publications :: LITT & cancer treatment >>
Thermal Ablation of Canine Cerebral Tumors Using 980-nm Diode Laser with MRTI-based Power Control Software
M Kangesniemi, RJ McNichols, JA Bankson, A Gowda, RE PRice, and JD Hazle, "Thermal Ablation of Canine Cerebral Tumors Using 980-nm Diode Laser with MRTI-based Power Control Software," Proceedings of the ISMRM. Vol. 10:246. 2002
We evaluated the feasibility of thermally ablating intracerebral tumors grown in dogs using a 980-nm diode laser with a novel diffusing fiber tip. The target volume was prescribed using MR temperature sensitive imaging (MRTI) feedback-based software, which regulated the laser power output during treatment to ablate the targeted tissue while avoiding excess heating. Treatment effects were verified from histology. This technology shows significant potential for minimally invasive treatment of small cerebral tumors.
Cooled-tip Diode Laser catheter for Improved Catheter Ablation of Ventricular Tachycardia
EP Snakard, M Miller, B Berridge, A Gowda, RJ McNichols, and TF Fossum, "Cooled-tip Diode Laser catheter for Improved Catheter Ablation of Ventricular Tachycardia," Journal of Investigative Surgery. Vol. 14(6):357-66. 2001
Catheter ablation for the treatment of arrhythmias has evolved dramatically over the past two decades. Researchers have investigated alternative energy sources and catheter constructs to improve the efficacy and safety of catheter ablation. This study tested the hypothesis that a new prototype cooled-tip laser catheter used with a low-power diode laser would improve catheter ablation of ventricular tachycardias. Four mongrel dogs underwent a median sternotomy. The cooled-tip laser catheter was advanced into the left ventricle via the left carotid artery and positioned adjacent to the endocardium. Laser powers of 3 and 4 W were delivered at four exposure times to select areas of the endocardium. During application of laser energy, room-temperature saline was circulated through the catheter. At necropsy the hearts were examined and fixed in formalin for histologic examination. Gross examination of the endocardial surfaces showed no indication of crater or thrombus formation. Cross-section of the lesions revealed sharply demarcated, circular-shaped areas of coagulative necrosis extending into the mid-myocardium. Areas of coagulative necrosis were identified within the myocardium extending into the mid- myocardium and occasionally the subepicardium. A sharp line of demarcation was observed between the lesions and the surrounding normal myocardium. The results of this study showed that we could use surface cooling during slow laser heating to create large subsurface lesions with characteristics appropriate for treatment of ventricular tachycardia and little to no surface damage. We believe our catheter system addresses many of the previous issues with laser-based approaches.
Closed-loop Feedback Control of Laser Therapy Using Magnetic Resonance Imaging
RJ McNichols, A Gowda, and SM Wright. "Closed-Loop Feedback Control of Laser Therapy using Magnetic Resonance Imaging." Proceedings of the SPIE. Vol. 4247:158-65. 2001
In the destructive treatment of tumors or other lesions, laser therapies such as laser induced thermal therapy (LITT) or interstitial laser phototherapy (ILP) offer tremendous potential to minimize surgical complications, reduce recovery time and hospital stays, and decrease associated health care costs. While laser procedures have gained wide popularity in dermatology and ophthalmology, their potential has yet to be fully realized in treatment of deep tissues where the damage front created by the laser can not be readily visualized. In the present work, we facilitate this visualization by producing an image of spatial temperature distribution via non-invasive magnetic resonance imaging (MRI). Further, we have implemented a control strategy which allows us to utilize this information for the feedback control of laser thermal therapies. We have begun to explore the feasibility of using this system for improving the safety and efficacy of laser thermal surgery.
Development of an Endoscopic Fluorescence Image Guided OCT Probe for Oral Cancer Detection.
RJ McNichols, A Gowda, BA Bell, RH Johnigan, KH Calhoun, and M Motamedi. "Development of an Endoscopic Probe for Detection of Oral Cancer." Proceedings of the SPIE. Vol. 4254:23-30. 2001
Oral squamous cell carcinoma is a disease which progresses through a number of well-defined morphological and biochemical changes. Optical coherence tomography (OCT) is a rapidly-evolving, non-invasive imaging modality which allows detailed probing of subsurface tissue structures with resolution on the order of microns. While this technique offers tremendous potential as a diagnostic tool for detection and characterization of oral cancer, OCT imaging is presently associated with a field of view (FOV) on the order of millimeters, and acquisition time on the order of seconds. Thus, OCT's utility as a rapid cancer screening technique is presently limited. On the other hand, imaging of tissue autofluorescence provides a very rapid, high-throughput method for cancer screening. However, while autofluorescence measures may be sensitive to cancer, they are often non-specific and lead to a large number of false positives. In the present work, we have developed a fluorescence image guided optical coherence tomographic (FIG-OCT) probe in which tissue autofluorescence images are simultaneously used to guide OCT image acquisition of suspicious regions in real time. We have begun pre-clinical pilot studies with this instrument in a DMBA-induced model of oral cancer in the hamster cheek pouch. Initial results indicate that the FIG-OCT approach shows promise as a rapid and effective tool for screening of oral cancer.
publications :: glucose sensing >>
Development of an Implantable Skin Port Sensor for Use as an In Vivo Optical Glucose Sensing Platform.
RJ McNichols and A Gowda, "Development of an Implantabel Skinport Sensor for Use as an In Vivo Optical Glucose Sensor." Proceedings of the SPIE. Vol. 4263:11-19. 2001
Factors that have limited the acceptance of optical spectroscopy methods for non-invasive blood glucose sensing include signal variations due in part to changes in the skin tissue optics between patients, the lack of a repeatable pathlength inherent in using diffusely reflected photon approaches, temperature variations on the skin, and the pressure with which a probe is applied to the skin surface. Unfortunately, most previous approaches to non-invasive glucose sensing have failed to address these important issues. In this work, we developed a novel skin port sensor (SPS) which eliminates the effect of skin optics by using a stable, infection-free, dermal implant to provide a skinless "window into the body". Our implant is designed to provide a fixed optical pathlength as well as features to minimize temperature and pressure variations. Preliminary experiments in a pig model demonstrate both a stable biological seal at the transcutaneous interface as well as ingrowth of vascular containing granulation tissue within the sensing chamber. Furthermore, optical spectra acquired from the port demonstrate changes in glucose signatures related to concentration changes induced in the blood. Our novel SPS may provide the necessary platform for successful implementation of an optical approach to in vivo glucose sensing.
Investigation of Near-Infrared Spectroscopy for Periodic Determination of Glucose in Cell Culture Media In Situ
CB. Lewis, RJ McNichols, A Gowda, and GL Coté, ,"Investigation of Near-Infrared Spectroscopy for Periodic Determination of Glucose in Cell Culture Media In Situ," Applied Spectroscopy Vol. 54(10):1453-7. 2000
Current techniques used to monitor glucose concentration of cell culture media (CCM) require invasive and tedious handling of the sample for sterile media removal and nutrient replacement. In order to optimize cell culture growth in bioreactors, biosensors must be developed that are capable of monitoring the cell culture processes noninvasively and continuously. In this study, on-line, non-invasive determinations of glucose in cell culture media were investigated via near-infrared spectroscopy (NIR) across the 2.0-2.5 µm combination region. A system was developed, using a unique fiber-optic coupling method and a commercial Fourier Transform Infrared (FT-IR) spectrometer, to characterize glucose single- beam spectra collected from cell culture media. This novel system is the first of its kind and integrates a completely noninvasive optical probe to measure glucose concentrations within cell culture media, in situ. Spectra recorded from a four-day fibroblast culture by using this fiber coupled system and an FTIR spectrometer have been analyzed and compared with standard clinical chemistry techniques. Partial least-squares (PLS) regression has been used to extract the analyte-dependent information and to build a successful multivariate calibration model. A combination of spectra from cell culture media and prepared media mixtures was used to eliminate unwanted correlations in the calibration data. The combined use of this unique fiber-optic system, PLS, and uncorrelated spectra resulted in a true glucose prediction error of 14.8 mg/dL in an independent validation set.
Optical Glucose Sensing in Biological Fluids: An Overview
RJ McNichols and GL Cote', "Optical Glucose Sensing in Biological Fluids: An Overview," Journal of Biomedical Optics. Vol. 5(1):5-16. 2000.
Recent technological advancements in the photonics industry have led to a resurgence of interest in optical glucose sensing and to realistic progress toward the development of an optical glucose sensor. Such a sensor has the potential to significantly improve the quality of life for the estimated 16 million diabetics in this country by making routine glucose measurements more convenient. Currently over 100 small companies and universities are working to develop noninvasive or minimally invasive glucose sensing technologies, and optical methods play a large role in these efforts. This article reviews many of the recent advances in optical glucose sensing including optical absorption spectroscopy, polarimetry, Raman spectroscopy, and fluorescent glucose sensing. In addition a review of calibration and data processing methods useful for optical techniques is presented.
TOP
Development of an Implantable Polymer "Smart Tattoo" for Glucose Sensing
Adaptation of Juvenile Diabetes Research Foundation (JDRF) Research Update presentations given by Dr. Roger McNichols and Dr. Ralph Ballerstadt to regional chapter meetings of the JDRF in:
Houston, Texas (June 27, 2001)
Oklahoma City, Oklahoma (November 3, 2001)
Little Rock, Arkansas (April 3, 2002)
Dallas, Texas (June 9, 2002).
Affinity-based Turbidity Sensor for Glucose Monitoring by Optical Coherence Tomography: Toward the Development of Implantable Sensor
Ballerstadt R, Kholodnykh A, Evans C, Boretsky A, Motamedi M, Gowda A, McNichols R, Affinity-based Turbidity Sensor for Glucose Monitoring by Optical Coherence Tomography: Toward the Development of Implantable Sensor, Anal. Chem. 79:6965-74, 2007.
We investigated the feasibility of constructing an implantable optical-based sensor for seminoninvasive continuous monitoring of analytes. In this novel sensor, analyte concentration-dependent changes induced in the degree of optical turbidity of the sensing element can be accurately monitored by optical coherence tomography (OCT), an interferometric technique. To demonstrate proof-of-concept, we engineered a sensor for monitoring glucose concentration that enabled us to quantitatively monitor the glucose-specific changes induced in bulk scattering (turbidity) of the sensor. The sensor consists of a glucose-permeable membrane housing that contains a suspension of macroporous hydrogel particles and concanavalin A (ConA), a glucose-specific lectin, that are designed to alter the optical scattering of the sensor as a function of glucose concentration. The mechanism of modulation of bulk turbidity in the sensor is based on glucose-specific affinity binding of ConA to pendant glucose residues of macroporous hydrogel particles. The affinity-based modulation of the scattering coefficient was significantly enhanced by optimizing particle size, particle size distribution, and ConA concentration. Successful operation of the sensor was demonstrated under in vitro condition where excellent reversibility and stability (160 days) of prototype sensors with good overall response over the physiological glucose concentration range (2.5-20 mM) and good accuracy (standard deviation 5%) were observed. Furthermore, to assess the feasibility of using the novel sensor as one that can be implanted under skin, the sensor was covered by a 0.4 mm thick tissue phantom where it was demonstrable that the response of the sensor to 10 mM glucose change could still be measured in the presence of a layer of tissue shielding the sensor aiming to simulate in vivo condition. In summary, we have demonstrated that it is feasible to develop an affinity-based turbidity sensor that can exhibit a highly specific optical response as a function of changes in local glucose concentration and such response can be accurately monitored by OCT suggesting that the novel sensor can potentially be engineered to be used as an implantable sensor for in vivo monitoring of analytes.
Fiber-Coupled Fluorescence Affinity Sensor for 3-Day In Vivo Glucose Sensing
Ballerstadt R, Evans C, Gowda A, Mc Nichols R, Fiber-Coupled Fluorescence Affinity Sensor for 3-Day In Vivo Glucose Sensing. J Diabetes Sci Technol. 2007 1:384-393.
To evaluate the feasibility of an implantable fiber-coupled fluorescence affinity sensor (FAS) for glucose monitoring in humans, we studied the acute and chronic in vivo performance in hairless rats and pigs.
Methods: The implantable fiber-coupled FAS was constructed by filling a dialysis chamber made of a regenerated cellulose membrane mounted to the distal tip of an optical fiber with fluorescent chemistry based on concanavalin A. Blood sugar changes in animals were induced by injections of insulin and dextrose. Determination of interstitial glucose concentrations in skin tissue was facilitated by measuring the fluorescence response of the FAS.
Results: The acute in vivo response of the fiber-coupled FAS exhibited good correlation coefficients (>0.77) with blood sugar changes and minimal lag times (2–10 min) after 2 hours of sensor implantation. Equilibrium of the sensor signal with interstitial fluid was required less than 60 min after implantation. For both rats and pigs, chronic response of the FAS to blood sugar modulations measured during the third day of implantation successfully demonstrated proof-of-concept for short-term glucose monitoring. A slight decrease in sensitivity after 3 days in the small animal model was assumed to be caused by excessive mechanical forces on the implanted device because of high animal motility.
Conclusions: Overall, the chronic in vivo performance of the FAS in two different animal models over 3 days was clinically acceptable and comparable to other continuous glucose monitoring platforms. The major benefit of the FAS is the absence of “autodestructive” side products and any device-related warm-up time after sensor reconnection.
Concanavalin A for In Vivo Glucose Sensing: A Biotoxicity Review
Ballerstadt R, Evans C, Gowda A, McNichols R, Concanavalin A for In Vivo Glucose Sensing: A Biotoxicity Review, Biosensors & Bioelectronics, 2006 22:275-84.
Over the last two decades there as has been surging scientific interest in employing the glucose- and mannose-specific lectin Concanavalin A (ConA) in affinity biosensors for in vivo glucose monitoring in diabetics. Numerous research groups have successfully shown in in vitro and in vivo studies that ConA-based affinity sensors can monitor glucose very accurately and reproducibly over many months, making ConA-based sensors an extremely interesting prospect for long-term implantation in humans. Despite this progress, there remains concern over the safety of ConA, which has widely been reported as a toxin in the literature. In this article, we review in vitro and in vivo studies related to ConA toxicity in order to assess the health risks posed by ConA in the context of an implantable biosensor. Based on the wealth of information available and on data from our own studies, we can conclude that the site of implantation (subcutaneous skin tissue) and the small amount of ConA (<10 microg/microl) being used in implantable glucose-sensitive detector devices like those proposed by various research groups would pose little or no health risk to its bearer even in the event of unexpected sensor rupture.
In Vivo Performance Evaluation of a Transdermal Near-Infrared FRET Affinity Sensor for Continuous Glucose Monitoring
Ballerstadt R, Gowda A, McNichols R: In Vivo Performance Evaluation of a Transdermal Near-Infrared FRET Affinity Sensor for Continuous Glucose Monitoring, Diabetes Technol Ther. 8:296-311, 2006.
The in vivo performance of a transdermal near-infrared fluorescence resonance energy transfer (FRET) affinity sensor was investigated in hairless rats, in order to validate its feasibility for glucose monitoring in humans. The sensor itself consists of a small hollow fiber implanted in dermal skin tissue, containing glucose-sensitive assay chemistry composed of agarose-immobilized Concanavalin A (ConA) and free dextran. The glucose-dependent fluorescence change is based on FRET between near-infrared-compatible donor and quencher dyes that are chemically linked to dextran and ConA, respectively. We conducted an acute in vivo evaluation of transdermal sensors with an optical fiber-coupled setup over 4 h, and a chronic in vivo evaluation of fully implanted sensors for up to 16 days. The fiber-coupled sensors followed trends of blood glucose concentrations very well with a delay of less than 5 min. The acute performance of the implanted sensors at the day of implantation was similar to that of the fiber-coupled sensors. After 2 weeks the implanted sensors remained functional, evidenced by an adequate correlation between sensor signal and changes in blood glucose excursions, but exhibited delays of approximately 10-15 min. Preliminary characterization of host response showed signs of mild inflammations around the implanted sensor, which were characterized by formation of a 10-20-microm-thick collagen band, typical for capsule formation. An acute study of systemic ConA biotoxicity was also conducted. A histological analysis of various organs and of clinical chemistry data showed no significant differences between rats receiving intradermal injections of ConA at 10 times the concentration in the sensor and rats in a control group (injection of saline solution). The absence of a toxicological or systemic response to ConA at a 10-fold larger amount than in the sensor should dispel concerns over the in vivo safety of ConA-based sensors. This study clearly demonstrates the feasibility of the proposed transdermal FRET-based sensor interrogation concept for glucose monitoring.
FRET-based Near-Infrared Fluorescence Sensor for Glucose Monitoring
Ballerstadt R, Gowda A, McNichols R: FRET-based Near-Infrared Fluorescence Sensor for Glucose Monitoring, Diabetes Technol Ther 6, 191-200, 2004.
novel near-infrared (NIR) fluorescence affinity sensor for continuous glucose monitoring was developed and characterized. The sensor operates by fluorescence resonance energy transfer between a NIR chromophore linked to concanavalin A (ConA) and an NIR fluorophore linked to free dextran. The binding of dextran with ConA in the absence of glucose results in low fluorescence due to quenching; however, the quenching is reversed by competitive displacement of dextran from ConA by glucose. In order to increase thermodynamic stability and the lifetime of the sensor, ConA was immobilized within a macroporous bead matrix. The sensor was contained within a sealed hollow dialysis fiber (o.d. 215 microm, wall thickness 20 microm), preventing the macromolecules from leaking out and enabling glucose to rapidly enter the fiber lumen. A glucose-insensitive reference fluorophore was also incorporated to allow for ratiometric measurements, resulting in a robust sensor output that is independent of positional and/or light intensity changes. The response of the fluorescence affinity sensor to glucose was tested continuously in an automated test chamber at 37 degrees C. The sensor showed good dynamic range within physiologically relevant glucose concentration range (15% change over 2.5-30 mM, no hysteresis), fast response time (2-4 min), and a remarkable long-term stability (6 months). We interpret the improved longevity of this sensor to be the result of an optimized photo exposure regime and immobilization of ConA to the matrix. Its small size, ratiometric output, and NIR fluorescence make this sensor well suited for dermal implantation and continuous transdermal monitoring.
publications :: microbial identification >>
Toward Universal Flavivirus Identification by Mass Cataloging
Jackson, GW, McNichols, RJ, Fox, GE, & Willson, RC.
Toward Universal Flavivirus Identification by Mass Cataloging. Journal of Molecular Diagnostics (2008) 10(2):135-141.
Development of rapid and specific molecular diagnostics for flaviviruses remains an important global health challenge. Herein a platform technology using mass spectrometry that can be used for universal identification and genotyping of these viruses is described. The feasibility of the approach is demonstrated by using it to correctly identify and serotype two strains of dengue virus. Predictive calculations show that the approach can be expected to be equally efficacious for the identification and epidemiological tracking of other flaviviruses including West Nile, Japanese encephalitis, and Yellow Fever. In the case of dengue at least, the method can also distinguish major subgroupings within each serotype. All process steps are amenable to high-throughput, automated implementation. The assay protocol is also compatible with miniature mass spectrometers currently in development, thereby allowing the assay to be brought to remote locations for rapid response to and tracking of outbreaks.
Universal Bacterial Identification by Mass Spectrometry of 16S Ribosomal RNA Cleavage Products
Jackson, GW, McNichols, RJ, Fox, GE, & Willson, RC. Universal
Bacterial Identification by Mass Spectrometry of 16S Ribosomal RNA
Cleavage Products. Int. J. Mass Spectrometry (2007) 261(2-3):218-226.
The public availability of over 180,000 bacterial 16S ribosomal RNA
(rRNA) sequences has facilitated microbial identification and
classification using nucleic acid hybridization and other molecular
approaches. Species-specific PCR, microarrays, and in situ
hybridization are based on the presence of unique subsequences in the
target sequence and therefore require prior knowledge of what
organisms are likely to be present in a sample. Mass spectrometry is
not limited by a pre-synthesized inventory of probe/primer sequences.
It has already been demonstrated that organism identification can be
recovered from mass spectra using various methods including
base-specific cleavage of nucleic acids. The feasibility of broad
bacterial identification by comparing such mass spectral patterns to
predictive databases derived from virtually all previously sequenced
strains has yet to be demonstrated, however. Herein, we present
universal bacterial identification by base-specific cleavage, mass
spectrometry, and an efficient coincidence function for rapid spectral
scoring against a large database of predicted "mass catalogs". Using
this approach in conjunction with universal PCR of the 16S rDNA gene,
four bacterial isolates and an uncultured clone were successfully
identified against a database of predicted cleavage products derived
from over 47,000 16S rRNA sequences representing all major bacterial
taxa. At present, the conventional DNA isolation and PCR steps require
approximately 2 h, while subsequent transcription, enzymatic cleavage,
mass spectrometric analysis, and database comparison require less than
45 min. All steps are amenable to high-throughput implementation.
Jackson, GW, McNichols, RJ, Fox, GE, & Willson, RC. Bacterial
genotyping by 16S rRNA mass cataloging. BMC-Bioinformatics (2006)
7(321).
Zhang, Z, Jackson, GW, Fox, GE, & Willson, RC. Microbial
identification by mass cataloging. BMC-Bioinformatics (2006) 7(117).
Jackson, GW, & Willson, RC. Preparative Electrophoresis with
On-column Optical Fiber Monitoring and Direct Elution into a Minimized
Volume. Biotechnology Letters. (2005) 27:1739-1743.
