Research

We are involved in a wide array of areas dealing with AFM related techniques for use in nanoscience, nanomedicine and nanoengineering. We have started projects in other areas within these fields as well.  Broadly our projects fall into 4 major categories A) Ion Channel Structure B) Instrument Development C) Nanomedicine D) Multiscale Biomechanics

 AION CHANNEL STRUCTURE
 Amyloid Channels




Amyloids are formed by misfolded proteins that underlie a series of neurodegenerative diseases, including Alzheimer’s disease and systemic diseases including diabetes mellitus and cystic fibrosis. In a series of studies, using AFM, biochemical assays, cell physiology and cell biology we have now defined clearly that small oligomeric amyloidogenic peptides and not their fibrillar form induce toxicty by forming ion channels (J Biol Chem 1998, FASEB J, 2001, 2000., 2000, Biochemistry, 1999; PNAS 2005). Thus protein misfolding diseases belong to the so-called “channelopathies” with defined structural features that could be used to screen, design and deliver therapeutic interventions. In collaboration with Dr. Ruth Nussinov at NCI and at Tel Aviv University, we have now used atomistic scale molecular dynamic simulation to define why these amyloids form ion channels. The findings are published in TIBS (2007) and PNAS (2010).

Hemichannels
Using AFM, we first showed that hemichannels exist naturally as an independent entity (Am. J. Physiol, 1995). We then showed that their 3D structure include pore region made of hydrophobic domains (JBC, 2005; Protein Data Bank), they are gated by physiological extracellular calcium activity (JBC, 20005; JCB, 2000), and serve an important physiological function: maintenance of normal cell volume and mechanics (JCB, 2000) and also regulate cell fate in oxidative stress and abnormal conditions (PLOS One, 2007).  We are now taking a system biology approach to examine the signal transduction pathways underlying the abovementioned oxidative stress induced pathophysiology.

B)  INSTRUMENT DEVELOPMENT
 1. Integration of AFM with Electrical Recording


Working with collaborators, we have developed technological advances centered on an atomic force microscope (AFM). We worked on a nanopore system for combined AFM and electrical recording of ion channels (ACS Appl. Mater. Interfaces, 2014, 6 (7), pp 5290–5296). We have developed custom cantilevers for combined AFM imaging and electrical recording (Sci Rep. 2014, 4, 4454). 

 
          
 2. Multifunctional AFM
We are now working on developing a multifunctional AFM array for structure function imaging of live synaptic networks. The new array-atomic force microscope (AFM-array) will consist of multifunctional cantilever array with independent sensors and actuators.This will enable 1) multipoint simultaneously imaging of synaptic networks at the scales of its organization, namely, nano-to-macro scale, 2) measuring localized electrical and chemical activity, and 3) interfacing with animal and human subjects.
 3. Biosensor for Alzheimer's Disease Biomarker Discovery 
We are also working on developing a biosensor that integrates optical components (diffraction grating couplers) into microelectromechanical systems(MEMS). This will make the device capable of total internal reflection fluorescence (TIRF) microscopy. This device aims to increase sensitivity and reduce noise in detection of multi-analytes in a biological sample. By choosing unique dyes for each target analyte, the fluorescence capability can differentiate between multiple target analytes (antigens), as well as reduce noise from the non-selective adhesion of prevalent, “sticky” biomolecules found in biological fluids. At the same time, the MEMS device can be used as a microresonator whose resonance frequency varies with the added mass from antigen-antibody binding. This resonance shift detection provides an accurate quantification of individual molecules beyond what relative fluorescence signals are capable of. The combined technologies allow for highly accurate detection of multiple target molecules simultaneously.
 4. Biosensor for SNP Detection




We have developed bio-sensors consisting of a graphene field effect transistor (GFET) with a nanoscale layer of DNA nano-device. The current through the graphene shows a characteristic response to single nucleotide gene mutation (SNP). Our SNP sensing & signaling platform will facilitate the development of the miniaturized, implantable, digital, and wireless point-of-care biosensors for early detection & monitoring of life threatening human diseases. We are expanding our target bi-molecules into proteins, bacteria and others.
 
                         

 C) NANOMEDICINE

We are expanding into the use of nanomaterials and material properties for biological sensing, diagnosis and devices, and to understand structure and properties of biological systems. We have been pursing colloidal systems, DNA, and other smart materials in this area. Our colloidal systems are intended as nanocarriers for traceable, targeted and controllable drug delivery. We have designed multifunctional silica and gold based nanocarriers with the aim of in vivo imaging, externally actuated guidance and controlled drug delivery. Superparamagnetic iron oxide is added to silica nanocarriers to enable external guidance with magnets. Gold and quantum dots are embedded in silica nanocarriers to enable optical and photoacoustic imaging. These smart nanocarriers employ biocompatible materials and have potential for controllable delivery of payloads. Most recently, we have used a pH and temperature sensitive polymer NIPAM-co-MAA to encapsulate our nanocarriers for controllable payload release. We are now developing assays to characterize the in vivo behavior of these nanocarriers.
Additionally, we have designed DNA-based nanomachines like tweezers and nanoswitches that can lend spatial and externally actuated control when integrated into complex systems. 
 


 D) MULTISCALE BIOMECHANICS

We have used AFM and coupled techniques to study the mechanical properties of biological systems across multiple length scales like the endothelial barrier, hemichannels and bacteria/biofilms. Most extensively, we studied the meniscus in humans and mice during aging, injury and osteoarthritis across multiple length scales from tissue to the molecular level.