Craig A Aspinwall
Professor, BIO5 Institute
Professor, Biomedical Engineering
Professor, Chemistry and Biochemistry-Sci
Primary Department
(520) 621-6338
Research Interest
Craig A. Aspinwall, PhD, is an Associate Professor of Chemistry and Biochemistry at the University of Arizona. Dr. Aspinwall’s research is focused on the development of novel technology that facilitates the investigation of the molecular underpinnings of disease states. His work encompasses a broad range of scientific disciplines and allows complex biochemical problems to be studied with an increasing level of molecular detail. Dr. Aspinwall has published over 40 original research papers and maintains active collaborations with several international investigators. His research has been funded by the National Institutes of Health, the National Science Foundation, the Arizona Biomedical Research Corporation, and other organizations. He is actively involved in mentoring and education of students and young scientists.

Publications

Heitz, B. A., Jones, I. W., Hall, H. K., Aspinwall, C. A., & Saavedra, S. S. (2010). Fractional polymerization of a suspended planar bilayer creates a fluid, highly stable membrane for ion channel recordings. Journal of the American Chemical Society, 132(20), 7086-93.

Suspended planar lipid membranes (or black lipid membranes (BLMs)) are widely used for studying reconstituted ion channels, although they lack the chemical and mechanical stability needed for incorporation into high-throughput biosensors and biochips. Lipid polymerization enhances BLM stability but is incompatible with ion channel function when membrane fluidity is required. Here, we demonstrate the preparation of a highly stable BLM that retains significant fluidity by using a mixture of polymerizable and nonpolymerizable phospholipids. Alamethicin, a voltage-gated peptide channel for which membrane fluidity is required for activity, was reconstituted into mixed BLMs prepared using bis-dienoyl phosphatidylcholine (bis-DenPC) and diphytanoyl phosphatidylcholine (DPhPC). Polymerization yielded BLMs that retain the fluidity required for alamethicin activity yet are stable for several days as compared to a few hours prior to polymerization. Thus, these polymerized, binary composition BLMs feature both fluidity and long-term stability.

Gallagher, E. S., Adem, S. M., Baker, C. A., Ratnayaka, S. N., Jones, I. W., Hall, H. K., Saavedra, S. S., & Aspinwall, C. A. (2015). Highly stabilized, polymer-lipid membranes prepared on silica microparticles as stationary phases for capillary chromatography. Journal of chromatography. A, 1385, 28-34.

The ability to rapidly screen complex libraries of pharmacological modulators is paramount to modern drug discovery efforts. This task is particularly challenging for agents that interact with lipid bilayers or membrane proteins due to the limited chemical, physical, and temporal stability of conventional lipid-based chromatographic stationary phases. Here, we describe the preparation and characterization of a novel stationary phase material composed of highly stable, polymeric-phospholipid bilayers self-assembled onto silica microparticles. Polymer-lipid membranes were prepared by photochemical or redox initiated polymerization of 1,2-bis[10-(2',4'-hexadieoyloxy)decanoyl]-sn-glycero-2-phosphocholine (bis-SorbPC), a synthetic, polymerizable lipid. The resulting polymerized bis-SorbPC (poly(bis-SorbPC)) stationary phases exhibited enhanced stability compared to particles coated with 1,2-dioleoyl-sn-glycero-phosphocholine (unpolymerized) phospholipid bilayers when exposed to chemical (50mM triton X-100 or 50% acetonitrile) and physical (15min sonication) insults after 30 days of storage. Further, poly(bis-SorbPC)-coated particles survived slurry packing into fused silica capillaries, compared to unpolymerized lipid membranes, where the lipid bilayer was destroyed during packing. Frontal chromatographic analyses of the lipophilic small molecules acetylsalicylic acid, benzoic acid, and salicylic acid showed >44% increase in retention times (P

Bränström, R., Aspinwall, C. A., Välimäki, S., Östensson, C., Tibell, A., Eckhard, M., Brandhorst, H., Corkey, B. E., Berggren, P. -., & Larsson, O. (2004). Long-Chain CoA esters activate human pancreatic beta-cell KATP channels: Potential role in Type 2 diabetes. Diabetologia, 47(2), 277-283.

PMID: 14740158;Abstract:

Aims/hypothesis. The ATP-regulated potassium (KATP) channel in the pancreatic beta cell couples the metabolic state to electrical activity. The primary regulator of the KATP channel is generally accepted to be changes in ATP/ADP ratio, where ATP inhibits and ADP activates channel activity. Recently, we showed that long-chain CoA (LC-CoA) esters form a new class of potent KATP channel activators in rodents, as studied in inside-out patches. Methods. In this study we have investigated the effects of LC-CoA esters in human pancreatic beta cells using the inside-out and whole-cell configurations of the patch clamp technique. Results. Human K ATP channels were potently activated by acyl-CoA esters with a chain length exceeding 12 carbons. Activation by LC-CoA esters did not require the presence of Mg2+ or adenine nucleotides. A detailed characterization of the concentration-dependent relationship showed an EC50 of 0.7±0.1 μmol/l. Furthermore, in the presence of an ATP/ADP ratio of 10 (1.1 mmol/l total adenine nucleotides), whole-cell KATP channel currents increased approximately six-fold following addition of 1 μmol/l LC-CoA ester. The presence of 1 μmol/l LC-CoA in the recording pipette solution increased beta-cell input conductance, from 0.5±0.2 nS to 2.5±1.3 nS. Conclusion/interpretation. Taken together, these results show that LC-CoA esters are potent activators of the KATP channel in human pancreatic beta cells. The fact that LC-CoA esters also stimulate K ATP channel activity recorded in the whole-cell configuration, points to the ability of these compounds to have an important modulatory role of human beta-cell electrical activity under both physiological and pathophysiological conditions.

Janczak, C. M., Calderon, I. A., Mokhtari, Z., & Aspinwall, C. A. (2018). Polystyrene-Core, Silica-Shell Scintillant Nanoparticles for Low-Energy Radionuclide Quantification in Aqueous Media. ACS applied materials & interfaces, 10(5), 4953-4960.

β-particle emitting radionuclides are useful molecular labels due to their abundance in biomolecules. Detection of β-emission fromH,S, andP, important biological isotopes, is challenging due to the low energies (E≤ 300 keV) and short penetration depths (≤0.6 mm) in aqueous media. The activity of biologically relevant β-emitters is usually measured in liquid scintillation cocktail (LSC), a mixture of energy-absorbing organic solvents, surfactants, and scintillant fluorophores, which places significant limitations on the ability to acquire time-resolved measurements directly in aqueous biological systems. As an alternative to LSC, we developed polystyrene-core, silica-shell nanoparticle scintillators (referred to as nanoSCINT) for quantification of low-energy β-particle emitting radionuclides directly in aqueous solutions. The polystyrene acts as an absorber for energy from emitted β-particles and can be loaded with a range of hydrophobic scintillant fluorophores, leading to photon emission at visible wavelengths. The silica shell serves as a hydrophilic shield for the polystyrene core, enabling dispersion in aqueous media and providing better compatibility with water-soluble analytes. While polymer and inorganic scintillating microparticles are commercially available, their large size and/or high density complicates effective dispersion throughout the sample volume. In this work, nanoSCINT nanoparticles were prepared and characterized. nanoSCINT responds toH,S, andP directly in aqueous solutions, does not exhibit a change in scintillation response between pH 3.0 and 9.5 or with 100 mM NaCl, and can be recovered and reused for activity measurements in bulk aqueous samples, demonstrating the potential for reduced production of LSC waste and reduced total waste volume during radionuclide quantification. The limits of detection for 1 mg/mL nanoSCINT are 130 nCi/mL forH, 8 nCi/mL forS, and

Baker, C. A., & Aspinwall, C. A. (2015). Emerging trends in precision fabrication of microapertures to support suspended lipid membranes for sensors, sequencing, and beyond. Analytical and bioanalytical chemistry, 407(3), 647-52.

Suspended lipid membranes, also called black lipid membranes (BLMs), are an important model system that approximates the lipid bilayer environment of cell membranes. Increasingly, BLMs are utilized in sensing strategies that harness high sensitivity measurements of ion flux across the membrane, typically facilitated by ion channel proteins. BLMs are suspended across microapertures that connect two otherwise isolated fluidic compartments, and the precision fabrication of such microapertures can contribute to the stability and performance of the resulting BLM. Here, we highlight two emerging trends in the precision fabrication of microapertures for BLM formation: microfabrication in silicon-based thin film substrates, and microfabrication in the negative photoresist material SU-8. Four unique fabrication strategies are outlined, and we project the impact that these microfabrication strategies will have for BLM-integrated bioanalytical technologies.