The advent of Nanomedicine has stirred increased interest in the interactions of nanomaterials or nanoparticles with biological molecules. Devices and structures in the 100 nm scale may revolutionize the way drugs are delivered into cells and even organelles. Nanomaterials such as fullerenes, carbon nanotubes and metallic nano particles are being studied for possible applications in development of these devices. The most promising of these nanomaterials are the carbon nanotubes (CNTs) due to their unique properties and dimensions. Suggested applications for CNTs range from medical and biological applications such as nanosyringes, force probes, drug delivery agents and gene therapy.

Nanosyringes are devices that could be used to transport therapeutic molecules or genetic information across the cell membrane. Existing technologies to deliver molecules into a cell include lipid fusion, viral vectors, gene guns, and microinjectors. Of all the above mentioned methods, microinjection being a physical method is easy to use and control. However, microinjection is presently performed using glass micropipettes. The glass capillaries are either too big and could cause difficulties such as membrane rupture and damage crucial cell organelles. Physical disruption of the cell plasma membrane by the micropipette depends upon the applied force magnitude and rate, and the size of the pore created by the tip. The dimensions of carbon nanotubes, their high aspect ratio and mechanical robustness make them suitable for their use as micropipette tips.

Carbon nanotubes were also suggested as scanning probe microscopy tips because of their precise definition and robustness. CNTs have a very high Young's modulus ( ~ 1TPa) and tensile strength and their small diameters and shape increase the accuracy of the probe and are effective in measuring sharp recess, high aspect ratio samples.

A thorough understanding of the interactions between nanoinjector and the cell plasma membrane is necessary. The dimensions of the membrane and the weak forces involved makes it a challenge in handling and manipulating cells and the atomic level interactions between the membrane and CNTs play a very important role. We use Molecular Dynamics simulations to study the interactions of penetrating nanotubes with a lipid bilayer. The minute forces involved in these interactions make them difficult to interpret from experimental results. Atomistic simulations provide excellent details of the physical interactions and an accurate measurement of the forces involved.

Preliminary simulations involving a simple bilayer system of phosphotidylcholine (POPC), CNT and water have been performed. The interactions between the lipid bilayer and the nanotube during the insertion and withdrawal of the CNT, as in a nanosyringe, were studied. These simulations suggested a quick healing of the cell membrane after rupture during the insertion. Also the forces involved during the insertion and withdrawal were studied, with the nanotube acting like a force probe tip. These forces showed a significant decrease in the membrane rupture force compared to the glass capillaries and are in agreement with previously observed rupture forces using CNT tips. Additional simulations are being performed to study the effects of variables such as insertion velocity, orientation and membrane composition on the forces involved and the healing process.