Stimuli-responsive peptide assemblies: Design, self-assembly, modulation, and biomedical applications

Peptide molecules have design flexibility, self-assembly ability, high biocompatibility, good biodegradability, and easy functionalization, which promote their applications as versatile biomaterials for tissue engineering and biomedicine. In addition, the functionalization of self-assembled peptide nanomaterials with other additive components enhances their stimuli-responsive functions, promoting function-specific applications that induced by both internal and external stimulations. In this review, we demonstrate recent advance in the peptide molecular design, self-assembly, functional tailoring, and biomedical applications of peptide-based nanomaterials. The strategies on the design and synthesis of single, dual, and multiple stimuli-responsive peptide-based nanomaterials with various dimensions are analyzed, and the functional regulation of peptide nanomaterials with active components such as metal/metal oxide, DNA/RNA, polysaccharides, photosensitizers, 2D materials, and others are discussed. In addition, the designed peptide-based nanomaterials with temperature-, pH-, ion-, light-, enzyme-, and ROS-responsive abilities for drug delivery, bioimaging, cancer therapy, gene therapy, antibacterial, as well as wound healing and dressing applications are presented and discussed. This comprehensive review provides detailed methodologies and advanced techniques on the synthesis of peptide nanomaterials from molecular biology, materials science, and nanotechnology, which will guide and inspire the molecular level design of peptides with specific and multiple functions for function-specific applications.

Synthesis of new chrysin derivatives with substantial antibiofilm activity

Multidrug resistance mechanism of microorganisms towards conventional antimicrobials nowadays faces a common health problem. So, searching and development of new antibacterials are in the frontier areas of biochemistry. Functionalizations of various natural products or synthesis of compounds through molecular modeling followed by virtual screening are the ways to obtain potential leads. Chrysin is one of the plant secondary metabolites and is ubiquitously present in majority of plants. It has multi-dimensional potentiality however, with a very low bioavailability causing a very low efficacy. Very few chrysin derivatives possessing antimicrobial activity with a low anti-biofilm efficacy have been found in the literature. Thus, it has been attempted to synthesize a series of new chrysin derivatives (CDs). In this study, twenty-two new derivatives have been synthesized via its 7-OH modulation and antibiofilm activity was evaluated against a model bacterium viz. Escherichia coli MTCC 40 (Gram negative). Eleven CDs coded as 2a, 2b, 2c, 2e, 2f, 2g, 2h, 2i, 3j, 3k and 3l have been found more potent compared to chrysin (precursor of CDs) against planktonic form of E. coli. Biofilm inhibition studies indicated a noteworthy results for 2a (93.57%), 2b (92.14%), 2f (92.14%) and 3l (93.57%) compared to chrysin (33.57%). E. coli motility was also highly restricted by 2a, 2b, 2f and 3l than chrysin at their sub-inhibitory concentrations. Solubility studies indicated an extended-release of 2a, 2b, 2f and 3l in physiological systems. Relatively higher bioavailability of 2a, 2b, 2f and 3l than chrysin was revealed from the dissolution experiments and was further validated through in silico ADME-based SAR analysis. Hence, this study is more interesting in regard to antibacterial potentiality of chrysin derivatives against Escherichia coli MTCC 40 (Gram negative). Thus, this article might be useful for further design and development of new leads in the context of biofilm-associated bacterial infections.

Identification of structural elements involved in fine-tuning of the transport activity of the rice ammonium transporter OsAMT1;3

Ammonium transporters (AMTs) are major routes for plant uptake of the NH₄⁺-form nitrogen. Plant AMTs mediate predominantly the uptake of NH₄⁺ and to a lesser extent, its organic analog methylammonium (MeA⁺). Mutagenesis studies on potential phosphorylation residues have achieved solid recognition that alteration of the phosphorylation status can result in allosteric regulation and impair the functionality of plant AMTs. However, molecular insights to the fine-tuning of a functional ammonium transporter remain less clear. In this report, we demonstrate that the rice root expressed OsAMT1;3 (Oryza sativa ammonium transporter 1;3) functions as a typical high-affinity NH₄⁺ transporter and is weakly permeable to MeA⁺ using growth assays in NH₄⁺ uptake defective yeast cells and electrophysiological measurements in Xenopus oocytes. Upon screening of six point mutations generated with the transporter, we identified two amino acid residues involved in the functional modulation of OsAMT1;3. The H199E mutation caused loss of transport activity whereas other five mutations retained the functionality of OsAMT1;3. Furthermore, the L56F mutation enabled respectively 5- and 3.5 -fold increased capability for NH₄⁺ and MeA⁺ uptake with several-fold decreased affinity (K_m) and accelerated V_max values. Surprisingly, yeast cells expressing the L56F mutation shown increased Na⁺ toxicity leading to a speculation that enhanced Na⁺ permeation occurred with this mutation. The phenomenon was further supported by the observation of significant Na⁺ uptake current in oocytes. Our results seemingly support a speculation that the L56F mutation of OsAMT1;3 widens the substrate passage tunnel and allows enhanced permeability to NH₄⁺ and larger ions MeA⁺ and Na⁺.