The role of l -arginine/NO/cGMP/K ATP channel pathway in the local antinociceptive effect of berberine in the rat formalin test

Berberine is an isoquinoline alkaloid naturally produced by several types of plants. Berberine has extensive pharmacological effects, such as anti-diabetic, anti-inflammatory, and antioxidant effects. In the current study, we assess the antinociceptive effects of berberine and its association with the l -arginine ( l -Arg)/NO/cGMP/K ATP channel pathway via intraplantar administration in rats. To examine the antinociceptive properties of berberine, the formalin test was conducted. The number of rat paw flinches was counted for an h. l -Arg (precursor of nitric oxide, 3-30  μ g/paw), l -NAME (NO synthase inhibitor, 10 and 100  μ g/paw), methylene blue (guanylyl cyclase inhibitor, 100 and 200  μ g/paw), and glibenclamide (ATP-sensitive potassium channel blocker, 10 and 30  μ g/paw) were locally injected, respectively, into the right hind paws of rats as a pre-treatment before berberine injection to understand how the l -Arg/NO/cGMP/K ATP pathway plays a role in the antinociceptive effect of berberine. The ipsilateral injection of berberine into the right paw (0.1-10 0   μ g/paw) showed a dose-dependent antinociceptive effect in both the first and second phases of the formalin test, almost similar to morphine (25  μ g/paw). Intraplantar injection of l -Arg (30 µg/paw) increased the antinociceptive effect of berberine in the second phase. In addition, injection of l -NAME, methylene blue, and glibenclamide caused a reduction in the antinociceptive effect of berberine throughout the second phase in a dose-dependent manner. However, the antinociceptive effects of berberine in the first phase of the rat formalin test were not affected by this pathway. As a novel local antinociceptive agent, berberine can exert a peripheral antinociceptive effect via the l -Arg/NO/cGMP/K ATP channel pathway.

Evaluation of topical methylene blue nanoemulsion for wound healing in diabetic mice

CONTEXT

Diabetic wounds (DW) are a complication of diabetes and slow wound healing is the main manifestation. Methylene blue (MB) has been shown to exhibit therapeutic effects on diabetes-related diseases.

OBJECTIVE

To investigate the mechanisms of action of MB-nanoemulsion (NE) in the treatment of DW.

MATERIALS AND METHODS

The concentration of MB-NE used in the in vivo and in vitro experiments was 0.1 mg/mL. Streptozocin-induced diabetic mice were used as models. The mice were separated into nondiabetic, diabetic, MB-NE treated, and NE-treated groups. Intervention of high glucose-induced human umbilical vein endothelial cells using MB-NE. The mechanism by which MB-NE promotes DW healing is investigated by combining histological analysis, immunofluorescence analysis, TUNEL and ROS assays and western blotting.

RESULTS

In diabetic mice, the MB-NE accelerated DW healing (p < 0.05), promoted the expression of endothelial cell markers (α-SMA, CD31 and VEGF) (p < 0.05), and reduced TUNEL levels. In vitro, MB accelerated the migration rate of cells (p < 0.05); promoted the expression of CD31, VEGF, anti-apoptotic protein Bcl2 (p < 0.05) and decreased the expression of the pro-apoptotic proteins cleaved caspase-3 and Bax (p < 0.05). MB upregulated the expression of Nrf2, catalase, HO-1 and SOD2 (p < 0.05). In addition, MB reduced the immunofluorescence intensity of TUNEL and ROS in cells and reduced apoptosis. The therapeutic effect of MB was attenuated after treatment with an Nrf2 inhibitor (ML385).

DISCUSSION AND CONCLUSION

This study provides a foundation for the application of MB-NE in the treatment of DW.

Anticholinergic Toxidrome as a Possible Explanation for Methylene Blue Toxicity

BACKGROUND Methylene blue has multiple uses in medicine. It is generally used to treat refractory vasoplegia and methemoglobin toxicity, and can be used as a dye to localize the parathyroid glands intra-operatively. In refractory vasoplegia, methylene blue inhibits endothelial nitric oxide and guanylate cyclase, causing vasoconstriction and potentially stabilizing blood pressure. Multiple complications have been associated with the use of methylene blue. These are related to either the sole effect of methylene blue or the combined effect of methylene blue and certain antidepressants, such as selective serotonin reuptake inhibitors (SSRIs). To the best of our knowledge, in the setting of post-cardiac surgery vasoplegia, there have been no reports of the neurological toxicity of methylene blue in the absence of SSRI use. In this case report, we describe the anticholinergic manifestations associated with the use of methylene blue in post-cardiac surgery vasoplegia. CASE REPORT A male patient in his mid-sixties with severe mitral regurgitation underwent elective mitral valve replacement. Postoperatively, he was hypotensive and required a high dose of vasopressors. Methylene blue was administered to treat refractory vasoplegia. The patient became anuric and febrile, with bilateral mydriasis. Internal cooling and continuous renal replacement therapy were initiated, and symptoms rapidly resolved. The patient was discharged after prolonged hospitalization with a permanent catheter for hemodialysis. CONCLUSIONS Anticholinergic toxidrome may explain the neurological adverse effects associated with high doses of methylene blue. Physicians should be cautious when using methylene blue in combination with other anticholinergic drugs and in conditions of renal failure. The development of methylene blue toxicity warrants the urgent discontinuation of the agent and early drug elimination.

Interaction of Methylene Blue with Severe Acute Respiratory Syndrome Coronavirus 2 Envelope Revealed by Molecular Modeling

Methylene blue has multiple antiviral properties against Severe Acute Respiratory Syndrome-related Coronavirus 2 (SARS-CoV-2). The ability of methylene blue to inhibit different stages of the virus life cycle, both in light-independent and photodynamic processes, is used in clinical practice. At the same time, the molecular aspects of the interactions of methylene blue with molecular components of coronaviruses are not fully understood. Here, we use Brownian dynamics to identify methylene blue binding sites on the SARS-CoV-2 envelope. The local lipid and protein composition of the coronavirus envelope plays a crucial role in the binding of this cationic dye. Viral structures targeted by methylene blue include the S and E proteins and negatively charged lipids. We compare the obtained results with known experimental data on the antiviral effects of methylene blue to elucidate the molecular basis of its activity against coronaviruses.

The effects of acute Methylene Blue administration on cerebral blood flow and metabolism in humans and rats

Methylene Blue (MB) is a brain-penetrating drug with putative neuroprotective, antioxidant and metabolic enhancing effects. In vitro studies suggest that MB enhances mitochondrial complexes activity. However, no study has directly assessed the metabolic effects of MB in the human brain. We used in vivo neuroimaging to measure the effect of MB on cerebral blood flow (CBF) and brain metabolism in humans and in rats. Two doses of MB (0.5 and 1 mg/kg in humans; 2 and 4 mg/kg in rats; iv) induced reductions in global cerebral blood flow (CBF) in humans (F(1.74, 12.17)5.82, p = 0.02) and rats (F(1,5)26.04, p = 0.0038). Human cerebral metabolic rate of oxygen (CMRO2) was also significantly reduced (F(1.26, 8.84)8.01, p = 0.016), as was the rat cerebral metabolic rate of glucose (CMRglu) (t = 2.6(16) p = 0.018). This was contrary to our hypothesis that MB will increase CBF and energy metrics. Nevertheless, our results were reproducible across species and dose dependent. One possible explanation is that the concentrations used, although clinically relevant, reflect MB's hormetic effects, i.e., higher concentrations produce inhibitory rather than augmentation effects on metabolism. Additionally, here we used healthy volunteers and healthy rats with normal cerebral metabolism where MB's ability to enhance cerebral metabolism might be limited.

Photodynamic Therapy Minimally Affects HEMA-DMAEMA Hydrogel Viscoelasticity

Soft matter implants are a rapidly growing field in medicine for reconstructive surgery, aesthetic treatments, and regenerative medicine. Though these procedures are efficacious, all implants carry risks associated with microbial infection which are often aggressive. Preventative and responsive measures exist but are limited in applicability to soft materials. Photodynamic therapy (PDT) presents a means to perform safe and effective antimicrobial treatments in proximity to soft implants. HEMA-DMAEMA hydrogels are prepared with the photosensitizer methylene blue included at 10 and 100 µM in solution used for swelling over 2 or 4 days. Thirty minutes or 5 h of LED illumination at9.20 m W c m 2 $9.20\frac{{mW}}{{c{m}^2}}$ is then used for PDT-induced generation of reactive oxygen species in direct contact with hydrogels to test viable limits of treatment. Frequency sweep rheological measurements reveal minimal overall changes in terms of loss modulus and loss factor but a statistically significant drop in storage modulus for some PDT doses, though within the range of controls and biological variation. These mild impacts suggest the feasibility of PDT application for infection clearing in proximity to soft implants. Future investigation with additional hydrogel varieties and current implant models will further detail the safety of PDT in implant applications.

Photodynamic reactions using high-intensity red LED promotes gingival wound healing by ROS induction

Photodynamic therapy is a treatment that combines a light source with a photosensitizer. LEDs have attracted considerable attention in clinical dentistry because they are inexpensive and safe to use. Although the interaction between photosensitizers and LEDs in dental practice is effective for treating periodontal disease by killing periodontopathic bacteria, little is known about the effects of LEDs on human gingival fibroblasts (HGnFs), which play an important role in gingival wound healing. In this study, we investigated the effects of high-intensity red LED irradiation on HGnFs after the addition of methylene blue (MB), one of the least harmful photosensitizers, on wound healing and reactive oxygen species (ROS) production induced by photodynamic reactions. We found that irradiation of MB with high-intensity red LED at controlled energy levels promoted cell proliferation, migration, and production of wound healing factors. Furthermore, ROS production by a photodynamic reaction enabled the translocation of phosphorylated Grb2-associated binder-1, activating Extracellular signal-regulated kinase 1/2 and c-Jun N-terminal kinase signals. Our findings suggest that proper control of ROS production has a beneficial effect on gingival fibroblasts, which constitute periodontal tissue, from the perspective of gingival wound healing.

Synthesis, electrospinning, and molecular docking of poly(methyl methacrylate) Schiff bases and their applications as polymeric antimicrobial agents and for dye removal

The antibacterial activity of a variety of modified poly(methyl methacrylate) Schiff bases against common microbial infections and removal of methylene blue (MB) dye were screened. The Schiff bases were synthesized from the reaction of the modified (PMMA) with vanillin (PMMA)Van and cinnamaldehyde (PMMA)Cin. By using Fourier transformer infrared (FT-IR), X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), the structures of the nanofibers of the synthesized Schiff bases were confirmed. The modified Kirky-Bauer method was used to screen the antibacterial activities of all the obtained materials against various bacterial species, including gram-positive bacterial (Bacillus subtilis (4k1p), Staphylococcus aureus), Gram-negative bacteria (Escherichia coli (7ab3), Pseudomonas aeruginosa). Inhibition zones against gram-positive bacteria ranged in diameter from 7 to 14 mm, whereas for the Gram-negative bacteria, the inhibition zones found to be ranged between 6 and 13 mm. With a minimum bactericidal concentration (MBC) of 8 mg/mL and a minimum inhibitory concentration (MIC) of 2 mg/mL, (PMMA)Van shown the greatest antibacterial activity. Lastly, molecular docking research was done to better understand the interactions between this series' targets and inhibitors for (PMMA)Van and (PMMA)Cin (4k1p and 7ab3). Molecular modeling of these surface-adsorbed polymers indicated that (PMMA)Van binds more strongly with Nitrogen than does (PMMA)Cin through extra hydrogen-bonding interactions. All the developed materials were evaluated for the removal of 0.1 g/L methylene blue dye (MB) from an aqueous solution. The elimination percentage of MB dye ranged from 26.67% by using 0.05 g powder of (PMMA)Cin to 85.63% by employing 0.05 g nanofibers of (PMMA)Van.

Phenylalanine-Arginine-β-Naphthylamide Enhances the Photobactericidal Effect of Methylene Blue on Pseudomonas aeruginosa

Objective: To investigate the effectiveness, dosing sequence, concentration, and mechanism of antimicrobial photodynamic inactivation (aPDI) using methylene blue (MB) plus phenylalanine-arginine-β-naphthylamide (PAβN) against Pseudomonas aeruginosa. Methods: P. aeruginosa bacterial suspension was incubated with MB for different times (5-240 min), and then, 10 J/cm2 red light was irradiated. The efflux pump inhibitor (EPI) PAβN (10-100 μg/mL) was combined with MB (1-20 μM) in different sequences (PAβN-first, PAβN+MB, PAβN-after). Colony-forming units were then determined by serial dilution. Results: Using MB 10 μM plus 10 J/cm2, the killing effect of MB-aPDI on P. aeruginosa increased first and then decreased with longer incubation time. The killing effect of MB+PAβN-aPDI on P. aeruginosa was better than that of MB-aPDI (p < 0.05) by up to 2 logs. PAβN-first had the best killing effect, whereas PAβN-after had the worst killing effect. The killing effect increased with PAβN concentration and at 100 μg/mL reached 5.1 logs. Conclusions: The EPI PAβN enhanced the bactericidal effect of MB-aPDI on P. aeruginosa, especially when added before MB. It is proposed that MB is a substrate of the resistance-nodulation-division family efflux pump.

Eco-friendly phytofabrication of Ficus Benjamina L. based ZnO-doped g-C3N4 nanocomposites for remarkable photocatalysis and antibacterial applications

The research reported here emphasizes the phytoextract route synthesized ZnO-doped g-C3N4 (GCN) for its photocatalytic activity, which helps to ensure a sustained & healthy environment. The leaf extract solution of Ficus Benjamina L. was used for the synthesis of ZnO nanoparticles, and GCN was prepared via urea using a thermal polymerization process. The flower extract functions as both stabilizers and capping agents during the process of synthesis of ZnO nanoparticles. The synthesized nanocomposites were then calcined at 400 °C and were further characterized with spectroscopy (UV-Vis), diffracted pattern (XRD), and infrared spectroscopy (FTIR). Further, the photocatalytic activity of auramine orange (AO) and methylene blue (MB) dye from phytoextract route synthesized pure ZnO NPs, GCN-Pure, and composites with varied millimolar concentrations of ZnO nanoparticles with GCN of the constant amount was checked. After the complete analysis, it was observed that the series that was prepared of ZnO-GCN nanocomposites showed notable enhancement in the degradation pattern of the methylene blue dye. Apparently, 1.5 mmol (mM) ZnO-GCN presented greater degradation patterns for Auramine orange and Methylene blue dye as compared to other nanocomposites that were synthesized. The observed increased photocatalytic activity has a conceivable explanation. The antibacterial activity studies of the prepared nanocomposites were also performed against the E. coli strain showing an enhanced zone of inhibition towards it.

Antibacterial and anti-corona virus (229E) activity of Nigella sativa oil combined with photodynamic therapy based on methylene blue in wound infection: in vitro and in vivo study

Microbial skin infections, antibiotic resistance, and poor wound healing are major problems, and new treatments are needed. Our study targeted solving this problem with Nigella sativa (NS) oil and photodynamic therapy based on methylene blue (MB-PDT). Antibacterial activity and minimum inhibitory concentration (MIC) were determined via agar well diffusion assay and broth microdilution, respectively. Transmission electron microscopy (TEM) proved deformations in Staphylococcus aureus ATCC 6538. Gas chromatography-mass spectrometry identified useful compounds that were suggested to be responsible for the potency of the oil. NS oil was tested as an antivirus against low pathogenic coronavirus (229E). Therapies examined, MB-PDT, NS, and MB-PDT + NS oil, to accelerate wound healing. The antibacterial efficacy against S. aureus was promising, with a MIC of 12.5% and TEM showing injured cells treated with NS oil. This oil inhibited 229E virus up to 42.85% and 32.14%. All tested therapies were successful in accelerating wound healing. The most successful was combined therapy (MB-PDT + NS oil), with a faster healing time. The combined therapy (MB-PDT + NS oil) reduced bacterial counts, which may be a key factor in accelerating wound healing. Skin wound histology was investigated; blood hematology and biochemical analysis did not change significantly after the safe combination treatment. A combination treatment could facilitate healing in a simple and inexpensive way in the future. Based on the results of the in vitro and in vivo studies, it was determined that NS oil had antibacterial and anti-corona virus activity when used in conjunction with photodynamic treatment based on methylene blue to treat wound infections.

In Situ Polymerization of Methylene Blue on Bacterial Cellulose for Photodynamic/Photoelectricity Synergistic Inhibition of Bacterial Biofilm Formation

In the context of long-term antimicrobial treatment, the emergence of bacterial resistance poses a significant challenge. Therefore, there is a pressing need to develop novel antimicrobial materials and methods that can effectively and safely combat microbial infections. This study focuses on the synthesis of bacterial cellulose-polymethylene blue (BC-PMB) with integrated photodynamic and photoelectric antimicrobial properties. The polymerization of methyl blue (MB) onto bacterial celluloses (BC) was achieved, and through comprehensive computational analyses using density functional theory (DFT) and molecular dynamics simulations, it was confirmed that this polymerization greatly enhanced the binding efficiency between methylene blue and BC. Additionally, polymethylene blue (PMB) exhibited superior photoexcitation efficiency and conductivity compared to its precursor. When BC-PMB was exposed to a 30 mW 660 nm light source for 30 min, the material demonstrated a remarkable antimicrobial efficacy of 93.99% against Escherichia coli and 98.58% against Staphylococcus aureus. Furthermore, the synergistic effect of photodynamic and photoelectric antimicrobial mechanisms exhibited long-term inhibitory capabilities against bacterial biofilms.

Methylene Blue-Doped Carbonized Polymer Dots: A Potent Photooxygenation Scavenger Targeting Alzheimer's β-Amyloid

The abnormal aggregation of β-amyloid protein (Aβ) is one of the main pathological hallmarks of Alzheimer's disease (AD), and thus development of potent scavengers targeting Aβ is considered an effective strategy for AD treatment. Herein, photosensitizer-doped carbonized polymer dots (PS-CPDs) were synthesized by a one-step hydrothermal method using photosensitizer (PS) and o-phenylenediamine (oPD) as precursors, and furtherly applied to inhibit Aβ aggregation via photooxygenation. The inhibition efficiency of such PS-CPDs can be adjusted by varying the type of photosensitizer, and among them, methylene blue-doped carbonized polymer dots (MB-CPDs) showed the strongest photooxygenation inhibition capability. The results demonstrated that under 650 nm NIR light irradiation, MB-CPDs (2 μg/mL) produced reactive oxygen species (ROS) to efficiently inhibit Aβ fibrillization and disaggregate mature Aβ fibrils and increased the cultured cell viability from 50% to 83%. In vivo studies confirmed that MB-CPDs extended the lifespan of AD nematodes by 4 days. Notably, the inhibitory capability of MB-CPDs is much stronger than that of MB and previously reported carbonized polymer dots. This work indicated that potent photooxygenation carbon dots can be obtained by using a photosensitizer as one of the precursors, and the results have provided new insights into the design of potent photooxygenation carbon nanomaterials targeting Aβ in AD treatment.

Methylene blue accelerates liquid-to-gel transition of tau condensates impacting tau function and pathology

Preventing tau aggregation is a potential therapeutic strategy in Alzheimer's disease and other tauopathies. Recently, liquid-liquid phase separation has been found to facilitate the formation of pathogenic tau conformations and fibrillar aggregates, although many aspects of the conformational transitions of tau during the phase transition process remain unknown. Here, we demonstrate that the tau aggregation inhibitor methylene blue promotes tau liquid-liquid phase separation and accelerates the liquid-to-gel transition of tau droplets independent of the redox activity of methylene blue. We further show that methylene blue inhibits the conversion of tau droplets into fibrils and reduces the cytotoxicity of tau aggregates. Although gelation slows down the mobility of tau and tubulin, it does not impair microtubule assembly within tau droplets. These findings suggest that methylene blue inhibits tau amyloid fibrillization and accelerates tau droplet gelation via distinct mechanisms, thus providing insights into the activity of tau aggregation inhibitors in the context of phase transition.

Antibacterial effectiveness of photo-sonodynamic treatment by methylene blue-incorporated poly(D, L-lactide-co-glycolide) acid nanoparticles to disinfect root canals

AIM

This in-vitro investigation aimed to assess the antibacterial effectiveness of photo-sonodynamic treatment using methylene blue (MTB)-incorporated poly(D, L-Lactide-Co-Glycolide) acid (PLGA)-nanoparticles for the disinfection of root canals.

METHODS

The synthesis of PLGA nanoparticles was achieved using a solvent displacement technique. The morphological and spectral characterization of the formulated PLGA nanoparticles were carried out using scanning electron microscopy (SEM) and Transformed-Fourier infrared spectroscopy (TFIR), respectively. One hundred human premolar teeth were sterilized and then their root canals were infected with Enterococcus faecalis (E. faecalis). Later, the bacterial viability evaluation of the following 5 research groups was conducted: (a) G-1: specimens treated with a diode laser; (b) G-2: specimens treated with antimicrobial photodynamic therapy (aPDT) and 50 µg/mL of MTB-incorporated PLGA nanoparticles; (c) G-3: specimens treated with ultrasound (US); (d) G-4: specimens treated with US and 50 µg/mL of MTB-incorporated PLGA nanoparticles; and (e) G-5: control group consisting of specimens that did not undergo any treatment.

RESULTS

Under SEM, the nanoparticles exhibited a uniform spherical shape and were around 100 nm. The formulated nanoparticles' size was validated through zeta potential analysis utilizing dynamic light scattering (DLS). The TFIR images of both PLGA nanoparticles and MTB-incorporated PLGA nanoparticles exhibited absorption bands ranging from around 1000 to 1200/cm and nearly from 1500 to 1750/cm. The G-5 samples (control group) demonstrated the greatest viability against E. faecalis, followed by G-3 (US-conditions specimens), G-1 (diode laser-conditioned specimens), G-2 (aPDT + MTB-incorporated PLGA-nanoparticles-conditioned specimens), and G-5 (US + MTB-incorporated PLGA-nanoparticles-conditioned specimens). Significant statistical differences (p < 0.05) were observed among all research groups, including both the experimental groups and control group.

CONCLUSION

The combination of US via MTB-incorporated PLGA nanoparticles exhibited the most effective eradication of E. faecalis, suggestive of a promising therapeutic modality against E. faecalis for disinfecting root canals with complex and challenging anatomy.

Prophylactic Administration with Methylene Blue Improves Hemodynamic Stabilization During Obstructive Jaundice-Related Diseases' Operation: a Blinded Randomized Controlled Trial

OBJECTIVES

Patients with obstruction jaundice are at a high risk of hypotension and need high volume of fluids and a high dose of catecholamine to maintain organ perfusion during operation procedure. All these likely contribute to high perioperative morbidity and mortality. The aim of the study is to evaluate the effects of methylene blue on the hemodynamics in patients undergoing surgeries associated with obstructive jaundice.

DESIGN

A prospective, randomized, and controlled clinical study.

SETTING

The enrolled patients randomly received 2 mg/kg of methylene blue in saline or saline (50 ml) before anesthesia induction. The primary outcome was the frequency and dose of noradrenaline administration to maintain mean arterial blood pressure over 65 mmHg or > 80% of baseline, and systemic vascular resistance (SVR) over 800 dyne/s/cm5 during operation. The secondary outcomes were liver and kidney functions, and ICU stay.

PATIENTS

Seventy patients were enrolled in the study and randomly assigned to receive either methylene blue or control (n = 35/group).

RESULTS

Fewer patients received noradrenaline in the methylene blue group when compared with the control group (13/35 vs 23/35, P = 0.017), and the noradrenaline dose administrated during operation was reduced in the methylene blue group when compared with the control group (0.32 ± 0.57 mg vs 1.787 ± 3.51 mg, P = 0.018). The blood level of creatinine, glutamic oxalacetic transaminase, and glutamic-pyruvic transaminase after the operation was reduced in the methylene blue group when compared with the control group.

CONCLUSIONS

Prophylactic administration of methylene blue before operation associated with obstructive jaundice improves hemodynamic stability and short-term prognosis.

QUESTION

Methylene blue use prevented refractory hypotension during cardiac surgery, sepsis, or anaphylactic shock. It is still unknown that methylene blue on the vascular hypo-tone associated with obstructive jaundice.

FINDINGS

Prophylactic administration with methylene blue improved peri-operative hemodynamic stability, and hepatic and kidney function on the patients with obstructive jaundice.

MEANINGS

Methylene blue is a promising and recommended drug for the patients undergoing the surgeries of relief obstructive jaundice during peri-operation management.

Increasing photoeradication's efficiency of Acinetobacter baumannii by polyphosphonic chelating agents

Ethylenediamine-N,N,N',N'-tetrakis(methylenephosphonic acid (EDTMP), nitrilotri(methylphosphonic acid (ATMP) and zoledronic acid were studied to enhance the methylene blue-mediated photodynamic inactivation of Acinetobacter baumannii. Laser light (wavelength 638 nm; standard light output 40 mW) was used in all experiment. Planktonic cultures were irradiated for 10, 20 and 30 min which corresponded to the light dose of 63 Jcm‒ 2, 126 Jcm‒2 and 189 Jcm‒2. Biocidal effect depended on the exposure time and it was shown that MB alone caused the highest reduction in the number of viable cells by 3.10 ± 0.2 log10 units after 30 min of irradiation. A significantly more effective killing effect was achieved when the bacteria were pre-treated with zoledronate, ATMP, or EDTMP (prior to photosensitisation) as the number of viable bacteria was reduced by 4.04±0.2 log10, 3.95±0.2 log10 and 4.01 ± 0.2 log10, respectively. The photo-killing effect caused by MB against biofilm pre-incubated with zoledronate, ATMP, or EDTMP and the number of viable bacteria was reduced by 0.80±0.1 log10, 1.25±0.05 log10 and 0.65±0.05 log10, respectively. Polyphosphonic chelating agents increased the efficiency of photo-destruction of A. baumannii by increasing the amount of bound photosensitizer by planktonic cells and biofilm, and increasing the detachment of live planktonic cells from the biofilm. The presence of glucose in the photosensitizing system significantly affected the bacterial photo-elimination. Pre-incubation of planktonic bacteria with the studied polyphosphonic chelating agents in the presence of glucose, and then exposure to light (with MB) for 30 min caused the lethal effect. This photo-eradication protocol (in the case of biofilms) reduced the number of viable bacteria by 2.05±0.2 log10, 3.2±0.2 log10 and 2.02±0.2 log10 for zoledronic acid, ATMP and EDTMP, respectively.

Methylene Blue-Loaded NanoMOFs: Accumulation in Chlamydia trachomatis Inclusions and Light/Dark Antibacterial Effects

Metal-organic framework nanoparticles (nanoMOFs) are promising nanomaterials for biomedical applications. Some of them, including biodegradable porous iron carboxylates are proposed for encapsulation and delivery of antibiotics. Due to the high drug loading capacity and fast internalization kinetics, nanoMOFs are more beneficial for the treatment of intracellular bacterial infections compared to free antibacterial drugs, which poorly accumulate inside the cells because of the inability to cross membrane barriers or have low intracellular retention. However, nanoparticle internalization does not ensure their accumulation in the cell compartment that shelters a pathogen. This study shows the availability of MIL-100(Fe)-based MOF nanoparticles to co-localize with Chlamydia trachomatis, an obligate intracellular bacterium, in the infected RAW264.7 macrophages. Furthermore, nanoMOFs loaded with photosensitizer methylene blue (MB) exhibit complete photodynamic inactivation of C. trachomatis growth. Simultaneous infection and treatment of RAW264.7 cells with empty nanoMOFs resulted in a bacterial load reduction from 100 to 36% that indicates an intrinsic anti-chlamydial effect of this iron-containing nanomaterial. Thus, our findings suggest the use of iron-based nanoMOFs as a promising drug delivery platform, which contributes to antibacterial effect, for the treatment of chlamydial infections.

Vaterite microparticle-loaded methylene blue for photodynamic activity in macrophages infected with Leishmania braziliensis

Calcium carbonate (CaCO3) exhibits a variety of crystalline phases, including the anhydrous crystalline polymorphs calcite, aragonite, and vaterite. Developing porous calcium carbonate microparticles in the vaterite phase for the encapsulation of methylene blue (MB) as a photosensitizer (PS) for use in photodynamic therapy (PDT) was the goal of this investigation. Using an adsorption approach, the PS was integrated into the CaCO3 microparticles. The vaterite microparticles were characterized by scanning electron microscopy (SEM) and steady-state techniques. The trypan blue exclusion method was used to measure the biological activity of macrophages infected with Leishmania braziliensis in vitro. The vaterite microparticles produced are highly porous, non-aggregated, and uniform in size. After encapsulation, the MB-loaded microparticles kept their photophysical characteristics. The carriers that were captured allowed for dye localization inside the cells. The results obtained in this study indicated that the MB-loaded vaterite microparticles show promising photodynamic activity in macrophages infected with Leishmania braziliensis.

Patent blue versus methylene blue and indigo carmine as a better dye for chromodiscography: in vitro staining efficacy and cytotoxicity study using bovine coccygeal intervertebral discs

BACKGROUND CONTEXT

Chromodiscography is an integral part of full-endoscopic discectomy (FED), comprising ordinary discography with radiopacity produced by contrast medium and intradiscal stain for visualizing annular defects in the endoscopic field. Nevertheless, concerns remain about the cytotoxicity of the stains used. The study of their staining efficacy is also lacking.

PURPOSE

To evaluate the feasibility of methylene blue, patent blue, and indigo carmine for intradiscal injection, investigate the effectiveness of each dye, and define critical concentration with adequate staining efficacy and tolerable cytotoxicity for use in chromodiscography during FED.

STUDY DESIGN

An experimental in vitro study.

METHODS

Dye stock solutions were prepared from powder. The stock was diluted with culture medium or balanced saline and used for cytotoxicity or intervertebral disc staining assays, respectively. Bovine tails were obtained from the local slaughterhouse and functional spine units of intervertebral discs were acquired by transverse incision at the disc level. Each disc was punctured over the posterolateral aspect using a surgical knife to simulate an annular defect. The intradiscal injection was performed with each dye at different concentrations using a 22G needle from the contralateral aspect of the punctured site. Staining efficacy was quantified using ImageJ software. Primary cells of bovine tails were cultivated in each dye at different concentrations. Cytotoxicity was assessed 24 hours after stain exposure using the CCK-8 toxicity assay.

RESULTS

Staining efficacy and cytotoxicity were proportional to the concentration of tested dyes. Lower limits of concentration producing significant staining efficacy of indigo carmine, methylene blue, and patent blue were 0.25 mg/mL, 0.25 mg/mL, and 0.05 mg/mL, respectively. Compared with controls, concentrations showing significant toxicity for indigo carmine, methylene blue, and patient blue were 1 mg/mL, 0.5 mg/mL, and 2.5 mg/mL, respectively.

CONCLUSIONS

Patent blue can serve as a more suitable tissue stain than either indigo carmine or methylene blue due to the widest range of tradeoff concentration within 0.05 to 2.5 mg/mL.

CLINICAL SIGNIFICANCE

Patent blue with the characteristic of good staining efficacy and lower cytotoxicity may be a promising option for chromodiscography during FED.

Photodynamic therapy mediated by a red LED and methylene blue inactivates resistant Leishmania amazonensis

Cutaneous leishmaniasis is a neglected parasitic disease that leads to destructive lesions. The emergence of drug resistance has been a global concern over the past years. Photodynamic therapy (PDT) mediated by a red LED and methylene blue (MB) involves the overproduction of oxidative stress, which oxidizes several cellular biomolecules and prevents the selection of resistant strains. Herein, we investigated the potential of PDT mediated by MB against wild-type and miltefosine-resistant strains of Leishmania amazonensis. As a result, both strains were susceptible to PDT, thus encouraging us to seek the best conditions to overcome the drug resistance problem in cutaneous leishmaniasis.

Near Infrared-Activatable Methylene Blue Polypeptide Codelivery of the NO Prodrug via π-π Stacking for Cascade Reactive Oxygen Species Amplification-Mediated Photodynamic Therapy

The application of photodynamic therapy (PDT) has attracted remarkable interest in cancer treatment because of the advantages of noninvasiveness and spatiotemporal selectivity. However, the PDT efficiency is considerably limited by photosensitizer (PS) quenching and severe hypoxia in solid tumors. Herein, a kind of near infrared (NIR)-activatable methylene blue (MB) peptide nanocarrier was developed for codelivery of nitric oxide (NO) prodrug JSK, expecting a cascade of reactive oxygen species (ROS) amplification-mediated antitumor PDT. In detail, MB was conjugated to water-soluble polyethylene glycol-polylysine (PEG-PLL) through NIR-photocleavable 10-N-carbamoyl bonds, and the subsequent amphiphilic conjugates (mPEG-PLL-MB) self-assembled into nanoparticles (NPs), which allowed JSK codelivery via π-π stacking interactions. MB in quenched state in mPEG-PLL-MB/JSK NPs could be photoactivated by NIR light locoregionally in a controlled manner due to the photocleavage of carbamoyl bonds. Apart from ROS production, assembly disturbance and even disintegration of mPEG-PLL-MB/JSK occurred along with MB activation that subsequently freed JSK, which was further triggered by intracellularly overexpressed glutathione (GSH) and glutathione S-transferase (GST) to sustain the release of NO. NO then served as a hypoxia relief agent through inhibition of cellular respiration to economize O₂, cooperating with MB activation and GSH depletion, which synergistically enabled a cascade of ROS amplification to augment PDT for mitochondrial apoptosis-mediated tumor inhibition in vitro and in vivo. Therefore, this pioneering strategy of cascade amplification of ROS addressed the key issues of PS inactivation, hypoxia resistance, and ROS neutralization in a three-pronged approach, which hold great promise in efficient antitumor PDT.

Early adjunctive methylene blue in patients with septic shock: a randomized controlled trial

PURPOSE

Methylene blue (MB) has been tested as a rescue therapy for patients with refractory septic shock. However, there is a lack of evidence on MB as an adjuvant therapy, its' optimal timing, dosing and safety profile. We aimed to assess whether early adjunctive MB can reduce time to vasopressor discontinuation in patients with septic shock.

METHODS

In this single-center randomized controlled trial, we assigned patients with septic shock according to Sepsis-3 criteria to MB or placebo. Primary outcome was time to vasopressor discontinuation at 28 days. Secondary outcomes included vasopressor-free days at 28 days, days on mechanical ventilator, length of stay in ICU and hospital, and mortality at 28 days.

RESULTS

Among 91 randomized patients, forty-five were assigned to MB and 46 to placebo. The MB group had a shorter time to vasopressor discontinuation (69 h [IQR 59-83] vs 94 h [IQR 74-141]; p < 0.001), one more day of vasopressor-free days at day 28 (p = 0.008), a shorter ICU length of stay by 1.5 days (p = 0.039) and shorter hospital length of stay by 2.7 days (p = 0.027) compared to patients in the control group. Days on mechanical ventilator and mortality were similar. There were no serious adverse effects related to MB administration.

CONCLUSION

In patients with septic shock, MB initiated within 24 h reduced time to vasopressor discontinuation and increased vasopressor-free days at 28 days. It also reduced length of stay in ICU and hospital without adverse effects. Our study supports further research regarding MB in larger randomized clinical trials. Trial registration ClinicalTrials.gov registration number NCT04446871 , June 25, 2020, retrospectively registered.

Mitochondrial dysfunction mediates neuronal cell response to DMMB photodynamic therapy

Photodynamic therapy (PDT) is a process in which a photosensitizer (PS) is exposed to specific wavelengths and generates reactive oxygen species (ROS) which act within nanometers. The low invasive nature and directed cytotoxicity of this approach render it attractive to the treatment of different conditions, including the ones that affect the central nervous system (CNS). The effect of PDT on healthy neurons is one main concern over its use in the CNS, since neuronal-like cells were shown to be particularly sensitive to certain PSs. Among available PSs, 1,9-dimethyl-methylene blue (DMMB) stands out as being resistant to reduction to its inactive leuco form and by being able to produce high levels of singlet‑oxygen. In this study, we aimed to investigate DMMB photodamage mechanisms in the hippocampal cell line HT22. Our results demonstrate that DMMB-PDT decrease in cell viability was linked with an increase in cell death and overall ROS production. Besides, it resulted in a significant increase in mitochondrial ROS production and decreased mitochondria membrane potential. Furthermore, DMMB-PDT significantly increased the presence of acidic autolysosomes, which was accompanied by an increase in ATG1 and ATG8 homologue GaBarap1 expression, and decreased DRAM1 expression. Taken together our results indicated that mitochondrial and autophagic dysfunction underlie DMMB-PDT cytotoxicity in neuronal cells.