This work reports an experimental methodology to study the connection between ultrafast optical Kerr effect spectroscopy and heat transfer and fluid mechanics from femtoseconds to real time. The methodology was applied to hexane and o-dichlorobenzene, two molecular liquids with contrasting thermal diffusion behavior. We show that the ultrafast spectroscopic signals are markedly different under equilibrium (off-resonant) and nonequilibrium (resonant) conditions. By varying the intensity of the resonant pump pulses, we modulate the photothermal effect and show how transient and cumulative heating effects are manifested in the ultrafast signals. We vary the rotation rate of a magnetic stirrer to show how turbulent flow influences the signatures of heating in single-shot ultrafast measurements. We show how the time delay between pump and probe pulses can be used to characterize real-time conductive and convective modes of heat transfer as well as microscopic heat dissipation rates on the femtosecond timescale. The methodology is generally applicable to other molecular liquids and also to transparent liquids containing absorbing chromophores, which have the advantage of allowing control of the amount of heat generated after light absorption across different fluids.

Antimicrobial Photodynamic Inactivation (aPDI) is a non-thermal, minimally invasive technique that uses light and photosensitizing compounds (PS) to generate reactive oxygen species, promoting the destruction of microorganisms without inducing microbial resistance. This study investigated the photosensitizing potential of the flower extract of Plumeria rubra L., a unconventional edible plant, in aPDI. The extract showed a high content of rutin, a flavonoid known to confer chemical stability to PS and promote its interaction with bacterial cell structures, increasing photodynamic efficiency. Tests conducted in the dark revealed a lack of antimicrobial activity, a desirable characteristic for photosensitizing compounds. Under white light irradiation and an optical fluence of 18 J/cm^2 , the extract inactivated the methicillin-resistant Staphylococcus aureus strain at a concentration of 0.78 mg/mL, in addition to demonstrating action against Listeria monocytogenes and Staphylococcus epidermidis. At an optical fluence of 27 J/cm^2 , inactivation of most of the strains evaluated was observed. These results indicate that P. rubra extract it is a promising natural photosensitizer, that combines a favorable phytochemical composition, absence of inactivation in the dark, and high photodynamic efficiency under white light, demonstrating potential for therapeutic and industrial applications.

Antimicrobial photodynamic inactivation (aPDT) is an effective technique for treating acne vulgaris, due to its efficiency in inactivating multiresistant bacteria and the absence of systemic side effects. This study investigated the potential of the dye Azure A (AZA), belonging to the phenothiazine class, as a photosensitizer (PS) in aPDT to combat the gram-positive bacteria Staphylococcus epidermidis and Cutibacterium acnes, both associated with inflammatory acne vulgaris. The efficiency of AZA was compared to Orthotoluidine Blue (OTB), evaluating the absorbance spectra, singlet oxygen generation rate, and minimum bactericidal concentration (MBC) at different optical fluence values and concentrations. The results demonstrated that AZA and OTB have similar spectroscopic characteristics and single oxygen generation rates, and they could inactivate both bacteria at an MBC of 0.78 μ M for the smallest tested optical fluence. These findings indicate that AZA is an excellent candidate for topical aPDT applications in treating acne vulgaris and other associated infections by such bacteria.

The mode-mismatched photothermal lens (PTL) technique can be used to investigate transient acoustic waves induced by pulsed laser excitation in liquids at the nanosecond time scale [1]–[3]. The recent advances in the theoretical description of optoacoustic waves have enabled the PTL technique to be used as a quantitative method for material characterization [2], [3]. The method allows quantitative determination of a complete set of physical properties, such as thermal diffusivity, optical absorption coefficient, sound speed, and piezo-optic coefficient [1].

The growing interest in using photodynamic therapy for cancer treatment and antimicrobial applications has prompted the search for different classes of dyes. In general, the protocols of these studies are different, making it difficult to compare their efficiency directly. Here, we apply a controlled protocol to analyze the photophysical properties of Erythrosin B, Eosin Y, and Rose Bengal using a set of optical techniques. The results show that Erythrosine has the best singlet oxygen generation capacity. This result, added to the well-known low toxicity of Erythrosine, makes it a good choice among the xanthenes for health applications.

The photoactive properties of organic dyes are paramount when foreseeing their applications. This study investigated a series of structurally related diketopyrrolopyrrole-based materials using time-resolved laserinduced lensing technique to evaluate the effects of solvent viscosity and molecular oxygen availability in their photophysical properties. The absorption and photoluminescence spectra were determined, and the molecules diluted in DMSO had their singlet oxygen (1O2) production measured. The thermal and photostability of the architectures under investigation are quantitatively measured and discussed. The results showed that the thermal conversion rate is - 30 % for all studied systems. Consequently, their high quantum yield efficiencies are - 70 %. The photoactive response results provided relevant information for current and future applications of these materials, which may broaden their technological relevance towards bifunctional probes.

The interaction of localized light with matter generates optical electrostriction within dielectric fluids, leading to a discernible change in the refractive index of the medium according to the excitation’s light profile. This optical force holds critical significance in optical manipulation and plays a fundamental role in numerous photonic applications. In this study, we demonstrate the applicability of the pump-probe, photo-induced lensing (PIL) method to investigate optical electrostriction in various dielectric liquids. Notably, the thermal and nonlinear effects are observed to be temporally decoupled from the electrostriction effects, facilitating isolated observation of the latter. Our findings provide a comprehensive explanation of optical forces in the context of the recently introduced microscopic Ampère electromagnetic formalism, which is grounded in the dipolar approximation of electromagnetic sources within matter and characterizes electrostriction as an electromagnetic-induced stress within the medium. Here, the optical force density is re-obtained through a new Lagrangian approach.

Background: The efficacy of photodynamic therapy (PDT) depends on the combination of light and a photo sensitizer for inactivation of microorganisms. However, finding the ideal conditions for the factors involved in this technique is time and cost-consuming. The rotational composite central design (RCCD) is a tool that can be allied with PDT to achieve precise results within a shorter working time. Methods: This study used the response surface methodology to optimize the parameters of PDT mediated by Erythrosine (ERY) and green light-emitting diodes (LED) in different Escherichia coli strains by applying RCCD. Results: The RCCD predicted optimum values of ERY and light exposure on PDT. According to the experimental results, the light exposure time showed the most significant influence on the inactivation of the evaluated bacteria. The optimized operating conditions were validated in laboratory tests, and no viable cells were recovered with ERY at 116 mu mol L-1 and 30 min of light (33.34 J cm(2)) for E. coli ATCC 25922, 108 mu mol L-1 and 40 min (44.38 J cm(2)) for E. coli ATCC 35218, and 108 mu mol L-1 and 29.3 min (32.5 J cm(2)) for E. coli O157:H7 EDL 933. Conclusion: The adjusted polynomial models provided accurate information on the combined effects of ERY and lighting time with green LED on PDT. The application of the RCCD, in addition to reducing the number of experiments, also allows for increased quantity and quality of the results. Therefore, surface response methodology combined with PDT is a promising approach to inactivate E. coli.

Staphylococcus aureus is a global challenge to the clinical field and food industry. Therefore, the development of antimicrobial photodynamic therapy (aPDT) has become one of the valuable methods to control this pathogen. The antibacterial activity of photoinactivation by erythrosine (Ery) against S. aureus has been reported, but its modes of action are unclear. This study aimed to employ a proteomic approach to analyze modes of action of Ery-aPDT against S. aureus. We determined the antibacterial effect by Ery-aPDT assays, quantified reactive oxygen species (ROS) and injury to the cell membrane, and determined protein expression using a proteomic approach combined with bioinformatic tools. Ery-aPDT was effective in reducing S. aureus to undetectable levels. In addition, the increment of ROS accompanied the increase in the reduction of cell viability, and damage to cellular membranes was shown by sublethal injury. In proteomic analysis, we found 17 differentially expressed proteins. These proteins revealed changes mainly associated with defense to oxidative stress, energy metabolism, translation, and protein biosynthesis. Thus, these results suggest that the effectiveness of Ery-aPDT is due to multi-targets in the bacterial cell that cause the death of S. aureus.

The combination of photodynamic and photothermal therapy is an interesting strategy for cancer treatment. In this work, we synthesized gold nanoparticles (AuNPs) loaded with methylene blue (MB) and coated with trimethylammonium functionalized chitosan (HTCC). Initially, HTCC was synthesized and characterized by 1 H NMR, FTIR and elemental analysis. The degree of substitution (DS) of HTCC of 69 % was obtained through 1 H NMR. The formulated HTCC-MB-AuNPs presented strong absorption in the visible range (500 - 800 nm), a small size of 150 nm, and zeta potential of about + 26 mV. The incorporation of MB in gold nanoparticles coated with HTCC modified the photophysical and photochemical properties, such as a decrease in the intensity of fluorescence emission and a decrease in the reactivity of MB with photo-oxidation model reactions. In vitro testing in MDA-MB231 breast cancer cells showed that HTCC-MB-AuNPs exert significant cytotoxicity in the presence of photo stimulation (red laser, 660 nm, 100 mW cm -2 ), possibly by combining photothermal and photodynamic effects (PTT + PDT). In the dark, under the same conditions, MB showed less cytotoxicity to cancer cells, especially when encapsulated in HTCC-MB-AuNPs. These results reveal a novel application potential of HTCCMB-AuNPs in phototherapies for the treatment of cancer.

Patients with cystic fibrosis are highly susceptible to bacterial infections, which can often lead to irreversible damage. In this context, inhalable liposomal systems have shown great promise as drug delivery mechanisms, significantly enhancing drug permeation and accumulation in the lungs. However, the development of inhalable liposomes for various therapeutic applications is still in its early stages, providing ample opportunities for extensive research by the scientific community. Within this scenario, antimicrobial photodynamic therapy may emerge as a relevant technique, promoting greater selectivity due to its light trigger. We have developed lipid-polymer hybrid liposomes (DPPC/F127) and compare the inclusion of two types of xanthenes, one more hydrophilic (Rose Bengal - RB) and one more hydrophobic (Rose Bengal butyl ester - RBBUT). The systems were characterized in terms of morphology, thermal and kinetic stability, incorporation and release efficiency, photophysical properties, and possible location of the PS in the liposome. The studies showed that incorporation into DPPC/F127 prevented self-aggregation and significantly improved the photophysical properties of RB and RBBUT. The bacterium Pseudomonas aeruginosa proved to be more resistant to the photodynamic effect, requiring long illumination times. For Staphylococcus aureus, we observed a dependence between pre-incubation time and illumination time. Our results showed that the more external photosensitizer (PS) was more effective in experiments performed without incubation. However, with pre-incubation, the efficacy of both systems became comparable. Notably, only 10 min of illumination (warm white light; fluence: 139.7 J cm-2) resulted in complete bacterial inactivation.

Edible vegetable oils are sources of polyunsaturated fatty acids, necessary for a balanced diet capable of providing elements that act on the energetic, structural, and hormonal composition of humans. The growing consumption of these foods has encouraged the search for techniques capable of characterizing their compositions and transformations when subjected to industrial processes or during domestic use. We propose to analyze the transformations undergone by edible vegetable oils originating from different plants due to thermal oxidation. For this, dynamic viscosity, oxidative stability index, fatty acid profile, and infrared spectra determined before and after being subjected to thermal oxidation. The results from infrared spectroscopy were improved through Principal Component Analysis (PCA). Among other results, it was possible to establish correlations between the FTIR spectra, dynamic viscosity, and the profile of fatty acids, allowing the prediction of the concentration of polyunsaturated fatty acids (PUFA) after thermal oxidation by measuring the spectrum of samples before the thermal oxidation process. Furthermore, it is observed that the dynamic viscosity is strongly altered by thermal oxidation, which is directly related to the decrease in PUFA content. The results obtained can be used to predict quality factors of edible vegetable oils, helping to choose the right type of oil for each industrial or domestic process.Practical Applications: This research holds significant practical implications, particularly in detecting adulteration and fraud of edible vegetable oils. The developed method uses physicochemical properties and infrared spectroscopy with principal component analysis to characterize oils and to determine the oil stability index. The association between FTIR and Principal Component Analysis allows the prediction of polyunsaturated fatty acid content and correlations between dynamic viscosity and oxidative stability index. image

Aim: To evaluate the photodynamic mechanism of hypericin nanoencapsulated in P123 copolymer micelles against Microsporum canis in vitro.Material & methods: Antifungal susceptibility tests were performed, including the determination of the minimum fungicidal concentration and time-kill curve. Flow cytometry was used to evaluate the internalization of P123-Hyp in conidia and the activation of PDT type I and II mechanisms via the detection of reactive oxygen species (ROS), as well as to assess changes in the cell membrane using propidium iodide (PI) and cell morphology.Results: P123-Hyp-PDT exerted a fungistatic action on fungus, maintaining this action up to 24 h after exposure, corroborating the PS internalization results, which showed satisfactory uptake of P123-Hyp from a concentration of 3.125 mu mol/l. Among the ROS studied, singlet oxygen was detected. Furthermore, the increased fluorescence intensity of PI in treated cells indicated necrotic cell death, while the size and granularity of the cells were also altered.Conclusion: Our results show, for the first time, a proposal for the mechanism of action of P123-Hyp-mediated PDT against M. canis, proving that it has a prolonged action on the fungus through activation of the type II photodynamic pathway, which resulted in disruption of the plasma membrane and cellular alterations.

Background: Sporothrix brasiliensis is a pathogenic dimorphic fungus that affects humans and animals causing sporotrichosis. The treatment of this disease with conventional antifungals commonly results in therapeutic failures and resistance. Therefore, this study aimed to evaluate the in vitro effect of curcumin (CUR) mediated by photodynamic therapy (PDT) in its pure state and incorporated into pharmaceutical formulation in gel form, on the filamentous and yeast forms of S. brasiliensis. Methods: Cells from both forms of the fungus were treated with pure curcumin (PDT-CUR). For this, CUR concentrations ranging from 0.09 to 50 & mu;M were incubated for 15 min and then irradiated with blue LED at 15 J/cm2. Similarly, it was performed with PDT-CUR-gel, at lower concentration with fungistatic action. After, a qualitative and quantitative (colony forming units (CFU)) analysis of the results was performed. Additionally, reactive oxygen species (ROS) were detected by flow cytometry. Results PDT with 0.78 & mu;M of CUR caused a significant reduction (p < 0.05) in cells of the filamentous and yeast form, 1.38 log10 and 1.18 log10, respectively, in comparison with the control. From the concentration of 1.56 & mu;M of CUR, there was a total reduction in the number of CFU (& GE; 3 log10). The PDT-CUR-gel, in relation to its base without CUR, presented a significant reduction (p < 0.05) of 0.83 log10 for the filamentous form and for the yeast form, 0.72 log10. ROS release was detected after the PDT-CUR assay, showing that this may be an important pathway of death caused by photoinactivation. Conclusion PDT-CUR has an important in vitro antifungal action against S. brasiliensis strains in both morphologies.

An all-optical photoinduced lensing method is used to excite and monitor acoustic waves in liquids. Following optical absorption, the laser pulse induces a localized temperature gradient that launches pressure waves in the excited region at the nanosecond time scale. This generates a lens-like optical element in the sample. A probe laser beam senses the refractive index change due to the acoustic and thermal effects. Piezo-optic and thermo-optic coefficients govern how the refractive index of a material changes in response to mechanical stress and temperature variations, respectively. These effects are connected to the physical properties of the liquids and can be accessed by theoretically describing the intensity signal. A complete set of physical properties of ten liquids are quantitatively described in this work. These effects find applications in a wide range of fields, from optical communication, ultrasonic imaging, and sensing to adaptive optics and fundamental research.

The search for more effective drugs and therapies for the treatment of microbial diseases has driven the development of nanomedicine in recent years. In this sense, the present work shows the combination of photodynamic therapy (PDT) and photothermal therapy (PTT) using the photoactive drugs: methylene blue (MB) and gold nanoparticles (AuNPs). The ABA triblock Pluronic (R) P-123 copolymer was employed both as a micellar nanocarrier and reductant/stabilizing agent for AuNPs. The synthesis of gold nanoparticles (AuNPs) was carried out in situ through the redox process of AuCl3 gold salt in the presence of different concentrations of P-123 ranging from 0.25 % to 8.00 % ( % w/V) following the solid dispersion method. The MB was incorporated into the copolymeric micellar system by passive and active incorporation methods. In general, the system containing 1.00 % and 2.00 % (w/V) of P-123 was the more efficient and reproducible to obtain P-123/AuNPs/MB samples. The AuNPs synthesized presented plasmonic resonance peaks ranging from 535 to 554 nm, characteristic of spherical AuNPs. Dynamic Light Scattering and transmission electronic microscopy confirm the structure of the polymeric micelle around 20 nm and the AuNPs 3 nm diameters. The fluorescence emission showed to be dependent on the excitation wavelength, a promising feature for biological applications, especially when considering an image-guided diagnosis. Furthermore, the Stern-Volmer study by fluorescence quenching with iodide showed that active incorporation favors greater internalization of MB at the hydrophobic core of the micelle. On the other hand, the passive incorporation method placed MB in the most hydrophilic region in the micelle. The photodynamic effect was confirmed by singlet oxygen generation using ABDA as a probe. Thermal Lens spectroscopy and heating studies also confirms the heat generation by the system. In addition, the results point to synergism both in the generation of 1O2 and heat. The in vitro susceptibility of the samples was evaluated in Candida albicans strain. Better antifungal activity was observed in the sample of 2.00 % P-123/AuNPs/MB by Passive incorporation, illuminated with red and green LEDs. The biological study in bacteria strains of E. coli and S. aureus has shown that both percentages of P-123 with MB and AuNPs/MB by passive incorporation were efficient in controlling the evaluated bacteria. In this way, the present work showed promise for the treatment of antimicrobials through the combined therapy of PDT and PTT.

Piezo-optic and thermo-optic coefficients are important material properties that play a critical role in the design and optimization of many optical devices. The ability to accurately measure and control these coefficients is essential for achieving high performance and reliability in a wide range of applications. In this article, we use the optical detection of the ultrasound-induced thermal lens effect to investigate these properties for water at low temperatures. The results show that the anomalous behavior of water around 4°C is easily observed. The thermal lens method is used to determine the temperature dependence of the piezo-optic and thermo-optic coefficients.

Considering the multifaceted and increasing application of photodynamic therapy (PDT), in recent years the antimicrobial employment of this therapy has been highlighted, because of the antiviral, antibacterial, antiparasitic, and antifungal activities that have already been demonstrated. In this context, research focussed on antimycological action, especially for treatment of superficial infections, presents promising growth due to the characteristics of these infections that facilitate PDT application as new therapeutic options are needed in the field of medical mycology. Among the more than one hundred classes of photosensitizers the antifungal action of hypericin (Hyp) stands out due to its ability to permeate the lipid membrane and accumulate in different cytoplasmic organelles of eukaryotic cells. In this review, we aim to provide a complete overview of the origin, physicochemical characteristics, and optimal alternative drug deliveries that promote the photodynamic action of Hyp (Hyp-PDT) against fungi. Furthermore, considering the lack of a methodological consensus, we intend to compile the best strategies to guide researchers in the antifungal application of Hyp-PDT. Overall, this review provides a future perspective of new studies and clinical possibilities for the advances of such a technique in the treatment of mycoses in humans.

Background: Onychomycosis (OM) is a common nail plate disorder caused by dermatophyte molds, yeasts, and non-dermatophyte molds, which use keratin in the nail plate as an energy source. OM is characterized by dys-chromia, increased nail thickness, subungual hyperkeratosis, and onychodystrophy, and is typically treated with conventional antifungals despite frequent reports of toxicity, fungal resistance, and OM recurrence. Photody-namic therapy (PDT) with hypericin (Hyp) as a photosensitizer (PS) stands out as a promising therapeutic modality. When excited by a specific wavelength of light and in the presence of oxygen, to lead to photochemical and photobiological reactions on the selected targets.Methods: OM diagnosis was made in three suspected cases, and the causative agents were identified by classical and molecular methods, and confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). Susceptibility of planktonic cells of the clinical isolates to conventional antifungals and PDT-Hyp was evaluated, and photoacoustic spectroscopy (PAS) of Hyp permeation in nail fragments ex vivo was analyzed. Furthermore, the patients opted to undergo PDT-Hyp treatment and were subsequently followed up. The protocol was approved by the human ethics committee (CAAE, number 14107419.4.0000.0104).Results: The etiological agents of OM in patients ID 01 and ID 02 belonged to the Fusarium solani species complex, being identified as Fusarium keratoplasticum (CMRP 5514) and Fusarium solani (CMRP 5515), respectively. For patient ID 03, the OM agent was identified as Trichophyton rubrum (CMRP 5516). PDT-Hyp demonstrated a fungicidal effect in vitro, with reductions of p3 log10 (p < 0.0051 and p < 0.0001), and the PAS analyses indicated that Hyp could completely permeate through both healthy and OM-affected nails. After four sessions of PDT-Hyp, mycological cure was observed in all three cases, and after seven months, clinical cure was confirmed. Conclusion: PDT-Hyp showed satisfactory results in terms of efficacy and safety, and thus can be considered a promising therapy for the clinical treatment of OM.

The Angular Spectrum Representation (ASR) is applied to describe semi-analytically the optical force densities acting on linear dielectric media when a quasi-monochromatic tightly focused Gaussian beam is applied. This method is seen to be inherently faster than conventional finite-difference schemes. Numerical simulations of the optical force densities were also performed and found to be in agreement with the literature, providing a complementary tool for the study of opto-mechanical effects in matter.