Fluorescent nanoparticles are widely used in bioimaging and sensing, yet their preparation relies on multistep synthetic routes that limit scalability and structural control. Here we introduce a one-pot strategy that couples aqueous ring-opening polymerization-induced self-assembly (ROPISA) of γ-propargyl-L-glutamate N-carboxyanhydride with copper-catalyzed azide-alkyne cycloaddition (CuAAC) to produce fluorescent polypeptide nanoparticles. This one-pot "Click'n ROPISA" process enables the simultaneous formation of polypeptide nano-objects and covalent incorporation of diverse azido-functionalized fluorophores. The resulting assemblies exhibit tunable emission across the visible spectrum and are accessible at high solids content while maintaining high brightness and structural uniformity. Dense fluorophore incorporation enables efficient Förster resonance energy transfer (FRET) both within the assemblies and with dye-labeled proteins, supporting sensing applications. The intense brightness of the red-emitting nanoparticles further enables single-particle tracking in microscopy toward advanced bioimaging.
Polypeptides are emerging as an integral part of biomaterial research because of their unique ability to mimic natural protein-like secondary structures in water; however, they require a multistep self-assembly process to yield desired nano-sized objects for intended biomedical applications. In this study, we report a one-pot photo-crosslink strategy for stable polypeptide nanoparticle self-assembly by ring-opening polymerization-induced self-assembly (ROPISA) route. For this purpose, a cinnamoyl functionalized l-serine based N-carboxyanhydride (NCA) monomer is designed and subjected to ROPISA using PEG-amine as a hydrophilic macroinitiator in water which produced stable opalescent dispersions of amphiphilic PEG-polypeptide di-block copolymers having narrow molecular weights. Dynamic light scattering and HR-TEM analysis revealed the formation of spherical nanoparticles of 25-30 nm in size. The cinnamoyl anchored polypeptides underwent [2+2] cycloaddition under UV irradiation (265 nm) and the occurrence of the photo-crosslinking and its kinetics is studied by UV-visible spectroscopy. Notably, the nanoparticle size and structural integrity is remained unchanged and the particle morphology is found to be very stable. The core-cross-linked nanoparticles is found to be stable and behave as efficient scaffold for loading both water soluble and insoluble cargoes. This report opens an avenue to access photo-crosslinkable polypeptide nano-assemblies in the literature.
A. Prasad, Parshuram Kambale, R. Nisal et al.· Chemistry - An Asian Journal· 0 citations
We report the rational engineering of a two-α-helix protein via site-directed mutagenesis, wherein histidine residues at the native catalytic active site were substituted with cysteines and tyrosine residues were introduced in close proximity to these cysteine residues. This modification enabled the site-directed reduction and nucleation of free gold ions into size-tunable gold nanoclusters (AuNCs) exhibiting red, green, and blue photoluminescence upon ultraviolet excitation. Furthermore, by modulating the solution pH, we successfully fabricated nanofibers via the co-assembly of the protein and AuNCs. Comprehensive structural characterization confirmed the architecture of these biohybrid materials. Protein-AuNCs can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB), exhibiting peroxidase-like activity under specific conditions. Furthermore, this peroxidase-like activity was successfully applied to the colorimetric detection of glutathione with a linear response in the concentration range of 100–300 μM.
Yaoyu Liang, Jingsong Ma, Lei Shang et al.· ACS Applied Nano Materials· 0 citations
We introduce a modular platform for engineering excimer-active fluorescent nanoclays by covalently installing pyrene onto imidazolium-functionalized polyionic nanoclays (PINCs) using thiol-maleimide Michael addition. Precise control of pyrene surface densities (0.1–15 mol %) affords a synthetically tunable monomer–excimer landscape, with systematic shifts in excimer-to-monomer intensity ratios (IE/IM) and solvent-dependent photophysics that confirm periodic probe spacing rather than clustering. The cationic PINC framework dramatically enhances analyte accessibility and local concentration, enabling solution-phase detection of nitroaromatic and nitrate-based explosives with Stern–Volmer constants of up to 1.56 × 104 M–1 for TNT, an order-of-magnitude enhancement over neutral pyrene (Py) controls. Py-PINCs also exhibit strong and selective quenching by halides, highlighting synergistic electrostatic and collisional pathways. In the solid state, PINC-immobilized pyrene functions as an environment-responsive oxygen sensor, displaying linear quenching (KSV = 5.29 bar–1) and a rapid reversible response (2.5 s). These results establish pyrene-tagged PINCs as an attractive class of charge-amplified, excimer-programmable 2D hybrid materials that unify tunable photophysics with multimodal chemical sensing, expanding the functional scope of designer PINCs for security, environmental, and analytical technologies.
Piyuni Ishtaweera, N. E. Larm, Gary A. Baker· ACS Applied Nano Materials· 0 citations
Herein, we report a modular and biocompatible platform of Cu-catalyzed azide–alkyne cycloaddition (CuAAC)-compatible acylgermanes. Broad functional-group tolerance is demonstrated by a library of novel derivatives that were isolated and characterized by NMR, UV/Vis spectroscopy, and mass spectrometry, with selected structures confirmed by single-crystal X-ray diffraction. We also disclose the first acylgermanes bearing unprotected carbohydrate motifs, whose marked polarity enabled initial biological assessment. Representative examples showed low cytotoxicity and measurable affinity for lipid bilayers in assays with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) large unilamellar vesicles. Photo-DSC and photo-CIDNP experiments confirmed efficient photoinitiation and radical pathways characteristic of this class. Coupling acylgermane chemistry with robust CuAAC click methodology expands the scope of acylgermane photoinitiators, enabling rapid late-stage functionalization with diverse motifs and opening routes to complex materials and entry into biological applications.
A. Ćulum, Julia Fuchs, Carolyn Vargas et al.· Organic Chemistry Frontiers· 0 citations
Polypeptides are protein-like synthetic macromolecules that often require tedious post-polymerization self-assembly to encapsulate drugs or genes. Developing nanotechnology platforms for the on-demand loading of cargoes during synthesis in water would yield directly injectable nanoformulations for immediate healthcare applications. Here, we report one of the first attempts to construct an aqueous-medium-stabilized β-sheet poly(L-tyrosine) block copolymer polypeptide nanoparticle formulation via a ring-opening polymerization-induced self-assembly (ROPISA) process. The synthetic scope of the methodology is further expanded to include the in situ encapsulation of biologically relevant fluorophore molecules, which are purified by a simple dialysis process and directly injected for in vitro and in vivo studies in biological systems. The β-sheet polypeptide nanoformulation is non-toxic to cells at up to 100 μg mL-1, non-hemolytic to red blood cells, and readily endocytosed across the cell membranes, as substantiated by confocal microscopy imaging. A deep-tissue penetrable near-infrared IR-780 biomarker-loaded nanoformulation is employed for biodistribution studies in live animals (mice). The β-sheet polypeptide formulation is stable under blood circulation, and ex vivo tissue imaging established their accumulation largely in the digestive organs. This approach paves the way for the direct injectable polypeptide nanoformulations in drug delivery.
Parshuram Kambale, Sayali H Jadhav, R. Nisal et al.· Nanoscale· 0 citations
In this work, a green and sustainable hydrothermal approach was employed to synthesize nitrogen-doped carbon dots (NCDs) using lemon juice as a natural precursor. The as-prepared NCDs served as eco-friendly reducing agents and stabilizing scaffolds for the subsequent in situ synthesis of gold nanoparticles (Au@NCDs). The structural and optical properties of the nanocomposite were comprehensively characterized using various analytical techniques. The intrinsic fluorescence of NCDs was significantly quenched upon formation of the composite, mainly due to non-radiative energy transfer processes. Interestingly, the quenched fluorescence could be efficiently restored upon the addition of N-acetylcysteine (NAC), enabling the development of an “off-on” fluorescent sensing platform. The sensing mechanism was systematically elucidated through a combination of spectroscopic studies and density functional theory calculations, revealing that fluorescence recovery originates from a ligand exchange process driven by the stronger binding affinity of NAC toward the gold surface, particularly via Au–S interactions. Under optimized conditions, the assay exhibited a robust linear response for NAC concentrations ranging from 4.0 to 20.0 mg/L, with a detection limit of 0.863 mg/L. These results demonstrate that the Au@NCDs system can function as a sensitive and selective OFF–ON fluorescent probe for NAC detection. This study provides a cost-effective and eco-friendly sensing platform with significant potential for analytical applications in pharmaceutical monitoring.
T. Nguyen, V. Nguyen, Ha Thi Thu Nguyen et al.· Beilstein Journal of Nanotec...· 0 citations
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