Methylene Blue Molecules Research Articles

Hydrothermal Synthesis of Highly Effective Carbon Sorbent Based on Renewable Resources

The synthesis of new sorption materials by hydrothermal carbonization of sunflower meal (HTS) with the addition of graphene oxide (GO) and subsequent carbonization (C) was developed. To assess the morphological and phase changes during carbonization, the materials were characterized by scanning electron microscopy and IR spectroscopy. According to the results obtained, carbonization promoted the development of latent porosity, as well as a decrease in the amount of oxygen-containing and alkyl groups. Kinetic sorption studies were also carried out on the example of the Pb+2 ions and organic dye molecules – methylene blue (MB), extraction. The experiment results showed that the adsorption capacity of HTS, HTS/C, HTS/GO, and HTS/GO/C composites for the Pb+2 ions extraction was 82.9; 108.6; 168.9; 148.3 mg/g, respectively; and for MB molecules – 1481.8; 1601.1; 1920.3; 2283 mg/g, respectively. It was found that during adsorption of MB molecules, the carbonization effects significantly on the contact time. Carbonized samples show high sorption activity. The equilibrium contact time fort them was 15 min, while for non-carbonized samples it was 60 min. The equilibrium time during the Pb+2 ions adsorption was 60 min for all samples. The adsorption kinetics was described using the following models: pseudo-first order, pseudo-second order, the Elovich model, and intraparticle diffusion. It was found that the adsorption process is limited by the chemical exchange reaction and proceeds in a mixed-diffusion mode.

In-situ monitoring of thiazine molecular aggregation in various solvents via a free-standing acoustic levitator

In this work, we explored the in-situ reaction modeling of the molecular self-aggregation of methylene blue (MB), which is a cationic thiazine dye, in different solvents via a container-less acoustic levitator by floating of a single droplet. Our in-situ spectroscopic study revealed that the dimer essentially has a sandwich structural geometry with a deviation from parallel stacking and horizontal arrangements in the molecular planes. The real time conversion of the monomer in MB into a dimer and their dynamics in water and ethanol media were monitored using a free-standing acoustic levitator droplet system. The absorption spectra revealed changes in the two resolved peaks (monomer and dimer) and orderliness when water and ethanol were used as the media. Interestingly, the enhancement in the dimerization of MB could be attributed to droplet evaporation, which is difficult to observe in typical reactor containers. Moreover, acidic protonation resulted in a change in the aggregation orientation direction of the MB molecules, forming an unusual J-aggregation. Theoretical DFT calculations revealed that MB underwent typical H-aggregation and J-aggregation in the different solvent environments, and their orientations well matched the spectroscopic data.

Understanding the effect of morphological change on photocatalytic activity of ZnO nanostructures and reaction mechanism by molecular dynamics

The photocatalytic activity of photocatalysts is often influenced by their particle morphology, dimension, size, exposed facets, porosity, etc. This work aims at gaining insights into the influence of the particle morphology of ZnO nanostructures on their photocatalytic activity. Under hydrothermal conditions, the Zn(NO3)2∙6 H2O:KOH (Zn:KOH) ratio is changed to 1:2, 1:8, and 1:12 to modulate the morphology of ZnO nanostructures. Particularly, the ZnO nanostructures with a nanostar-like morphology, synthesized at the Zn:KOH ratio of 1:8, exhibit the highest photocatalytic activity in comparison to ZnO nanoparticles and nanorods synthesized at the Zn:KOH ratios of 1:2 and 1:12, respectively. The enhanced photocatalytic activity for the degradation of methylene blue (MB) of ZnO nanostructures with a nanostar-like morphology is due to the presence of a large number of oxygen vacancy-related defects, which are preferably formed on the (1 0 1) facet of ZnO. The results from X-ray diffraction and photoluminescence spectroscopy analyses confirm it. Further, molecular dynamics (MD) simulation is involved to explore the interaction of oxygen atoms (as a representative of hydroxyl radical) with methylene blue molecules to understand the mechanism of enhanced MB degradation at the atomic level. The results of the computational study indicate the formation of hydroxyl radicals and the cleavage and the formation of some bonds in the side and central aromatic rings of MB molecules, which ultimately leads to the degradation of MB. Our findings reveal that it is important to control the morphology and facets of nanostructures for achieving high efficiency in the photocatalytic processes to be applied in practical application.

Dielectric Barrier Discharge Plasma Coupled with Cobalt Oxyhydroxide for Methylene Blue Degradation.

In this study, the coupled use of a double dielectric barrier discharge (DDBD) and CoOOH catalyst was investigated for the degradation of methylene blue (MB). The results indicated that the addition of CoOOH significantly promoted MB degradation performance compared to the DDBD system alone. In addition, both the removal rate and energy efficiency increased with an increase in CoOOH dosage and discharge voltage. After 30 min of discharge treatment in the coupled system (with CoOOH of 150 mg), the removal rate reached 97.10% when the discharge voltage was 12 kV, which was 1.92 times that in the single DDBD system. And when the discharge time was 10 min, the energy efficiency could reach 0.10 g (k·Wh)-1, which was 3.19 times better than the one in the single DDBD system. Furthermore, the addition of CoOOH could also significantly enhance the TOC and COD removal rates of MB. In the DDBD-coupled-with-CoOOH system, TOC and COD were 1.97 times and 1.99 times those of the single DDBD system after 20 min of discharge treatment with a discharge voltage of 12 kV and 100 mg of CoOOH. The main active substances detected in the coupled system indicated the conversion of the active species H2O2 and O3 into a more oxidizing ·OH was enhanced through the addition of a CoOOH catalyst, resulting in the more effective decomposition of MB and intermediate molecules.

Green Synthesis for Carbon Quantum Dots via Opuntia ficus-indica and Agave maximiliana: Surface-Enhanced Raman Scattering Sensing Applications.

In this study, we present an alternative method for synthesizing carbon quantum dots (CQDs) using a green synthesis approach via extracts from Agave maximiliana and Opuntia ficus-indica(Ofi). The extracts from both plants were used as the carbon source for the CQDs. The synthesis method employs mesoporous zeolite 4A as a refractory for the thermal treatment of the samples. Transmission electron microscopy analysis established that the size of the CQDs shows a narrow distribution centered around 2 nm with a maximum size of less than 3 nm for both cases. The CQDs exhibit absorption bands associated with π-π* transitions located around 220 nm. In both cases, photoluminescence (PL) phenomenon was detected by irradiating the samples with a UV wavelength and detecting emissions close to the blue wavelength. Additionally, both kinds of CQDs were tested as surface-enhanced Raman scattering (SERS) substrates against methylene blue (MB), indicating an enhancement associated with ring deformation and stretching modes of the v(C-C) and v(C-N) bonds located around 1400 and 1620 cm-1, respectively. Complementarily, in the framework of density functional theory, H2nC2(2m+1) structures (with n = 3-5 and m = 1-3) were used as a theoretical representation of CQDs in interaction with the MB molecule. It is used for developing the analysis of charge transfer effects between both systems and for specifying elements that generate the SERS effect associated with the chemical enhancement mechanism.

Plasmon Energy Transfer Driven by Electrochemical Tuning of Methylene Blue on Single Gold Nanorods.

Plasmonic photocatalysis has attracted interest for its potential to generate energy-efficient reactions, but ultrafast internal conversion limits efficient plasmon-based chemistry. Resonance energy transfer (RET) to surface adsorbates offers a way to outcompete internal conversion pathways and also eliminate the need for sacrificial counter-reactions. Herein, we demonstrate RET between methylene blue (MB) and gold nanorods (AuNRs) using in situ single-particle spectroelectrochemistry. During electrochemically driven reversible redox reactions between MB and leucomethylene blue (LMB), we show that the homogeneous line width is broadened when spectral overlap between AuNR scattering and absorption of MB is maximized, indicating RET. Additionally, electrochemical oxidative oligomerization of MB allowed additional dipole coupling to generate RET at lower energies. Time-dependent density functional theory-based simulated absorption provided theoretical insight into the optical properties, as MB molecules were electrochemically oligomerized. Our findings show a mechanism for driving efficient plasmon-assisted processes by RET through the change in the chemical states of surface adsorbates.

Facile construction of lignin-based network composite hydrogel for efficient adsorption of methylene blue from wastewater

Adsorption method is an effective approach to treat wastewater containing methylene blue. Herein, a cost-effective and eco-friendly lignin-based network composite hydrogel adsorbent (PAA@SML) was constructed by using polyacrylic acid (PAA) to crosslink with sulfomethylated lignin (SML) via free radical polymerization for adsorption of methylene blue (MB) from wastewater. The constructed PAA@SML-0.2 exhibited remarkable adsorption performance towards removal of MB, with a maximum theoretical adsorption capacity of 777.1 mg·g−1. The improved efficiency can be attributed to the well-established network structure and abundant hydrophilic functional groups present in the adsorbent, promoting the interaction between methylene blue (MB) molecules and the adsorption sites of the adsorbent. The adsorption process of the adsorbent for MB followed the pseudo-second-order kinetic and the Langmuir isotherm models, which illustrated the adsorption process attributed to monolayer chemisorption. Mechanism investigation confirmed that the adsorption of MB by PAA@SML-0.2 primarily relied on hydrogen bonding and electrostatic interactions. Moreover, the recyclability test demonstrated excellent regeneration usability and stability of PAA@SML-0.2, and the adsorption capacity maintained above 74.0 % after five cycles. This constructed lignin-based network composite hydrogel is considered to have great potential in the treatment of organic dye in wastewater.

Electrochemical detection of protein kinases with methylene blue-functionalized Zr-based metal-organic frameworks as signal labels

Protein kinases play a vital regulatory role in various biological processes. In this work, we developed an electrochemical biosensor for the detection of protein kinases using methylene blue (MB)-functionalized Zr-based metal-organic frameworks (MOFs, UiO-66-NH2) as the signal labels. The results of UV-Vis spectroscopy, X-ray diffraction and N2 adsorption–desorption experiments confirmed the successful encapsulation of MB into UiO-66-NH2. The phosphate groups in phosphorylated peptides were recognized by UiO-66-NH2 via the robust coordination with Zr-O clusters on the surface of MOFs. The encapsulated MB molecules in UiO-66-NH2 produced a strong electrochemical signal for highly sensitive detection of protein kinases, which was recorded by square wave voltammetry (SWV). With protein kinase A (PKA) as a model target, the biosensor achieved a detection limit of 0.02 U/mL and a linear range from 0.05 to 20 U/mL. The proposed biosensor was utilized to screen potential inhibitors and determine PKA in serum samples with satisfactory results. This work provided an effective strategy for electrochemical assays of phosphorylation-related biological events in clinical diagnosis.

A Novel Vermiculite/TiO2 Composite: Synergistic Mechanism of Enhanced Photocatalysis towards Organic Pollutant Removal.

There has been increasing concern over water pollution, which poses a threat to human life and health. Absorption by low-cost absorbents is considered to be a cost-effective and efficient route. However, the non-reusability of absorbents greatly limits their applications. In this study, a novel vermiculite/TiO2 composite combining the inexpensive absorbent with the commonly used photocatalyst was firstly synthesized via the sol-gel method. On the one hand, the organic pollutants are absorbed by vermiculite and then decomposed through the photocatalysis process, enabling the next round of absorption and creating an absorption-decomposition reusable cycle. On the other hand, the modulation effect of optical and electronic structure on the prepared TiO2 photocatalyst by the vermiculite incorporation could significantly improve the photocatalytic activity and eventually enhance the aforementioned cyclic degradation capacity. The layer-structured vermiculite (Vt) supports a uniform coverage of TiO2 at an optimized ratio, providing an optimal adsorption environment and contact area between the photocatalyst and methylene blue (MB) molecules. Vt/TiO2 heterojunction is formed with Si-O-Ti bonding, at which electrons transfer from Vt to TiO2, enriching electron density in TiO2 and favoring its photocatalytic activity. Furthermore, the incorporation of Vt increases the light absorption of TiO2 in the visible range by narrowing the optical band gap to 1.98 eV, which could promote the generation of photo-excited carriers. In addition, PL measurements revealed that the carrier recombination is substantially suppressed, and the charge separation and migration are greatly enhanced by a factor of 3. As a result, the decomposition rate of MB is substantially increased 5.3-fold, which is ascribed to the synergistic effects of the elevated photocatalysis and the large absorption capacity governed by the chemisorption mechanism of the intra-particle diffusion. These results pave the way for composite design towards efficient, economical, and pragmatic water pollution treatment.

Multifunctional Ni(OH)2/Ag composites for ultrasensitive SERS detection and efficient photocatalytic degradation of ciprofloxacin and methylene blue

To enable the widespread application of surface-enhanced Raman scattering (SERS) technique in practical sensing of organic pollutants, it is essential to develop a reliable SERS substrate that offers both high sensitivity and reusability. In this study, we employed a simple and rapid in-situ deposition method to coat Ag nanoparticles onto flower-like Ni(OH)2 spheres, resulting in the formation of Ni(OH)2/Ag composites with excellent photocatalytic performance and SERS activity. These composites were used as a promising SERS analysis tool for effective detection of organic pollutants, including ciprofloxacin hydrochloride (CIP) and methylene blue (MB). Notably, the composites exhibited outstanding detection limits of 10−8 M for MB and 10−7 M for CIP, respectively, and showed a strong linear relationship between SERS intensities and the logarithmic concentration (R2 ≥ 0.97). Moreover, under simulated sunlight irradiation, the Ni(OH)2/Ag composites efficiently degraded MB and CIP molecules within a short period of 120 min for MB and 130 min for CIP. This demonstrated their practical reusability, as evidenced by their consistent performance over five cycles of SERS sensing. These findings underscore the significant potential of these composites for SERS-based detection of trace pollutants and ecological restoration through photocatalytic reactions in the future.

Methylene blue functionalized 3D MXene aerogel: Self-assembly by interfacial electrostatic interaction for asymmetric supercapacitors

2D MXene materials show great potential in energy storage systems. However, 2D layered materials always face challenges of stacking and collapsing, inhibiting its application. Herein, an efficient and facile strategy has been employed to induce self-assembly of MXene nanosheets by introducing Methylene blue (MB) molecule, forming a 3D porous MXene/MB (MX/MB) composite. The unique structure suppresses stacking and oxidation of MXene flakes, ensures sufficient electrochemical active sites as well as shortens ion transport length. At the mass ratio of MXene/MB is 3/1, MX/MB-3 exhibits optimal specific capacitance of 327 F g − 1 at 2 A g − 1 and retains its initial capacitance without attenuation (10,000 cycles at 10 A g − 1). Furthermore, the as-assembled TH/N-rGO//MX/MB-3 asymmetric device not only possesses high energy density of 23.3 Wh kg−1 at power density of 780.2 W kg−1, but also demonstrates excellent cycling stability (94.4% capacitance retention after 10,000 cycles). This device design demonstrates that the preparation of high-performance MXene-based electrodes is an effective strategy to facilitate the development of energy storage device.

Polyol method and surface functionalization of silver nanowires using bovine serum albumin for surface-enhanced Raman scattering application

Silver nanowires (AgNWs) with diverse applications are attracting the attention of many researchers around the world. In this study, we applied the polyol method to synthesize AgNWs based on Polyvinyl-pyrrolidone (PVP) average molecular weight of 360,000, ethylene glycol (EG), and AgNO3 precursor with a fresh AgCl preparation. To synthesize this material we first investigate optimal parameters through the influence of reaction temperature, time of creating AgNWs using plasmon absorption spectroscopy, and scanning electron microscope (SEM) images. The obtained AgNWs are high efficiency, large aspect ratio, and good dispersion in the solution. This sample continues to be conducted to surface functionalization by bovine serum albumin (BSA) molecules to develop AgNW@BSA complexes. We apply UV-Vis absorption spectroscopy to evaluate the optical properties of these complexes. Besides, we conduct research on the application of this material on surface-enhanced Raman scattering (SERS). The results show that the optical properties of these complexes obtained from UV-Vis absorption spectroscopy are comparable with the numerical modeling. In addition, AgNWs can be used to study the effective surface-enhanced Raman scattering (SERS) to detect methylene blue (MB) molecules at low concentrations as 10-12 M.

Gold Nanobipyramid Hotspot Aggregation-Induced Surface-Enhanced Raman Scattering for the Ultrasensitive Detection of miRNA.

Herein, a surface-enhanced Raman scattering (SERS) biosensor was constructed by gold nanobipyramid (Au NBP) hotspot aggregation-induced SERS (HAI-SERS) for the ultrasensitive detection of microRNA-221 (miRNA-221). Impressively, compared with single Au NBP, the multiple Au NBPs assembled by tetrahedral DNA nanostructures (TDNs) could increase hotspot aggregation to significantly enhance the SERS signal of Raman molecule methylene blue (MB). Meanwhile, in the aid of Exo-III assisted target cycle amplification and TDNs-induced catalytic hairpin assembly (CHA) amplification, the biosensor could achieve the sensitive detection of miRNA-221 with a linear range of 1 fM-10 nM, and the limit of detection (LOD) was 0.59 fM, which could be used for practical application in MHCC-97L and MCF-7 cell lysates. This work provided a method for hotspot aggregation to enhance SERS for the detection of biomarkers and disease diagnosis.

A filter-electrochemical microfluidic chip for multiple surface protein analysis of exosomes to detect and classify breast cancer

Breast cancer (BC) is a complex disease with high variability and no specific tumor markers available for diagnosis. Exosomes contain rich maternal tumor information and are a novel non-invasive biomarker with the potential for cancer diagnosis and prognosis. However, analysis of exosomal protein markers in blood samples is challenging due to lengthy sample workups and insufficient sensitivity. To address this difficulty, we developed a novel filter-electrochemical microfluidic chip (FEMC) to detect and classify BC directly in whole blood without requiring heavy purification methods. In our system, exosome enrichment was performed using a dual filtration system. The target was directed through a curved channel onto four screen-printed electrodes (SPEs), where it was captured by the previously modified antibodies. Simultaneously, Zr-MOFs encapsulated with a large number of methylene blue molecules (MB@UiO-66) were absorbed on the surface of exosomes due to the high affinity for phosphate groups. This process leads to the amplification of electrical signals. The approach demonstrated that the utilization of BC exosome-associated tumor biomarkers (i.e., PMSA, EGFR, CD81, and CEA), enabled the classification of various BC mouse models samples and clinical BC samples. The entire FEMC assay was completed in 1 h with a limit of detection of 1 × 104 particles/mL. Thus, the FEMC assay can provide real-time detection information, allowing timely and better-informed opportunities for clinical BC diagnosis and typing.

Fabrication of pH-responsive poly(vinyl alcohol)-based microfibers crosslinked with copolymers containing benzoxaborole and carboxy groups

Water-insoluble pH-responsive poly (vinyl alcohol) (PVA)-based microfibers were prepared using terpolymer of poly ([2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC)-co-methacrylic acid (MAAc)-co-5-methacrylamido-1,2-benzoxaborole (MAAmBO)) (TP) containing a quaternary ammonium cation, as well as carboxy and benzoxaborole groups. The surface of the microfibers could be positively charged by the permanent positive charge of the METAC units owing to the presence of the quaternary ammonium cation. The MAAc units formed a covalent bond with the hydroxy group of the vinyl alcohol unit by thermal treatment at 135 °C for 24 h, and the MAAmBO units formed a dynamic covalent bond with the diol group in PVA. After thermal crosslinking for 24 h, the PVA/TP microfibers exhibited almost 100% of the residual weight after immersion in water at 80 °C for 30 min. The diameters of the dried PVA/TP_25 wt% fibers were 21.4 ± 3.9 μm, and the swelling ratio was 1.65 ± 0.16 after immersing in water for 24 h. All microfibers showed a low degree of hemolysis (<5%). The PVA/TP_25 wt% fibers were strongly dyed with anionic acid red 1 (AR1) molecules at pH 3 and with cationic methylene blue (MB) molecules at pH 12, since the balance of the surface charge depend on the solution pH. These microfibers could be bundled and twisted to improve their mechanical properties; the required fracture energy after twisting was 2.30 ± 0.91 times higher than that before twisting.

Nanofiltration Performance of Poly(p-xylylene) Nanofilms with Imidazole Side Chains.

Herein, we report the nanofiltration performance of poly(p-xylylene) thin films with imidazole side chains that were deposited onto commercial polyethersulfone ultrafiltration membranes using a chemical vapor deposition process. The resulting thin films with a few tens of nanometers exhibited water permeation under a pressure difference of 0.5 MPa and selectively rejected water-soluble organic dyes based on their molecular sizes. Additionally, thin flaky ZIF-L crystals (Zn(mim)2·(Hmim)1/2·(H2O)3/2) (Hmim = 2-methylimidazole) formed on the surface of imidazole-containing poly(p-xylylene) films, and the composite films demonstrated the ability to adsorb methylene blue molecules within the cavities of ZIF-L.

Self-powered dual-mode sensing strategy based on graphdiyne and DNA nanoring for sensitive detection of tumor biomarker

MicroRNA-21 (miRNA-21) is currently the only known oncogenic miRNA that is upregulated in almost all malignant tumors and exhibits a broad spectrum of tumor recognition characteristics. It holds significant value in the early diagnosis, malignant degree assessment, and prognostic evaluation of tumors. In this study, a novel dual-mode self-powered sensing platform is developed using Au nanoparticles/graphdiyne as the electrode substrate and combined with DNA nanoring for highly sensitive and specific detection of miRNA-21. The DNA nanoring structure, which is easy to prepare and contains multiple recognition sites, induces significant electrochemical/colorimetric signal responses of the signaling molecule methylene blue. Under optimal conditions, the linear ranges of the electrochemical and colorimetric detection modes of this self-powered sensor are 0.1 fM-100 pM and 0.1 fM-10 nM, respectively, with the detection limits of 35.1 aM and 61.6 aM (S/N=3). This strategy provides a new reference for the sensitive detection of microRNA and has immense potential for application in the screening and detection of clinical nucleic acid diseases.

Biomorphic inspired octopus-three mode aptamer sensor without immobilization, label and enzyme for HER2 detection in whole blood

The ability to efficiently detect trace biomarkers of disease in whole blood remains a significant challenge. Multi-mode signals - electrochemical, fluorescence, and ultraviolet-visible spectroscopy (Uv-vis spectra) have self-correction capabilities that can overcome the interference of experimental and environmental factors on the output. Based on the "functionalized UiO-67 MOF", biomorphic inspired the octopus-three mode aptamer sensor (OTMBapt sensor) was constructed by imitating the structure of octopus without immobilization, labes and enzymes. Ultra-sensitive and high-precision biosensor detection of HER2 in human whole blood was achieved by using Uv-vis, fluorescence and electrochemical homogeneous techniques. This sensor uses a functionalized UiO-67 (aptamer@UiO-67) as the "octopus body". Due to targeting HER2, the HER2 aptamer is looped, and as a result of the folded aptamer, a large number of " tentacles " are extended, resulting in the ability to adsorb methylene blue (MB) molecules in a homogeneous solution. Finally, the active molecule MB is electrically doped in the folding aptamer structure to form a "sucker". This will enrich and adsorb negatively charged MB molecules onto the ITO surface, leading to the enhanced electrochemical, fluorescence and Uv-vis signal intensity. A detection time of 10 min, limit of detection (LOD) is 0.2 fg/mL with the linear range of 0.3–1000 pg/mL.

Fabrication of nano composite membrane filter from graphene oxide(GO) and banana rachis cellulose nano crystal(CNC) for industrial effluent treatment

Agricultural bio-waste based cellulosic materials are highly biodegradable and naturally occurring with high adsorption and capable of outstanding physico-chemical properties. This study elicits neoteric upliftment and impending significance of graphene oxide(GO) – cellulose nanocrystal(CNC) nano-filter composite membrane (NFCM) for high removal of Cr3+, Co2+, Ni2+, Pb2+, Cd2+ and Methylene blue molecules from industrial wastewater. We tried to direct comparison between conventional filter and NFCM composites filter and their physical and chemical properties, production costs, use and disposal in order to show the potential of Nano structural cellulose materials as a sustainable replacement for NFCM filter for removal of heavy metals and dyes from industrial wastewater treatment technologies. The prepared GO, CNC, and NFCM were characterized by using X-ray Diffraction(XRD), Fourier Transform Infrared (FTIR), Field Emission Scanning Electron Microscopy(FESEM), Thermogravimetric Analysis(TGA) etc. The efficiency of wastewater purification of fabricated NFCM were determined by Ultra Violet(UV)-vis spectrophotometer and Inductively Couple Plasma Optical Emission Spectroscopy(ICP-OES). Whereas the fabricated NFCM were highly crystalline, thermally stable, have good surface activity, exhibit remarkable removal efficiency against the toxic heavy metals and soluble dye. The maximum R% was found for Cd2+ and Pb2+, around 99%. Beside this all dye molecules were removed from the wastewater simultaneously and successfully.

Effect of amphiphilic polymers and sodium alginate on the activity of methylene blue in photogeneration of singlet oxygen 1О2

The influence of amphiphilic polymers (APs): poly-N-vinylpyrrolidone, polyethylene glycol and pluronics F127, F108, as well as sodium alginate (SA) on the activity of methylene blue (MB) in the photogeneration of singlet oxygen 1О2, specifically, in a model photooxidation reaction of tryptophan in water was studied. It was shown that in the presence of all the above-mentioned AP, an increase in the effective rate constant (k eff) of tryptophan photooxidation is observed. It was suggested that the observed effect is associated with the interaction of MB with APs, which leads to disaggregation of dye associates. Such disaggregation leads to an increase in the optical density and intensity of MB luminescence. It was also shown that the photocatalytic activity of MB decreases by a factor of 1.5–3.5 in the presence of SA, which is due to the ionic interaction of the cationic MB with polyanionic SA. The interaction of MB with polysaccharide is confirmed by changes in the absorption and fluorescence spectra of the dye. The introduction of APs into a solution containing MB and SA prevents the interaction between MB and polysaccharide, which leads to an increase in the k eff values of tryptophan photooxidation in the presence of MB-AP-SA system, as well as to an increase in the optical density and fluorescence intensity of MB when AP and SA are added. The existence of weak interactions between the hydrophobic groups of MB molecules and the AP (polyvinylpyrrolidone) is also evidenced by the data obtained through 1H-NMR spectroscopy and the degree of MB fluorescence anisotropy. The AFM method shows the change in the surface structure of a thin film obtained by evaporating an aqueous solution of MB-F108-SA compared to the corresponding structure of a film obtained by evaporating an aqueous solution of MB-SA. MB-AP and MB-AP-SA systems may be promising for practical application in the aPDT treatment of chronic microbial superficial infections.