Inga Cicenaite

Composition of PLGA and PEI/DNA nanoparticles improves ultrasound-mediated gene delivery in solid tumors in vivo

The goal of this study was to enhance gene delivery and tumor cell transfection in vivo by using a combination of ultrasonication with complex nanoparticles consisting of two types of nanoparticles: PEI/DNA beta-gal plasmid with highly positive zeta-potential and air-filled poly (lactic-co-glycolic acid) (PLGA) particles (with negative zeta-potential) manufactured in our laboratory. The PLGA/PEI/DNA nanoparticles were a colloid with positive zeta-potential and injected i.v. in nude mice with DU145 human prostate tumors. We found that the combination of PLGA/PEI/DNA nanoparticles with ultrasonication substantially enhanced tumor cell transfection in vivo. The overexpression of beta-gal gene was evaluated histochemically and by Western blot analysis. At least an 8-fold increase of the cell transfection efficacy was obtained in irradiated tumors compared to non-irradiated controls, while little to no cell death was produced by ultrasonication.

Optoacoustic monitoring of cerebral venous blood oxygenation though intact scalp in large animals

Monitoring (currently invasive) of cerebral venous blood oxygenation is a key to avoiding hypoxia-induced brain injury resulting in death or severe disability. Noninvasive, optoacoustic monitoring of cerebral venous blood oxygenation can potentially replace existing invasive methods. To the best of our knowledge, we report for the first time noninvasive monitoring of cerebral venous blood oxygenation through intact scalp that was validated with invasive, “gold standard” measurements. We performed an in vivo study in the sheep superior sagittal sinus (SSS), a large midline cerebral vein, using our novel, multi-wavelength optoacoustic system. The study results demonstrated that: 1) the optoacoustic signal from the sheep SSS is detectable through the thick, intact scalp and skull; 2) the SSS signal amplitude correlated well with wavelength and actual SSS blood oxygenation measured invasively using SSS catheterization, blood sampling, and measurement with “gold standard” CO-Oximeter; 3) the optoacoustically predicted oxygenation strongly correlated with that measured with the CO-Oximeter. Our results indicate that monitoring of cerebral venous blood oxygenation may be performed in humans noninvasively and accurately through the intact scalp using optoacoustic systems because the sheep scalp and skull thickness is comparable to that of humans whereas the sheep SSS is much smaller than that of humans.

In vivo study of glucose-induced changes in skin properties assessed with optical coherence tomography

Recently, our in vivo studies demonstrated a strong correlation between blood glucose concentration and the slope of the optical coherence tomography (OCT) signal when the probing beam was scanned over a straight line. To improve the sensitivity of OCT for blood glucose monitoring, two-dimensional (2D) lateral scanning of the OCT probing beam was proposed. Depth-dependent changes in pig skin properties with variation of blood glucose concentration were revealed due to significant suppression of speckle noise and motion artefacts in 2D scanning mode. The correlation coefficient of the OCT signal slope with blood glucose concentration varied periodically in the range from -0.9 to +0.9 depending on depth. The period of variation of the correlation coefficient was 100-150 microm that corresponded to the distance between neighbour collagen bundles. We also observed a decrease of skin thickness by 10 +/- 7.5 microm with an increase of blood glucose concentration by 277 +/- 56 mg dl(-1). Mechanisms of glucose-induced changes in skin properties owing to tissue layer shift caused by dehydration associated with the glucose osmotic effect were considered.

Optoacoustic monitoring of cerebral venous blood oxygenation through extracerebral blood

There is strong clinical evidence that controlling cerebral venous oxygenation (oxyhemoglobin saturation) is critically important for patients with severe traumatic brain injury as well as for patients undergoing cardiac surgery. However, the only available method for cerebral venous blood oxygenation monitoring is invasive and requires catheterization of the internal jugular vein. We designed and built a novel optoacoustic monitor of cerebral venous oxygenation as measured in the superior sagittal sinus (SSS), the large midline cerebral vein. To the best of our knowledge, optical monitoring of cerebral venous blood oxygenation through overlying extracerebral blood is reported for the first time in this paper. The system was capable of detecting SSS signals in vivo at 700, 800, and 1064 nm through the thick (5–6 mm) sheep skull containing the circulating blood. The high (submillimeter) in-depth resolution of the system provided identification of the SSS peaks in the optoacoustic signals. The SSS peak amplitude closely followed the actual SSS blood oxygenation measured invasively using catheterization, blood sampling, and “gold standard” CO-Oximetry. Our data indicate the system may provide accurate measurement of the SSS blood oxygenation in patients with extracerebral blood over the SSS.

Effect on blood glucose monitoring of skin pressure exerted by an optical coherence tomography probe

We proposed to use optical coherence tomography (OCT) for continuous noninvasive blood glucose monitoring, and recently we significantly improved the sensitivity of this technique. The accuracy of OCT glucose monitoring is limited by several factors, including variation of tissue pressure exerted by the OCT probe. We studied the influence of high (>10 kPa) and low (<1 kPa) pressure levels on OCT blood glucose monitoring. We showed that controlling external pressure to <1 kPa substantially improved the accuracy and reproducibility of OCT-based glucose monitoring.

Prediction Capability of Optical Coherence Tomography for Blood Glucose Concentration Monitoring

Background: Optical coherence tomography (OCT) has been shown to be a promising optical approach to noninvasive monitoring of blood glucose concentration because of its capability of probing optical properties at different depths in tissue with high resolution. This article investigates the capability of OCT to predict changes in blood glucose concentration. Methods: We varied blood glucose concentration in the physiological range in three sets of experiments. In the first set, we investigated large variations of blood glucose concentration (=400 mg/dl) and used 2100 OCT A scans for signal averaging. In the second set, we varied blood glucose concentration by approximately 200 mg/dl and used 8400 A scans for signal averaging. In the third set, we improved OCT blood glucose monitoring by increasing and controlling skin temperature under the OCT probe. In this set of experiments we increased the glucose concentration by approximately 300 mg/dl and used 4200 A scans for averaging. Results: The predicted glucose concentrations in the first two sets were lower than actual glucose concentration by 10–20% (the mean shift), while the heating and temperature control in the third set of experiments reduced the mean shift down to 1.5%. Therefore, the mean shift was reduced substantially by tissue heating and temperature control. However, it did not depend on the number of A scans to be averaged. In contrast, the uncertainty in OCT prediction of glucose concentration (the standard deviation) did not depend on heating and temperature control, but was reduced substantially from 56 to 24 mg/dl by increasing the number of A scans from 2100 to 8400, respectively. Conclusion: These results suggest that the accuracy of OCT-based glucose monitoring is approaching that of standard invasive and minimally invasive techniques.

Influence of osmolytes on in vivo glucose monitoring using optical coherence tomography.

Diabetes mellitus and its complications are the third leading cause of death in the world, exceeded only by cardiovascular disease and cancer. Tighter monitoring and control of blood glucose could minimize complications associated with diabetes. Recently, optical coherence tomography (OCT) for noninvasive glucose monitoring was proposed and tested in vivo. The aim of this work was to investigate the influence of changes in blood glucose concentration ([glu]) and sodium concentration ([Na+]) on the OCT signal. We also investigated the influence of other important analytes on the sensitivity of glucose monitoring with OCT. The experiments were carried out in anesthetized female pigs. The OCT images were acquired continuously from skin, while [glu] and [Na+] were experimentally varied within their physiological ranges. Correlations of the OCT signal slope with [glu] and [Na+] were studied at different tissue depths. The tissue area probed with OCT was marked and cut for histological examination. The correlation of blood [glu] and [Na+] with the OCT signal slope was observed in separate tissue layers. On average, equimolar changes in [glu] produced 2.26 ± 1.15 greater alterations of the OCT signal slope than changes in [Na+]. Variation of concentrations of other analytes did not Influence the OCT signal slope. The influence of [Na+] on relative changes in the OCT signal slope was generally less than [glu]-induced changes. OCT is a promising method for noninvasive glucose monitoring because of its ability to track the influence of changing [glu] on individual tissue layers.

Real-time, noninvasive optoacoustic monitoring of nanoparticle-mediated photothermal therapy of tumors

We proposed and have been developing real-time, noninvasive monitoring of blood oxygenation, total hemoglobin concentration, and thermotherapy including hyperthermia, coagulation, and cryotherapy. In this paper we propose to use the optoacoustic technique for monitoring of nanoparticle-mediated photothermal therapy (NPT) of tumors. NPT is based on heating exogenous strongly-absorbing nanoparticles selectively delivered in tumors. Real-time monitoring of NPT is necessary for precise tumor therapy with minimal damage to normal tissues. In this study we injected PEGylated and non-PEGylated carbon nanoparticles in nude mice bearing human tumors (5-15 mm) and irradiated the tumors for 10 minutes with nanosecond Nd:YAG laser pulses which produced both thermal damage to the tumors and optoacoustic signals for monitoring NPT in real time. Irradiation of tumors was performed during or after (3 or 24 hours) nanoparticle injection. Amplitude and temporal parameters of optoacoustic signals (measured with a custom-made wide-band optoacoustic probe) correlated well with nanoparticle injection, temperature rise in tumors, and tumor coagulation. Substantial thermal damage in large areas of the tumors was produced when optimal irradiation parameters were used. Monte Carlo modeling of light distribution in tumors and optoacoustic theory were applied to study kinetics of nanoparticle concentration in the tumors. Our results demonstrated that the optoacoustic technique can be used for real-time monitoring of NTP and provide precise tumor therapy with minimal damage to normal tissues.

Correlation between optical coherence tomography images and histology of pigskin

Noninvasive imaging techniques such as optical coherence tomography (OCT) are being widely used for early diagnostics of a variety of pathologies. Traditional tissue preparation for histological evaluation alters the dimensions of histological images such that differences between the dimensions of histologic and OCT images can be as great as 2.5-fold. This discrepancy complicates quantitative interpretation of OCT images. Here we used a steel ring sewn to the pigskin to avoid tissue deformation due to excision and fixation and used a surgical suture as a fixed tissue marker. With these techniques, we achieved good correlation between OCT and histological images with differences of less than 10%. The resulting method significantly enhances the diagnostic capabilities of the OCT technique.

In vivo application of 2-D lateral scanning mode optical coherence tomography for glucose sensing

Optical Coherence Tomography (OCT) was recently proposed by our group for noninvasive, continuous monitoring of blood glucose concentration in diabetics as well as in critically ill patients (both diabetic and nondiabetic). In our previous studies we tested OCT-based glucose sensing using one-dimensional (1-D) lateral scanning of the OCT probing beam over the tissue surface. The measured OCT signal was prone to motion artifacts and had high level of speckle noise. In this study we used two-dimensional (2-D) lateral scanning of the OCT probing beam and achieved 3.6-fold reduction of the speckle noise level. We also applied a post-processing Fourier filtration technique that resulted in an additional 2-2.5-fold suppression of noise. Our data indicate that the combination of acquisition time of 30-40s and the Fourier filtration technique may provide OCT monitoring of blood glucose concentration with a sensitivity of 1mM (18 mg/dL).