Optimal Synthesis of Horizontally Aligned Single-Walled Carbon Nanotubes and Their Biofunctionalization for Biosensing Applications

As an influential candidate for highly sensitive biomolecule sensor, which can capture disease related biomolecules, carbon nanotube is useful material due to its unique properties. To adopt as a sensing platform, it is strongly needed to find optimal refined synthetic condition. In order to find the optimal synthetic conditions of horizontally aligned CNT, we performed quantity control of themixed gases of H-2 and CH4 injected. We successfully find that the formation of amorphous-like carbon was critically affected by some gas condition such as the flow rate of injected gases and ratios of gas mixture. Moreover, it should be noted that our horizontally aligned carbon nanotube array platform developed would offer another potential in developing nanoscale light source, where light emission results from electron-hole carrier recombinationope

Nanomechanical In Situ Monitoring of Proteolysis of Peptide by Cathepsin B

Characterization and control of proteolysis of peptides by specific cellular protease is a priori requisite for effective drug discovery. Here, we report the nanomechanical, in situ monitoring of proteolysis of peptide chain attributed to protease (Cathepsin B) by using a resonant nanomechanical microcantilever immersed in a liquid. Specifically, the detection is based on measurement of resonant frequency shift arising from proteolysis of peptides (leading to decrease of cantilever's overall mass, and consequently, increases in the resonance). It is shown that resonant microcantilever enables the quantification of proteolysis efficacy with respect to protease concentration. Remarkably, the nanomechanical, in situ monitoring of proteolysis allows us to gain insight into the kinetics of proteolysis of peptides, which is well depicted by Langmuir kinetic model. This implies that nanomechanical biosensor enables the characterization of specific cellular protease such as its kinetics

Aptamer-functionalized nano-pattern based on carbon nanotube for sensitive, selective protein detection

We have developed a horizontally aligned carbon nanotube sensor that enables not only the specific detection of biomolecules with ultra-sensitivity, but also the quantitative characterization of binding affinity between biomolecules and/or interaction between a carbon nanotube and a biomolecule, for future applications in early diagnostics. In particular, we have fabricated horizontally aligned carbon nanotubes, which were functionalized with specific aptamers that are able to specifically bind to biomolecules (i.e. thrombin). Our detection system is based on scanning probe microscopy (SPM) imaging for horizontally aligned aptamer-conjugated carbon nanotubes (ACNTs) that specifically react with target biomolecules at an ultra-low concentration. It is shown that the binding affinity between thrombin molecule and ACNT can be quantitatively characterized using SPM imaging. It is also found that the smart carbon nanotube sensor coupled with SPM imaging permits us to achieve the high detection sensitivity even up to similar to 1 pM, which is much higher than that of other bioassay methods. Moreover, we have shown that our method enables a quantitative study on small molecule-mediated inhibition of specific biomolecular interactions. In addition, we have shown that our ACNT-based system allows for the quantitative study of the effect of chemical environment (e.g. pH and ion concentration) on the binding affinity. Our study sheds light on carbon nanotube sensor coupled with SPM imaging, which opens a new avenue to early diagnostics and drug screening with high sensitivity.close2

Mechanical Properties of Silicon Nanowires

Nanowires have been taken much attention as a nanoscale building block, which can perform the excellent mechanical function as an electromechanical device. Here, we have performed atomic force microscope (AFM)-based nanoindentation experiments of silicon nanowires in order to investigate the mechanical properties of silicon nanowires. It is shown that stiffness of nanowires is well described by Hertz theory and that elastic modulus of silicon nanowires with various diameters from ~100 to ~600 nm is close to that of bulk silicon. This implies that the elastic modulus of silicon nanowires is independent of their diameters if the diameter is larger than 100 nm. This supports that finite size effect (due to surface effect) does not play a role on elastic behavior of silicon nanowires with diameter of >100 nm

Experimental and Computational Characterization of Biological Liquid Crystals: A Review of Single-Molecule Bioassays

Quantitative understanding of the mechanical behavior of biological liquid crystals such as proteins is essential for gaining insight into their biological functions, since some proteins perform notable mechanical functions. Recently, single-molecule experiments have allowed not only the quantitative characterization of the mechanical behavior of proteins such as protein unfolding mechanics, but also the exploration of the free energy landscape for protein folding. In this work, we have reviewed the current state-of-art in single-molecule bioassays that enable quantitative studies on protein unfolding mechanics and/or various molecular interactions. Specifically, single-molecule pulling experiments based on atomic force microscopy (AFM) have been overviewed. In addition, the computational simulations on single-molecule pulling experiments have been reviewed. We have also reviewed the AFM cantilever-based bioassay that provides insight into various molecular interactions. Our review highlights the AFM-based single-molecule bioassay for quantitative characterization of biological liquid crystals such as proteins

Different Aggregation Pathways and Structures for Aβ40 and Aβ42 Peptides

Self-aggregation of amyloid-β (Aβ) peptides has been known to play a vital role in the onset stage of neurodegenerative diseases, indicating the necessity of understanding the aggregation process of Aβ peptides. Despite previous studies on the aggregation process of Aβ peptides, the aggregation pathways of Aβ isoforms (i.e., Aβ40 and Aβ42) and their related structures have not been fully understood yet. Here, we study the aggregation pathways of Aβ40 and Aβ42, and the structures of Aβ40 and Aβ42 aggregates during the process, based on fluorescence and atomic force microscopy (AFM) experiments. It is shown that in the beginning of aggregation process for both Aβ40 and Aβ42, a number of particles (i.e., spherical oligomers) are formed. These particles are subsequently self-assembled together, resulting in the formation of different shapes of amyloid fibrils. Our finding suggests that the different aggregation pathways of Aβ isoforms lead to the amyloid fibrils with contrasting structure

Microwave Irradiation-Driven Conformational Diversity of Amyloid

Amyloid fibrils have been highlighted due to their pathological role, which is determined by their conformations. For instance, the conformations of prion amyloid fibrils determine the prion infectivity. Despite recent findings regarding the important role of the conformational diversity of amyloid fibrils in their pathological role, the underlying mechanisms in amyloid fibril formation with conformational heterogeneity have remained elusive. In this work, we employed the microwave-based chemical synthesis which allows us to finely tune the thermodynamics of self-assembly process leading to the conformational diversity of amyloid fibrils. It is shown that the length of amyloid fibril and the helical structure of the fibril can be controlled using microwave irradiation. This study sheds light on the microwave-based chemical synthesis for studying the conformational heterogeneity of amyloid fibrils and for developing novel design protocol, which allows for delicately manipulating the molecular structure of protein fibrils

Different Aggregation Pathways and Structures for Aβ40 and Aβ42 Peptides

Self-aggregation of amyloid-β (Aβ) peptides has been known to play a vital role in the onset stage of neurodegenerative diseases, indicating the necessity of understanding the aggregation process of Aβ peptides. Despite previous studies on the aggregation process of Aβ peptides, the aggregation pathways of Aβ isoforms (i.e., Aβ40 and Aβ42) and their related structures have not been fully understood yet. Here, we study the aggregation pathways of Aβ40 and Aβ42, and the structures of Aβ40 and Aβ42 aggregates during the process, based on fluorescence and atomic force microscopy (AFM) experiments. It is shown that in the beginning of aggregation process for both Aβ40 and Aβ42, a number of particles (i.e., spherical oligomers) are formed. These particles are subsequently self-assembled together, resulting in the formation of different shapes of amyloid fibrils. Our finding suggests that the different aggregation pathways of Aβ isoforms lead to the amyloid fibrils with contrasting structure

Design and Implementation of a UUV Tracking Algorithm for a USV

In a departure from the past, unmanned underwater vehicles (UUVs) and unmanned surface vehicles (USVs) are increasingly needed for complementary cooperation in military, scientific, and commercial applications, because this is more efficient than standalone operations. Information sharing through acoustic underwater communication is vital for complementary cooperation between USVs and UUVs. Normally, since USVs have advantages in terms of wide operational boundaries compared to UUVs, they are efficient for tracking UUVs. In this paper, we suggest a UUV tracking algorithm for a USV. The tracking algorithm’s development consists of three main software models: an estimation based on an extended Kalman filter (EKF) with a navigation smoothing method, guidance based on multimode guidance, and re-searching based on a pattern. In addition, the algorithm provides a procedure for tracking UUVs in complex acoustic underwater communication environments. The tracking algorithm was tested in a simulated environment to check the performance of each method, and implemented with a USV system to verify its validity and stability in sea trials. The UUV tracking algorithm of the USV shows stable and efficient performance