Numerical simulation of nanopost-guided self-organization dendritic architectures using phase-field model.

Self-organized dendritic architecture is of fundamental importance and its application can be used in many natural and industrial processes. Nanopost arrays are usually used in the applications of reflecting grating and changing the material surface wettability. However, in recent research, it is found that nanopost arrays can be fabricated as passive components to induce the dendritic self-organizaed hierarchical architectures. Via this simplified Phase-Field based finite element simulation, the surface dendritic self-organized architecture morphology and expanding speed in the growing path can be controlled by nanopost structures. In addition, nanopost array arrangement on the surface affects the hierarchal architecture branching distribution. Finally, with an external applied force introduced to the system, it enables the nanopost as an active component. It is found that nanopost surroundings significantly impact the final distribution of dendritic architectures which is qualitatively in agreement with experiments and induce these dendritic architectures to form assigned character patterns after the external driving forces are introduced into the system. This novel study can fundamentally study the dynamic physics of dendritic self-organized architecutes provide an indicator for the development of smart self-organized architecture, and a great opportunity for the creation of large-scale hierarchical structures.

Nanopost-guided self-organization of dendritic inorganic salt structures.

The formation of hierarchical architectures is of fundamental importance and yet a relatively elusive problem concerning many natural and industrial processes. In this paper, a nanopost array platform, or a nanopost substrate, has been developed to address this issue through a model study of the drying structures of phosphate buffered saline (PBS) solution. Unlike on a plain surface, highly ramified salt structures are formed by simply allowing the nanopost substrate wetted with the salt solution to dry, a process that completes within minutes at room temperature. The branches of salt structures have similar shapes repeating at different length scales, ranging from ∼200 nm up to a few centimeters in length, covering a 2 × 2 cm(2) area patterned with nanoposts fabricated in photoresist via laser interference lithography (LIL). Scanning electromicrograph (SEM) images show that salt structures are formed around nanoposts, and characteristic features of these salt structures can be modulated and predicted based on the surface properties and geometrical arrangements of nanoposts, suggesting that nanoposts can be used to guide the organization and crystallization of salts. This nanopost-guided crystallization approach is robust, rapid, versatile, and amenable to real-time observation and mass production, providing a great opportunity for the study and creation of large-scale hierarchical structures.

Investigation of C-terminal domain of SARS nucleocapsid protein-Duplex DNA interaction using transistors and binding-site models.

AlGaN/GaN high electron mobility transistors (HEMTs) were used to sense the binding between double stranded DNA (dsDNA) and the severe acute respiratory syndrome coronavirus (SARS-CoV) nucleocapsid protein (N protein). The sensing signals were the drain current change of the HEMTs induced by the protein-dsDNA binding. Binding-site models using surface coverage ratios were utilized to analyze the signals from the HEMT-based sensors to extract the dissociation constants and predict the number of binding sites. Two dissociation constants, K D1 = 0.0955 nM, K D2 = 51.23 nM, were obtained by fitting the experimental results into the two-binding-site model. The result shows that this technique is more competitive than isotope-labeling electrophoretic mobility shift assay (EMSA). We demonstrated that AlGaN/GaN HEMTs were highly potential in constructing a semiconductor-based-sensor binding assay to extract the dissociation constants of nucleotide-protein interaction.

AlGaN/GaN high electron mobility transistors for protein-peptide binding affinity study.

Antibody-immobilized AlGaN/GaN high electron mobility transistors (HEMTs) were used to detect a short peptide consisting of 20 amino acids. One-binding-site model and two-binding-site model were used for the analysis of the electrical signals, revealing the number of binding sites on an antibody and the dissociation constants between the antibody and the short peptide. In the binding-site models, the surface coverage ratio of the short peptide on the sensor surface is relevant to the electrical signals resulted from the peptide-antibody binding on the HEMTs. Two binding sites on an antibody were observed and two dissociation constants, 4.404×10(-11) M and 1.596×10(-9) M, were extracted from the binding-site model through the analysis of the surface coverage ratio of the short peptide on the sensor surface. We have also shown that the conventional method to extract the dissociation constant from the linear regression of curve-fitting with Langmuir isotherm equation may lead to an incorrect information if the receptor has more than one binding site for the ligand. The limit of detection (LOD) of the sensor observed in the experimental result (~10 pM of the short peptide) is very close to the LOD (around 2.7-3.4 pM) predicted from the value of the smallest dissociation constants. The sensitivity of the sensor is not only dependent on the transistors, but also highly relies on the affinity of the ligand-receptor pair. The results demonstrate that the AlGaN/GaN HEMTs cannot only be used for biosensors, but also for the biological affinity study.

Detection of Severe Acute Respiratory Syndrome (SARS) Coronavirus Nucleocapsid Protein Using AlGaN/GaN High Electron Mobility Transistors.

AlGaN/GaN high electron mobility transistors (HEMTs) were used to detect the SARS coronavirus (SARS-CoV) nucleocapsid protein interaction without fluorescent labeling. The detection limit in our system was approximately 0.003 nM of protein sample. Our result showed that this technique was more competitive than isotope-labeling EMSA. We demonstrated AlGaN/GaN was highly potential in constructing a semiconductor-based-sensor binding assay to extract the dissociation constants of nucleic acid-protein interaction.