Fluorescent proteins, such as the green fluorescent protein (GFP) discovered in Aequorea victoria, have revolutionized biological researches. Their fluorescence is primarily governed by a dye containing an imidazolinone motif that is buried within the protein core, as well as by its stabilization by the surrounding protein scaffold. Inspired by this structure-property relationship, researchers have developed synthetic imidazolinone-based dyes and engineered confined environments that emulate the folded protein cage. These complementary strategies overcome key limitations of the isolated natural dyes, including low brightness and quenching via twisted intramolecular charge transfer (TICT). This review examines the structural and photophysical properties of unnatural imidazolinone-based dyes, as well as the role of confinement in modulating their fluorescence. We compare covalent and non-covalent confinement approaches, highlighting their effects on brightness, stability, and functional versatility. Finally, we discuss emerging applications in imaging, sensing, photocatalysis, phototherapy, and optical devices. We also outline the challenges and opportunities of advancing confined imidazolinone fluorophores beyond natural protein frameworks.

The development of stimuli-responsive liposomes paves the way for targeted and controlled drug delivery. This includes thermoresponsive liposomes, in which increased temperature can promote bilayer destabilization. This thermoresponsiveness can be achieved by incorporating lipids with defined melting transitions or LCST-type polymers that are anchored to the membrane. In this study, we developed nanometric liposomes decorated with lipopolyproline, an LCST-type polymer anchored to the membrane. These systems, termed polyprolinated liposomes, were characterized by cryoSEM, cryoTEM, DLS, and 2H and 31P solid-state NMR to highlight the temperature-dependent changes in surface properties and morphology. Quantitative measurement of sulforhodamine B release demonstrated increased membrane permeability with temperature changes, highlighting the potential of polyprolinated liposomes as thermoresponsive drug delivery systems or drug reservoirs in multicompartmental systems.

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.

Creating platforms that support long-term cell culture under controlled conditions while preserving biological activity remains a major challenge. Liquefied microcapsules surrounded by a semi-permeable multilayered membrane prepared by the electrostatic-driven layer-by-layer (LbL) assembly of polyelectrolytes provide protective environments for cell encapsulation while preserving the mass transport required to sustain cell viability. However, strategies to enable on-demand capsule degradation and controlled release of encapsulated contents are limited. Herein, we report the design and development of alginate-based multilayered microcapsules encapsulating primary human adipose-derived mesenchymal stem cells and light-responsive biocompatible polymersomes loaded with alginate lyase. Upon light irradiation, polymersomes release the encapsulated enzyme into the surrounding medium, where it retains its catalytic activity, triggering the degradation of the microcapsule's core in a temporal manner and, ultimately, cell release. The critical role of the LbL-driven multilayered membrane shell in modulating the release profile is demonstrated, together with the biocompatibility of the compartmentalized system. This work proposes an unprecedented on-demand light-triggered cell delivery platform that integrates the stimuli-responsiveness of polymersomes with the protective nature, versatility, and structural advantages imparted by multilayered microcapsules, paving the way for the development of advanced (multi)compartmentalized stimuli-responsive systems for controlled drug/therapeutics/cell delivery, tissue engineering and regenerative medicine.

Amphiphiles based on elastin-like polypeptides (ELPs) offer a versatile platform for the design of nanostructured assemblies. However, the specific role of the hydrophobic tail architecture in governing the layer formation, assembly, and behavior remains largely unexplored. In this study, we compare the interfacial properties of two tailored ELP amphiphiles, ELP80-g-squalene (ELP80-g-SQ) and ELP80-g-dodecyl (ELP80-g-C12), which share an identical ELP backbone but differ in their hydrophobic substitution. Langmuir isotherms and Brewster angle microscopy were utilized to confirm the emergence of compact multilayer domains in ELP80-g-SQcontrasting with the homogeneous and fluid morphology of ELP80-g-C12. UV-vis reflection spectroscopy, ellipsometry, and contact angle studies align with the notion that these bio-based polymers readily scale up to bilayer and multilayer structures, while exhibiting divergent water retention properties. Squalene-based films are characterized by surface hydration and, consequently, a hydrophilic surface with the ELP exposed. This organization is instrumental in the promotion of water reduction through the process of evaporation. However, for ELP80-g-C12, the exposure of the dodecyl chains during layer transfer results in the promotion of a hydrophobic surface. Furthermore, their surface coverage facilitates enhanced water retention within the system. These findings suggest that, in the presence of bulky hydrophilic moieties, such as ELPs, trans-unsaturated chain interdigitation can promote the formation of rigid, multilayered architectures, in contrast to the disordered packing of saturated alkyl tails. The present study establishes a direct correlation between tail chemistry and interfacial packing, thereby providing mechanistic insight into the design of protein-based films for colloidal assemblies, membrane coatings, and biointerfacial engineering.

The development of stimuli-responsive liposomes paves the way for targeted and controlled drug delivery. This includes thermoresponsive liposomes, in which increased temperature can promote bilayer destabilization. This thermoresponsiveness can be achieved by incorporating lipids with defined melting transitions or LCST-type polymers that are anchored to the membrane. In this study, we developed nanometric liposomes decorated with lipopolyproline, an LCST-type polymer anchored to the membrane. These systems, termed polyprolinated liposomes, were characterized by cryoSEM, cryoTEM, DLS, and 2H and 31P solid-state NMR to highlight the temperature-dependent changes in surface properties and morphology. Quantitative measurement of sulforhodamine B release demonstrated increased membrane permeability with temperature changes, highlighting the potential of polyprolinated liposomes as thermoresponsive drug delivery systems or drug reservoirs in multicompartmental systems.

Neurological diseases remain a leading cause of disability and mortality, in part because systemically administered therapies poorly access diseased brain regions and lack spatiotemporal control. While innovative nanotechnologies offer stable and versatile carriers for drug delivery, they do not inherently enable localized, on-demand release. In parallel, optical neurotechnologies provide precise control of brain activity but cannot deliver bioactive molecules. Here, we bridge these approaches by developing photoactivatable vesicles based on polymeric amphiphiles (polymersomes) that enable light-triggered, spatially confined release of encapsulated compounds in brain tissue. We assessed their safety in primary cell cultures and in vivo. Through the photorelease of CNQX, a competitive AMPA/kainate receptor antagonist, we demonstrated the stability and precise spatiotemporal control of molecular delivery. This work establishes a platform for optically-guided chemical neuromodulation. Beyond applications in basic and preclinical neuroscience, this strategy opens new avenues for targeted therapies in localized brain disorders, including glioblastoma.

While polymersomes hold great promise as innovative drug delivery systems, their formulation is often hindered by the inherent complexity of self-assembly, where the competition between thermodynamically favored structures and kinetically trapped nonequilibrium states makes it particularly challenging to obtain homogeneous vesicle populations. We here report a robust and reproducible formulation method for the preparation of biodegradable polymersomes from PEG-b-PDLLA and PEG-b-PLGA block copolymers. By systematically varying solvent quality, water content and temperature, we demonstrate a sphere-to-worm-to-vesicle transition and how chain mobility and kinetic barriers dictate the self-assembly pathway from micelles to polymersomes. We thus establish a simple formulation strategy by finely balancing solvent quality and temperature to produce monodisperse, nanosized and dynamically stable polymersomes with a tunable membrane thickness. The incorporation of glycolide units further provides control over hydrolytic degradation while preserving the vesicle formation. Overall, this study establishes a rational framework for designing biodegradable polymersomes with predictable structural properties, reinforcing their potential for advanced nanomedicine applications.

Polypeptide-based block copolymers are promising platforms for creating hierarchical nanostructures because their secondary structures can direct mesoscale self-assembly. This study investigates how polypeptide chain length and thermal annealing govern the hierarchical organization of PEG-b-poly(ε-benzyloxycarbonyl-L-lysine) (PZLL) thin films. Combined FTIR, AFM, AFM-IR, and synchrotron GIWAXS/GISAXS analyses reveal that PZLL segments predominantly form α-helical conformations that assemble into hexagonally packed domains with nearly constant lattice parameters across compositions. Increasing the PZLL degree of polymerization stabilizes the α-helical structure, promotes preferential in-plane orientation of cylindrical domains, and enables the formation of long-range ordered fibrillar morphologies, whereas short PZLL chains partially transform into β-sheet structures during film formation and after high-temperature annealing. These findings establish a direct relationship between secondary structure, orientational ordering, and mesoscale morphology in self-assembled polypeptide block copolymer films.

Elastin-like polypeptides (ELPs) are promising drug delivery vehicles, yet their bioactivities remain underexplored, likely due to the lack of applicable protein delivery systems. To address this, here, a fusion protein ELP19 (19.5 kDa) and a β-glucan nanogel (for short, BGNG) system were designed and constructed. The BGNGs formed using dual phenylboronic acid (PBA)-functionalized poly(ethylene glycol) as a cross-linker through a reverse microemulsion method were utilized to individually load two different ELP variants (another ELP with a molecular weight of 17.035 kDa, termed as ELP17) for intracellular delivery and bioactivity investigation. The synthesized BGNGs with a size of 77.9 nm exhibit excellent protein-loading and delivery capabilities, and the developed BGNG/ELP complexes retain excellent colloidal stability and cytocompatibility. In vitro studies reveal that the BGNG-mediated intracellular delivery of ELP19 significantly promotes macrophage polarization toward the M2 phenotype, whereas the delivery of ELP17 shows no such effect. In addition, the BGNG/ELP19 complexes are able to maturate dendritic cells to generate immunogenicity, while BGNG/ELP17 complexes do not have such immunogenicity. These findings highlight the functional divergence between the two different ELP variants and underscore the potential of BGNGs as a protein carrier and ELP19 as a modulator of macrophages, providing a reference for the future biomedical application of BGNG-based nanoplatforms and ELP-based therapeutics.

Heme enzymes catalyze key oxidative reactions, yet their use in biotechnology is often limited by high production costs, low stability, and intricate operational conditions. Hemin, the catalytic iron-porphyrin cofactor of heme enzymes, has been explored as an alternative. However, its practical use is limited by its aggregation and deactivation in aqueous media. Here, we report a minimal biomimetic nanozyme based on the stabilization of hemin with bovine serum albumin (BSA) to enable aqueous catalysis and hydrogel formation under mild aqueous conditions. Through alkaline-mediated synthesis, hemin was stabilized with BSA, allowing the generation of a Hemin@BSA noncovalent hybrid with peroxidase- and catalase-like activity, outperforming free hemin or BSA complexed with hemin prepared under physiological conditions. Beyond standard peroxidase assays, Hemin@BSA catalyzed the oxidative C-C coupling of N-acetyl-tyrosine (NAT), yielding dityrosine as the main product. This enzymatic-like property was successfully applied at the macromolecular level, enabling the crosslinking of hyaluronic acid-tyramine (HA-TyrA) conjugates, yielding the formation of hydrogel networks with mechanical properties comparable to HRP-mediated crosslinked hydrogels. The cytotoxicity of hemin and Hemin@BSA was evaluated in both U87 glioblastoma and normal human astrocytes (NHA) cells, while cellular uptake and reactive oxygen species (ROS) generation were investigated in U87 cells, demonstrating efficient cellular uptake of Hemin@BSA and higher ROS levels induced by free hemin compared with Hemin@BSA. Overall, simple heme-protein complexes lie as the interface between molecular catalysts and functional biomaterials. They provide a low-cost and robust alternative to natural peroxidases, making them promising tools for creating redox-based hydrogels towards biomedical applications.

The extracellular matrix (ECM) is one of the most striking natural self-assembled landscapes, essential for tissue integrity and cellular functions, where it orchestrates cell fate through a dynamic interplay of noncovalent interactions. Despite decades of research, there is still no scaffold that can replicate its nanostructural elegance and functional dynamic behavior. In this Perspective, we summarize cutting-edge approaches to reconstruct the ECM, putting an emphasis on either dynamic supramolecular designs or naturally sourced biopolymers. We then propose merging the natural with the synthetic world to enable hybrid cell-instructive materials that combine the dynamic mechanical profile, biomolecular composition and structural features of the ECM at all scales, from the nano- to the mesoscale, aiming to create a fully functional artificial ECM.

Guest Editors João Borges, Patricia Y. W. Dankers, João F. Mano and Sébastien Lecommandoux introduce a Journal of Materials Chemistry B themed collection presenting the latest developments in the field of bioinspired functional supramolecular systems.

Polypeptide-based nanocarriers are key to the field of drug delivery, however the influence of morphology on their performance remains underexplored. In this study, we present a novel method for the synthesis of fluorescent worm-like nanoparticles, namely the one-step aqueous ring-opening polymerization-induced self-assembly (ROPISA) of γ-benzyl-l-glutamate N-carboxyanhydride (BLG-NCA). To assess the comparative efficacy of this formulation, we prepared spherical analogues via solvent displacement, enabling direct evaluation of their cellular uptake and in vivo biodistribution. Using CT26 (colorectal carcinoma) and 4T1 (triple-negative breast cancer) models, which have been shown to exhibit different tumor vascularity and permeability, we first examined internalization in 2D cultures and 3D spheroids. The results demonstrated that both morphologies efficiently internalized, with faster uptake observed in CT26 cells but higher accumulation seen in 4T1 cells. In 3D spheroids, both nanoparticles penetrated tumor-like structures, although diffusion was slower in 4T1 spheroids but resulted in higher final accumulation. In vivo, prolonged circulation and significant tumor accumulation were then monitored in both models, especially in 4T1 tumors. These findings highlight ROPISA of NCA as a robust platform for polypeptide nanocarrier synthesis, thereby paving the way for drug-loaded nanoparticles via covalent grafting or in situ encapsulation and thus advancing nanomedicine for precision drug delivery.

Over the past three decades, the field of peptide-based materials has been rapidly expanding and evolving, becoming a multidisciplinary area, with new developments and applications being consistently discovered. The purpose of this Peptide Materials Special Issue is to highlight research presented at the first Gordon Research Conference on Peptide Materials in January, 2023. Consequently, we invited eminent scientists with primary research interests in Peptide Materials to contribute original research articles or short reviews in this area. This thematic issue is focused on the materials aspects of peptides and their derivatives and mimics, including both fundamental research in peptide design, synthesis, assembly, micellization, gelation, and coacervation, as well as disparate technological applications, including functional materials for energy storage, catalysis, drug delivery, regenerative medicine, adhesion, protein purification, and nanotechnology. As peptides are composed of amino acids─the fundamental building blocks of proteins─they serve as a natural bridge between small-molecule supramolecular assemblies and large biomacromolecular constructs. Their ability to adopt well-defined secondary and tertiary structures, undergo hierarchical self-assembly, and exhibit tunable biochemical properties and distinct structural features highlights their importance and relevance within the broader landscape of biomacromolecular research. The peptide materials field has become a well-established, interdisciplinary area that attracts chemists, chemical engineers, material scientists, physicists, and biomedical engineers. The papers collected in this special issue demonstrate the growing recognition of peptides, polypeptides, proteins, and their derivatives and mimics as a versatile and critical class of biomacromolecules, poised to drive continued growth and innovation across diverse scientific and technological disciplines.

Secondary alpha-helix and beta-sheet structures are key scaffolds around which the rest of the residues condense during protein folding. Despite their key role in numerous processes to maintain life, little is known about their properties under force. Their stability under mechanical stress, as constantly experienced in the turbulent environment of cells, is however essential. Here, we designed and synthesized two pH-responsive polypeptides, poly(l-glutamic acid) and poly(l-lysine), for single-molecule mechanochemistry experiments using AFM to probe the mechanical unfolding of alpha-helix and beta-sheet secondary motifs. The force experiments, supported by simulations, reveal a superior mechanical stability of the poly(l-lysine) alpha-helix, which we attribute to hydrophobic interactions of the alkyl side chains. Most importantly, our results show that these interactions play a key role in inhibiting the formation of a metastable beta-sheet-like structure when the polypeptide is subjected to mechanical deformations, which might have important implications in the mechanism behind polyQ diseases.

A recent method for producing amphiphilic block copolymers and nano-objects based on the ring-opening polymerization-induced self-assembly (ROPISA) in aqueous buffer is explored with respect to the tunability toward nanostructures. ROPISA gives rise to polypeptide copolymers with unprecedented levels of organization. By employing amphiphilic block copolymers of poly(ethylene glycol) (PEG) with the synthetic polypeptide poly(γ-benzyl-l-glutamate) (PBLG) and a combination of static (13C NMR, X-ray scattering, polarizing optical microscopy), thermodynamic (differential scanning calorimetry), and dynamic (dielectric spectroscopy) probes, we demonstrate a record of six levels of organization only found before in natural materials. These levels of organization could not be obtained in earlier morphology investigations of copolymers based on PEG and PBLG prepared by different methods. Furthermore, the type of NCA monomer (BLG-NCA vs Leu-NCA) and the solvent treatment method had an influence on the degree of segregation, the α-helical content, and the order-to-disorder transition temperature in the PEG-b-PBLG and PEG-b-PLeu copolymers.