The aim of this study was to develop a microfluidic-powered optical platform to real-time monitor microbial biofilm formation at the single-cell level under a precisely controlled laminar flow condition and to rapidly evaluate the cleaning effect of laser irradiation on a mature microbial biofilm. A 405-nm laser light was used to evaluate the cleaning effects on both mature biofilms. The results show that Staphylococcus aureus biofilm was reduced by 80% in population, which was 20% higher than that of Candida albicans biofilm. A further study will be conducted in a poly-microbial biofilm commonly causing urinary tract infections.
A balloon-integrated diffusing applicator has been developed to treat urethral stenosis. To deliver uniform light, the balloon was inflated by inserting water. However, the air trap in the balloon can cause non-uniform ablation in the tissue due to different thermal boundary conditions between air and water. The current study aims to evaluate optical and thermal effects of the air trap on cylindrical laser treatment of urethral stenosis. Although a siginificant decrease of the air volume in the balloon, at least two deflations were required to entail uniform coagulation in a tubular structure and to avoid the unpredictable optical/thermal effects from the air trap.
The aim of the current study was to investigate the effect of spatial light distribution from flat (FA) and diffusing applicator (DA) on photothermal therapy (PTT) of tumor treatment in in vivo models. Due to cylindrical and wide light distribution, DA yielded uniform thermal coagulation as well as covering the entire tumor region while FA partially ablated the tumor (i.e., two-fold larger). In vivo tests presented that the DA group significantly reduced the tumor volume (i.e., 0.7 cm3), whereas the FA group yielded unpredictable tumor removal and remarkably tumor growth (i.e., 1.6 cm3) after seven-days treatment (Day 7). The proposed DA-assisted PTT can be a feasible way to treat prostate tumor in an effective and safe manner.
Flexible endoscope reprocessing is an important requirement to minimize the risk of cross-infection between patients due to incomplete disinfection of a bacteria biofilm. The present study introduces a novel opto-chemical treatment to disinfect microbial biofilms (both Gram-positive and Gram-negative bacterial biofilms), commonly found in flexible endoscopes. A low concentration disinfectant combined with infrared and blue light irradiations was applied to disinfect the bacterial biofilms in the endoscope. A basket-integrated optical device was designed to deliver uniform and concentric light onto the channel surface of the endoscope. Colony-forming unit assays were performed to quantify the vial cells while scanning electron microscopy (SEM) illustrated an extracellular matrix (ECM) of the bacterial biofilm. The infrared light irradiation heated the surface of the bacterial biofilm to ~ 65°C. The blue light irradiation induced a relative temperature increase of 30°C on the bacterial biofilm. The results showed that the opto-chemical treatment reduced approximately 7.5-log10 of the bacterial biofilm, which was four times higher than that of a standard disinfectant solution (2% glutaraldehyde). In comparison with the control untreated samples with intact ECMs, the SEM images showed significant damage to the bacterial biofilm under the opto-chemical treatment. The combined treatment induced antimicrobial effects in terms of inhibition of protein synthesis, thermal destruction, and oxidative stress, eradicating the bacterial biofilm more than the standard chemical disinfection. The proposed technique could be an alternative approach to disinfect the microbial biofilms and minimize the risk of secondary infection in endoscopy-related medical facilities.
A diffusing applicator integrated with a balloon catheter has been developed to treat various types of stenosis [1,2]. To deliver uniform laser light to the tubular tissue, the balloon was inflated by inserting water. However, the residual air trapped in the balloon can cause non-uniform ablation in the tissue due to different thermal boundary conditions between air and water. The current study aims to evaluate optical and thermal effects of the air trap on cylindrical laser treatment on the tubular tissue. A balloon-integrated diffusing applicator was fabricated to deliver 532-nm laser light and to expand an ex vivo liver ductal tissue. The balloon was deflated by using a syringe and then inflated with water. Various numbers of deflations were tested for ex vivo experiments using porcine liver duct. For each deflation condition, the 532 nm laser light was delivered to the tissue at 10 W for 45 s. The liver tissue experienced more coagulation near the air trap region than the water-filled region. In spite of a significant decrease of the air volume in the balloon, at least two deflations were required to entail uniform tissue coagulation in a tubular structure and to avoid the unpredictable optical/thermal effects from the air trap. Further in vivo experiments will be performed to evaluate the effect of the air trap on chronic tissue responses after the cylindrical laser treatment for clinical translations.
Endoscopic biliary drainage including stent are a well-accepted clinical method for treating common bile duct (CBD) stenosis, but the treatment is only successful in the short term with stent exchange at 3 to 6 months. The current study aims to demonstrate a novel endoscopic retrograde cholangiopancreatography (ECRP)-guided laser ablation technique on CBD stenosis by using a balloon catheter-integrated diffusing applicator (BCDA) for uniform treatment of tubular tissue. A 532 nm laser system was employed with BCDA to thermally coagulate the CBD tissue. For performance assessments, photothermal and mechanical responses of the tissue were evaluated in both ex vivo and in vivo mini-pig models in terms of structural and histological variations after the laser treatment. The ex vivo results confirmed the irreversible thermal denaturation in liver tissue without carbonization. The in vivo mini-pig tests confirmed high durability of BCDA during the ERCP procedures and no evidence of CBD perforation. Histological analysis validated a thin circumferential coagulation in the CBD with no or minimal injury to the peripheral organs. The proposed BCDA-assisted treatment may be a feasible endoscopic ablation method for treating disease or disorder in a tubular tissue structure. Further in vivo studies will investigate CBD stenosis-developed animal models to evaluate the chronic response of the laser-treated CBD tissue as well as the recurrence of CBD stenosis.
KEYWORDS: Microfluidics, Bacteria, Laser therapeutics, Visualization, Systems modeling, Process modeling, Modulation, Microscopes, Medicine, Medical research
Microfluidics technology holds a great promise in evaluating the biofilm growth and the effectiveness of real-time cleaning. We have developed a microfluidic-assisted optical system to evaluate the cleaning effect of bacteria using lasers.
Endoscopic ultrasound (EUS)-guided laser ablation (LA) has been recently investigated for the treatment of pancreatic tumor. This study aimed to demonstrate the feasibility of EUS-guided LA in porcine pancreatic tissue to treat pancreatic tumor ablation with minimal thermal injury to adjacent tissue. A 1064-nm Nd:YAG laser was applied to both ex vivo and in vivo porcine pancreatic tissue through a diffusing applicator. Overall, coagulation diameter increased linearly with the applied power without carbonization and fiber degradation on ex vivo tests (i.e., R2 = 0.87). Thediffusing applicator created a uniformly symmetrical laser ablation in pancreatic tissue. In vivo tests with EUS confirmed easy insertion and high durability of the diffusing applicator. The proposed EUS-guided diffusing LA can be a feasible therapeutic approach to effectively treat pancreatic tumor with predictable thermal ablation and enhanced safety
The present research proposed a combination of a chemical (glutaraldehyde - GTA) with either 808 nm or 405 nm laser light to disinfect bacterial biofilms (both gram-positive and gram-negative bacteria) inside polytetrafluoroethene tubes that mimic the working channels of the flexible ureteroscopes. The combination of (GTA+405 nm) was hypothesized to be more effective than the combination of (GTA+ 808 nm) for ureteroscope reprocessing to prevent any secondary infection in the urinary tract during the ureteroscopy.
Recently, laser-induced interstitial thermotherapy (LITT) has been investigated and considered a minimally invasive treatment method to achieve deep coagulation in prostate tumor. However, excessive heating in the target region adversely affects the adjacent healthy tissue, possibly leading to thermal injury to critical organs such as urethra, sphincter, erectile nerves, and bowel. The aim of the current study was to develop a pulse-processing model to predict and manage the temperature development and thermal coagulation region during LITT-prostate cancer treatment. A CW 532-nm laser beam was expanded and then focused on the fiber connector by using a combination of concave and convex lens. A shutter was placed in-between the two lens, and all cycle parameters including exposure, delay, and duty cycle were driven by using a control system in conjunction with LabView software. The 5-W 532 nm laser system connected with the pulse–processing model was employed with a diffusing applicator to thermally coagulate liver tissue. The cyclic parameters were divided into three sequential periods: CW mode, pulse-processing mode, and laser-off mode. The results showed that after 15-s irradiation, the local tissue temperature achieved 70 °C. Based on optical and thermal properties of the tissue, the pulse-processing mode with a duty cycle of 70% (exposure time = 350-ms vs. delay time = 150-ms) was calculated and used in the experiment. Due to the pulse-processing mode, the surface temperature was initially maintained at 70 °C for 60 s with a steady-state error of less than 2 °C. The proposed pulse-processing model can be a feasible tool to provide the optimal therapeutic conditions for the LITT-prostate cancer treatment.
Flexible cystoscopy is a widely used diagnostic and therapeutic procedure in urology. However, some dangerous bacteria are resistant to traditional antibiotics. Thus, the current study introduced a combination of glutaraldehyde (GTA), 808- nm, and 405-nm laser to disinfect Staphylococcus aureus bacterial biofilms inside flexible cystoscopes based upon a Teflon tubing model. Based upon the pilot study, the samples were exposed either under GTA (0.5% in 180 s), 808-nm (1.6 W/cm2 in 180 s), and 405-nm laser (1.6 W/cm2 in 180 s) alone or their combinations. An infrared (IR) camera was deployed to provide the real-time monitoring of temperature development on the biofilm surface while colony forming unit (CFU) analysis was employed to count viable cells before and after the treatment. The preliminary results showed that GTA, 808-nm, and 405-nm laser alone could induce a 2.2-, 1.4-, and 2-log10 CFU/cm2 reduction of S. aureus bacterial biofilm, respectively. However, their triple combination could eradicate around 6.5-log10 CFU/cm2 reduction in microorganism population. Therefore, the triple combination may be a useful modality for cystoscope reprocessing to prevent any secondary infection in the urinary tract during the cystoscopy.
Cystoscope cleaning and sterilization are one of the most important procedures to prevent infection in urological surgery. The current cleaning techniques have demonstrated lengthy process times or insufficient decontamination of flexible cystoscopes. Thus, high-level disinfection and sterilization are still needed to enhance cleaning efficacy. The current study demonstrated the feasibility of a combination of 405-nm laser and infrared (IR) lights to inactivate bacterial biofilms inside the working channels. Staphylococcus strains in suspension (concentration ~ 108 CFU/mL) were incubated in 24 hours at 37 0C to form biofilms on multi-well plates. Each sample initially experienced 5-minute IR dehydration (intensity = 1.5 W/cm2), and 405-nm laser system was then used for bacterial disinfection at various conditions: 19.1, 38.2, 57.3, and 76.4 J/cm2. An IR camera was deployed for real-time monitoring temperature on the biofilm surface. MTT assay was employed to assess cell viability after the treatment. The results showed that staphylococcus bacteria in liquid suspension were more resistant to 405-nm laser light than those in hard surfaces. In addition, the 405-nm laser treatment resulted in less decontaminating effectiveness while the 405-nm laser in conjunction with IR light could induce bacterial reduction up to 75% possibly due to effect low temperature dehydration. The proposed technique can be a useful modality for cystoscope cleaning and sterilization to prevent any secondary infection in the urinary tract during urological procedures. Further experiments will be conducted to validate reprocessing efficacy on various types of bacterial biofilm models along with high-level disinfectants to find the optimal cleaning doses.
For last two decades, endovenous laser therapy (EVLT) is one of the most widely accepted surgical options for treating incompetent great and small saphenous veins. However, due to excessive heating during EVLT, the major complications include pain and burning that often increase the risk of dermatitis disease. The aim of the current study was to quantitatively compare commercially-available radial fibers with newly-developed diffusing applicators for 1470 nm-EVLA in terms of temperature elevation and vein deformation. Rabbit veins were used as an ex vivo model for EVLA. A 5-W 1470 nm laser system in conjunction with the radial and diffusing fibers was employed to thermally coagulate the venous tissue. A goniometric measurement validated uniform and isotropic distribution of laser light in polar and longitudinal directions (i.e., normalized intensity = 0.84±0.08). The diffusing applicator induced a 20 % lower maximum temperature than the radial fiber did (maximum temperature = 79.2 °C for radial vs. 63.3 °C for diffusing). Due to higher irradiance, the radial fiber was associated with a transient temperature change of 5.9 °C/s, which was 1.5-fold faster than the diffusing applicator (i.e., 2.4 °C/s). However, the degree of cross-sectional area reduction in the veins was almost comparable for both the fibers (i.e., 53% for radial vs. 48% for diffusing). Due to longer irradiation length, the diffusing applicator demonstrated wider treatment coverage and less fiber speed-dependent. On account of easy pullback technique and uniform thermal effect, the proposed cylindrically diffusing applicator can be a feasible optical device to effectively treat varicose veins. Further in vivo studies will be performed to identify the complete removal of the vein disease and healing response of the venous tissue.
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