(8): 4114-4124, 2024 Feb 22.
Artículo en Inglés | MEDLINE | ID: mdl-38353098

RESUMEN

Nucleic acid-based drugs are changing the scope of emerging medicine in preventing and treating diseases. Nanoparticle systems based on lipids and polymers developed to navigate tissue-level and cellular-level barriers are now emerging as vector systems that can be translated to clinical settings. A class of polymers, poly(ß-amino esters) (PBAEs) known for their chemical flexibility and biodegradability, has been explored for gene delivery. These polymers are sensitive to changes in the monomer composition affecting transfection efficiency. Hence to add functionality to these polymers, we partially substituted ligands to an identified effective polymer chemistry. We report here a new series of statistical copolymers based on PBAEs where the backbone is modified with sugar alcohols to selectively facilitate the caveolae-mediated endocytosis pathway of cellular transport. These ligands are grafted at the polymer's backbone, thereby establishing a new strategy of modification in PBAEs. We demonstrate that these polymers form nanoparticles with DNA, show effective complexation and cargo release, enter the cell via selective caveolae-mediated endocytosis, exhibit low cytotoxicity, and increase transfection in neuronal cells.


Asunto(s)
Nanopartículas , Poliésteres , Poliésteres/farmacología , Caveolas , Transfección , Polímeros/química , Endocitosis , Nanopartículas/química
6.
Biomacromolecules ; 25(2): 853-863, 2024 Feb 12.
Artículo en Inglés | MEDLINE | ID: mdl-38214450

RESUMEN

Injectable hydrogels with nonlinear mechanical attributes to emulate natural biopolymers hold paramount significance in tissue engineering, offering the potential to create scaffolds that seamlessly mimic the biomechanical intricacies of living tissues. Herein, we unveil a synthetic design strategy employing Schiff base chemistry to furnish a peptide-polymer hierarchical contractile injectable hydrogel network. This innovative design demonstrates cross-linking of supramolecular peptide nanostructures such as nanofibers, 1NF, and twisted bundles, 1TB, with a thermosensitive aldehyde-functionalized polymer, PCHO. These networks exhibit interesting nonlinear mechanical stiffening responses to temperature and external stress. Furthermore, the hydrogels transform into a gel state at physiological temperature to exhibit injectable behavior and demonstrate compression load-bearing capabilities. Finally, the hydrogel network exhibits excellent biocompatibility and cell proliferation toward fibroblast, L929, and myoblast, C2C12, to validate their use as potential extracellular matrix mimetic injectable scaffolds.


Asunto(s)
Calor , Hidrogeles , Hidrogeles/farmacología , Hidrogeles/química , Ingeniería de Tejidos , Polímeros , Biopolímeros , Proliferación Celular , Péptidos , Músculos
7.
Langmuir ; 40(5): 2754-2763, 2024 02 06.
Artículo en Inglés | MEDLINE | ID: mdl-38275136

RESUMEN

Peptide amphiphiles (PAs) are known for their remarkable ability to undergo molecular self-assembly, a process that is highly responsive to the local microenvironment. Herein, we design a pyrene tethered peptide amphiphile Py-VFFAKK, 1 that exhibits pathway-driven self-assembly from metastable nanoparticles to kinetically controlled nanofibers and thermodynamically stable twisted bundles upon modulations in pH, temperature, and chemical cues. The presence of the pyrene moiety ensures donation of the electron to an electron acceptor, namely, 7,7,8,8-tetracyanoquinodimethane (TCNQ), to form a supramolecular charge transfer complex in aqueous solution that was studied in detail with microscopic and spectroscopic techniques. Excitation of the donor species in its excimer state facilitates electron donation to the acceptor moiety, paving away a long-lived charge-separated state that persists for over a nanosecond, as ascertained through transient absorption spectroscopy. Finally, the self-assembled charge transfer complex is explored toward antimicrobial properties with Escherichia coli while maintaining biocompatibility toward L929 mice fibroblast cells.


Asunto(s)
Señales (Psicología) , Nanofibras , Animales , Ratones , Péptidos/farmacología , Péptidos/química , Análisis Espectral , Nanofibras/toxicidad , Nanofibras/química , Pirenos
8.
Chem Commun (Camb) ; 59(88): 13195-13198, 2023 Nov 02.
Artículo en Inglés | MEDLINE | ID: mdl-37850559

RESUMEN

We design amphiphilic di-block copolymers (P-b-F and P-b-C) tethered with stimuli-responsive ferrocene and coumarin hydrophobic pendants that exhibit chain collapse behaviour in response to light, redox and chemical cues, with subsequent transformation of the vesicles into micelles. Interestingly, the co-assembled vesicles of the polymer blend under orthogonal stimuli furnish self-sorted micelles and vesicles.

9.
Angew Chem Int Ed Engl ; 62(37): e202306751, 2023 Sep 11.
Artículo en Inglés | MEDLINE | ID: mdl-37483166

RESUMEN

Designing polymeric systems with ultra-high optical activity is instrumental in the pursuit of smart artificial chiroptical materials, including the fundamental understanding of structure/property relations. Herein, we report a diacetylene (DA) moiety flanked by chiral D- and L-FF dipeptide methyl esters that exhibits efficient topochemical photopolymerization in the solid phase to furnish polydiacetylene (PDA) with desired control over the chiroptical properties. The doping of the achiral gold nanoparticles provides plasmonic interaction with the PDAs to render asymmetric shape to the circular dichroism bands. With the judicious design of the chiral amino acid ligand appended to the AuNPs, we demonstrate the first example of selective chiral amplification mediated by stereo-structural matching of the polymer-plasmonic AuNP hybrid pairs. Such ordered self-assembly aided by topochemical polymerization in peptide-tethered PDA provides a smart strategy to produce soft responsive materials for applications in chiral photonics.

10.
ACS Appl Mater Interfaces ; 15(21): 25110-25121, 2023 May 31.
Artículo en Inglés | MEDLINE | ID: mdl-35767722

RESUMEN

Supramolecular assemblies with well-defined structural attenuation toward varied functional implications are an emerging area in mimicking natural biomaterials. In that regard, the redox stimuli-responsive ferrocene moiety can reversibly change between a nonpolar ferrocenyl and polar ferrocenium cation that endows interesting modular features to the building blocks with respect to self-assembly/disassembly. We design a series of ferrocene anchored peptide fragment NVFFAKKC using hydrophobic alkyl spacers of different chain lengths. Increasing the spacer length between the redox-responsive and self-assembling motifs increases the propensity to form robust nanofibers, which can be physically cross-linked to form hydrogels. The controlled redox response of the ferrocene moiety tandem with pH control provides access to structural control over the peptide nanostructures and tunable mechanical strengths. Further, such redox-sequestered dormant states hinder the spontaneous nucleation process that we exploit toward seeded supramolecular polymerization to form block cofibers composed of redox-responsive periphery and nonresponsive cores. Finally, such redox sequestration of peptide self-assembly renders an on-off piezoelectric response for potential utilization in peptide bioelectronics.


Asunto(s)
Nanofibras , Nanoestructuras , Metalocenos , Péptidos/química , Nanoestructuras/química , Nanofibras/química
11.
Nanoscale ; 14(40): 15079-15090, 2022 Oct 21.
Artículo en Inglés | MEDLINE | ID: mdl-36200975

RESUMEN

Stimuli-responsive self-assembled and supramolecular hydrogels derived from peptide amphiphiles have opened exciting new avenues in biomedicine and drug delivery. Herein, we screened a series of phenylalanine-amphiphiles possessing polyamine and oxyethylene appendages for their self-assembly and anion-responsiveness and found that the tris(aminoethyl)amine (TREN) containing amphiphile NapF-TREN formed injectable hydrogels that could be disrupted upon the addition of stoichiometric amounts of tetrahedral monovalent anions such as H2PO4- and HSO4-, while the addition of other anions such as Cl-, HPO42-, CO32-, HCO3- or SO42- did not affect the gel stability. The anion-gelator interaction was investigated by 1H and 31P NMR spectroscopy as well as by Isothermal Titration Calorimetry (ITC). These studies confirmed a 1 : 1 stoichiometry and revealed negative enthalpy and negative entropy for the binding of H2PO4- with NapF-TREN. Microscopic investigations by TEM, AFM, and SAXS revealed that H2PO4- anions induced a nanofiber-to-nanoglobule morphological change in the aqueous self-assemblies of NapF-TREN. However, upon ageing the samples, slow reformation of the nanofibers was also observed, reflecting the reversibility of the anion-gelator interaction. The anion- and pH-responsive nature of the NapF-TREN hydrogels was exploited to program sequential release of entrapped drugs propranolol and doxorubicin.


Asunto(s)
Hidrogeles , Fenilalanina , Hidrogeles/química , Propranolol , Dispersión del Ángulo Pequeño , Difracción de Rayos X , Aniones/química , Doxorrubicina/farmacología , Péptidos , Poliaminas
12.
Carbohydr Polym ; 297: 120007, 2022 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-36184135

RESUMEN

According to the global mapping of dry eye disease (DED), nearly 5 to 50 % of people suffer from DED, and this number is on the rise. The drug of choice Cyclosporine A (CsA) exhibits poor ocular bioavailability due to high molecular weight and lipophilicity. Moreover, formulations of CsA currently available are in the form of oil-based emulsions that are known to cause ocular irritation and pain. In this study, sulfobutylether-ß-cyclodextrin (SBE-ß-CD) based binary and ternary supramolecular complexes of CsA were developed as completely oil-free, and particle-free eye drops to treat DED. The physicochemical characterizations were supplemented with relevant in silico studies, to ascertain the findings. Further, the efficacy of the complexes was evaluated in the scopolamine-induced mouse model of DED. The complexation improved the CsA solubility by ~21-fold, with ~4-fold improvement in dissolution and transcorneal permeation. The non-irritancy and non-toxicity were confirmed by hen's egg chorioallantoic membrane assay and cytotoxicity assay using human corneal epithelial cells, respectively. The in vivo treatment with the ternary CD complex demonstrated better management of the dry eye supported by the tear volume assessment, corneal fluorescein staining, and histopathological studies of the cornea, lacrimal gland, and harderian gland. The study demonstrates the potential of the supramolecular complex as an alternative to the oil-based formulation of eye drops for drugs that show low solubility and poor corneal permeation.


Asunto(s)
Ciclodextrinas , Síndromes de Ojo Seco , Animales , Pollos , Córnea , Ciclosporina/química , Ciclosporina/farmacología , Ciclosporina/uso terapéutico , Síndromes de Ojo Seco/tratamiento farmacológico , Femenino , Fluoresceína , Humanos , Ratones , Soluciones Oftálmicas/farmacología , Soluciones Oftálmicas/uso terapéutico , Derivados de Escopolamina/uso terapéutico
13.
Mol Pharm ; 19(5): 1309-1324, 2022 05 02.
Artículo en Inglés | MEDLINE | ID: mdl-35333535

RESUMEN

Nucleic acids, both DNA and small RNAs, have emerged as potential therapeutics for the treatment of various lung disorders. However, delivery of nucleic acids to the lungs is challenging due to the barrier property imposed by mucus, which is further reinforced in disease conditions such as chronic obstructive pulmonary disease and asthma. The presence of negatively charged mucins imparts the electrostatic barrier property, and the mesh network structure of mucus provides steric hindrance to the delivery system. To overcome this, the delivery system either needs to be muco-inert with a low positive charge such that the interactions with mucus are minimized or should have the ability to transiently dismantle the mucus structure for effective penetration. We have developed a mucus penetrating system for the delivery of both small RNA and plasmid DNA independently. The nucleic acid core consists of a nucleic acid (pDNA/siRNA) and a cationic/amphipathic cell penetrating peptide. The mucus penetrating coating consists of the hydrophilic biopolymer chondroitin sulfate A (CS-A) conjugated with a mucolytic agent, mannitol. We hypothesize that the hydrophilic coating of CS-A would reduce the surface charge and decrease the interaction with negatively charged mucins, while the conjugated mannitol residues would disrupt the mucin-mucin interaction or decrease the viscosity of mucus by increasing the influx of water into the mucus. Our results indicate that CS-A-mannitol-coated nanocomplexes possess reduced surface charge, reduced viscosity of artificial mucus, and increased diffusion in mucin suspension as well as increased penetration through the artificial mucus layer as compared to the non-coated ones. Further, the coated nanocomplexes showed low cytotoxicity as well as higher transfection in A-549 and BEAS-2B cells as compared to the non-coated ones.


Asunto(s)
Péptidos de Penetración Celular , Nanopartículas , Ácidos Nucleicos , Péptidos de Penetración Celular/metabolismo , Portadores de Fármacos/química , Pulmón/metabolismo , Manitol/metabolismo , Mucinas/metabolismo , Moco/metabolismo , Nanopartículas/química , Ácidos Nucleicos/metabolismo
14.
ACS Biomater Sci Eng ; 7(12): 5798-5809, 2021 12 13.
Artículo en Inglés | MEDLINE | ID: mdl-34761897

RESUMEN

Tissue engineering demands intelligently designed scaffolds that encompass the properties of the target tissues in terms of mechanical and bioactive properties. An ideal scaffold for engineering a cartilage tissue should provide the chondrocytes with a favorable 3D microarchitecture apart from possessing optimal mechanical characteristics such as compressibility, energy dissipation, strain stiffening, etc. Herein, we used a unique design approach to develop a hydrogel having a dynamic interpenetrating network to serve as a framework to support chondrocyte growth and differentiation. An amyloid-inspired peptide amphiphile (1) was self-assembled to furnish kinetically controlled nanofibers and incorporated in a dynamic covalently cross-linked polysaccharide network of carboxymethyl cellulose dialdehyde (CMC-D) and carboxymethyl chitosan (CMCh) using Schiff base chemistry. The dynamic noncovalent interaction played a pivotal role in providing the desired modulation in the structure and mechanical properties of the double-network hydrogels that are imperative for cartilage scaffold design. The adaptable nature supported shear-induced extrusion of the hydrogel and facilitated various cellular functions while maintaining its integrity. The potential of the as-developed hydrogels to support in vitro chondrogenesis was explored using human chondrocytes. Evidence of improved cell growth and cartilage-specific ECM production confirmed the potential of the hydrogel to support cartilage tissue engineering while reaffirming the significance of mimicking the biophysical microenvironment to induce optimal tissue regeneration.


Asunto(s)
Condrogénesis , Hidrogeles , Condrocitos , Humanos , Péptidos , Ingeniería de Tejidos
15.
Nanoscale ; 13(31): 13401-13409, 2021 Aug 21.
Artículo en Inglés | MEDLINE | ID: mdl-34477745

RESUMEN

Enzymes are the most efficient catalysts in nature that possess an impressive range of catalytic activities, albeit limited by stability in adverse conditions. Functional peptides have emerged as alternative robust biocatalysts to mimic complex enzymes. Here, a rational design of minimalistic amyloid-inspired peptides 1-2 is demonstrated, which leads to pathway-driven self-assembly triggered by heat, light and chemical cues to render 1D and 2D nanostructures by the interplay of hydrogen bonding, host-guest interaction and reversible photodimerization. Such in situ transformable peptide nanostructures by means of external cues are envisaged as a catalytic amyloid for the first time to mimic the hydrolase enzyme activity. Michaelis Menten's enzyme kinetic parameters for the hydrolysis rate correlate the external cue-mediated structure-function augmentation with the twisted bundles, 1TB being the most efficient biocatalyst among all the dimensionally diverse nanostructures. Unlike the natural enzyme, the peptide nanostructures exhibited the robust nature of the hydrolase activity over a broad range of temperature and pH. Finally, the peptide nanostructures are explored as efficient heterogeneous flow catalysts to improve the turnover number for the hydrolase activity.


Asunto(s)
Hidrolasas , Nanoestructuras , Catálisis , Enlace de Hidrógeno , Péptidos
16.
ACS Omega ; 6(7): 4776-4782, 2021 Feb 23.
Artículo en Inglés | MEDLINE | ID: mdl-33644585

RESUMEN

The chemistry of the host-guest complex formation has received much attention as a highly efficient approach for use to develop economical adsorbents for water purification. In the present study, the synthesis of three ß-cyclodextrin (ß-CD) inclusion complexes with the oil orange SS (OOSS) azo dye as a guest molecule and their potential applications in water purification are described. The complexes were synthesized by the coprecipitation method and characterized by Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). FTIR and thermal analyses confirmed the encapsulation of OOSS dye within the hydrophobic cavity of ß-CD. The encapsulation of hydrophobic dye inside the ß-CD cavity was mainly due to the hydrophobic-hydrophobic interaction. The results showed that the stability of the OOSS dye had been improved after the complexation. The effect of three different compositions of the host-guest complexes was analyzed. The present study demonstrated that the hydrophobic dye could be removed from aqueous solution via inclusion complex formation. Thus, it can play a significant role in removing the highly toxic OOSS dye from the industrial effluent.

17.
RSC Adv ; 11(62): 39376-39386, 2021 Dec 06.
Artículo en Inglés | MEDLINE | ID: mdl-35492467

RESUMEN

Efficacy and durability of the photovoltaic device mandates its protection against hot, humid weather condition, high energy of UV light and unwanted scratches. Such challenges can be mitigated by smart polymeric coating with inherent properties e.g. hydrophobicity to prevent moisture, optimal viscocity for better processibility and crack-healing. The hydrophobic polymers TP1-TP4 containing pendant photo-crosslinkable thymine moieties are designed that undergo [2 + 2] photocycloaddition upon UVB irradiation and can be dynamically reverted back upon irradiation with UVC light. A judicious control of solvent environment, chain length, functionality% and concentration of the polymers regulate the aspects of photodimerization thereby, rendering intra or inter-chain collapse to form diverse nanostructures. Photodimerization of the thymine moieties renders coil to globule transformation in dilute condition whereas irradiation performed at high macromolecular concentration regime exhibits higher order nanostructures. The photoresponsive chain collapse leads to the formation of rigid crosslinked domains within flexible polymer chains akin to the hard-soft phases of thermoplastic elastomers. Such rigidification of the crosslinked segments endows a tool to photomodulate the glass transition temperature (T g) that can dynamically revert back upon decrosslinking. Further, the structural modulation of the polymers is explored towards autonomic and nonautonomic self-healing behaviour at ambient conditions. Moreover, the self-healing efficacy can be tuned with the film thickness and it remains unaltered upon using solar simulator or direct sunlight. Overall, such hydrophobic low T g polymers display photo-regulated self-healing mechanism consisting of both autonomic and non-autonomic self-healing and may find applications in designing smart protective coatings for photovoltaic devices.

18.
Nanoscale ; 12(36): 18692-18700, 2020 Sep 28.
Artículo en Inglés | MEDLINE | ID: mdl-32970093

RESUMEN

Self-sorting is a spontaneous phenomenon that ensures the formation of complex yet ordered multicomponent systems and conceptualizes the design of artificial and orthogonally functional compartments. In the present study, we envisage chirality-mediated self-sorting in ß-amyloid-inspired minimalistic peptide amphiphile (C10-l/d-VFFAKK)-based nanofibers. The fidelity and stereoselectivity of chiral self-sorting was ascertained by Förster resonance energy transfer (FRET) by the judicious choice of a pyrene (Py)-hydroxy coumarin (HOCou) donor-acceptor pair tethered to the peptide sequences. Seed-promoted elongation of the homochiral peptide amphiphiles investigated by AFM image analyses and Thioflavin-T (ThT) binding study further validated the chiral recognition of the l/d peptide nanofibers. Moreover, direct visualization of the chirality-driven self-sorted nanofibers is reported using super-resolution microscopy that exhibits enantioselective enzymatic degradation for l-peptide fibers. Such enantioselective weakening of the hydrogels may be used for designing stimuli-responsive orthogonal compartments for delivery applications.


Asunto(s)
Nanofibras , Péptidos , Secuencia de Aminoácidos , Amiloide , Hidrogeles
19.
Soft Matter ; 16(10): 2506-2515, 2020 Mar 11.
Artículo en Inglés | MEDLINE | ID: mdl-32090231

RESUMEN

Synthetic systems mimicking the natural self-folding process are attractive to impart multiple structural control over polymer crosslinking and the subsequent alteration of their macroscopic self-healing properties. In that regard, polymers P1-P5 containing pendant photo-crosslinkable moieties were designed and underwent intra- or interchain collapse to form diverse nanostructures. The shape and dimension of the nanostructures could be efficiently controlled by the concentration, solvent compatibility and characteristics of the polymers. Photodimerization of the coumarin moieties transformed the extended coiled chain of the polymer to uniform sized nanoparticles in a dilute condition, while in the crowded macromolecular concentration regime, the polymer folded into nanostructures with polydisperse topologies that were far from a condensed globule or partially swollen globule conformation. Scaling law exponents for polymer chain compaction suggested an interchain collapse with rigid compact segments connected by flexible polymer chains that draws an analogy with elastomers. Such a hardening of the rigid segment as a consequence of photodimerization rendered a significant increase in the glass transition temperature (Tg), which could be reversibly controlled upon decrosslinking. Lastly, the structural variation of this class of polymers over self-healing was explored and the crosslinked polymers showed phototriggered non-autonomic and intrinsic self-healing behaviour under ambient conditions. This is an interesting approach to access a photomodulated self-healing system with low Tg polymers that shows the coexistence of autonomic and nonautonomic self-healing pathways and that may find application in designing smart coatings for photovoltaic devices.

20.
ACS Appl Mater Interfaces ; 11(31): 28213-28220, 2019 Aug 07.
Artículo en Inglés | MEDLINE | ID: mdl-31305990

RESUMEN

Peptide 1 with an Aß42 amyloid nucleating core and a photodimerizable 4-methylcoumarin moiety at its N terminus demonstrates the step-wise self-assembly in water to form nanoparticles, with eventual transformation into 1D nanofibers. Addition of γ-cyclodextrin to 1 with subsequent irradiation with UV light at 320 nm resulted in morphological conversion to free-standing 2D nanosheets mediated by the host-guest interaction. Mechanical agitation of the 1D and 2D nanostructures led to seeds with narrow polydispersity indices, which by mediation of seeded supramolecular polymerization found seamless control over the dimensions of the nanostructures. Such structural and temporal control to differentiate the pathway was exploited to tune the mechanical strength of hierarchical hydrogel materials. Finally, the dimensional characteristics of the positively charged peptide fibers and sheets were envisaged as excellent exfoliating agents for inorganic hybrid materials, for example, MoS2.

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