The creation of nanoscale materials for advanced structures has led to a growing interest in the area of biomineralization. Numerous microorganisms are capable of synthesizing inorganic-based structures. For example, diatoms use amorphous silica as a structural material, bacteria synthesize magnetite (Fe3O4) particles and form silver nanoparticles, and yeast cells synthesize cadmium sulphide nanoparticles. The process of biomineralization and assembly of nanostructured inorganic components into hierarchical structures has led to the development of a variety of approaches that mimic the recognition and nucleation capabilities found in biomolecules for inorganic material synthesis. In this report, we describe the in vitro biosynthesis of silver nanoparticles using silver-binding peptides identified from a combinatorial phage display peptide library.

The discoidin domain receptors (DDRs) are receptor tyrosine kinases that recognize collagens as their ligands. DDRs display unique structural features and distinctive activation kinetics, which set them apart from other members of the kinase superfamily. DDRs regulate cell-collagen interactions in normal and pathological conditions and thus are emerging as major sensors of collagen matrices and potential novel therapeutic targets. New structural and biological information has shed light on the molecular mechanisms that regulate DDR signaling, turnover, and function. This minireview provides an overview of these areas of DDR research with the goal of fostering further investigation of these intriguing and unique receptors. The discoidin domain receptor (DDR)2 family comprises two distinct members, DDR1 and DDR2, which were initially discovered in the early 1990s and characterized as receptor tyrosine kinases (RTKs) based on the presence of a catalytic kinase domain (KD) (1-7). Subsequently, collagens were identified as ligands for DDRs (8), thus establishing the unique characteristic of these receptors among other members of the RTK superfamily. Upon collagen binding, DDRs undergo tyrosine autophosphorylation with distinctive activation kinetics, which elicits genetic and cellular programs that regulate a variety of cell-collagen interactions. Despite their unique characteristics, the biochemical and cellular mechanisms by which DDRs mediate their multiple biological effects remain poorly defined. This minireview provides an overview of current information on DDR structure, regulation, and signaling. For information on specific DDR biological functions in processes such as cell adhesion, migration, and invasion over collagen matrices and their role in normal and pathological processes, the reader is directed to the following recent reviews (9 -11) DDR StructureThe DDR1 subfamily is composed of five membrane-anchored isoforms, and the DDR2 subfamily is represented by a single protein. The five DDR1 isoforms are generated by alternative splicing. DDR1a, DDR1b, and DDR1c are full-length functional receptors, and DDR1d and DDR1e are truncated or kinase-inactive receptors (10, 12). Two additional secreted splice variants of DDR1 have also been identified (13). DDR1b and DDR1c contain an additional 37 residues within the intracellular juxtamembrane (IJXM) region. With the exception of the two secreted DDR1 isoforms, all DDRs are single-pass type I transmembrane glycoproteins that are characterized by the presence of six distinct protein domains: a discoidin (DS) domain, a DS-like domain, an extracellular juxtamembrane (EJXM) region, a transmembrane (TM) segment, a long IJXM region, and an intracellular KD (Fig. 1A). The presence of the N-terminal DS and DS-like domains is the defining feature of the DDR RTK subfamily. The DS domain exhibits high homology to a protein module originally identified in proteins from Dictyostelium discoideum (14). In this organism, the DS domain functions as a galactose-binding lectin, whic...

The use of magnetic force microscopy (MFM) to detect probe-sample interactions from superparamagnetic nanoparticles in vitro in ambient atmospheric conditions is reported here. By using both magnetic and nonmagnetic probes in dynamic lift-mode imaging and by controlling the direction and magnitude of the external magnetic field applied to the samples, it is possible to detect and identify the presence of superparamagnetic nanoparticles. The experimental results shown here are in agreement with the estimated sensitivity of the MFM technique. The potential and challenges for localizing nanoscale magnetic domains in biological samples is discussed.

This work presents a comprehensive open-source simulation and design tool for Soft pneumatic actuators (SPAs) using finite element method, compatible and extensible to a diverse range of soft materials and design parameters. Thorough characterization of the hyperelastic and viscoelastic behavior is illustrated using a sample soft material (Ecoflex 00_30), and an appropriate material constitutive law. SPA performance (displacement and blocked-force) are simulated for two types of SPA and validated with experimental testing. Real-world case studies are presented in which SPA designs are iteratively optimized through simulation to meet specified performance criteria and geometric constraints.

Activation of discoidin domain receptor (DDR) 1 by collagen is reported to regulate cell migration and survival processes. While the oligomeric state of DDR1 is reported to play a significant role in collagen binding, not much is known about the effect of collagen binding on DDR1 oligomerization and cellular distribution. Using fluorescence resonance energy transfer (FRET) microscopy, we monitored the interaction between DDR1 tagged with cyan fluorescent protein and DDR1 tagged with yellow fluorescent protein in live cells. Significant FRET signal indicative of receptor dimerization was found even in the absence of collagen stimulation. Collagen stimulation induced aggregation of DDR1, followed by a sharp increase in FRET signal, localized in the regions of aggregated receptor. Further analysis of DDR1 aggregation revealed that DDR1 undergoes cytoplasmic internalization and incorporation into the early endosome. We found the kinetics of DDR1 internalization to be fast, with a significant percentage of the receptor population being internalized in the first few minutes of collagen stimulation. Our results indicate that collagen stimulation induces the aggregation and internalization of DDR1 dimers at timescales much before receptor activation. These findings provide new insights into the cellular redistribution of DDR1 following its interaction with collagen type I.

Soft actuators made from elastomeric active materials can find widespread potential implementation in a variety of applications ranging from assistive wearable technologies targeted at biomedical rehabilitation or assistance with activities of daily living, bioinspired and biomimetic systems, to gripping and manipulating fragile objects, and adaptable locomotion. In this manuscript, we propose a novel two-component soft actuator design and design tool that produces actuators targeted towards these applications with enhanced mechanical performance and manufacturability. Our numerical models developed using the finite element method can predict the actuator behavior at large mechanical strains to allow efficient design iterations for system optimization. Based on two distinctive actuator prototypes’ (linear and bending actuators) experimental results that include free displacement and blocked-forces, we have validated the efficacy of the numerical models. The presented extensive investigation of mechanical performance for soft actuators with varying geometric parameters demonstrates the practical application of the design tool, and the robustness of the actuator hardware design, towards diverse soft robotic systems for a wide set of assistive wearable technologies, including replicating the motion of several parts of the human body.

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Dip-pen nanolithography (DPN) is becoming a popular technique to "write" molecules on a surface by using the tip of an atomic force microscope (AFM) coated with the desired molecular "ink". In this work, we demonstrate that poly-histidine-tagged peptides and proteins, and free-base porphyrins coated on AFM probes, can be chelated to ionized regions on a metallic nickel surface by applying an electric potential to the AFM tip in the DPN process. DPN has been accomplished in the Tapping Mode of AFM, which creates many possible applications of positioning and subsequently imaging biomolecules, especially on soft surfaces.