IMAGING, CHARACTERIZATION, AND MANIPULATION OF NANOBIOPARTICLES BY SPM IN FLUID

 

Natalia Farkas and John A. Dagata

 

Precision Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899

 

 

As nanotechnology rapidly advances into cancer research, increasing emphasis is placed on physical characterization of nano-scale biomaterials development for early detection and treatment of the disease.† Fluid scanning probe microscopy (SPM) is a powerful tool to obtain high-resolution images and dynamical information of biological systems in solution.† Sample preparation plays a critical role because the size, shape and stability of the nanobioparticles are influenced by the interactions between them and the immobilizing substrate and SPM tip.† We view sample preparation as a multi-step process:† First, we are using co-adsorption of gold nanoparticle reference material prototypes along with the system of interest in order to make direct comparison between rigid and pliable nanoparticles and to perform in-situ tip calibration under different fluid conditions.† Then we investigate model protein and phospholipid systems, i.e., casein micelles and cholesterol particles. †Next, working with collaborators from Georgetown University Medical Center (GUMC), we implement the previous results to develop sample preparation methods and measurement techniques for more complex systems such as liposome-based nanoparticle delivery systems (NDS) with encapsulated gene therapy or MRI contrast agent payloads. †We demonstrate that the adsorption and structure of the immobilized NDS depend on the substrate potential, pH and salt concentration of the solution in agreement with zeta-potential measurements. †Interpretation of the SPM images requires careful consideration because the structural properties of the nanobioparticles are interrelated and depend on the instrumental parameters. †In particular, we show that imaging with low setpoint compresses the empty liposomes resulting in substantial height decrease while the width remains the same. †This exercise is reversible, in that the liposomes regain their original height when the setpoint is increased, pointing to the intact nature of the liposomes.† In addition to acquiring topographic images of intact NDS with gene therapy or MRI contrast agent payloads, phase imaging, lift mode, and magnetic force microscopy are employed to gather further information on the assembly of the components and functional properties of the NDS.† We show examples where phase contrast reveals material differences between co-adsorbed phospholipid systems. †In addition, phase contrast in lift mode can be used to investigate long-range ionic and hydrodynamic or magnetic interactions between the SPM tip and proteins attached to the NDS surface and payloads encapsulated in the NDS.† Finally we present a demonstration of mechanical manipulation of intact NDS with a gene therapy payload.† Utilizing the force applied by the SPM tip, we can extract and unspool encapsulated plasmid DNA from the NDS. †Our effort to develop sample preparation and measurement techniques for physical characterization of nanobioparticles by high-resolution fluid SPM recognizes the intrinsic challenges of bioimaging and, in conjunction with in-vivo GUMC efficacy studies, facilitate drug discovery and development.

 

 

Author Information

Name:†††††††††††††††††††††††††††††††††††† Natalia Farkas

Mentorís name:††† ††††††††††††††† John A. Dagata

Division:††††††††††††††††††††††††††††††† Precision Engineering Division

Laboratory:†††††††††††††††††††††††††† Manufacturing Engineering Laboratory

Room/Building:††† ††††††††††††††† E103/217

Mail Stop:††††††††††††††††††††††††††††† MS 8212

Telephone #:†††††††††††††††††††††††† 301 975 3597

Fax #:††††† ††††††††††††††††††††††††††††††† 301 869 0822

Email:††††††††††††††††††††††††††††††††††††† natalia.farkas@nist.gov

Sigma Xi:†††††††††††††††††††††††††††††† Non-member

Category:†††††††††††††††††††††††††††††† Biotechnology