Bioinspired re-entrant structures have been proved to be effective in achieving liquid superrepellence (including anti-penetration, anti-adhesion, and anti-spreading). However, except for a few reports relying on isotropic etching of silicon wafers, most fluorination-dependent surfaces are still unable to repel liquids with extreme low surface energy (i.e., γ < 15 mN m ), especially those fluorinated solvents. Herein, triply re-entrant structures, possessing superrepellence to water (with surface tension γ of 72.8 mN m ) and various organic liquids (γ = 12.0-27.1 mN m ), are fabricated via two-photon polymerization based 3D printing technology. Such structures can be constructed both on rigid and flexible substrates, and the liquid superrepellent properties can be kept even after oxygen plasma treatment. Based on the prepared triply re-entrant structures, micro open capillaries are constructed on them to realize directional liquid spreading, which may be applied in microfluidic platforms and lab-on-a-chip applications. The fabricated arrays can also find potential applications in electronic devices, gas sensors, microchemical/physical reactors, high-throughput biological sensors, and optical displays.

Cathepsin K is the major collagenolytic protease in bone that facilitates physiological as well as pathological bone degradation. Despite its key role in bone remodeling and for being a highly sought-after drug target for the treatment of osteoporosis, the mechanism of collagen fiber degradation by cathepsin K remained elusive. Here, we report the structure of a collagenolytically active cathepsin K protein dimer. Cathepsin K is organized into elongated C-shaped protease dimers that reveal a putative collagen-binding interface aided by glycosaminoglycans. Molecular modeling of collagen binding to the dimer indicates the participation of nonactive site amino acid residues, Q21 and Q92, in collagen unfolding. Mutations at these sites as well as perturbation of the dimer protein-protein interface completely inhibit cathepsin-K-mediated fiber degradation without affecting the hydrolysis of gelatin or synthetic peptide. Using scanning electron microscopy, we demonstrate the specific binding of cathepsin K at the edge of the fibrillar gap region of collagen fibers, which suggest initial cleavage events at the N-and C-terminal ends of tropocollagen molecules. Edman degradation analysis of collagen fiber degradation products revealed those initial cleavage sites. We propose that one cathepsin K molecule binds to collagen-bound glycosaminoglycans at the gap region and recruits a second protease molecule that provides an unfolding and cleavage mechanism for triple helical collagen. Removal of collagen-associated glycosaminoglycans prevents cathepsin K binding and subsequently fiber hydrolysis. Cathepsin K dimer and glycosaminoglycan binding sites represent novel targeting sites for the development of nonactive site-directed secondgeneration inhibitors of this important drug target.cathepsin K | collagen | glycosaminoglycan | enzyme mechanism

Background: Collagen macromolecules are biologically relevant substrates in tissue remodeling and bone-related diseases. Results: We investigated the action of cysteine proteases on the structural integrity and mechanical functionality of collagen fibers. Conclusion: Using ultrastructural and biochemical techniques, we present a model of collagen fiber degradation via cathepsin K. Significance: Our data provide new insights in matrix degradation and may allow new strategies to inhibit it.

Here we propose a new method for constructing highly color fast non-iridescent structural color materials by assembling self-adhesive poly-dopamine coated SiO nanoparticles (PDA@SiO) for amorphous colloidal arrays through a "spraying" process. Simply by alkaline vapor treatment, the adhesive forces and fastness of the amorphous colloidal arrays were significantly improved. This was demonstrated by lap shear tests of tape tearing and cohesive failure as well as a series of fastness tests like sandpaper abrasion, finger wiping and ultrasonic cleaning. Besides, the strengthening fastness reaction could occur on different substrates, including glass, metals, polymers and paper, regardless of their chemical and physical properties. Moreover, the structural color of the PDA@SiO arrays was bright due to the broadband absorption of PDA, and was tunable according to the size, PDA content and arrangement of the PDA@SiO arrays.

Light-promoted precise spatial control of target molecules on surfaces is crucial in the development of novel bioanalytical, diagnostic, or sensor tools. Proteins, DNA fragments, peptides and antibodies, [1][2][3][4][5][6] as well as hydrogels, [7] have been immobilized and patterned using a number of photochemical methods, such as thiol-yne, [8] thiol-ene, [9] azide-yne (by photoreduction of copper II), [10] terazole-ene, [11] photo-triggered Diels-Alder reaction, [12] Paterno-Buchi reaction, [13] and some other chemistries capable of photo-triggered formation of reactive functional groups. [14][15][16][17] However, most of the existing photochemical methods lead to irreversible permanent surface functionalization, limiting possible applications in the formation of materials and surfaces with dynamic and responsive properties or reusable 2 functionalities. Reversible surface functionalization methods can be applied to introduce, exchange, or remove a functionality and, thus, generate "smart" surfaces and patterns.Examples of possible applications of such dynamic surfaces are reusability of substrates, possibility to perform "write and erase" procedures (i.e., rewritable surfaces), formation of complex, multi-component and gradient patterns, capture-and-release properties, and the possibility of in-situ manipulation of local environments.To the best of our knowledge, only two photo-induced reversible patterning strategies have been reported so far. Popik et al. [18] showed that reactive o-naphthoquinone methides (oNQMs) produced under UV light from 3-(hydroxymethyl)-2-naphtholcould react with surface thiol groups to yield thioether conjugates, which could be subsequently cleaved by a secondary UV irradiation to regenerate surface thiol groups. [18] In a recent publication, Anseth et al. described the use of allyl sulfides incorporated into a hydrogel to achieve reversible modification with thiol-containing biomolecules.[19]Here, we present a new reversible photo-patterning strategy based on a photo-induced disulfide exchange reaction that allows for reversible photo-functionalization, patterning, as well as exchange or removal of surface functional groups (Figure 1).Disulfide bonds are known to undergo reversible cleavage under basic conditions via thiol-disulfide exchange reactions through intermediate thiolate anions. [20][21][22] However, disulfides can also undergo dynamic exchange reactions by homolytic photo-cleavage to become sulfanyl radicals (Figure1a). This reaction was recently adopted for the synthesis of self-healing polymers. [23,24] We hypothesized that the dynamic nature of disulfide homolysis and recombination under UV irradiation could be utilized to achieve reversible dynamic .In order to demonstrate the reversibility of the photo-induced disulfide exchange, the reaction was repeated 20 times (10 cycles). The results shown in Figure 2b confirm perfect 4 reversibility of the surface modification without significant change of wettability even after 20 consecutive UV-induced functionalizations ar...