Paul Hansma

Publications of Paul Hansma

• In situ Materials Characterization using the Tissue Diagnostic Instrument.

  Authors: Simon Y Tang, Phillip Mathews, Connor Randall, Eugene Yurtsev, Kirk Fields, Andrew Wong, Alfred Kuo, Tamara Alliston, Paul Hansma

  Polymer testing. 04/2010; 29(2):159-163.

  An understanding of the mechanical behavior of polymers is critical towards the design, implementation, and quality control of such materials. Yet experiments and method for the characterization ofAn understanding of the mechanical behavior of polymers is critical towards the design, implementation, and quality control of such materials. Yet experiments and method for the characterization of material properties of polymers remain challenging due the need to reconcile constitutive assumptions with experimental conditions. Well-established modes of mechanical testing, such as unconfined compression or uniaxial tension, require samples with specific geometries and carefully controlled orientations. Moreover, producing specimens that conform to such specifications often requires a considerable amount of sample material. In this study we validate a micromechanical indentation device, the Tissue Diagnostic Instrument (TDI), which implements a cyclic indentation method to determine the material properties of polymers and elastomeric materials. Measurements using the TDI require little or no sample preparation, and they allow the testing of sample materials in situ. In order to validate the use of the TDI, we compared measurements of modulus determined by the TDI to those obtained by unconfined compression tests and by uniaxial tension tests within the limit of small stresses and strains. The results show that the TDI measurements were significantly correlated with both unconfined compression (p<0.001; r(2) = 0.92) and uniaxial tension tests (p<0.001; r(2)=0.87). Moreover, the measurements across all three modes of testing were statistically indistinguishable from each other (p=0.92; ANOVA) and demonstrate that TDI measurements can provide a surrogate for the conventional methods of mechanical characterization.

• The bone diagnostic instrument III: testing mouse femora.

  Authors: Connor Randall, Phillip Mathews, Eugene Yurtsev, Nadder Sahar, David Kohn, Paul Hansma

  The Review of scientific instruments. 07/2009; 80(6):065108.

  Here we describe modifications that allow the bone diagnostic instrument (BDI) [P. Hansma et al., Rev. Sci. Instrum. 79, 064303 (2008); Rev. Sci. Instrum. 77, 075105 (2006)], developed to test humanHere we describe modifications that allow the bone diagnostic instrument (BDI) [P. Hansma et al., Rev. Sci. Instrum. 79, 064303 (2008); Rev. Sci. Instrum. 77, 075105 (2006)], developed to test human bone, to test the femora of mice. These modifications include reducing the effective weight of the instrument on the bone, designing and fabricating new probe assemblies to minimize damage to the small bone, developing new testing protocols that involve smaller testing forces, and fabricating a jig for securing the smaller bones for testing. With these modifications, the BDI was used to test the hypothesis that short-term running has greater benefit on the mechanical properties of the femur for young growing mice compared to older, skeletally mature mice. We measured elastic modulus, hardness, and indentation distance increase (IDI), which had previously been shown to be the best discriminators in model systems known to exhibit differences in mechanical properties at the whole bone level. In the young exercised murine femora, the IDI was significantly lower than in young control femora. Since IDI has a relation to postyield properties, these results suggest that exercise during bone development increases post yield mechanical competence. We were also able to measure effects of aging on bone properties with the BDI. There was a significant increase in the IDI, and a significant decrease in the elastic modulus and hardness between the young and old groups. Thus, with the modifications described here, the BDI can take measurements on mouse bones and obtain statistically significant results.

• The tissue diagnostic instrument.

  Authors: Paul Hansma, Hongmei Yu, David Schultz, Azucena Rodriguez, Eugene A Yurtsev, Jessica Orr, Simon Tang, Jon Miller, Joseph Wallace, Frank Zok [......] Carol Chen, Mathilde Peters, David Kohn, Jenni Buckley, Xiaojuan Li, Lisa Pruitt, Adolfo Diez-Perez, Tamara Alliston, Valerie Weaver, Jeffrey Lotz

  The Review of scientific instruments. 06/2009; 80(5):054303.

  Tissue mechanical properties reflect extracellular matrix composition and organization, and as such, their changes can be a signature of disease. Examples of such diseases include intervertebral diskTissue mechanical properties reflect extracellular matrix composition and organization, and as such, their changes can be a signature of disease. Examples of such diseases include intervertebral disk degeneration, cancer, atherosclerosis, osteoarthritis, osteoporosis, and tooth decay. Here we introduce the tissue diagnostic instrument (TDI), a device designed to probe the mechanical properties of normal and diseased soft and hard tissues not only in the laboratory but also in patients. The TDI can distinguish between the nucleus and the annulus of spinal disks, between young and degenerated cartilage, and between normal and cancerous mammary glands. It can quantify the elastic modulus and hardness of the wet dentin left in a cavity after excavation. It can perform an indentation test of bone tissue, quantifying the indentation depth increase and other mechanical parameters. With local anesthesia and disposable, sterile, probe assemblies, there has been neither pain nor complications in tests on patients. We anticipate that this unique device will facilitate research on many tissue systems in living organisms, including plants, leading to new insights into disease mechanisms and methods for their early detection.

• The tissue diagnostic instrument

  Authors: Paul Hansma, Hongmei Yu, David Schultz, Eugene A. Yurtsev, Jessica Orr, Simon Tang, Jon Miller, Frank Zok, Richard Souza, Alexander Proctor, Xavier Nogues-Solan, M.Jesus Peña, Lisa Pruitt, Adolfo Diez-Perez, Tamara Alliston, Valerie Weaver, Jeff Lotz

  Review of Scientific Instruments. 05/2009;

  Tissue mechanical properties reflect extracellular matrix composition and organization, and as such, their changes can be a signature of disease. Examples of such diseases include intervertebralTissue mechanical properties reflect extracellular matrix composition and organization, and as such, their changes can be a signature of disease. Examples of such diseases include intervertebral disk degeneration, cancer, atherosclerosis, osteoarthritis, osteoporosis, and tooth decay. Here we introduce the tissue diagnostic instrument �TDI�, a device designed to probe the mechanical properties of normal and diseased soft and hard tissues not only in the laboratory but also in patients. The TDI can distinguish between the nucleus and the annulus of spinal disks, between young and degenerated cartilage, and between normal and cancerous mammary glands. It can quantify the elastic modulus and hardness of the wet dentin left in a cavity after excavation. It can perform an indentation test of bone tissue, quantifying the indentation depth increase and other mechanical parameters. With local anesthesia and disposable, sterile, probe assemblies, there has been neither pain nor complications in tests on patients. We anticipate that this unique device will facilitate research on many tissue systems in living organisms, including plants, leading to new insights into disease mechanisms and methods for their early detection. © 2009 American Institute of Physics. �DOI: 10.1063/1.3127602� I. INTRODUCTION The tissue diagnostic instrument �TDI� was redesigned from the bone diagnostic instrument1,2 so as to measure tissue mechanical properties subcutaneously and in vivo with additional probe assemblies and an adjustable compliance �Fig. 1�. It consists of a thin probe assembly that can penetrate skin and soft tissue to reach deep tissues. The disposable, sterilizable probe assembly consists of an outer reference probe made from a 23 gauge hypodermic needle and an inner test probe made from stainless steel wire ranging from 175 to 300 �m in diameter and from 2 to 90 mm in length. Since friction between the test probe and the reference probe increases with length, it is desirable to use only the length needed to access the desired tissue location. The test probe is held in a nickel tube that couples to a magnet, which in turn is linked to a force generator. During operation the force generator oscillates the probe within the tissue of interest and concurrently measures the force and displacement. The maximum values for force and displacement are 12 N and 600 �m. The probe is typically operated at a frequency of 4 Hz because this is rapid enough to allow hand holding yet sufficiently slow to allow easy decoupling of the elastic and viscous response of the tissue �see supplementary material3 for more details including force and displacement ranges.� II. MEASUREMENTS We first illustrate TDI use in human spinal disks that are composed of a thick outer ligament �annulus fibrosus� and a central swelling hydrogel �nucleus pulposus�. Spinal disk degeneration can be the underlying cause of back pain leading to significant morbidity and societal expense. Intervertebral disks are one of the most highly loaded tissues in the body, and consequently material property insufficiency can lead to damage accumulation, inflammation, and pain. Disk degen- REVIEW OF SCIENTIFIC INSTRUMENTS 80, 054303 �2009� 0034-6748/2009/80�5�/054303/6/$25.00 80, 054303-1 © 2009 American Institute of Physics Downloaded 28 May 2009 to 72.215.163.35. Redistribution subject to AIP license or copyright; see http://rsi.aip.org/rsi/copyright.jsp

• The bone diagnostic instrument II: Indentation distance increase.

  Authors: Paul Hansma, Patricia Turner, Barney Drake, Eugene Yurtsev, Alexander Proctor, Phillip Mathews, Jason Lelujian, Connor Randall, Jonathan Adams, Ralf Jungmann, Federico Garza-de-Leon, Georg Fantner, Haykaz Mkrtchyan, Michael Pontin, Aaron Weaver, Morton B. Brown, Nadder Sahar, Ricardo Rossello, David Kohn

  The Review of scientific instruments. 07/2008; 79(6):064303.

  The bone diagnostic instrument (BDI) is being developed with the long-term goal of providing a way for researchers and clinicians to measure bone material properties of human bone in vivo. SuchThe bone diagnostic instrument (BDI) is being developed with the long-term goal of providing a way for researchers and clinicians to measure bone material properties of human bone in vivo. Such measurements could contribute to the overall assessment of bone fragility in the future. Here, we describe an improved BDI, the Osteoprobe IItrade mark. In the Osteoprobe IItrade mark, the probe assembly, which is designed to penetrate soft tissue, consists of a reference probe (a 22 gauge hypodermic needle) and a test probe (a small diameter, sharpened rod) which slides through the inside of the reference probe. The probe assembly is inserted through the skin to rest on the bone. The distance that the test probe is indented into the bone can be measured relative to the position of the reference probe. At this stage of development, the indentation distance increase (IDI) with repeated cycling to a fixed force appears to best distinguish bone that is more easily fractured from bone that is less easily fractured. Specifically, in three model systems, in which previous mechanical testing and/or tests reported here found degraded mechanical properties such as toughness and postyield strain, the BDI found increased IDI. However, it must be emphasized that, at this time, neither the IDI nor any other mechanical measurement by any technique has been shown clinically to correlate with fracture risk. Further, we do not yet understand the mechanism responsible for determining IDI beyond noting that it is a measure of the continuing damage that results from repeated loading. As such, it is more a measure of plasticity than elasticity in the bone.

• Exploring molecular and mechanical gradients in structural bioscaffolds.

  Authors: J Herbert Waite, Helga C Lichtenegger, Galen D Stucky, Paul Hansma

  Biochemistry. 07/2004; 43(24):7653-62.

  Most organisms consist of a functionally adaptive assemblage of hard and soft tissues. Despite the obvious advantages of reinforcing soft protoplasm with a hard scaffold, such composites can lead toMost organisms consist of a functionally adaptive assemblage of hard and soft tissues. Despite the obvious advantages of reinforcing soft protoplasm with a hard scaffold, such composites can lead to tremendous mechanical stresses where the two meet. Although little is known about how nature relieves these stresses, it is generally agreed that fundamental insights about molecular adaptation at hard/soft interfaces could profoundly influence how we think about biomaterials. Based on two noncellular tissues, mussel byssus and polychaete jaws, recent studies suggest that one natural strategy to minimize interfacial stresses between adjoining stiff and soft tissue appears to be the creation of a "fuzzy" boundary, which avoids abrupt changes in mechanical properties. Instead there is a gradual mechanical change that accompanies the transcendence from stiff to soft and vice versa. In byssal threads, the biochemical medium for achieving such a gradual mechanical change involves the elegant use of collagen-based self-assembling block copolymers. There are three distinct diblock copolymer types in which one block is always collagenous, whereas the other can be either elastin-like (soft), amorphous polyglycine (intermediate), or silk-like (stiff). Gradients of these are made by an incrementally titrated expression of the three proteins in secretory cells the titration phenotype of which is linked to their location. Thus, reflecting exactly the composition of each thread, the distal cells secrete primarily the silk- and polyglycine-collagen diblocks, whereas the proximal cells secrete the elastin- and polyglycine-collagen diblocks. Those cells in between exhibit gradations of collagens with silk or elastin blocks. Spontaneous self-assembly appears to be by pH triggered metal binding by histidine (HIS)-rich sequences at both the amino and carboxy termini of the diblocks. In the polychaete jaws, HIS-rich sequences are expanded into a major block domain. Histidine predominates at over 20 mol % near the distal tip and diminishes to about 5 mol % near the proximal base. The abundance of histidine is directly correlated to transition metal content (Zn or Cu) as well as hardness determined by nanoindentation. EXAFS analyses of the jaws indicate that transition metals such as Zn are directly bound to histidine ligands and may serve as cross-linkers.

• Publisher’s Note: “The bone diagnostic instrument II: Indentation distance increase” [Rev. Sci Instrum. 79, 064303 (2008)]

  Authors: Paul Hansma, Patricia Turner, Barney Drake, Eugene Yurtsev, Alexander Proctor, Phillip Mathews, Jason Lulejian, Connor Randall, Jonathan Adams, Ralf Jungmann, Federico Garza-de-Leon, Georg Fantner, Haykaz Mkrtchyan, Michael Pontin, Aaron Weaver, Morton B. Brown, Nadder Sahar, Ricardo Rossello, David Kohn

• Giant bent-core mesogens in the thread forming process of marine mussels.

  Authors: Tue Hassenkam, Thomas Gutsmann, Paul Hansma, Jason Sagert, J Herbert Waite

  Biomacromolecules. 5(4):1351-5.

  In marine mussels (Mytilus), byssal threads are made in minutes from prefabricated smectic polymer liquid crystals by a process resembling reaction injection molding. The mesogens in these arrays areIn marine mussels (Mytilus), byssal threads are made in minutes from prefabricated smectic polymer liquid crystals by a process resembling reaction injection molding. The mesogens in these arrays are known to be natural block copolymers with rodlike collagen cores. Using atomic force microscopy, it was shown that these collagenous mesogens are bent-core or banana-shaped in a manner that is consistent with and predictable from their amino acid sequence. The overall bend angle in preCOL-NG in Mytilus galloprovincialis is about 130 degrees. The mesogens have a center-to-center separation of approximately 22 nm and a length of 200 nm. It is evident that the smectic structure of the prefabricated mesophases remains largely intact over 1-3 microm distances in the molded fibers and is presumably locked in place during molding by cross-linking. Like the smectic liquid crystals of many synthetic banana mesogens, the collagenous mesogens of the byssal threads exhibit SmC(2) symmetry with a characteristic tilt of 24.6 degrees. At about 100% extension, this tilt is considerably reduced and the globular end domains are no longer visible presumably because they have been unraveled.