Prausnitz One of the greatest challenges in drug delivery is the delivery of molecules to precise locations in the body. Recent studies in our laboratory and in the laboratories of others have shown that ultrasound can temporarily disrupt biological membranes, thereby delivering large compounds such as proteins and DNA into cells and across tissues. By transiently disrupting biological membranes using ultrasound, chemotherapuetic agents could be targeted to tumors thereby reducing side effects elsewhere in the body of cancer patients and drugs like insulin could be delivered across the skin and thereby reduce the pain of needle-sticks endured by diabetics.
The focus of this proposal is to develop a robust method to control cavitation and thereby control its bioeffects. Our approach is to use the acoustic spectrum (i.e. sounds) given off by cavitation bubbles to characterize the cavitation and then identify correlations between features of the cavitational acoustic spectrum and bioeffects on cells. Preliminary work in our lab using bovine red blood cells and DU145 prostate cancer cells have shown that both the pressure measured at one-half the driving frequency (a signal known to be associated with stable cavitation) and the broadband noise between peaks in the spectrum (a signal know to be associated with transient cavitation) correlate with measured bioeffects over a wide range of different acoustic conditions. This validates the idea that cavitation-based signals in the acoustic spectrum correlate with bioeffects. The central question posed in this proposal asks whether this correlation identified over a certain range of experimental conditions can be generalized to include a much broader range of conditions and thereby might serve as a universal correlation to apply in any physical scenario, whether in the laboratory or the clinic.
To determine if there is a universal correlation between features of the acoustic spectrum and bioeffects which can be used for real-time feedback control, we will correlate features of the acoustic spectrum with two bioeffects of significance for drug delivery (molecular uptake and cell viability) over a broad range of acoustic conditions (including a range of frequencies) and a broad range of environmental conditions (notably, different numbers and types of cavitation nuclei). Then, using this data in combination with other data collected through other studies, we will determine if there is a "universal" correlation for all the many different experimental conditions studied. Our experiments will use DU145 prostate cancer cells as a model cell line, calcein and Texas Red-labeled bovine serum albumin as fluorescent model drugs, and propidium iodide as a viability stain. A custom-designed apparatus will apply ultrasound under well controlled and characterized conditions and permit accurate collection of acoustic spectra. Analysis will be done using flow cytometry.
