This study investigated the long-term safety of 222nm far-ultraviolet light, a promising technology for continuous disinfection that is believed to be safe for human exposure. To address concerns about its practical efficacy and potential long-term effects, an accelerated 90-day toxicological study was conducted on rats. The animals were exposed to graded doses of 222nm light: high (5000mJ/cm2/day), medium (1000mJ/cm2/day), and low (500mJ/cm2/day). The results were dose-dependent. The high-dose group exhibited significant adverse effects, including skin damage (inflammatory cell infiltration, thickening), systemic weight loss, and thymic atrophy. In stark contrast, the low and medium-dose groups showed no abnormal clinical symptoms, behavioral changes, or weight abnormalities throughout the entire study. Comprehensive analysis of hematological, biochemical, and histopathological indicators confirmed no toxicologically relevant changes at these lower doses. Based on these findings, the study established a No Observed Adverse Effect Level (NOAEL) of 1000 mJ/cm2/day for subchronic exposure in rats. This indicates that continuous exposure to 222 nm far-UV light at or below this dose level is not associated with any detectable adverse biological effects, supporting its potential for safe use in occupied spaces.

Recently, the use of antimicrobial blue light (aBL) has gained interest across various applications. However, a comprehensive framework that addresses the key factors driving bacterial photoinhibition remains lacking-particularly concerning biofilms, the predominant bacterial lifestyle. The goal of this work was to evaluate the potential of photokilling in this wide-spread microbial adherent community type, and to decipher the specific mechanisms at stake. To investigate aBL killing efficiency, we conducted experiments in a Pseudomonas aeruginosa biofilm model using a well-defined millifluidic device that allows real-time microscopy and quantitative analysis of a living biofilm under local irradiation at a defined light dose. In addition, we developed a theoretical model for light-biofilm interaction that accounts for the three-dimensional structure of the bacterial biofilm. To inform our model, we examined the light dose-response in isolated cells and found a profile indicative of a multi-target mechanism of lethality. By comparing the experimental and theoretical results, we identified a loss in killing efficiency as the biofilm grows, due in part to the increase in thickness of the living material inherent to this mode of development. Our findings also highlight a reduction in the intrinsic bacterial sensitivity to blue light as biofilm development progresses, which we attribute to the low oxygen levels typical of densely populated bacterial environments. These findings reveal new features of the photokilling mechanism and redefine the approach to designing effective antimicrobial photoinactivation strategies by integrating the key physical characteristics of bacterial biofilms. Awareness of the bacterial world's global importance is steadily growing in both science and society. Among the critical challenges, the continuing increase in multidrug resistance to antibiotics represents a major public health concern reinforcing the urgency of alternative antimicrobial therapies with photoinactivation as a promising approach. However, its full potential can only be achieved through a better understanding of the involved mechanisms in relevant environments. In this study, we combined experimental and theoretical approaches to investigate the photoinactivation of bacteria within a developing biofilm, the dominant bacterial lifestyle. Our comprehensive analysis sheds light on the mechanisms and limitations of photoinactivation in the fight against microbes, which is essential for designing novel antibacterial phototherapies.

Excessive use of antibiotics contributes to the development of multidrug-resistant microorganisms, making bacterial infections more difficult to treat. As an alternative method, photodynamic therapy is being explored. This therapy relies on generating cytotoxic concentrations of reactive oxygen species (ROS) during the interaction of a photosensitizer with light and molecular oxygen. In the presented work, we investigated the antibacterial efficacy of four different photosensitizers: 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (TmPyP), 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin zinc (ZnTPPS), zinc phthalocyanine disulfonate (ZnPcS), and tetramethylthionine chloride (methylene blue, MB) on Escherichia coli. The results showed that this type of bacteria is susceptible to all of the studied photosensitizers. Our measurements revealed that a bacteriostatic or bactericidal effect can be achieved either by exposure to high-dose (50J/cm2) violet (414nm) light or by combining high-dose violet light with TmPyP or ZnTPPS. However, when using red-light-sensitive ZnPcS or MB, significant inhibition of bacterial growth occurred after three cycles of light exposure at a relatively low individual light dose (10J/cm2), rather than a single high dose (50J/cm2). Additionally, the fluorescent probe CellROX Red, which monitors ROS production, showed a significant increase in fluorescence in the presence of porphyrin photosensitizers as early as after the first irradiation.

Stimulated emission depletion (STED) microscopy is a super-resolution imaging technique that uses a high light dose to surpass the diffraction limit. The excellent spatiotemporal resolution achieved by STED, combined with its nontoxic labeling, facilitates super-resolution imaging in living cells. However, the use of high-intensity lasers, along with repeated fluorophore excitation-depletion cycles, may cause phototoxic effects. In this study, we examined the invasiveness of live-cell STED microscopy to validate its use. Investigating cell proliferation is among the best strategies for detecting and quantifying potential phototoxic effects. Therefore, we studied long-term (20h) cell proliferation and survival after high-resolution (50nm) STED imaging using a 775nm depletion beam. We observed no significant differences in proliferation and mortality rates between STED- and non-STED-imaged control cells for various human cell lines (U2OS, HeLa, and RPE-1), with STED imaging performed on different cellular structures (nuclear pore complex, Golgi, actin, and mitochondria). Importantly, the STED-imaged cells showed no significant mitotic delay compared to the control when timing the onset of mitosis. In addition to long-term effects, we measured short-term stress response by observing cytosolic calcium levels after high-resolution STED imaging and during low-resolution STED scanning, and found no significant stress. These results show the applicability of STED microscopy for noninvasive super-resolution imaging in living cells.

Photodynamic therapy (PDT) is a unique oxidative stress-based anti-tumor modality that has proven highly effective for various solid malignancies. Intrinsic and acquired resistance is a significant challenge for all cancer treatments, including PDT. We showed previously that several human cancer cell lines in 2D cultures can exploit nitric oxide (NO) from stress-upregulated inducible nitric oxide synthase (iNOS) to (i) resist photokilling sensitized by 5-aminolevulinic acid (ALA)-induced protoporphyrin IX, and (ii) promote growth and mobility aggressiveness of surviving tumor cells. We describe here a mixed-spheroid model consisting of glioblastoma (LN229 or U87) cells and normal human (HMEC-1) epithelial cells. To systematically investigate the interactions between tumor and endothelial cells in a 3D microenvironment, we developed a stepwise workflow: first, generating mixed spheroids with defined cell ratios; second, characterizing their growth, mechanical properties, and cellular organization using fluorescent labeling and confocal microscopy; third, assessing ALA-induced PpIX distribution and PDT efficacy; and finally, evaluating post-PDT responses including iNOS upregulation, proliferation, migration, and the impact of iNOS inhibition. Using high resolution confocal microscopy, we visualized the process of development of heterospheroid models. We analyzed the distribution of ALA-induced protoporphyrin IX within preformed spheroids. PpIX formed initially in the periphery of spheroid reaches even distribution within the spheroid in ~ 12 h of equilibration time. The survival of spheroid cells subjected to photodynamic action was determined. In general, higher doses of LED light were needed to achieve the same killing ratio for spheroids, as compared to 2D cultures. The effects of ALA/light treatment on the expression of iNOS, and proliferative potential of surviving tumor cells are reported. The impact of iNOS inhibitor (1400W) on the process of spheroid re-growth after induced photodynamic action was also analyzed. Photodynamic stress of glioma cells spheroids increases their intrinsic iNOS expression and NO-dependent proliferation. This increase is inversely proportional to the initial/constitutive expression of iNOS: less aggressive LN229 cells show greater stress-induced increase of iNOS and proliferation, than constitutively more aggressive U87 cells. The results presented suggest, that introduction of an iNOS inhibitor could significantly increase the effectiveness of photodynamic therapy.

Reversibly switchable fluorescent proteins (RSFPs) transition many times between dark and fluorescent states under minimal light doses. The photoswitching can happen at different speed, contrast and length, and it is often challenging for users to select the optimal imaging scheme to generate images with high contrast and spatial resolution. Here, we experimentally investigate the photophysical properties of different RSFPs under imaging conditions, together with an in silico exploration of their role in nanoscale image formation. We developed open-source software that uses measured parameters such as brightness, switching speed, photoswitching fatigue, labelling densities, noise and illumination type to generate the related RESOLFT (reversible saturable/switchable optical fluorescence transition) super-resolution image. This tool can be used to select optimal imaging schemes for known RSFPs and to guide the rational development of new proteins.

The article provides an overview of current paper on the use of natural photosensitizers for photodynamic therapy and photodynamic inactivation of microorganisms. The existing photosensitizers with high selectivity, high singlet oxygen quantum yield and minimal dark toxicity are considered. It has been shown that natural compounds, such as curcumin, hypericin, riboflavin, berberine, chlorophyloids, psoralenes, and anthracyclines, are promising candidates for photodynamic therapy due to their biocompatibility and rich spectrum of photo and biochemical properties. Also, a review of promising rare and less studied photosensitizers was conducted. A generalized analysis of modern publications to date has been performed as well as an analysis of the authors’ experimental data on stationary, timeresolved fluorescence and microscopy (confocal and Fluorescence-lifetime imaging microscopy) of natural as well as their therapeutic and antimicrobial activity in vitro and in vivo. It has been shown that hypericin and perylene quinones achieve a quantum yield of singlet oxygen ≈ 0.5–0.6 at ε > 4·104 l·mol–1·cm–1, providing effective photodynamic therapy of tumors and a logarithmic decrease (6–7 lg CFU) bacterial load at moderate doses of light (less 20 J·cm–2). Curcumin and riboflavin combine the therapeutic effect with bright fluorescence, allowing optical monitoring in real time. Psoralenes implement an alternative mechanism for DNA crosslinking under a long-wavelength, high-energy radiation, which underlies therapy based both on psoralens and long-wavelength ultraviolet radiation and also blood disinfection. Complexing with lanthanide ions or upconversion nanoparticles expands the excitation spectrum to the nearinfrared range and enhances the diagnostic signal. Thus, natural photosensitizers are evolving into a versatile platform for the simultaneous treatment and optical monitoring of oncological and infectious diseases, while their incorporation into nanostructures —including rareearthion–based systems — extends lightpenetration depth and enables precise visualization of deepseated tissues, paving the way for the clinical adoption of nextgeneration hybrid phototherapeutic technologies.

From brood pouch to complex behavior: Tracking nanoplastic toxicity in Daphnia magna.

Basal cell carcinoma (BCC) is the most prevalent non-melanoma skin cancer, with surgical excision as the gold standard-though it carries risks of cosmetic scarring and functional impairment. Photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA) or methyl aminolevulinate (MAL) emerges as a non-invasive alternative, yet evidence on its relative efficacy across superficial (sBCC) and nodular (nBCC) subtypes remains inconsistent. This systematic review and meta-analysis adhered to PRISMA 2020 guidelines, with a comprehensive search of PubMed, Embase, Cochrane Library, and Web of Science up to December 31, 2025. Eligible studies included randomized controlled trials (RCTs) and single-arm studies evaluating ALA-PDT/MLA-PDT for histologically confirmed sBCC or nBCC. Study quality was assessed via the Methodological Index for Non-Randomized Studies (MINORS) scale, and statistical analyses were performed using Review Manager 5.4. A comprehensive literature search identified 3832 records, with 55 eligible studies (41 for sBCC, 34 for nBCC) ultimately included, involving 2123 patients and 2995 lesions. For sBCC, the pooled complete response (CR) rate was 0.88 (95% CI: 0.85-0.91, p<0.00001) with high heterogeneity (I²=87%); no significant difference in CR rate was observed between ALA-PDT (0.87) and MAL-PDT (0.90) (p=0.47), and BF-200 ALA-PDT achieved a CR rate of 0.90. The pooled beauty effect rate for sBCC was 0.91 (95% CI: 0.87-0.95, p<0.00001), with a low pooled adverse event incidence of 0.08 (95% CI: 0.03-0.14, p=0.004) and a pooled recurrence rate of 0.13 (95% CI: 0.09-0.18, p<0.00001). For nBCC, the pooled CR rate was 0.75 (95% CI: 0.70-0.80, p<0.00001, I²=92%), with MAL-PDT (0.78) showing a statistically significant higher CR rate than ALA-PDT (0.69) (p=0.04); BF-200 ALA-PDT and AFL-MAL-PDT achieved CR rates of 0.89 and 0.84, respectively. The pooled beauty effect rate for nBCC was 0.90 (95% CI: 0.83-0.96, p<0.00001), with a pooled recurrence rate of 0.15 (95% CI: 0.10-0.20, p<0.00001); adverse event data were insufficient for pooling, with individual studies reporting mild, manageable local reactions. Subgroup analyses revealed that study design, light dose, and number of treatment sessions were the main factors contributing to heterogeneity in key outcomes. ALA/MAL-PDT is an effective and safe non-invasive therapeutic option for both sBCC and nBCC, with excellent cosmetic outcomes for both subtypes. MAL-PDT exhibits significantly superior efficacy in nBCC compared with ALA-PDT, while the two photosensitizers show comparable therapeutic effects in sBCC. Novel PDT formulations including BF-200 ALA-PDT and AFL-MAL-PDT demonstrate promising CR rates for BCC, providing new treatment alternatives for clinical practice. Standardization of treatment parameters (e.g., light dose, treatment sessions) and differentiation of study design types can effectively reduce heterogeneity in PDT efficacy evaluation, and ALA/MAL-PDT should be prioritized for patients seeking minimally invasive treatment, those with multiple lesions, or those with contraindications to surgical excision.

Photocages are light-responsive chemical protecting groups that enable the controlled release of bioactive molecules. As the need for precise spatiotemporal manipulation in increasingly complex systems continues to grow, the development of novel photocage scaffolds remains essential. Herein, we show how the structural and electronic properties of xanthenium photocages determine their ground state stability. Based on rational design, we introduce their next generation built on the julolidine auxochrome, resulting in ultra efficient, green to red light activatable photocages, X590 and X600H. X590 was applied in the light-controlled delivery of a potent tubulin inhibitor, monomethyl auristatin E (MMAE) and a topoisomerase inhibitor (SN38) with low light doses above 600 nm. The light activatable prodrugs possess high photoindices both in 2D cell cultures and 3D tumor spheroids and show antitumor effects in the chorioallantoic membrane (CAM) assay in live chicken embryos. The versatility of this new scaffold was demonstrated using a caged agonist for the light activation of serotonin 2C G protein-coupled receptor. Overall, these photocages should find wide applications in photopharmacology and the detailed studies presented herein could contribute to the clinical translation of photoactivated chemotherapy.

Lipid-stabilized ICG nanoaggregates for the photodisruption of vitreous opacities.

PDT using Photofrin® (P-PDT) has been applied to over 900 gynecologic tumor cases since 1989, demonstrating excellent efficacy and fertility preservation; however, post-treatment photosensitivity has limited its clinical application for CIN and cervical cancer. This study aimed to establish a safe, effective, and fertility-preserving alternative to cervical conization. To overcome photosensitivity, we conducted a prospective Phase I/II clinical study to evaluate the safety, efficacy, oncological control, and fertility outcomes of L-PDT using talaporfin sodium (Laserphyrin®) and a diode laser for CIN grades 2-3. Forty-three women with biopsy-confirmed CIN2-3 were enrolled. Phase I determined the optimal light dose (50, 75, or 100 J/cm²), and Phase II assessed efficacy and safety at 100 J/cm². Talaporfin sodium (40 mg/m²) was administered intravenously 4 hours before laser irradiation under colposcopic guidance. Complete response (CR) was achieved in 95% (95% CI: 89.1-100%) at 3 months and 98% (95% CI: 93.2-100%) at 6 months after treatment. Original high-risk human papillomavirus clearance was 92.5% at 3 months and 95% at 12 months. Adverse events were mild and transient, including abdominal pain and low-grade fever. No recurrences occurred during a median follow-up of 66.4 months among patients achieving CR. Among women desiring pregnancy, the conception rate was 74% (23/31) and the live birth rate was 79% (27/34), with a low preterm birth rate of 3.7% (1/27). These results suggest that L-PDT is a safe and highly effective non-excisional treatment for CIN that may contribute to fertility preservation; however, potential advantages over conventional conization and laser vaporization need to be confirmed in comparative studies.

LED-based illumination device for efficacy assessment of the photosensitizers in photodynamic therapy.

Abstract A practical and selective method for the oxidation of thioethers to sulfoxides under visible light irradiation is reported. The reaction is catalyzed by inexpensive and readily available FeBr3, using molecular oxygen from air as the sole oxidant under mild and clean conditions. A wide range of thioethers can be efficiently converted to the corresponding sulfoxides with high selectivity under low-power (15 W, light dose = 1.29 × 104 J/cm2) blue light irradiation. Mechanistic studies indicate that superoxide radical anions (•O₂−) generated under photoexcitation play a key role in the selective oxidation process. This protocol provides a simple and energy-efficient approach for sulfoxide synthesis using an earth-abundant iron salt photocatalyst.

While computer simulations can accurately model light dose delivery in interstitial photodynamic therapy (iPDT), predicting individual clinical outcomes remains difficult. In addition to biological uncertainties, inaccuracies in light delivery must be considered. Using simulations on virtual brain tumour (glioblastoma) models, we analyze two sources of uncertainty: light source power variations of [Formula: see text], [Formula: see text], and [Formula: see text], and positional deviations during source insertion, modelled as angular errors producing up to [Formula: see text] displacement. Simulated outcomes show minimal impact from power uncertainty, even at worst-case [Formula: see text]: the percent difference between maximum and minimum [Formula: see text] does not exceed [Formula: see text], with tumour coverage only dropping from the targeted [Formula: see text] to [Formula: see text]. Using a new power-uncertainty-aware option in the PDT-SPACE planning tool improves the worst-case minimum coverage from [Formula: see text] to [Formula: see text], eliminating the risk of under-treating. Position uncertainty was simulated by discretizing the space and randomizing source placements, showing a larger negative effect. Power re-optimization on measured post-insertion positions restores tumour coverage to [Formula: see text], while PDT-SPACE source-position optimization reduces average healthy tissue damage by [Formula: see text]. Combining both yields the most robust performance and minimizes sensitivity to positional deviations, thereby limiting light-delivery errors in iPDT.

Silica nanoparticles (SiNPs) are widely explored as biocompatible platforms for the delivery of photosensitizers in photodynamic therapy (PDT). In this work, porphyrins bearing amine (PNH2) or carboxyl (PCOOH) groups were covalently conjugated onto functionalized SiNP surfaces via carbodiimide-mediated amide coupling, yielding the silica-porphyrin nanohybrids H-PNH2 and H-PCOOH. Successful surface functionalization was confirmed by Fourier-transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Photophysical studies demonstrated that both nanohybrids retained efficient singlet oxygen (1O2) generation. In vitro biological assays revealed a strong dependence of photodynamic activity on the nature of the conjugated porphyrin, with H-PCOOH exhibiting markedly enhanced photocytotoxicity with respect to the free porphyrins, while H-PNH2 showed an attenuated light-dose response. Notably, H-PCOOH induced pronounced cell death at low light doses (1 J/cm2), with a half-maximal inhibitory concentration (IC50) below 0.3 µM. These findings highlight the potential of silica-porphyrin nanohybrids as efficient photosensitizers for PDT applications.

Dynamic LED spectral strategy enhances lettuce (Lactuca sativa) productivity via periodic activation of light-responsive genes and improved light energy use efficiency

Abstract Triple-negative breast cancer is a highly aggressive subtype with the poorest prognosis among breast cancers. It is defined by the absence of estrogen (ER), progesterone (PR), and human epidermal growth factor receptor 2 (HER2), limiting the effectiveness of conventional hormone-based therapies. Around 20% of the 2.3 million annual breast cancer cases are triple-negative, and this subtype is linked to high metastasis and mortality rates. Its molecular heterogeneity and therapeutic resistance highlight the urgent need for alternative treatment strategies. Photodynamic therapy is a promising, minimally invasive technique already employed in Brazil’s public health system (SUS) for the treatment of basal cell carcinoma. It relies on the activation of a photosensitizer (PS) by a specific light source, leading to the generation of reactive oxygen species (ROS) that trigger oxidative stress, cell death, and immune response activation. This in vitro study assessed the cytotoxicity of photodynamic therapy using a nanoemulsion containing chloroaluminum phthalocyanine (ClAlPc/Ne) in breast cancer cell lines exposed to varying PS concentrations and light doses. The MCF-7 and MDA-MB-231 cell lines, representing luminal A and triple-negative breast cancer respectively, were incubated with ClAlPc/Ne for 24 hours before photoactivation, followed by a further 24-hour incubation before metabolic viability analysis using the MTT assay. Three experimental conditions were tested: (I) nanoemulsion without PS, (II) ClAlPc/Ne without irradiation, and (III) photoactivated ClAlPc/Ne. PS concentrations ranged from 0.01 µM to 2.0 µM, with light doses from 1 J/cm2 to 16 J/cm2. Absorbance was measured at 545 nm. Results showed selective phototoxicity of ClAlPc/Ne against the triple-negative breast cancer cell line MDA-MB-231, with IC50 (50% inhibitory concentration) values of 1.96 µM at 1 J/cm2, 0.19 µM at 4 J/cm2, and &amp;lt;0.01 µM at 16 J/cm2. In contrast, MCF-7 cells demonstrated greater resistance, with IC50 values of &amp;gt;2.0 µM at 1 J/cm2, 0.14 µM at 4 J/cm2, and &amp;lt;0.06 µM at 16 J/cm2. These findings indicate that phototoxicity is dose-dependent and more pronounced in triple-negative breast cancer cells. The differential response between cell lines suggests that triple-negative breast cancer may be more sensitive to oxidative stress induced by photodynamic therapy. These findings reinforce the importance of molecular profiling in guiding treatment decisions and support the potential of photodynamic therapy as a targeted, less invasive approach for hard-to-treat breast cancer subtypes. Citation Format: H. R. Luz, L. P. Franchi, A. C. Tedesco, E. d. Lacerda. A Promising Approach for Hard-to-Treat Breast Cancer: Photodynamic Therapy with ClAlPc Nanoemulsion Against Triple-Negative Cells [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS4-06-10.

Corrole photosensitizers for photodynamic therapy (PDT) have garnered significant attention due to their promising potential in cancer treatment. Advances in understanding their photophysical and photochemical properties have facilitated the development of more efficient and targeted PDT strategies. This study reports the synthesis and characterization of a series of alkyne-substituted gallium(iii) corrole complexes, as well as their conjugation to azide-functionalized glycofullerenes via copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions. The resulting glycofullerene-corrole conjugates were obtained and fully characterized using standard spectroscopic techniques. Their photodynamic efficacy was evaluated in vitro using HeLa cells. Among the series, the mono- and tris-alkyne-substituted corroles, as well as the monofunctionalized glycofullerene conjugate, exhibited the most potent PDT effects in cells, achieving IC50 values below 1.0 µM under blue irradiation at 420 nm with a total light dose as low as 5 J cm-2. These findings highlight the potential of gallium(iii) corrole-based nanostructures as water-soluble and efficient photosensitizers for PDT applications.

Transbronchial photodynamic therapy for peripheral lung cancer - A pilot study.