Facile synthesis of black phosphorus-zinc oxide nanohybrids for antibacterial coating of titanium surface

Bacterial infection is a major complication associated with bioimplant materials, including titanium (Ti) based orthopedic joints and dental implants. Thus, the fabrication of Ti surfaces with antibacterial activity is highly important. Black phosphorus (BP) is a recently discovered promising two-dimensional semiconductor for various biomedical applications due to its tunable bandgap and physicochemical properties. The present study aimed to synthesize zinc oxide (ZnO) laden BP nanohybrids (NH) and their coatings on a Ti bioimplant surface for improving the antibacterial activities against pathogenic bacteria with and without near-infrared (NIR) light irradiation. Nanohybrids were produced with the slightly oxidized BP NF and electrostatically laden ZnO NP. The produced BP-ZnO NH was a NIR active nanomaterial (up to ∼1000 nm), demonstrating a photothermal effect against bacterial infection and showing improved activity by damaging the cell membrane towards S. aureus in comparison to E. coli. Ti surface coated with BP-ZnO NH embedded chitosan (CS) demonstrated better antibacterial activity than BP NF, especially with NIR light treatment. Additionally, the produced BP nanoflakes and BP-ZnO NH, and their coatings over the Ti surface were found to be toxic at a negligible level. Electrochemical studies revealed the high corrosion resistance of the Ti surface coated with the synthesized antibacterial agents without altering its characteristic passive behavior. Owing to the interactions between the charged groups between chitosan and cell surfaces, a slight increase in antibacterial activities was noticed. Chitosan-based coating matrix embedded with nanoagents has adhered well over the Ti surface due to its inherent film-forming and high adhesion properties.

Real-time monitoring of mono- and dual-species biofilm formation and eradication using microfluidic platform

In a human host, bacterial Staphylococcus aureus and fungal Candida albicans pathogens form a mixed biofilm that causes severe mortality and morbidity. However, research on the formation and eradication of mixed biofilms under dynamic conditions is lacking. Thus, this study employed a microfluidic technique to analyze the real-time formation of mono- and dual-species (S. aureus and C. albicans) biofilms and noninvasive optical treatment of the established mature biofilm using 405-nm laser light. A herringbone mixer thoroughly mixed both bacterial and fungal cells in the growth media before being injected into the observation channels on the microfluidic chip. At a flow rate of 1.0 µL/min of growth media for 24 h, the bacterial biofilm coverage was up to 15% higher than that of the fungal biofilm (50% for bacteria vs. 35% for fungus). On the other hand, the dual-species biofilm yielded the highest coverage of ~ 96.5% because of the collective interaction between S. aureus and C. albicans. The number of cell proliferation events in S. aureus was higher than that of C. albicans for 12 h, which indicates that the S. aureus biofilm was developed faster than C. albicans. The novel in situ test platform showed a significant bactericidal effect (80%) of the 405-nm laser light at 1080 J/cm² towards the established S. aureus biofilm, whereas the same treatment removed approximately 69% of the mixed cells in the dual-species biofilm. This study revealed that the developed microfluidic platform could be utilized to monitor the formation of dual-species biofilms in real-time and laser-induced antimicrobial effects on dual-species biofilms.

Collective bacterial disinfection by opto-chemical treatment on mature biofilm in clinical endoscope

The present study proposes an innovative opto-chemical treatment using a basket-integrated optical device (BIOD) to disinfect mature bacterial biofilm on endoscope channels. A BIOD was designed to position an optical diffuser on the central axis of an endoscope channel and to distribute laser light concentrically to the bacterial biofilm on the channel surface. To apply thermal damage and oxidative stress to the bacterial biofilm, a low concentration of a crosslinking agent (glutaraldehyde ~0.5%) was combined with 808 nm infrared (IR) and 405 nm blue (BL) laser lights. The applied irradiances of IR and BL were 10 W/cm² and 1.6 W/cm² for Teflon channel model and 20 W/cm² and 3.2 W/cm² for a clinical model, respectively. Individual irradiation of either IR or BL for 180 s induced the maximum temperatures of 62 ± 2 °C and 53 ± 3 °C on the biofilm, respectively. The simultaneous opto-chemical treatment reduced a significant population of the bacterial biofilms (7.5-log₁₀ for Staphylococcus aureus and 7.1-log₁₀ for Pseudomonas aeruginosa), which were 2.9-fold and 3.9-fold higher than that of the standard treatment with 2% glutaraldehyde (GA) solution, respectively. The proposed opto-chemical disinfection method can help reduce multi-drug resistant bacteria and prevent cross-infection during the clinical usage of a flexible endoscope.

Multiple cylindrical interstitial laser ablations (CILAs) of porcine pancreas in ex vivo and in vivo models

BACKGROUND

The therapeutic capacity of multiple cylindrical interstitial laser ablations (CILAs) of pancreatic tissue was evaluated with 1064 nm laser light in ex vivo and in vivo porcine pancreatic models.

METHODS

A diffusing applicator was sequentially employed to deliver 1064 nm laser light in a cylindrical distribution to ablate a large volume of pancreatic tissue. Ex vivo tissue was tested at various power levels (5, 7, and 10 W) under US imaging. An in vivo porcine model was used to evaluate the clinical feasibility of multiple CILAs on pancreatic tissue at 5 W via laparotomy (N = 3).

RESULTS

Multiple CILAs symmetrically ablated a range of ex vivo tissue volumes (2.4-6.0 cm³) at various power levels. Multiple CILAs warranted a therapeutic capacity of symmetrically ablating in vivo pancreatic tissue. Both ex vivo and in vivo pancreatic tissues after multiple CILAs at 5 W confirmed the absence of or minimal thermal injury to the peripheral tissue and carbonization.

CONCLUSIONS

The current findings suggest that the collective thermal effects from multiple CILAs can help widely ablate pancreatic tissue with minimal thermal injury. Further in vivo studies will investigate the safety of the proposed CILA treatment as well as acute/chronic responses of pancreatic tissue for clinical translations.

Opto-chemical treatment for enhanced high-level disinfection of mature bacterial biofilm in a Teflon-based endoscope model

Medical societies and public health agencies rigorously emphasize the importance of adequate disinfection of flexible endoscopes. The aim of this work was to propose a novel opto-chemical disinfection treatment against Staphylococcus aureus grown in mature biofilm on Teflon-based endoscope channel models. Laser irradiation using near-infrared and blue wavelengths combined with a low concentration of chemical disinfectant induced both irreversible thermal denaturation and intercellular oxidative stress as a combined mechanism for an augmented antimicrobial effect. The opto-chemical method yielded a 6.7-log₁₀ reduction of the mature Staphylococcus aureus biofilms (i.e., approximately 1.0-log₁₀ higher than current requirement of standard treatment). The proposed technique may be a feasible disinfection method for mitigating the risk associated with infection transmission.

Endoscopic ultrasound (EUS)-guided cylindrical interstitial laser ablation (CILA) on in vivo porcine pancreas

This study aims to demonstrate the feasibility of cylindrical interstitial laser ablation (CILA) in porcine pancreatic tissue to develop a EUS-guided PC ablation technique with enhanced safety. A diffusing applicator created a uniformly symmetrical laser ablation in pancreatic tissue. Ex vivo tests presented that both ablation thickness and volume increased linearly with the applied power (R² = 0.96 and 0.90, respectively) without carbonization and fiber degradation. The numerical simulations matched well with the experimental results in terms of temperature development and thermal damage (deviation of ≤ 15%). In vivo tests with EUS confirmed easy insertion and high durability of the diffusing applicator. EUS-guided CILA warranted a feasible therapeutic capacity of ablating in vivo pancreatic tissue. The proposed EUS-guided CILA can be a feasible therapeutic approach to treat PC with predictable thermal ablation and enhanced safety.

Re-entrant ventricular tachycardia as a complication of ablation of idiopathic ventricular premature beats from the right outflow tract: a case report

Background

We report an unusual case of non-sustained ventricular tachycardia (NSVT) from the epicardial part of the right ventricular outflow tract (RVOT).

Case summary

A 37-year-old woman who underwent in 2006 an ablation for idiopathic ventricular premature beats (VPBs) from the RVOT presented with pre-syncopal NSVT in 2016. A cardiac workup showed no coronary disease, normal biventricular function, and no enhancement on cardiac magnetic resonance imaging. A metabolic positron emission tomography scan excluded inflammation. Biopsies revealed normal desmosomal proteins. An endocardial mapping revealed an area of low voltage potential (<0.5 mV) at the antero-septal aspect of the RVOT corresponding to the initial site of ablation from 2006. Activation mapping revealed poor prematurity and pace-mapping showed unsatisfactory morphologies in the RVOT, the left ventricle outflow tract and the right coronary cusp. An epicardial map revealed a low voltage area at the antero-septal aspect of the RVOT with fragmented potentials opposite to the endocardial scar. Pace-mapping demonstrated perfect match. An NSVT was induced and local electrocardiogram showed mid-diastolic potentials. Ablation was applied epicardially and endocardially without any complication. The patient was arrhythmia free at 4-year follow-up.

Discussion

Cardiac workup allowed to exclude specific conditions such as arrhythmogenic cardiomyopathy, tetralogy of Fallot, sarcoidosis, or myocarditis as a cause for NSVT from the RVOT. The epi and endocardial map showed residual scar subsequent to the first ablation which served as substrate for the re-entrant NSVT. This is the first case which describes NSVT from the epicardial RVOT as a complication from a previous endocardial ablation for idiopathic VPB.

Effect of optical energy modulation on the thermal response of biological tissue: computational and experimental validations

This study develops an energy modulation technique to attain a constant interstitial tissue temperature and to induce the predetermined thermal coagulation without carbonization in tissue. An optical diffuser was employed to deliver 1064 nm light to the biological tissue. The combined mode maintained the interstitial temperature at 70 °C for longer durations compared to the continuous wave mode. Coagulation volumes increased linearly with the time and met the predetermined treatment volume range (0.32-0.52 cm³) after the combined treatment for 100 s. The combined modulation can be a feasible modality to induce the predetermined extent of thermal coagulation for treating papillary thyroid microcarcinoma.

Outcome of video-assisted thoracoscopic implantation of epicardial left ventricular leads with visual targeting for cardiac resynchronization therapy

OBJECTIVES

Our goal was to analyse the implantation and outcome of thoracoscopic epicardial leads after a failed endovascular approach or follow-up (FU) complications after endovascular implantation.

METHODS

We reviewed the records of patients with failed endovascular left ventricular (LV) lead placement or complications during FU, who were subsequently referred to cardiac surgeons for treatment with thoracoscopic LV lead implantation. We analysed the reasons for endovascular failure; the indications for the surgical procedures; and the clinical, echocardiographic and device FU results.

RESULTS

Between 2010 and 2013, a total of 23 patients were included. Among them, 17 of the patients had no previous cardiothoracic surgery, 13 (76%) had successful video-assisted thoracoscopy (VAT) LV lead implantation, 3 (18%) had a conversion to thoracotomy and 1 (6%) failed. Of the 6 patients with prior cardiothoracic surgery, 2 (33%) had VAT only, 3 (50%) had primary thoracotomies and 1 (17%) had a conversion. Two major complications occurred. The reasons for LV endovascular lead failure were subclavian vein occlusion (n = 2), implant failure (n = 13) and complications during the FU period (n = 8). FU information was available for 20 patients: 17 (85%) had improved symptoms. The median FU period was 33 months. A total of 78% of patients were in New York Heart Association (NYHA) functional class III-IV before the operation; 30% were in NYHA functional class III-IV at the last FU examination. The left ventricular ejection fraction increased from 25% before surgery to 31% at the last FU examination. Overall, sensing and pacing threshold values remained stable over time. In 1 patient, lead revision was necessary due to an increase in the pacing threshold.

CONCLUSIONS

VAT implantation of LV leads had an excellent response rate with an improvement in NYHA functional class and left ventricular ejection fraction. The lead measurements were mainly stable over time.

Antibacterial activity of Staphylococcus aureus biofilm under combined exposure of glutaraldehyde, near-infrared light, and 405-nm laser

Healthcare-associated infections have increasingly become problematic in the endoscopic procedures resulting in several severe diseases such as carbapenem-resistant Enterobacteriaceae (CRE)-related infections, pneumonia, and bacteremia. Especially, some bacterial strains are resistant to traditional antimicrobials. Therefore, the necessity of developing new antibiotics or management to deal with bacterial infections has been increasing. The current study combined a low concentration of glutaraldehyde (GTA) with near-infrared (NIR) light and 405-nm laser to entail antibacterial activity on Staphylococcus aureus biofilm. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and colony forming unit (CFU) counting were used to quantify the viable cells while fluorescent and scanning electron microscopic images were used to qualitatively evaluate the cell membrane integrity and structural deformation, respectively. Practically, S. aureus biofilm was highly susceptible (7% cell viability and 6.8-log CFU/cm2 bacterial reduction for MTT assay and CFU analysis, respectively) to the combination of GTA (0.1%), NIR light (270 J/cm2), and 405-nm laser (288 J/cm2) exposure. GTA could form either DNA-protein or protein-protein crosslinks to inhibit DNA and protein synthesis. The NIR light induced the thermal damage on protein/enzymes while 405-nm laser could induce reactive oxygen species (ROS) to damage the bacterial membrane. Thus, the proposed technique may be a feasible modality for endoscope cleaning to prevent any secondary infection in the healthcare industry.

Effect of spatial light distribution on the thermal response of vascular tissue

The aim of the current study is to investigate the effect of radial and cylindrical light distributions on the response of vascular tissue during 1470-nm irradiation in ex vivo models. Due to a low irradiance (5.3 W/cm²) and wide light distribution, cylindrically diffusing irradiation yielded uniform thermal coagulation while radial irradiation accompanied delamination of layers in leporine veins. Bovine foot model testing verified that the diffusing irradiation was associated with the steady maximum temperature and no tissue attachment, compared with the radial irradiation. The proposed cylindrical light application can be a feasible way to treat varicose veins in an effective manner.

Computational analysis of linear energy modulation for laser thermal coagulation

Accurate treatment planning and monitoring are critical factors to ensure safe and effective outcomes of laser thermal coagulation (LTC). Computational and experimental models based upon linear energy modulation were deployed to predict temperature distribution and thermal damage within ex vivo porcine liver. 1470-nm Gaussian emission was confirmed by using digital imaging and the customized goniometry. The tissue temperature was maintained in the pre-determined range (65~75 °C) to induce thermally destructive volumes of 0.23 cm³ (simulation) and 0.17 ± 0.05 cm³ (experiment) once the applied power was linearly reduced from 3.5 W to 0.2 W in 50 s ("3.5 W fast slope" laser modulation mode). The proposed model may be a useful tool to predict thermal responses of the tissue during LTC.

Depolymerization of sodium polyphosphates on an iron oxide surface at high temperature

Density functional theory (DFT) and first principles molecular dynamics (FPMD) studies of pyrophosphate cluster Na₄P₂O₇ and triphosphate cluster Na₅P₃O₁₀ absorbed and decomposed on an Fe₂O₃(0001) surface have been conducted. Comparative analyses of the structure properties and adsorption processes during the simulation at elevated temperature have been carried out. The results depict the key interactions including the covalent P-O bonds, pure ionic Na-O or Fe-O interactions. The iron oxide surface plays an important role in the bridging bond decomposition scheme which can both promote and suppress phosphate depolymerization. It is found that the chain length of polyphosphates does not have considerable effects on the decomposition of phosphate clusters. This study provides detailed insights into the interaction of a phosphate cluster on an iron oxide surface at high temperature, and in particular the depolymerization/polymerization of an inorganic phosphate glass lubricant, which has an important behavior under hot metal forming conditions.

Spatial effect of conical angle on optical-thermal distribution for circumferential photocoagulation

A uniformly diffusing applicator can be advantageous for laser treatment of tubular tissue. The current study investigated various conical angles for diffuser tips as a critical factor for achieving radially uniform light emission. A customized goniometer was employed to characterize the spatial uniformity of the light propagation. An ex vivo model was developed to quantitatively compare the temperature development and irreversible tissue coagulation. The 10-mm diffuser tip with angle at 25° achieved a uniform longitudinal intensity profile (i.e., 0.90 ± 0.07) as well as a consistent thermal denaturation on the tissue. The proposed conical angle can be instrumental in determining the uniformity of light distribution for the photothermal treatment of tubular tissue.

[Cardiology update in 2016]

In 2016 the European Society of Cardiology (ESC) published new guidelines. These documents update the knowledge in various fields such as atrial fibrillation, heart failure, cardiovascular prevention and dyslipidemia. Of course it is impossible to summarize these guidelines in detail. Nevertheless, we decided to highlight the major modifications, and to emphasize some key points that are especially useful for the primary care physician.

[Very long term follow-up after radiofrequency ablation for atrial fibrillation: the Geneva experience]

Catheter ablation (CA) has emerged as an increasingly popular treatment option for selected patients with atrial fibrillation (AF) because drugs are frequently limited by side effects and poor effectiveness. However, very little data is available regarding outcomes of CA of AF beyond 5 years. Guidelines' recommendations are not clear regarding long-term oral anticoagulation (OAC) after 2 years. We assessed thromboembolic events (TE) and AF ablation outcomes at very long-term follow-up (> 5 years) after CA. During a mean follow-up of 9 years after CA, 68% patients were in stable sinus rhythm without anti-arrhythmic drugs and the TE event rate was 0.41 per 100 patients/year. Our data suggests that patients post ablation with a high risk for stroke (CHA2DS2-VASc ≥ 2) should however continue OAC treatment.