Peptide nanostructures are biodegradable and are suitable for many biomedical applications. However, to be useful imaging probes, the limited intrinsic optical properties of peptides must be overcome. Here we show the formation of tryptophan-phenylalanine dipeptide nanoparticles (DNPs) that can shift the peptide's intrinsic fluorescent signal from the ultraviolet to the visible range. The visible emission signal allows the DNPs to act as imaging and sensing probes. The peptide design is inspired by the red shift seen in the yellow fluorescent protein that results from π-π stacking and by the enhanced fluorescence intensity seen in the green fluorescent protein mutant, BFPms1, which results from the structure rigidification by Zn(II). We show that DNPs are photostable, biocompatible and have a narrow emission bandwidth and visible fluorescence properties. DNPs functionalized with the MUC1 aptamer and doxorubicin can target cancer cells and can be used to image and monitor drug release in real time.
Over 130 y have passed since Charles Darwin first discovered that the adventitious roots of English ivy (Hedera helix) exude a yellowish mucilage that promotes the capacity of this plant to climb vertical surfaces. Unfortunately, little progress has been made in elucidating the adhesion mechanisms underlying this high-strength adhesive. In the previous studies, spherical nanoparticles were observed in the viscous exudate. Here we show that these nanoparticles are predominantly composed of arabinogalactan proteins (AGPs), a superfamily of hydroxyproline-rich glycoproteins present in the extracellular spaces of plant cells. The spheroidal shape of the AGP-rich ivy nanoparticles results in a low viscosity of the ivy adhesive, and thus a favorable wetting behavior on the surface of substrates. Meanwhile, calciumdriven electrostatic interactions among carboxyl groups of the AGPs and the pectic acids give rise to the cross-linking of the exuded adhesive substances, favor subsequent curing (hardening) via formation of an adhesive film, and eventually promote the generation of mechanical interlocking between the adventitious roots of English ivy and the surface of substrates. Inspired by these molecular events, a reconstructed ivy-mimetic adhesive composite was developed by integrating purified AGP-rich ivy nanoparticles with pectic polysaccharides and calcium ions. Information gained from the subsequent tensile tests, in turn, substantiated the proposed adhesion mechanisms underlying the ivy-derived adhesive. Given that AGPs and pectic polysaccharides are also observed in bioadhesives exuded by other climbing plants, the adhesion mechanisms revealed by English ivy may forward the progress toward understanding the general principles underlying diverse botanic adhesives.ivy nanoparticle | ivy adhesive | arabinogalactan protein | adhesion mechanism | reconstructed adhesive A lthough there is a growing interest in exploring mechanisms regulating a variety of adhesive behaviors in the animal kingdom (1-6), the molecular basis allowing creeping plants, such as English ivy (Hedera helix), to generate sufficient adhesive force, aiding in clinging to vertical surfaces, is rarely discussed (Fig. 1A). Previous studies have emphasized mechanical strategies exploited by multiple climbing organs that evolve in plants (7-11). Nevertheless, the role of the glue-like viscous exudates that are observed on the majority of these organs and that cement the plants to the substrates has been less explored (10,12,13). Diverse polysaccharides and glycoproteins, comprising mucilaginous pectins, arabinogalactans, arabinogalactan proteins (AGPs), and many others, have been identified to be the predominant components in these adhesive substances (14-17); however, the molecular mechanisms underlying the high-strength adhesion remain elusive.By means of atomic force microscopy (AFM), bulk spherical organic nanoparticles have been observed in the exudates derived from the root hairs of English ivy (18-20). These proteinaceous nanoparticles are presum...
While tremendous efforts have been made in investigating scalable approaches for fabricating nanoparticles, less progress has been made in scalable synthesis of cyclic peptide nanoparticles and nanotubes, despite their great potential for broader biomedical applications. In this paper, tunable synthesis of self-assembled cyclic peptide nanotubes and nanoparticles using three different methods, phase equilibrium, pH-driven, and pH-sensitive methods, were proposed and investigated. The goal is scalable nanomanufacturing of cyclic peptide nanoparticles and nanotubes with different sizes in large quality by controlling multiple process parameters. Cyclo-(L-Gln-D-Ala-L-Glu-D-Ala-)2 was applied to illustrate the proposed ideas. In the study, mass spectrometry and high performance liquid chromatography were employed to verify the chemical structures and purity of the cyclic peptides. Morphology and size of the synthesized nanomaterials were characterized using atomic force microscopy and dynamic light scattering. The dimensions of the self-assembled nanostructures were found to be strongly influenced by the cyclic peptide concentration, side chain modification, pH values, reaction time, stirring intensity, and sonication time. This paper proposed an overall strategy to integrate all the parameters to achieve optimal synthesis outputs. Mechanisms of the self-assembly of the cyclic peptide nanotubes and nanoparticles under variable conditions and tunable parameters were discussed. This study contributes to scalable nanomanufacturing of cyclic peptide based self-assembled nanoparticles and nanotubes for broader biomedical applications.
Bioadhesives have drawn increasing interest in recent years, owing to their ecofriendly, biocompatible and biodegradable nature. As a typical bioadhesive, sticky exudate observed on the stalked glands of sundew plants aids in the capture of insects and this viscoelastic adhesive has triggered extensive interests in revealing the implied adhesion mechanisms. Despite the significant progress that has been made, the structural traits of the sundew adhesive, especially the morphological characteristics in nanoscale, which may give rise to the viscous and elastic properties of this mucilage, remain unclear. Here, we show that the sundew adhesive is a naturally occurring hydrogel, consisting of nanonetwork architectures assembled with polysaccharides. The assembly process of the polysaccharides in this hydrogel is proposed to be driven by electrostatic interactions mediated with divalent cations. Negatively charged nanoparticles, with an average diameter of 231.9 + 14.8 nm, are also obtained from this hydrogel and these nanoparticles are presumed to exert vital roles in the assembly of the nano-networks. Further characterization via atomic force microscopy indicates that the stretching deformation of the sundew adhesive is associated with the flexibility of its fibrous architectures. It is also observed that the adhesion strength of the sundew adhesive is susceptible to low temperatures. Both elasticity and adhesion strength of the sundew adhesive reduce in response to lowering the ambient temperature. The feasibility of applying sundew adhesive for tissue engineering is subsequently explored in this study. Results show that the fibrous scaffolds obtained from sundew adhesive are capable of increasing the adhesion of multiple types of cells, including fibroblast cells and smooth muscle cells, a property that results from the enhanced adsorption of serum proteins. In addition, in light of the weak cytotoxic activity exhibited by these scaffolds towards a variety of mammal cells, evidence is sufficient to propose that sundew adhesive is a promising nanomaterial worth further exploitation in the field of tissue engineering.
The construction of a new set of [(eta5-C5Me5)MoS3Cu3]-based supramolecular compounds with different one-dimensional (1D) arrays from two preformed clusters [PPh4][(eta5-C5Me5)MoS3(CuX)3] (X = Br (1a), NCS (1b)) with 1,2-bis(4-pyridyl)ethane (bpe) and 1,3-bis(4-pyridyl)propane (bpp) is presented. Reactions of 1a with bpe in different molar ratios afforded ([((eta5-C5Me5)MoS3Cu3) 2(mu-bpe)3.5Br4].MeCN) n (2), ([((eta5-C5Me5)MoS3Cu3)2(mu-bpe)3Br4].Sol)n (3a: Sol = DMSO.3MeCN; 3b: Sol = 2aniline.3MeCN), ([((eta5-C 5Me5)MoS3Cu3)2(mu-bpe)3(bpe)Br4].0.35DMF)n (4), and ([((eta5-C5Me5)MoS3Cu3)2(mu-bpe)2(mu-Br)(mu3-Br)Br2].DMF.MeCN)n (5). On the other hand, treatment of 1a or 1b with bpp produced [(eta5-C5Me5)MoS3Cu3(mu-bpp)(mu-Br)Br]n (6) and ([((eta5-C5Me5)MoS3Cu3)2(mu-bpp)3(mu-NCS)2(NCS)](NCS))n (7). Compounds 2-7 have been characterized by elemental analysis, UV-vis spectroscopy, IR spectroscopy, 1H NMR, and X-ray analysis. In 2, each [(eta5-C5Me5)MoS3Cu3] core serves as an angular two-connecting node to link other equivalent cores by single and double bpe bridges to form a 1D "Great Wall"-like chain. In 3a and 3b, the [(eta5-C5Me5)MoS3Cu3] cores are linked alternatively by single and double bpe bridges to give a 1D zigzag chain. In 4, six cluster cores (two as a two-connecting node and four as a three-connecting node) are connected by four single bpe and two double bpe bridges to form a cyclohexane-shaped repeating unit, which is further fused with other units to generate a 1D double-stranded chain. Compound 5 has a simple 1D zigzag chain consisting of the cluster cores linked by single bpe bridges. In 6, the cluster cores are linked by single bpp bridges to give a 1D helical chain, which further holds two symmetry-related chains through C-H...Br hydrogen-bonding interactions, thereby forming a 1D H-bonded triple-stranded chain. Compound 7 has a rare 1D quadruple chain, in which the [(eta5-C5Me5)MoS3Cu3] cores work as planar four- and five-connecting nodes to interconnect other equivalent cores through single bpp bridges and single and double thiocyanate bridges. In addition, the third-order nonlinear optical properties of 1a, 2, 3a, and 4-7 in aniline were also investigated by using the Z-scan technique with a 4.5 ns pulse laser at 532 nm.
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