A Hydroxylamine-Mediated Amidination of Lysine Residues That Retains the Protein's Positive Charge.

Lysine-specific peptide and protein modification strategies are widely used to study charge-related functions and applications. However, these strategies often result in the loss of the positive charge on lysine, significantly impacting the charge-related properties of proteins. Herein, we report a strategy to preserve the positive charge and selectively convert amines in lysine side chains to amidines using nitriles and hydroxylamine under aqueous conditions. Various unprotected peptides and proteins were successfully modified with a high conversion rate. Moreover, the reactive amidine moiety and derived modification site enable subsequent secondary modifications. Notably, positive charges were retained during the modification. Therefore, positive charge-related protein properties, such as liquid‒liquid phase separation behaviour of α-synuclein, were not affected. This strategy was subsequently applied to a lysine rich protein to develop an amidine-containing coacervate DNA complex with outstanding mechanical properties. Overall, our innovative strategy provides a new avenue to explore the characteristics of positively charged proteins.

Biomimetic Mineralization: From Microscopic to Macroscopic Materials and Their Biomedical Applications.

Biomineralization is an attractive pathway to produce mineral-based biomaterials with high performance and hierarchical structures. To date, the biomineralization process and mechanism have been extensively studied, especially for the formation of bone, teeth, and nacre. Inspired by those, abundant biomimetic mineralized materials have been fabricated for biomedical applications. Those bioinspired materials generally exhibit great mechanical properties and biological functions. Nevertheless, substantial gaps remain between biomimetic materials and natural materials, particularly with respect to mechanical properties and mutiscale structures. This Review summarizes the recent progress of micro- and macroscopic biomimetic mineralization from the perspective of materials synthesis and biomedical applications. To begin with, we discuss the progress of biomimetic mineralization at the microscopic level. The mechanical strength, stability, and functionality of the nano- and micromaterials are significantly improved by introducing biominerals, such as DNA nanostructures, nanovaccines, and living cells. Next, numerous biomimetic strategies based on biomineralization at the macroscopic scale are highlighted, including in situ mineralization and bottom-up assembly of mineralized building blocks. Finally, challenges and future perspectives regarding the development of biomimetic mineralization are also presented with the aim of offering insights for the rational design and fabrication of next-generation biomimetic mineralized materials.

Exploring the generality of ligands for Silica-Encapsulated nanoclusters as SERS labels.

The surface enhanced Raman scattering (SERS) reporters are rather limited, and the Raman peaks still overlap in varying degrees, making SERS multiplex coding a critical bottleneck in the exploration of SERS nanotechnology. Herein, we design a general strategy to expand the SERS probe scope to 26 probes of six types, which can be further expanded within a limited range, with stable performance and structure. By constructing (Au-aggregate)@Ag@silica and (Au-aggregate)@silica nanocomposites, we develop optimal enhancement strategies for each Raman molecules. Mixed signal-ligand SERS probes improve the complexity of Raman spectra and expand the coding capacity. By integrating the strategies, SERS inks are produced and applied in anti-counterfeiting. With these improvements, this work breaks the constrains of probe selection, bringing SERS one step closer to the sensor or anti-counterfeiting application.

Engineering DNA-Guided Hydroxyapatite Bulk Materials with High Stiffness and Outstanding Antimicrobial Ability for Dental Inlay Applications.

Programmable base pair interactions at the nanoscale make DNA an attractive scaffold for forming hydroxyapatite (HAP) nanostructures. However, engineering macroscale HAP mineralization guided by DNA molecules remains challenging. To overcome this issue, a facile strategy is developed for the fabrication of ultrastiff DNA-HAP bulk composites. The electrostatic complexation of DNA and a surfactant with a quaternary ammonium salt group enables the formation of long-range ordered scaffolds using electrospinning. The growth of 1D and 2D HAP minerals is thus realized by this DNA template at a macroscale. Remarkably, the as-prepared DNA-HAP composites exhibit an ultrahigh Young's modulus of ≈25 GPa, which is comparable to natural HAP and superior to most artificial mineralized composites. Furthermore, a new type of dental inlay with outstanding antibacterial properties is developed using the stiff DNA-HAP. The encapsulated quaternary ammonium group within the dense HAP endows the composite with long-lasting and local antibacterial activity. Therefore, this new type of super-stiff biomaterial holds great potential for oral prosthetic applications.

Designing caps for colloidal Au nanoparticles.

The plasmonic property of a nanostructure is highly dependent on its morphology, but there are few methods for appending a domain as the "functional group" or modifier. As a means of modulating plasmonic properties, we create and modulate Au hats on Au nanoparticles, including mortarboards, beret hats, helmets, crowns, antler hats and antenna hats. The structural control arises from the active surface growth as a result of dynamic competition between ligand absorption and metal deposition. It allows the continuous tuning of hat morphologies, from the facet-controlled growth of mortarboards, to the spreading-favored growth of beret hats and helmets, and to the vertical growth of pillars in crowns, antler hats and antenna hats. Among these plasmonic nanostructures, the mortarboards show excellent SERS enhancement of 8.1 × 105, which is among the best in colloidal nanostructures; and the antler hats show the photothermal conversion efficiency of 66.2%, which compares favorably with the literature reports.

Multiplexed SERS Barcodes for Anti-Counterfeiting.

Forged signature threatens the authenticity of personal identity. Here, an effective SERS anti-counterfeiting system is designed for personal signatures. Mixed ligands improve the complexity of Raman spectra and expand the coding capacity. Fourteen distinct combinations are created from mere five ligands, and great expansion is possible with modest expansion of the ligand library. On the other hand, the (Au-aggregate)@Ag@PSPAA nanostructure significantly increases the surface-enhanced Raman scattering (SERS) intensity and stability so that excellent performance is achieved in SERS detection. By integrating these strategies, SERS inks are produced and applied in signature anti-counterfeiting. The resulting spectra are converted to barcodes that are readily detected through a smart phone APP. With these improvements, this work brings SERS one step closer toward practical applications in signature anti-counterfeiting.

Self-Healing of Polarizing Films via the Synergy between Gold Nanorods and Vitrimer.

Conventional self-healing is about the recovery of shape and mechanical properties. In contrast, recovery of functional properties is still a great challenge, especially for optical functional materials, as the known self-healing methods are incompatible with optical properties. By utilizing the synergistic effect between Au nanorods and vitrimer, the alignment of Au nanorods can be achieved in the crosslinked polymer. The optical properties of the resulting polarizing film, such as light transmittance and polarization degree, can be fully recovered without an external repair agent. With simple laser irradiation to induce the photothermal effect of Au nanorods, the shape-memory effect of vitrimer returns the Au nanorods to their initial orientation, and the plasticity achieves in situ self-healing of the cutting area. The self-healing of polarizing film provides a new research direction and reference for the application of self-healing systems in functional materials.