The development of dip-pen nanolithography techniques for the patterning of soft complex surfaces

Marcus Kramer, Purdue University

Abstract

Naturally derived tissue constructs are soft and biodegradable containing many natural cues for cell growth. Thusly, they are favorable candidates for tissue engineering and regeneration. However, tissue engineers often focus on diseased tissues, in such cases the autologous explant is unsuitable for cell seeding. Therefore, these explants require modifications. In the first part of this dissertation, the scanning probe lithography technique termed dip-pen nanolithography has been used to create micron scale surface features on a tissue collagen surface. These features have the capability to control cell binding and morphology. Nonetheless, dip-pen nanolithography is principally limited to serial (single-probe) techniques which create a limitation towards mass replication and application to the engineering community as a whole. A great deal of work is being applied to expand from serial to parallel (multi-probe) techniques. However, the relatively hard and sharp tip used in dip-pen nanolithography to produce nanometer patterns, would damage the soft heterogeneous and topographically uneven surfaces used in tissue engineering. It would be extremely difficult to avoid damaging such a soft complex surface with current parallel patterning techniques. Therefore, in the second part of this dissertation soft microparticle based tips were developed for scanning probe lithography. These tips were composed of spores and colloids and were used to pattern both hard and soft surfaces in parallel. The patterning techniques were validated and characterized with biomolecules and alkane thiols. These techniques provide analogous methods for producing relatively large micron scale patterns to both hard and soft surfaces with a diverse set of biomolecules. In the culmination of this research the parallel array of colloid based tips was used to produce low force parallel patterning by means of environmentally controlled probe actuation. In which swelling colloid tips were brought into contact with the surface using meniscus force for the patterning of fibronectin. The serial and parallel patterning techniques developed in this work provide a unique methodology to create lithographic patterns on a soft surface with micron scale control. With the development of new microfabrication techniques for tissue engineering the natural architecture of the microscaffold must be verified. In the third part of this dissertation a non-destructive Fourier transform infrared spectroscopy based technique for characterization of the biomolecules on a tissue surface was developed. This work provides a foundation for the development of a microspectroscopy based mapping technique for lithographically deposited microscaffolds on tissue surfaces. By which microscaffolds could be imaged and characterized non-destructivel,y as to allow further use in tissue engineering, while allowing verification of the proper architecture of the microscaffold.

Degree

Ph.D.

Advisors

Panitch, Purdue University.

Subject Area

Biomedical engineering

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