The large size of lasers limits their applications in confined spaces, such as in biosensing and in vivo brain tissue imaging. In this regard, micron-sized lasers have been developed. They exhibit great potential for biological detecting, remote sensing, and depth tracking due to their small sizes, sensitive properties of their spectral fingerprints, and flexible positional modulation in the microenvironment. Lanthanide-based luminescent materials that possess long excited-state lifetime, narrow emission bandwidth, and upconversion behaviors are promising as gain mediums for novel microlasers. In addition, lanthanide-based microlasers could be generated under natural ambient conditions with pumped or continuous light sources, which significantly promotes the practical applications of microlasers. Recent progress in the design, synthesis, and biomedical applications of lanthanide-based microlasers has been outlined in this review. Lanthanide ions doped and upconverted lanthanide-based microlasers are highlighted, which exhibit advantageous structures, miniaturized dimensions, and high lasing performance. The applications of lanthanide-based microlasers are further discussed, the upconverted microlasers show great advantages for biological applications owing to their tunable excitation and emission characteristics and excellent environmental stability. Moreover, perspectives and challenges in the field of lanthanide-based microlasers are presented.

Spider silks are well known for their exceptional mechanical properties that are tougher than Kevlar and steel. However, the restricted production amounts from their native sources limit applications of spider silks. Over the decades, there have been significant interests in fabricating man-made silk fibers with comparable performance to natural silks, inspiring many efforts both for biosynthesizing recombinant spider silk proteins (spidroins) in amenable heterologous hosts and biomimetic spinning of artificial spider silks. These strategies provide promising routes to produce high-performance and functionally optimized fibers with diverse applications. Herein, we summarize the hosts that have been applied to produce recombinant spidroins. In addition, the fabrication and mechanical properties of recombinant spidroin fibers and their composite fibers are also introduced. Furthermore, we demonstrate the applications of recombinant spidroin-based fibers. Finally, facing the challenges in biosynthesis, scalable production, and hierarchical assembly of high-performance recombinant spidroins, we give a summary and perspective on future development.

Rheumatoid arthritis (RA) is a relatively common inflammatory disease that affects the synovial tissue, eventually results in joints destruction and even long-term disability. Although Janus kinase inhibitors (Jakinibs) show a rapid efficacy and are becoming the most successful agents in RA therapy, high dosing at frequent interval and severe toxicities cannot be avoided. Here, we developed a new type of fully compatible nanocarriers based on recombinant chimeric proteins with outstanding controlled release of upadacitinib. In addition, the fluorescent protein component of the nanocarriers enabled noninvasive fluorescence imaging of RA lesions, thus allowing real-time detection of RA therapy. Using rat models, the nanotherapeutic is shown to be superior to free upadacitinib, as indicated by extended circulation time and sustained bioefficacy. Strikingly, this nanosystem possesses an ultralong half-life of 45 h and a bioavailability of 4-times higher than pristine upadacitinib, thus extending the dosing interval from one day to 2 weeks. Side effects such as over-immunosuppression and leukocyte levels reduction were significantly mitigated. This smart strategy boosts efficacy, safety and visuality of Jakinibs in RA therapy, and potently enables customized designs of nanoplatforms for other therapeutics.

Numerous strategies involving multiple cross-linking networks have been applied for fabricating robust hydrogels. Inspired by this, the development of mechanically strong and tough biological fibers by the incorporation of intermolecular linking networks is becoming important. Herein, we present a versatile strategy for the fabrication of protein-saccharide composite fibers through protein-initiated double interacting networks. Three types of lysine-rich bioengineered proteins were introduced and the present multiple cross-linking interactions including electrostatic forces and covalent bonds significantly enhanced the mechanical properties of as-obtained composite fibers. In stark contrast to pristine saccharide or other polymer fibers, the as-obtained composite fibers exhibited outstanding mechanical performance, showing a breaking strength of ~768 MPa, Young’s modulus of ~24 GPa, and toughness of ~69 MJ∙m^–3, respectively. Thus, this established approach has great potentials to fabricate new generation renewable biological fibers with high performance.