Kazuhiro Kaneko

Development of near infrared-fluorescent nanophosphors and applications for cancer diagnosis and therapy

The use of near infrared (NIR) light for biomedical photonics in the wavelength region between 800 and 2000 nm, which is called biological window, has received particular attention since water and biological tissues have minimal optical loss due to scattering and absorption as well as autofluorescence in this region. Recent development of InGaAs CCD enables observations in this wavelength region. In the present paper, we report development of Yb and Er-doped yttrium oxide nanoparticles (Y2O3:YbEr-NP) which show strong NIR emission under NIR excitation (NIR-NIR emission). We also demonstrate that NIR emission can be observed through swine colon wall. Based on these results, we propose a possible application of Y2O3:YbEr-NP for cancer diagnosis and therapy using NIR-NIR imaging system. Our results also suggest potential applications of Y2O3:YbEr-NP for noninvasive detection of various diseases.

Extra-luminal detection of assumed colonic tumor site by near-infrared laparoscopy

BackgroundLocalization of colorectal tumors during laparoscopic surgery is generally performed by tattooing into the submucosal layer of the colon. However, faint and diffuse tattoos may lead to difficulties in recognizing cancer sites, resulting in inappropriate resection of the colon. We previously demonstrated that yttrium oxide nanoparticles doped with the rare earth ions (ytterbium and erbium) (YNP) showed strong near-infrared (NIR) emission under NIR excitation (1550xa0nm emission with 980xa0nm excitation). NIR light can penetrate deep tissues. In this study, we developed an NIR laparoscopy imaging system and demonstrated its use for accurate resection of the colon in swine.MethodsThe NIR laparoscopy system consisted of an NIR laparoscope, NIR excitation laser diode, and an NIR camera. Endo-clips coated with YNP (NIR clip), silicon rubber including YNP (NIR silicon mass), and YNP solution (NIR ink) were prepared as test NIR markers. We used a swine model to detect an assumed colon cancer site using NIR laparoscopy, followed by laparoscopic resection. The NIR markers were fixed at an assumed cancer site within the colon by endoscopy. An NIR laparoscope was then introduced into the abdominal cavity through a laparoscopy port.ResultsNIR emission from the markers in the swine colon was successfully recognized using the NIR laparoscopy imaging system. The position of the markers in the colon could be identified. Accurate resection of the colon was performed successfully by laparoscopic surgery under NIR fluorescence guidance. The presence of the NIR markers within the extirpated colon was confirmed, indicating resection of the appropriate site.ConclusionsNIR laparoscopic surgery is useful for colorectal cancer site recognition and accurate resection using laparoscopic surgery.

Development of Novel Endoscope with NIR Camera Using Real-time Video Composite Method

Recently, a near-infrared (NIR) Fluorescence Biomedical Imaging (FBI) attracts increasing attention from many researchers. The light wavelength region in 1000 nm to 1700 nm has been known to be a “biological window” where the both tails of scattering and infrared absorption decrease to form a valley in optical loss spectra of biological objects. The inside of biological objects which cannot be usually seen in a normal endoscopy can be seen by using NIR, because of NIR light can penetrate in biological objects, and the further development of medical equipment is expected by using NIR. We are developing towards the realization of a NIR laparoscope which composes of a NIR camera and a visible light camera. The visible light camera can observe the surface in biological objects, and the NIR camera can observe the inside of biological objects. The NIR laparoscope has a potential of the helpful in the early detection of tumor. In our current system, the images captured by a NIR laparoscope and a normal laparoscope are shown on the separate screens simultaneously. The operator need to more experience to use the system. It was difficult to figure out the clinical usefulness of the NIR laparoscope with a visible light camera. We proposed the image composite method using a projection transform and a distance correction. The proposed method, compared to existing methods, is simple and fast. The proposed composite method of the two video images from a NIR camera and a visible light camera can facilitate the diagnosis and the surgery. The proposed system can reduce not only operator’s burden but also patient one’s. We are applying the proposed method to a laparoscope and conducting the evaluation experiment of the proposed method.

The reduced ph method with indirect plasma for safe and effective disinfection in dentistry and surgery

For the purpose of disinfecting human bodies in dental and surgical therapies, sterilization experiments in solution have been conducted with low-temperature atmospheric-pressure plasmas. For the plasma disinfection in the body fluid, we have successfully developed the reduced pH method that strong bactericidal activity can be achieved when the solution is sufficiently acidic [1]. It is interesting that a critical pH value of about 4.7 exists for the bactericidal activity. This critical value may be associated with pKa of the dissociation equilibrium between superoxide anion radicals (O 2 −•) and hydroperoxy radicals (HOO•), which is known to be approximately 4.8. As the nature without electric charge, HOO• can diffuse into bacterial cytosol via hydrophobic cell membrane, therefore HOO• shows extremely stronger bactericidal activity than negative charged O 2 −•. O 2 −• generated in gas penetrate into liquid via plasma-air-liquid interactions [2, 3]. For the enough long lifetime of O 2 −• in gas as air ion, O 2 −• can be supplied into liquid by non-contact plasma. The non-contact plasma with 400 cm extra tube has e quivalent strong bactericidal activity only with the reduced pH method. In addition, we found that the plasma treated water has strong bactericidal activity for a few minutes with the reduced pH method. This suggests that the disinfection can be done by the plasma treated water which contains short-lived active species (cannot supplied by chemical reagent) and it would bring safety plasma medicine considering usual contact or non-contact plasmas to human body. Currently, animal experiments for root canal therapy in dentistry [4] and surgical site infection prevention in surgery have been done with indirect plasma disinfection techniques of non-contact plasma and plasma treated water.