Porphyrin and nonporphyrin photosensitizers in oncology: preclinical and clinical advances in photodynamic therapy

Porphyrin-Derived Carbon Dots for Red-Light Activated Photodynamic Therapy of Breast Cancer

In recent years, cancer has emerged as a major global health threat, ranking among the top causes of mortality. While treatments such as surgery, immunotherapy, radiation therapy, and chemotherapy remain widely used, photodynamic therapy has been gaining significant interest. Most of the photosensitizing agents employed in clinical settings are derived from tetrapyrrolic frameworks, including porphyrins, chlorins, and phthalocyanines. Although these compounds have demonstrated therapeutic effectiveness, they suffer from critical drawbacks, such as limited solubility in water and inadequate (photo)stability. To address these issues, herein, the formulation of the previously reported and promising photosensitizer tetrakis(4-carboxyphenyl) porphyrin into carbon dots is reported. The carbon dots were found with enhanced aqueous solubility, high (photo)stability, and greater singlet oxygen quantum yield overcoming the limitations of the molecular photosensitizer. While being nontoxic in the dark, the carbon dots induced a phototherapeutic effect in breast cancer cells and multicellular tumor spheroids.

Green synthesis of hypericin from Hypericum perforatum (St. John's Wort) for photodynamic Antibacterial treatment against Staphylococcus aureus and Escherichia coli

Hypericin, also known as naphthodianthrone, is a naturally occurring photosensitiser derived from anthraquinone. It has gained attention owing to its prospective use in photodynamic therapy (PDT) for cancer treatment. PDT is a minimally invasive treatment that utilises light, a photosensitiser, and oxygen to kill the target cells. However, conventional synthesis methods of hypericin harm the environment and human health. Therefore, researchers focused on developing green extraction methods for hypericin to overcome these limitations. In this study, hypericin was extracted from Hypericum perforatum using a green -synthesis method and characterised using Fourier-transform infra-red spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV), high-performance liquid chromatography (HPLC) and high-performance thin-layer chromatography (HPTLC). Hypericin generates reactive oxygen species (ROS) upon light activation, which disrupts bacterial cell walls and inhibits vital metabolic processes. This mechanism ensures potent antibacterial effects against both gram-positive S. aureus and gram-negative E. coli, making hypericin a prominent photosensitiser for photodynamic antibacterial therapy.

Bismuth doped carbon nanospheres conjugated to boronated porphyrins for photodynamic therapy

Novel 4- (5,10,15)-tris-boronphenyl-20-(4-formylphenoxy) porphyrin (complex 1) and its Zn-metalated derivative (complex 2) were synthesized and conjugated to bismuth doped carbon nanospheres (BiCNS) through non-covalent bonds (π-π). The conjugation of BiCNS to porphyrin complexes enhanced the singlet oxygen production of porphyrin complexes, as it was observed that porphyrin complex 1 gave a singlet oxygen quantum yield (Φ∆) value of 0.17 and complex 2 gave Φ∆ of 0.23, and upon conjugation with BiCNS the Ф∆ values increased to 0.52 and 0.67, respectively. Photodynamic therapy (PDT) studies were performed against MDA-MB-231 breast cancer cell line using these complexes and their conjugates and it was observed that BiCNS conjugates resulted in enhanced PDT activity when compared to CNS conjugates. Conjugates 2-CNS, and 2-BiCNS at the concentration of 100 µg/mL they resulted with cell viabilities of 28.43 and 26.82 %, respectively.

Cancer Photodynamic Therapy Enabled by Water-Soluble Chlorophyll Protein

Photodynamic therapy (PDT) has been utilized to treat various malignant cancers for more than a century. However, many photosensitizers (e.g., derivatives of porphyrins, chlorins, etc.) central to PDT are still suffering from limitations such as water insolubility, dark toxicity, photo/thermal-instability, difficult synthesis/preparation, and poor tumor selectivity. Numerous effective strategies include designing new synthetic photosensitizers by exploiting heavy atom effect, aggregation-induced emission effect (AIE), and electronic/energy effects (donor-acceptor, and Förster resonance energy transfer: FRET), and the linkage of activatable and targeting molecules has been developed to address one or more of these limitations. However, these structural modifications of photosensitizing organic molecules are synthetically challenging and unpredictable in terms of efficacy versus toxicity. Herein, we report a new and simple strategy for effective PDT by combining natural spinach-derived chlorophylls (photosensitizer) with natural water-soluble chlorophyll proteins (WSCPs) derived originally from plants and produced heterologously by bacteria (E. coli). The recombinant WSCPs (chlorophyll-WSCP) are tetrameric and stable under air/thermal conditions and importantly can produce highly reactive singlet oxygen under red/far-red light irradiation to induce cancer cell death. Our in vivo mouse model studies (melanoma xenografts) further validate the efficacy of the recombinant WSCPs as a new class of water-soluble, nontoxic, and highly efficient photosensitizers for PDT. This work represents the first example of the application of WSCPs in PDT and may advance the clinical applications of PDT for cancer treatment.

Evolution of nMOFs in photodynamic therapy: from porphyrins to chlorins and bacteriochlorins for better efficacy

Photodynamic therapy (PDT) has gained significant attention due to its non-invasive nature, low cost, and ease of operation. Nanoscale metal-organic frameworks (nMOFs) incorporating porphyrins, chlorins, and bacteriochlorins have emerged as one of the most prominent photoactive materials for tumor PDT. These nMOFs could enhance the water solubility, stability and loading efficiency of photosensitizers (PSs). Their highly ordered porous structure facilitates O2 diffusion and enhances the generation of 1O2 from hydrophobic porphyrins, chlorins, and bacteriochlorins, thereby improving their efficacy of phototherapy. This review provides insights into the PDT effects of nMOFs derived from porphyrins, chlorins, and bacteriochlorins. It overviews the design strategies, types of reactive oxygen species (ROS), ROS generation efficiency, and the unique biological processes involved in inhibiting tumor cell proliferation, focusing on the mechanism by which molecular structure leads to enhanced photochemical properties. Finally, the review highlights the new possibilities offered by porphyrins, chlorins, and bacteriochlorins-based nMOFs for tumor PDT, emphasizing how optimized design can further improve the bioapplication of porphyrin derivatives represented PSs. With ongoing research and technological advancements, we anticipate that this review will garner increased attention from scientific researchers toward porphyrin-based nMOFs, thereby elevating their potential as a prominent approach in the treatment of malignant tumors.

Surface-engineered core-shell upconversion nanoparticles for effective hypericin delivery and multimodal imaging

Early diagnosis and treatment of cancer is rapidly advancing thanks to the development of nanotechnology. Here, upconversion nanoparticles (UCNPs) are particularly promising as they are finding a wide range of applications in drug delivery and tumor imaging. In this report, a novel UCNP-based transport system is proposed for the delivery of the hypericin (Hyp) photosensitizer into malignant tumors. Core-shell NaYF4:Yb3+,Er3+@NaYF4:Nd3+ UCNPs were prepared by thermal decomposition and coated with poly(N,N-dimethylacrylamide-co-2-aminoethyl acrylate)-alendronate [P(DMA-AEA)-Ale], which endowed them with colloidal and chemical stability; finally, Hyp was conjugated. Internalization of CS-UCNP@P(DMA-AEA)-Ale-Hyp nanoparticles by Jurkat cells was successfully validated by multimodal imaging using a microstructural chamber, upconversion luminescence, and Raman microspectroscopy. After irradiation at 590 nm, CS-UCNP@P(DMA-AEA)-Ale-Hyp nanoparticles provided a markedly more effective photodynamic effect than Hyp alone at identical Hyp concentrations due to apoptosis as confirmed by caspase-3 activation. MTT assays showed that Hyp-free nanoparticles were non-cytotoxic, whereas CS-UCNP@P(DMA-AEA)-Ale-Hyp particles significantly reduced cell viability after irradiation. Considering that Hyp release from the nanoparticles was higher in the acidic environment typical of tumors compared to physiological ones, UCNP@P(DMA-AEA)-Ale-Hyp particles are a suitable candidate for future in vivo applications.

Single-Photon DNA Photocleavage up to 905 nm by a Benzylated 4-Quinolinium Carbocyanine Dye

This paper describes the DNA interactions of near-infrared (NIR) benzylated 4-quinolinium dicarbocyanine dyes containing a pentamethine bridge meso-substituted either with a bromine (4) or hydrogen (5) atom. In pH 7.0 buffered aqueous solutions, the 4-quinolinium dyes absorb light that extends into the near-infrared range up to ∼950 nm. The unique direct strand breakage of pUC19 DNA that is sensitized by irradiating either dicarbocyanine with an 850 nm LED laser constitutes the first published example of DNA photocleavage upon single-photon chromophore excitation at a wavelength greater than 830 nm. Brominated dye 4, which is more stable than and achieves DNA strand scission in higher yield than its hydrogen-bearing counterpart 5, cleaves plasmid DNA under 830 and 905 nm laser illumination. The addition of increasing amounts of DNA to aqueous pH 7.0 solutions converted an aggregated form of dye 4 to a monomer with bathochromic absorption that overlaps all three laser emission wavelengths. No induced circular dichroism and fluorescence signals were detected when DNA was present, pointing to possible external binding of the dye to the DNA. Experiments employing radical-specific fluorescent probes and chemical additives showed that brominated dye 4 likely breaks DNA strands by photosensitizing hydroxyl radical production. Micromolar concentrations of the dye were relatively nontoxic to cultured Escherichia coli cells in the dark but dramatically reduced survival of the cells under 830 nm illumination. As NIR light wavelengths deeply penetrate biological tissues, we envisage the future use of carbocyanine dyes as a sensitizing agent in phototherapeutic applications.

Study of the Influence of Structure-Chemical Properties of Electron Beam-Polymerized PEGDA/Gelatin Hybrid Hydrogels on the Uptake and Release Dynamics of Different Photosensitizer Molecules

Hybrid hydrogels are promising for wound dressing, tissue engineering, and drug delivery due to their exceptional biocompatibility and mechanical stability. This study synthesized hybrid hydrogels for photodynamic therapy using electron beam-initiated polymerization with varying PEGDA/gelatin ratios and irradiation doses to evaluate their effectiveness as uptake and release systems for five photosensitizers. Toluidine blue, O (TBO); methylene blue (MB); eosin, Y; indocyanine, green; and sodium meso-tetraphenylporphine-4,4',4″,4‴-tetrasulfonate were studied for their uptake and release dynamics in relation to their structural properties and the hydrogels' composition. Uptake was influenced by the gelatin ratio and ionic properties, with anionic photosensitizers achieving over 80% uptake while cationic ones remained below 45%. Increased irradiation doses highlighted the roles of ionic interactions, hydrophilicity, and surface polarity. Cationic photosensitizers produced singlet oxygen 9-10 times more efficiently. Nontoxic PEGDA/gelatin hydrogels demonstrated photosensitizer-dependent cytotoxicity, with TBO and MB consistent with previous findings. These results confirm their potential in photodynamic therapy.

Shift of cell-death mechanisms in primary human neutrophils with a ruthenium photosensitizer

Primary human neutrophils are the most abundant human white blood cells and are central for innate immunity. They act as early responders at inflammation sites, guided by chemotactic gradients to find infection or inflammation sites. Neutrophils can undergo both apoptosis as well as NETosis. NETosis is a form of neutrophil cell death that releases chromatin-based extracellular traps (NETs) to capture and neutralize pathogens. Understanding or controlling the balance between these cell-death mechanisms is crucial. In this study, the chemical synthesis and biologic assessment of a ruthenium complex as a light-activated photosensitizer that creates reactive oxygen species (ROS) in primary human neutrophils is reported. The ruthenium complex remains non-toxic in the dark. However, upon exposure to blue light at 450 nm, it exhibits potent cytotoxic effects in both cancerous and non-cancerous cell lines. Interestingly, the metal complex shifts the cell-death mechanism of primary human neutrophils from NETosis to apoptosis. Cells irradiated directly by the light source immediately undergo apoptosis, whereas those further away from the light source perform NETosis at a slower rate. This indicates that high ROS levels trigger apoptosis and lower ROS levels NETosis. The ability to control the type of cell death undergone in primary human neutrophils could have implications in managing acute and chronic infectious diseases.

NIR-activated multifunctional agents for the combined application in cancer imaging and therapy

Anticancer therapies that combine both diagnostic and therapeutic capabilities hold significant promise for enhancing treatment efficacy and patient outcomes. Among these, agents responsive to near-infrared (NIR) photons are of particular interest due to their negligible toxicity and multifunctionality. These compounds are not only effective in photodynamic therapy (PDT), but also serve as contrast agents in various imaging modalities, including fluorescence and photoacoustic imaging. In this review, we explore the photophysical and photochemical properties of NIR-activated porphyrin, cyanine, and phthalocyanines derivatives as well as aggregation-induced emission compounds, highlighting their application in synergistic detection, diagnosis, and therapy. Special attention is given to the design and optimization of these agents to achieve high photostability, efficient NIR absorption, and significant yields of fluorescence, heat, or reactive oxygen species (ROS) generation depending on the application. Additionally, we discuss the incorporation of these compounds into nanocarriers to enhance their solubility, stability, and target specificity. Such nanoparticle-based systems exhibit improved pharmacokinetics and pharmacodynamics, facilitating more effective tumor targeting and broadening the application range to photoacoustic imaging and photothermal therapy. Furthermore, we summarize the application of these NIR-responsive agents in multimodal imaging techniques, which combine the advantages of fluorescence and photoacoustic imaging to provide comprehensive diagnostic information. Finally, we address the current challenges and limitations of photodiagnosis and phototherapy and highlight some critical barriers to their clinical implementation. These include issues related to their phototoxicity, limited tissue penetration, and potential off-target effects. The review concludes by highlighting future research directions aimed at overcoming these obstacles, with a focus on the development of next-generation agents and platforms that offer enhanced therapeutic efficacy and imaging capabilities in the field of cancer treatment.

Revolutionizing oral care: Reactive oxygen species (ROS)-Regulating biomaterials for combating infection and inflammation

The human oral cavity is home to a delicate symbiosis between its indigenous microbiota and the host, the balance of which is easily perturbed by local or systemic factors, leading to a spectrum of oral diseases such as dental caries, periodontitis, and pulp infections. Reactive oxygen species (ROS) play crucial roles in the host's innate immune defenses. However, in chronic inflammatory oral conditions, dysregulated immune responses can result in excessive ROS production, which in turn exacerbates inflammation and causes tissue damage. Conversely, the potent antimicrobial properties of ROS have inspired the development of various anti-infective therapies. Therefore, the strategic modulation of ROS by innovative biomaterials is emerging as a promising therapeutic approach for oral infection and inflammation. This review begins by highlighting the state-of-the-art of ROS-regulating biomaterials, which are designed to generate, scavenge, or modulate ROS in a bidirectional manner. We then delve into the latest innovations in these biomaterials and their applications in treating a range of oral diseases, including dental caries, endodontic and periapical conditions, periodontitis, peri-implantitis, and oral candidiasis. The review concludes with an overview of the current challenges and future potential of these biomaterials in clinical settings. This review provides novel insights for the ongoing development of ROS-based therapeutic strategies for oral diseases.

Metal (M = Cr, Mo, W, Re) carbonyl complexes with porphyrin and carborane isocyanide ligands: light-induced oxidation and carbon oxide release for antitumor efficacy

The tetrapyrrolic macrocycle as a scaffold for various chemical modifications provides broad opportunities for the preparation of complex multifunctional conjugates suitable for binary antitumor therapies. Typically, illumination with monochromatic light triggers the photochemical generation of reactive oxygen species (ROS) (photodynamic effect). However, more therapeutically valuable effects can be achieved upon photoactivation of tetrapyrrole derivatives. Herein we report the novel porphyrin-based complexes of transition metals with isocyanide and carbonyl ligands. Synthesis of complexes presumed the use of 5-(p-isocyanophenyl)-10,15,20-triphenylporphyrin as a ligand in reactions with metal carbonyl complexes, M(CO)6 (M = Cr, Mo, W), Re2(CO)10 and Re(CO)5Cl. Based on these complexes and isocyanocarborane, the heteroleptic carbonyl complexes with porphyrin and carborane isocyanide ligands were prepared. In cell-free systems, the new compounds retained photochemical characteristics of the parental porphyrin derivative, such as triplet state formation and ROS generation, upon light-induced activation. In the cell culture, the carborane-containing derivatives demonstrated a more pronounced intracellular accumulation than their nonboronated counterparts. As expected, illumination at the Soret band (405 nm) of cells loaded with the new complexes caused photodynamic cell damage. In contrast, illumination at 530 nm instead initiated the release of carbon oxide (CO) followed by cell death independently of the photodynamic effect. Light-induced CO release was analyzed using second derivatives of UV-Vis spectra and our originally developed Spectrophotometric elimiNAtion of Photoinduced Side reactions (SNAPS) method. The yield of CO release decreased in the raw depending on metals in the carbonyl moiety: Mo ≥ Cr > W > Re ≥ Re2. Overall, our novel metal carbonyl complexes with porphyrin and carborane isocyanide ligands emerge as potent bi-functional conjugates for combined photodynamic and photoinducible CO-releasing antitumor agents.

Toluidine blue O demethylated photoproducts as type II photosensitizers

Toluidine blue O (TBO) is a type I-type II photosensitizer that has shown good efficacy and selectivity in antimicrobial and anticancer photodynamic therapy applications. However, its complex photochemistry with multiple photoproducts hinders its application as a photosensitizer. We have previously described the mechanism for photooxidative demethylation of TBO which in acetonitrile yields two main products: demethylated-TBO (d-TBO) and double-demethylated-TBO (dd-TBO). In the current work, we describe the photophysical properties of these two photoproducts. In acetonitrile and phosphate buffer, demethylation induces an hypsochromic shift in the absorption and fluorescence emission maxima. Fluorescence quantum yields increase slightly for the demethylated photoproducts, in agreement with the lengthening of the fluorescence lifetimes. Triplet excited states lifetimes in the presence of oxygen decreased slightly upon demethylation. However, the singlet oxygen quantum yield increased significantly reaching unity for the dd-TBO photoproduct. These results are interpreted in terms of the competing pathways of TBO photochemistry. For TBO, demethylation is the main pathway for deactivation of the excited state, while for d-TBO, demethylation and singlet oxygen generation are significant. For dd-TBO, singlet oxygen generation is the main deactivation pathway. Overall, TBO demethylated photoproducts demonstrate good potential as candidates for photodynamic therapy applications.

The Effects of Photodynamic Therapy with Low-Level Diode Laser Compared with Doxorubicin on HT-29 Colorectal Adenocarcinoma Cells Viability

Background and Objective: Colorectal adenocarcinoma is considered one of the major causes of cancer-related lethality among other type of malignancies. Given the several limitations and adverse outcomes of conventional therapeutic regimens against colorectal cancer, the focus of many investigations has been attributed to the introduction of a novel combined regimen with harmless agents. The purpose of the present study was to investigate the effect of combined doxorubicin (DOX) treatment and photodynamic therapy (PDT) on colorectal adenocarcinoma cells. Material and Methods: HT-29 cells were exposed to different concentrations of DOX, low-level (630 nm) diode laser, and methylene blue (MB) as a photosensitizer substrate separately and a combination of them. The cytotoxic effect of the DOX, laser, MB, and their combination and the IC50 value for each treatment group were calculated by 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT). The malondialdehyde (MDA) content as a biomarker of the lipid peroxidation process and liberated lactate dehydrogenase (LDH) enzyme into supernatant was determined. Results: The results of our study evidenced that a combination of photodynamic light (laser plus MB) and DOX caused a significant reduction in the percentage of HT-29 viable cells compared with control and other treatment groups. In addition, this mentioned combination led to a considerable decrease in IC50 of DOX. Increased cell membrane lipid peroxidation and cell destruction processes in the combination therapy group were proven through significant elevation of MDA content and LDH activity in the medium, respectively. Conclusion: The findings of the present study suggested that DOX combined with PDT had a better therapeutic impact on HT-29 colorectal adenocarcinoma cells. Hence, the simultaneous application of PDT along with antineoplastic drugs improves the chemosensitivity of cancerous cells via the disruption of their membrane and triggering death processes that lead to the decrease of chemotherapeutic agents required doses and undesirable effects.

Supramolecular nanotherapeutics based on cucurbiturils

Polymeric biomaterials have important applications in aiding clinical disease treatment, including drug delivery, bioimaging, and tissue engineering. Currently, conventional tumor chemotherapy faces obstacles such as poor solubility/stability, inability to target, and uncontrolled drug release in clinical trials, for which the emergence of supramolecular material therapeutics combining non-covalent interactions with conventional therapies is a very promising candidate. Due to their molecular recognition abilities with a range of biomolecules, cucurbit[n]uril (CB[n]), a type of macrocyclic receptors with robust backbones, hydrophobic cavities, and carbonyl-binding channels, have garnered a lot of attention. Therefore, this paper reviews recent advances in CB[n] material-based supramolecular therapeutics for clinical treatments, including targeted delivery applications and related imaging and sensing systems. This study also covers the distinctive benefits of CB materials for biological applications, as well as the trends and prospects of this interdisciplinary subject, based on numerous state-of-the-art research findings.

Blue light-activated 5,10,15,20-tetrakis(4-bromophenyl)porphyrin for photodynamic eradication of drug-resistant Staphylococcus aureus

Photodynamic therapy (PDT) has emerged as an effective way to deal with drug-resistant bacterial infections. Especially, blue light (BL) mediated PDT (BL-PDT) presents unique advantages in the treatments of skin infection due to the strong light absorption of superficial skin, weak penetration of BL and little damage to deep tissues. However, the photosensitizers used for BL-PDT are very limited, and the ongoing development of novel BL photosensitizers is indispensable. Porphyrins are good sources for developing efficient photosensitizers. Herein, for developing more effective BL photosensitizers, five porphyrin derivatives that can be excited by BL [5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetrakis(4-bromophenyl)porphyrin (TBPP), 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin (TCPP), 5,10,15,20-tetrakis(4-fluorophenyl)porphyrin (TFPP), 5,10,15,20-tetrakis(4-iodophenyl)porphyrin (TIPP)] are subjected to the investigation of PDT against MRSA (methicillin resistant Staphylococcus aureus). The results reveal that TBPP-mediated BL-PDT shows outstanding bactericidal effects. Mechanism studies show that TBPP + BL can induce reactive oxygen species (ROS) up-regulated in MRSA, rupture cell membrane, inhibit ATP (adenosine triphosphate) production and virulence factor expression. Furthermore, TBPP + BL effectively eliminates MRSA form biofilms, inhibits biofilm formation and disintegrates mature biofilms. More importantly, TBPP-PDT significantly accelerate mouse skin wound healing in a biofilm infection model. Our work offers new insights into the development of novel BL photosensitizers.

Role of Dark States and Stokes Shift Simulations for Tetraphenylpyrazine Compared to Other Donor-Acceptor Photosensitizers

An excellent agreement for simulated and measured absorption and emission spectra is found for four donor-acceptor aromatic molecules (tetraphenylpyrazine, tetraphenylethene, distirylanthracene and hexaphenylsilole) whose derivatives serve as solid state photosensitizers. After comparing several hybrid TDDFT functionals, EOM-CCSD, and experiments, the best agreement was found with TD-B3LYP and double zeta basis sets (6-31G** and def2-SVP) for one molecule in gas phase. A full characterisation of twelve to twenty electronic excited states was performed in every system. Symmetry-forbidden bands are found in the absorption spectra by sampling fifty to hundred geometries from a Wigner distribution. The density of states in the region 2-6 eV was also analysed, showing a very packed region of excited states and suggesting that dark electronic states may play a role in the dynamics of some of the photoexcited systems. Further calculations were done with QM/xTB at geometries extracted from previously published X-ray data to evaluate the influence of the environment on the excitations of the four aggregated molecular crystals.

Engineering Radiocatalytic Nanoliposomes with Hydrophobic Gold Nanoclusters for Radiotherapy Enhancement

Chemoradiation therapy is on the forefront of pancreatic cancer care, and there is a continued effort to improve its safety and efficacy. Liposomes are widely used to improve chemotherapy safety, and may accurately deliver high-Z element- radiocatalytic nanomaterials to cancer tissues. In this study, the interaction between X-rays and long-circulating nanoliposome formulations loaded with gold nanoclusters is explored in the context of oxaliplatin chemotherapy for desmoplastic pancreatic cancer. Hydrophobic gold nanoclusters stabilized with dodecanethiol (AuDDT) are efficiently incorporated in nanoliposomal bilayers. AuDDT-nanoliposomes significantly augmented radiation-induced •OH production, which is most effective with monochromatic X-rays at energies that exceed the K-shell electron binding energy of Au (81.7 keV). Cargo release assays reveal that AuDDT-nanoliposomes can permeabilize lipid bilayers in an X-ray dose- and formulation-dependent manner. The radiocatalytic effect of AuDDT-nanoliposomes significantly augments radiotherapy and oxaliplatin-chemoradiotherapy outcomes in 3D pancreatic microtumors. The PEGylated AuDDT-nanoliposomes display high tumor accumulation in an orthotopic mouse model of pancreatic cancer, showing promise for nanoliposomes as carriers for radiocatalytic nanomaterials. Altogether, compelling proof for chemo-radiation dose-enhancement using AuDDT-nanoliposomes is presented. Further improving the nanoliposomal loading of high-Z elements will advance the safety, efficacy, and translatability of such chemoradiation dose-enhancement approaches.

Advances in nanotechnology-assisted photodynamic therapy for neurological disorders: a comprehensive review

Neurological disorders such as neurodegenerative diseases and nervous system tumours affect more than one billion people throughout the globe. The physiological sensitivity of the nervous tissue limits the application of invasive therapies and leads to poor treatment and prognosis. One promising solution that has generated attention is Photodynamic therapy (PDT), which can potentially revolutionise the treatment landscape for neurological disorders. PDT attracted substantial recognition for anticancer efficacy and drug conjugation for targeted drug delivery. This review thoroughly explained the basic principles of PDT, scientific interventions and advances in PDT, and their complicated mechanism in treating brain-related pathologies. Furthermore, the merits and demerits of PDT in the context of neurological disorders offer a well-rounded perspective on its feasibility and challenges. In conclusion, this review encapsulates the significant potential of PDT in transforming the treatment landscape for neurological disorders, emphasising its role as a non-invasive, targeted therapeutic approach with multifaceted applications.

Advancements and challenges in brain cancer therapeutics

Treating brain tumors requires a nuanced understanding of the brain, a vital and delicate organ. Location, size, tumor type, and surrounding tissue health are crucial in developing treatment plans. This review comprehensively summarizes various treatment options that are available or could be potentially available for brain tumors, including physical therapies (radiotherapy, ablation therapy, photodynamic therapy, tumor-treating field therapy, and cold atmospheric plasma therapy) and non-physical therapies (surgical resection, chemotherapy, targeted therapy, and immunotherapy). Mechanisms of action, potential side effects, indications, and latest developments, as well as their limitations, are highlighted. Furthermore, the requirements for personalized, multi-modal treatment approaches in this rapidly evolving field are discussed, emphasizing the balance between efficacy and patient safety.

Photodynamic therapy-induced precise attenuation of light-targeted semicircular canals for treating intractable vertigo

Vertigo is a common symptom of various diseases that affects a large number of people worldwide. Current leading treatments for intractable peripheral vertigo are to intratympanically inject ototoxic drugs such as gentamicin to attenuate the semicircular canal function but inevitably cause hearing injury. Photodynamic therapy (PDT) is a noninvasive therapeutic approach by precisely targeting the diseased tissue. Here, we developed a PDT-based method for treating intractable peripheral vertigo in a mouse model using a polymer-coated photosensitizer chlorin e6 excited by red light. We found that a high dose of PDT attenuated the function of both semicircular canals and otolith organs and damaged their hair cells. Conversely, the PDT exerted no effect on hearing function or cochlear hair-cell viability. These results suggest the therapeutic potential of PDT for treating intractable peripheral vertigo without hurting hearing. Besides, the attenuation level and affected area can be precisely controlled by adjusting the light exposure time. Furthermore, we demonstrated the potential of this therapeutic approach to be minimally invasive with light irradiation through bone results. Thus, our PDT-based approach for attenuating the function of the semicircular canals offers a basis for developing a less-invasive and targeted therapeutic option for treating vertigo.

Exploring the potential of 7,4'-di(diethylamino)flavylium as a novel photosensitizer for topical photodynamic therapy of skin cancer

Photodynamic therapy (PDT) is a minimally invasive therapeutic approach that has shown promising results in recent years, particularly in the dermatological clinical treatment of several pathologies, including neoplastic skin diseases. In light of the recent discovery of the photosensitizing properties of a water-soluble group of amino-based flavylium dyes, research efforts have led to the development of a novel synthetic dye with two diethylamino moieties in its structure, 7,4'-di(diethylamino)flavylium (7,4'diN(Et)2). This dye was tested as a potential photosensitizer for PDT of skin cancer. A single light dose of 22.5 J/cm2 efficiently killed SCC-25 (squamous cell carcinoma) and A375 (melanoma) cells, reducing cellular viability by more than 80% in the presence of the flavylium at 0.75 µM. Meanwhile, the negligible cellular toxicity of the dye in the absence of light stimulus points out a wide and safe therapeutic window. Interestingly, significant light-induced toxicity effects were still observed after washing out the compound before cell irradiation. Moreover, out of the three prototype flavylium-loaded hydrogels, each one based on a different polymer (Carbomer, Caesalpinia Spinosa Gum and Hydroxypropyl methyl cellulose), carbomer-based formulation stood out for its substantial absorbance and fluorescence increment and enhanced1O2 photogeneration activity compared to the flavylium in aqueous solution. The findings of this study provide valuable insights concerning the potential of this flavylium dye as a candidate for photodynamic therapy of skin cancer and strongly support the need for further testing in more advanced biological settings to fully assess its efficacy and safety.

Preclinical Photodynamic Therapy Targeting Blood Vessels with AGuIX® Theranostic Nanoparticles

Background: Glioblastoma multiforme (GBM) is the most common highly aggressive, primary malignant brain tumor in adults. Current experimental strategies include photodynamic therapy (PDT) and new drug delivery technologies such as nanoparticles, which could play a key role in the treatment, diagnosis, and imaging of brain tumors. Objectives: The purpose of this study was to test the efficacy of PDT using AGuIX-TPP, a polysiloxane-based nanoparticle (AGuIX) that contains TPP (5,10,15,20-tetraphenyl-21H,23H-porphine), in biological models of glioblastoma multiforme and to investigate the vascular mechanisms of action at multiple complexity levels. Methods: PDT effects were studied in monolayer and spheroid cell culture, as well as tumors in chicken chorioallantoic membranes (CAMs) and in mice were studied. Results: Treatment was effective in both endothelial ECRF and glioma U87 cells, as well as in the inhibition of growth of the glioma spheroids. PDT using AGuIX-TPP inhibited U87 tumors growing in CAM and destroyed their vascularization. The U87 tumors were also grown in nude mice. Their vascular network, as well as oxygen partial pressure, were assessed using ultrasound and EPR oximetry. The treatment damaged tumor vessels and slightly decreased oxygen levels. Conclusions: PDT with AGuIX-TPP was effective against glioma cells, spheroids, and tumors; however, in mice, its efficacy appeared to be strongly related to the presence of blood vessels in the tumor before the treatment.

Leveraging the Photofunctions of Transition Metal Complexes for the Design of Innovative Phototherapeutics

Despite the advent of various medical interventions for cancer treatment, the disease continues to pose a formidable global health challenge, necessitating the development of new therapeutic approaches for more effective treatment outcomes. Photodynamic therapy (PDT), which utilizes light to activate a photosensitizer to produce cytotoxic reactive oxygen species (ROS) for eradicating cancer cells, has emerged as a promising approach for cancer treatment due to its high spatiotemporal precision and minimal invasiveness. However, the widespread clinical use of PDT faces several challenges, including the inefficient production of ROS in the hypoxic tumor microenvironment, the limited penetration depth of light in biological tissues, and the inadequate accumulation of photosensitizers at the tumor site. Over the past decade, there has been increasing interest in the utilization of photofunctional transition metal complexes as photosensitizers for PDT applications due to their intriguing photophysical and photochemical properties. This review provides an overview of the current design strategies used in the development of transition metal complexes as innovative phototherapeutics, aiming to address the limitations associated with PDT and achieve more effective treatment outcomes. The current challenges and future perspectives on the clinical translation of transition metal complexes are also discussed.

Binding of a Tricationic meso-Substituted Porphyrin to poly(A)⋅poly(U): an Experimental Study

The porphyrins are macrocyclic compounds widely used as photosensitizers in anticancer photodynamic therapy. The binding of a tricationic meso-tris(N-methylpyridinium)-porphyrin, TMPyP3+, to poly(A)⋅poly(U) polynucleotide has been studied in neutral buffered solution, pH6.9, of low and near-physiological ionic strength in a wide range of molar phosphate-to-dye ratios (P/D). Effective TMPyP3+ binding to the biopolymer was established using absorption spectroscopy, polarized fluorescence, fluorimetric titration and resonance light scattering. We propose a model in which TMPyP3+ binds to the polynucleotide in two competitive binding modes: at low P/D ratios (< 4) external binding of the porphyrin to polynucleotide backbone without self-stacking dominates, and at higher P/D (> 30) the partially stacked porphyrin J-dimers are embedded into the polymer groove. Enhancement of the porphyrin emission was observed upon binding in all P/D range, contrasting the binding of this porphyrin to poly(G)⋅poly(C) with significant quenching of the porphyrin fluorescence at low P/D ratios. This observation indicates that TMPyP3+ can discriminate between poly(A)⋅poly(U) and poly(G)⋅poly(C) polynucleotides at low P/D ratios. Formation of highly scattering extended porphyrin aggregates was observed near the stoichiometric in charge binding ratio, P/D = 3. It was revealed that the efficiency of the porphyrin external binding and aggregation is reduced in the solution of near-physiological ionic strength.

Recent development of nanomaterials-based PDT to improve immunogenic cell death

Photodynamic therapy (PDT) is a clinically approved therapeutic modality for treating oncological and non-oncological disorders. PDT has proclaimed multiple benefits over further traditional cancer therapies including its minimal systemic toxicity and selective ability to eliminate irradiated tumors. In PDT, a photosensitizing substance localizes in tumor tissues and becomes active when exposed to a particular wavelength of laser light. This produces reactive oxygen species (ROS), which induce neoplastic cells to die and lead to the regression of tumors. The contributions of ROS to PDT-induced tumor destruction are described by three basic processes including direct or indirect cell death, vascular destruction, and immunogenic cell death. However, the efficiency of PDT is significantly limited by the inherent nature and tumor microenvironment. Combining immunotherapy with PDT has recently been shown to improve tumor immunogenicity while decreasing immunoregulatory repression, thereby gently modifying the anticancer immune response with long-term immunological memory effects. This review highlights the fundamental ideas, essential elements, and mechanisms of PDT as well as nanomaterial-based PDT to boost tumor immunogenicity. Moreover, the synergistic use of immunotherapy in combination with PDT to enhance immune responses against tumors is emphasized.

Rational design of a red-light absorbing ruthenium polypyridine complex as a photosensitizer for photodynamic therapy

Herein, the computer-guided design, chemical synthesis, and biological evaluation of a RuC polypyridine complex, that could eradicate cancerous cells upon excitation with red light at 630 nm, is reported.

A novel photosensitizer based on hypocrellin B activated by cysteine over-expressed in cancer cells

L-Cysteine (Cys)-activatable photosensitizer 3 was designed and synthesized based on hypocrellin B (1). Cys is a novel tumor-associated biomarker. 3 exhibited negligible photosensitizing ability without Cys. However, when 1 was released from 3 by reaction with Cys, the photosensitizing activity was restored. Furthermore, 3 showed selective and effective photo-cytotoxicity against only cancer cells such as HeLa and A549 cells that highly express Cys when irradiated with 660 nm light, which is inside the phototherapeutic window.

Porphyrin derivatives inhibit tumor necrosis factor α-induced gene expression and reduce the expression and increase the cross-linked forms of cellular components of the nuclear factor κB signaling pathway

The transcription factor nuclear factor κB (NF-κB) is activated by proinflammatory cytokines, such as tumor necrosis factor α (TNF-α) and Toll-like receptor (TLR) ligands. Screening of NPDepo chemical libraries identified porphyrin derivatives as anti-inflammatory compounds that strongly inhibited the up-regulation of intercellular adhesion molecule-1 (ICAM-1) expression induced by TNF-α, interleukin-1α, the TLR3 ligand, and TLR4 ligand in human umbilical vein endothelial cells. In the present study, the mechanisms of action of porphyrin derivatives were further elucidated using human lung adenocarcinoma A549 cells. Porphyrin derivatives, i.e., dimethyl-2,7,12,18-tetramethyl-3,8-di(1-methoxyethyl)-21H,23H-porphine-13,17-dipropionate (1) and pheophorbide a (2), inhibited TNF-α-induced ICAM-1 expression and decreased the TNF-α-induced transcription of ICAM-1, vascular cell adhesion molecule-1, and E-selectin genes. 1 and 2 reduced the expression of the NF-κB subunit RelA protein for 1 h, which was not rescued by the inhibition of proteasome- and lysosome-dependent protein degradation. In addition, 1 and 2 decreased the expression of multiple components of the TNF receptor 1 complex, and this was accompanied by the appearance of their cross-linked forms. As common components of the NF-κB signaling pathway, 1 and 2 also cross-linked the α, β, and γ subunits of the inhibitor of NF-κB kinase complex and the NF-κB subunits RelA and p50. Cellular protein synthesis was prevented by 2, but not by 1. Therefore, the present results indicate that porphyrin derivative 1 reduced the expression and increased the cross-linked forms of cellular components required for the NF-κB signaling pathway without affecting global protein synthesis.

In Vitro Effect of Epigallocatechin Gallate on Heme Synthesis Pathway and Protoporphyrin IX Production

Photodynamic therapy (PDT) treats nonmelanoma skin cancer. PDT kills cells through reactive oxygen species (ROS), generated by interaction among cellular O2, photosensitizer and specific light. Protoporphyrin IX (PpIX) is a photosensitizer produced from methyl aminolevulinate (MAL) by heme group synthesis (HGS) pathway. In PDT-resistant cells, PDT efficacy has been improved by addition of epigallocatechin gallate (EGCG). Therefore, the aim of this work is to evaluate the effect of EGCG properties over MAL-TFD and PpIX production on A-431 cell line. EGCG's role over cell proliferation (flow cytometry and wound healing assay) and clonogenic capability (clonogenic assay) was evaluated in A-431 cell line, while the effect of EGCG over MAL-PDT was determined by cell viability assay (MTT), PpIX and ROS detection (flow cytometry), intracellular iron quantification and gene expression of HGS enzymes (RT-qPCR). Low concentrations of EGCG (<50 µM) did not have an antiproliferative effect over A-431 cells; however, EGCG inhibited clonogenic cell capability. Furthermore, EGCG (<50 µM) improved MAL-PDT cytotoxicity, increasing PpIX and ROS levels, exerting a positive influence on PpIX synthesis, decreasing intracellular iron concentration and modifying HGS enzyme gene expression such as PGB (upregulated) and FECH (downregulated). EGCG inhibits clonogenic capability and modulates PpIX synthesis, enhancing PDT efficacy in resistant cells.

Chitosan- and hyaluronic acid-based nanoarchitectures in phototherapy: Combination cancer chemotherapy, immunotherapy and gene therapy

Cancer phototherapy has been introduced as a new potential modality for tumor suppression. However, the efficacy of phototherapy has been limited due to a lack of targeted delivery of photosensitizers. Therefore, the application of biocompatible and multifunctional nanoparticles in phototherapy is appreciated. Chitosan (CS) as a cationic polymer and hyaluronic acid (HA) as a CD44-targeting agent are two widely utilized polymers in nanoparticle synthesis and functionalization. The current review focuses on the application of HA and CS nanostructures in cancer phototherapy. These nanocarriers can be used in phototherapy to induce hyperthermia and singlet oxygen generation for tumor ablation. CS and HA can be used for the synthesis of nanostructures, or they can functionalize other kinds of nanostructures used for phototherapy, such as gold nanorods. The HA and CS nanostructures can combine chemotherapy or immunotherapy with phototherapy to augment tumor suppression. Moreover, the CS nanostructures can be functionalized with HA for specific cancer phototherapy. The CS and HA nanostructures promote the cellular uptake of genes and photosensitizers to facilitate gene therapy and phototherapy. Such nanostructures specifically stimulate phototherapy at the tumor site, with particle toxic impacts on normal cells. Moreover, CS and HA nanostructures demonstrate high biocompatibility for further clinical applications.

Recent advances in the development of poly(ester amide)s-based carriers for drug delivery

Biodegradable and biocompatible biomaterials have several important applications in drug delivery. The biomaterial family known as poly(ester amide)s (PEAs) has garnered considerable interest because it exhibits the benefits of both polyester and polyamide, as well as production from readily available raw ingredients and sophisticated synthesis techniques. Specifically, α-amino acid-based PEAs (AA-PEAs) are promising carriers because of their structural flexibility, biocompatibility, and biodegradability. Herein, we summarize the latest applications of PEAs in drug delivery systems, including antitumor, gene therapy, and protein drugs, and discuss the prospects of drug delivery based on PEAs, which provides a reference for designing safe and efficient drug delivery carriers.

Enhancing antitumor efficacy of NIR-I region zinc phthalocyanine@upconversion nanoparticle through lysosomal escape and mitochondria targeting

Accurately visualizing the intracellular trafficking of upconversion nanoparticles (UCNPs) loaded with phthalocyanines and achieving precise photodynamic therapy (PDT) using near-infrared (NIR) laser irradiation still present challenges. In this study, a novel NIR laser-triggered upconversion luminescence (UCL) imaging-guided nanoparticle called FA@TPA-NH-ZnPc@UCNPs (FTU) was developed for PDT. FTU consisted of UCNPs, folic acid (FA), and triphenylamino-phenylaniline zinc phthalocyanine (TPA-NH-ZnPc). Notably, TPA-NH-ZnPc showcases aggregation-induced emission (AIE) characteristic and NIR absorption properties at 741 nm, synthesized initially via molybdenum-catalyzed condensation reaction. The UCL emitted by FTU enable real-time visualization of their subcellular localization and intracellular trafficking within ovarian cancer HO-8910 cells. Fluorescence images revealed that FTU managed to escape from lysosomes due to the "proton sponge" effect of TPA-NH-ZnPc. The FA ligands on the surface of FTU further directed their transport and accumulation within mitochondria. When excited by a 980 nm laser, FTU exhibited UCL and activated TPA-NH-ZnPc, consequently generating cytotoxic singlet oxygen (1O2), disrupted mitochondrial function and induced apoptosis in cancer cells, which demonstrated great potential for tumor ablation.

Amphiphilic Chlorin-β-cyclodextrin Conjugates in Photo-Triggered Drug Delivery: The Role of Aggregation

Conjugates of chlorins with β-cyclodextrin connected either directly or via a flexible linker were prepared. In aqueous medium these amphiphilic conjugates were photostable, produced singlet oxygen at a rate similar to clinically used temoporfin and formed irregular nanoparticles via aggregation. Successful loading with the chemotherapeutic drug tamoxifen was evidenced in solution by the UV-Vis spectral changes and dynamic light scattering profiles. Incubation of MCF-7 cells with the conjugates revealed intense spotted intracellular fluorescence suggestive of accumulation in endosome/lysosome compartments, and no dark toxicity. Incubation with the tamoxifen-loaded conjugates revealed also practically no dark toxicity. Irradiation of cells incubated with empty conjugates at 640 nm and 4.18 J/cm2 light fluence caused >50 % cell viability reduction. Irradiation following incubation with tamoxifen-loaded conjugates resulted in even higher toxicity (74 %) indicating that the produced reactive oxygen species had triggered tamoxifen release in a photochemical internalization (PCI) mechanism. The chlorin-β-cyclodextrin conjugates displayed less-lasting effects with time, compared to the corresponding porphyrin-β-cyclodextrin conjugates, possibly due to lower tamoxifen loading of their aggregates and/or their less effective lodging in the cell compartments' membranes. The results suggest that further to favorable photophysical properties, other parameters are important for the in vitro effectiveness of the photodynamic systems.

Understanding the Novel Approach of Nanoferroptosis for Cancer Therapy

As a new form of regulated cell death, ferroptosis has unraveled the unsolicited theory of intrinsic apoptosis resistance by cancer cells. The molecular mechanism of ferroptosis depends on the induction of oxidative stress through excessive reactive oxygen species accumulation and glutathione depletion to damage the structural integrity of cells. Due to their high loading and structural tunability, nanocarriers can escort the delivery of ferro-therapeutics to the desired site through enhanced permeation or retention effect or by active targeting. This review shed light on the necessity of iron in cancer cell growth and the fascinating features of ferroptosis in regulating the cell cycle and metastasis. Additionally, we discussed the effect of ferroptosis-mediated therapy using nanoplatforms and their chemical basis in overcoming the barriers to cancer therapy.

Research Progress of Natural Product Photosensitizers in Photodynamic Therapy

Photodynamic therapy is a noninvasive cancer treatment that utilizes photosensitizers to generate reactive oxygen species upon light exposure, leading to tumor cell apoptosis. Although photosensitizers have shown efficacy in clinical practice, they are associated with certain disadvantages, such as a certain degree of toxicity and limited availability. Recent studies have shown that natural product photosensitizers offer promising options due to their low toxicity and potential therapeutic effects. In this review, we provide a summary and evaluation of the current clinical photosensitizers that are commonly used and delve into the anticancer potential of natural product photosensitizers like psoralens, quinonoids, chlorophyll derivatives, curcumin, chrysophanol, doxorubicin, tetracyclines, Leguminosae extracts, and Lonicera japonica extract. The emphasis is on their phototoxicity, pharmacological benefits, and effectiveness against different types of diseases. Novel and more effective natural product photosensitizers for future clinical application are yet to be explored in further research. In conclusion, natural product photosensitizers have potential in photodynamic therapy and represent a promising area of research for cancer treatment.

Application of photosensitive dental materials as a novel antimicrobial option in dentistry: A literature review

The formation of dental plaque is well-known for its role in causing various oral infections, such as tooth decay, inflammation of the dental pulp, gum disease, and infections of the oral mucosa like peri-implantitis and denture stomatitis. These infections primarily affect the local area of the mouth, but if not treated, they can potentially lead to life-threatening conditions. Traditional methods of mechanical and chemical antimicrobial treatment have limitations in fully eliminating microorganisms and preventing the formation of biofilms. Additionally, these methods can contribute to the development of drug-resistant microorganisms and disrupt the natural balance of oral bacteria. Antimicrobial photodynamic therapy (aPDT) is a technique that utilizes low-power lasers with specific wavelengths in combination with a photosensitizing agent called photosensitizer to kill microorganisms. By inducing damage through reactive oxygen species (ROS), aPDT offers a new approach to addressing dental plaque and associated microbial biofilms, aiming to improve oral health outcomes. Recently, photosensitizers have been incorporated into dental materials to create photosensitive dental materials. This article aimed to review the use of photosensitive dental materials for aPDT as an innovative antimicrobial option in dentistry, with the goal of enhancing oral health.

Design of AsLOV2 domain as a carrier of light-induced dissociable FMN photosensitizer

Flavin mononucleotide (FMN) is a highly efficient photosensitizer (PS) yielding singlet oxygen (1 O2 ). However, its 1 O2 production efficiency significantly decreases upon isoalloxazine ring encapsulation into the protein matrix in genetically encoded photosensitizers (GEPS). Reducing isoalloxazine ring interactions with surrounding amino acids by protein engineering may increase 1 O2 production efficiency GEPS, but at the same time weakened native FMN-protein interactions may cause undesirable FMN dissociation. Here, in contrast, we intentionally induce the FMN release by light-triggered sulfur oxidation of strategically placed cysteines (oxidation-prone amino acids) in the isoalloxazine-binding site due to significantly increased volume of the cysteinyl side residue(s). As a proof of concept, in three variants of the LOV2 domain of Avena sativa (AsLOV2), namely V416C, T418C, and V416C/T418C, the effective 1 O2 production strongly correlated with the efficiency of irradiation-induced FMN dissociation (wild type (WT) < V416C < T418C < V416C/T418C). This alternative approach enables us: (i) to overcome the low 1 O2 production efficiency of flavin-based GEPSs without affecting native isoalloxazine ring-protein interactions and (ii) to utilize AsLOV2, due to its inherent binding propensity to FMN, as a PS vehicle, which is released at a target by light irradiation.

Enhancing Precision in Photodynamic Therapy: Innovations in Light-Driven and Bioorthogonal Activation

Over the past few decades, photodynamic therapy (PDT) has evolved as a minimally invasive treatment modality offering precise control over cancer and various other diseases. To address inherent challenges associated with PDT, researchers have been exploring two promising avenues: the development of intelligent photosensitizers activated through light-induced energy transfers, charges, or electron transfers, and the disruption of photosensitive bonds. Moreover, there is a growing emphasis on the bioorthogonal delivery or activation of photosensitizers within tumors, enabling targeted deployment and activation of these intelligent photosensitive systems in specific tissues, thus achieving highly precise PDT. This concise review highlights advancements made over the last decade in the realm of light-activated or bioorthogonal photosensitizers, comparing their efficacy and shaping future directions in the advancement of photodynamic therapy.

Photochemistry in Medicinal Chemistry and Chemical Biology

Photochemistry has emerged as a transformative force in organic chemistry, significantly expanding the chemical space accessible for medicinal chemistry. Light-induced reactions enable the efficient synthesis of intricate organic structures and have found applications throughout the different stages of the drug discovery and development processes. Moreover, photochemical techniques provide innovative solutions in chemical biology, allowing precise spatiotemporal drug activation and targeted delivery. In this Perspective, we highlight the already numerous remarkable applications and the even more promising future of photochemistry in medicinal chemistry and chemical biology.

Recent progress on polySarcosine as an alternative to PEGylation: Synthesis and biomedical applications

Biotherapeutic PEGylation to prolong action of medications has gained popularity over the last decades. Various hydrophilic natural polymers have been developed to tackle the drawbacks of PEGylation, such as its accelerated blood clearance and non-biodegradability. Polypeptoides, such as polysarcosine (pSar), have been explored as hydrophilic substitutes for PEG. pSar has PEG-like physicochemical characteristics such as water solubility and no reported cytotoxicity and immunogenicity. This review discusses pSar derivatives, synthesis, characterization approaches, biomedical applications, in addition to the challenges and future perspectives of pSar based biomaterials as an alternative to PEG.

Photophysical, photobiological, and mycobacteria photo-inactivation properties of new meso-tetra-cationic platinum(II) metalloderivatives at meta position

In this manuscript, we report the photo-inactivation evaluation of new tetra-cationic porphyrins with peripheral Pt(II) complexes ate meta N-pyridyl positions in the antimicrobial photodynamic therapy (aPDT) of rapidly growing mycobacterial strains (RGM). Four different metalloderivatives were synthetized and applied. aPDT experiments in the strains of Mycobacteroides abscessus subsp. Abscessus (ATCC 19977), Mycolicibacterium fortuitum (ATCC 6841), Mycobacteroides abscessus subsp. Massiliense (ATCC 48898), and Mycolicibacterium smegmatis (ATCC 700084) conducted with adequate concentration of photosensitizers (PS) under white-light conditions at 90 min (irradiance of 50 mW cm-2 and a total light dosage of 270 J cm-2) showed that the Zn(II) derivative is the most effective PS significantly reduced the concentration of viable mycobacteria. The effectiveness of the molecule as PS for PDI studies is also clear with mycobacteria, which is strongly related with the porphyrin peripheral charge and coordination platinum(II) compounds and consequently about the presence of metal center ion. This class of PS may be promising antimycobacterial aPDT agents with potential applications in medical clinical cases and bioremediation.

Inactivation of Nosema spp. with zinc phthalocyanine

Most honey bee pathogens, such as Vairimorpha (Nosema), cannot be rapidly and definitively diagnosed in a natural setting, consequently there is typically the spread of these diseases through shared and re-use of beekeeping equipment. Furthermore, there are no viable treatment options available for Nosema spores to aid in managing the spread of this bee disease. We therefore aimed to develop a new method using novel Zinc Phthalocyanine (ZnPc) as a photosensitizer for the photodynamic inactivation of Nosema spores that could be used for the decontamination of beekeeping equipment. Nosema spores were propagated for in vitro testing using four caged Apis mellifera honey bees. The ZnPc treatment was characterized, encapsulated with a liposome, and then used as either a 10 or 100 µM treatment for the freshly harvested Nosema spores, for either a 30 and or 60-minute time period, under either light or dark conditions, in-vitro, in 96-well plates. In the dark treatment, after 30-min, the ZnPc 100 µM treatment, caused a 30 % Nosema mortality, while this increased to 80 % at the same concentration after the light treatment. The high rate of anti-spore effects, in a short period of time, supports the notion that this could be an effective treatment for managing honey bee Nosema infections in the future. Our results also suggest that the photo activation of the treatment could be applied in the field setting and this would increase the sterilization of beekeeping equipment against Nosema.

Nanoparticles as carriers of photosensitizers to improve photodynamic therapy in cancer

Photodynamic therapy (PDT) has emerged as a promising non invasive therapeutic approach for cancer treatment, offering unique advantages over conventional treatments. The combination of light activation and photosensitizing agents allows for targeted and localized destruction of cancer cells, reducing damage to surrounding healthy tissues. In recent years, the integration of nanoparticles with PDT has garnered significant attention due to their potential to enhance therapeutic outcomes. This review article aims to provide a comprehensive overview of the current state-of-the-art in utilizing nanoparticles for photodynamic therapy in cancer treatment. We summarized various nanoparticle-based approaches, their properties, and their implications in optimizing PDT efficacy, and discussed challenges and prospects in the field.

Activity-Based Nitric Oxide-Responsive Porphyrin for Site-Selective and Nascent Cancer Ablation

Nitric oxide (NO) generated within the tumor microenvironment is an established driver of cancer progression and metastasis. Recent efforts have focused on leveraging this feature to target cancer through the development of diagnostic imaging agents and activatable chemotherapeutics. In this context, porphyrins represent an extraordinarily promising class of molecules, owing to their demonstrated use within both modalities. However, the remodeling of a standard porphyrin to afford a responsive chemical that can distinguish elevated NO from physiological levels has remained a significant research challenge. In this study, we employed a photoinduced electron transfer strategy to develop a panel of NO-activatable porphyrin photosensitizers (NOxPorfins) augmented with real-time fluorescence monitoring capabilities. The lead compound, NOxPorfin-1, features an o-phenylenediamine trigger that can effectively capture NO (via N2O3) to yield a triazole product that exhibits a 7.5-fold enhancement and a 70-fold turn-on response in the singlet oxygen quantum yield and fluorescence signal, respectively. Beyond demonstrating excellent in vitro responsiveness and selectivity toward NO, we showcase the potent photodynamic therapy (PDT) effect of NOxPorfin-1 in murine breast cancer and human non-small cellular lung cancer cells. Further, to highlight the in vivo efficacy, two key studies were executed. First, we utilized NOxPorfin-1 to ablate murine breast tumors in a site-selective manner without causing substantial collateral damage to healthy tissue. Second, we established a nascent human lung cancer model to demonstrate the unprecedented ability of NOxPorfin-1 to halt tumor growth and progression completely. The results of the latter study have tremendous implications for applying PDT to target metastatic lesions.

Combining photodynamic therapy and cascade chemotherapy for enhanced tumor cytotoxicity: the role of CTT2P@B nanoparticles

The mitochondria act as the main producers of reactive oxygen species (ROS) within cells. Elevated levels of ROS can activate the mitochondrial apoptotic pathway, leading to cell apoptosis. In this study, we devised a molecular prodrug named CTT2P, demonstrating notable efficacy in facilitating mitochondrial apoptosis. To develop nanomedicine, we enveloped CTT2P within bovine serum albumin (BSA), resulting in the formulation known as CTT2P@B. The molecular prodrug CTT2P is achieved by covalently conjugating mitochondrial targeting triphenylphosphine (PPh3), photosensitizer TPPOH2, ROS-sensitive thioketal (TK), and chemotherapeutic drug camptothecin (CPT). The prodrug, which is chemically bonded, prevents the escape of drugs while they circulate throughout the body, guaranteeing the coordinated dispersion of both medications inside the organism. Additionally, the concurrent integration of targeted photodynamic therapy and cascade chemotherapy synergistically enhances the therapeutic efficacy of pharmaceutical agents. Experimental results indicated that the covalently attached prodrug significantly mitigated CPT cytotoxicity under dark conditions. In contrast, TPPOH2, CTT2, CTT2P, and CTT2P@B nanoparticles exhibited increasing tumor cell-killing effects and suppressed tumor growth when exposed to light at 660 nm with an intensity of 280 mW cm-2. Consequently, this laser-triggered, mitochondria-targeted, combined photodynamic therapy and chemotherapy nano drug delivery system, adept at efficiently promoting mitochondrial apoptosis, presents a promising and innovative approach to cancer treatment.

Design and Synthesis of Metalloporphyrin Nanoconjugates for Dual Light-Responsive Antimicrobial Photodynamic Therapy

Antimicrobial photodynamic therapy (APDT) utilizes photosensitizers (PSs) that eradicate a broad spectrum of bacteria in the presence of light and molecular oxygen. On the other hand, some light sources such as ultraviolet (UVB and UVC) have poor penetration and high cytotoxicity, leading to undesired PDT of the PSs. Herein, we have synthesized conjugatable mesosubstituted porphyrins and extensively characterized them. Time-dependent density functional theory (TD-DFT) calculations revealed that metalloporphyrin EP (5) is a suitable candidate for further applications. Subsequently, the metalloporphyrin was conjugated with lignin-based zinc oxide nanocomposites (ZnOAL and ZnOKL) to develop hydrophilic nanoconjugates (ZnOAL@EP and ZnOKL@EP). Upon dual light (UV + green light) exposure, nanoconjugates showed enhanced singlet oxygen generation ability and also demonstrated pH responsiveness. These nanoconjugates displayed significantly improved APDT efficiency (4-7 fold increase) to treat bacterial infection under dual light irradiation.

Phototherapy for age-related brain diseases: Challenges, successes and future

Brain diseases present a significant obstacle to both global health and economic progress, owing to their elusive pathogenesis and the limited effectiveness of pharmaceutical interventions. Phototherapy has emerged as a promising non-invasive therapeutic modality for addressing age-related brain disorders, including stroke, Alzheimer's disease (AD), and Parkinson's disease (PD), among others. This review examines the recent progressions in phototherapeutic interventions. Firstly, the article elucidates the various wavelengths of visible light that possess the capability to penetrate the skin and skull, as well as the pathways of light stimulation, encompassing the eyes, skin, veins, and skull. Secondly, it deliberates on the molecular mechanisms of visible light on photosensitive proteins, within the context of brain disorders and other molecular pathways of light modulation. Lastly, the practical application of phototherapy in diverse clinical neurological disorders is indicated. Additionally, this review presents novel approaches that combine phototherapy and pharmacological interventions. Moreover, it outlines the limitations of phototherapeutics and proposes innovative strategies to improve the treatment of cerebral disorders.

Luminescent lanthanide-based molecular materials: applications in photodynamic therapy

Luminescent lanthanide molecular compounds have recently attracted attention as potential photosensitizers (PSs) for photodynamic therapy (PDT) against malignant cancer tumours because of their predictable systemic toxicity, temporospatial specificity, and minimal invasiveness. A photosensitizer exhibits no toxicity by itself, but in the presence of light and oxygen molecules, it can generate reactive oxygen species (ROS) to cause damage to proteins, nucleic acids, lipids, membranes, and organelles, which can induce cell apoptosis. This review focuses on the latest developments in luminescent lanthanide-based molecular materials as photosensitizers and their applications in photodynamic therapy. These molecular materials include lanthanide coordination complexes, nanoscale lanthanide coordination polymers, and lanthanide-based nanoscale metal-organic frameworks. In the end, the future challenges in the development of robust luminescent lanthanide molecular materials-based photosensitisers are outlined and emphasized to inspire the design of a new generation of phototheranostic agents.

Light-Responsive and Dual-Targeting Liposomes: From Mechanisms to Targeting Strategies

In recent years, nanocarriers have played an ever-increasing role in clinical and biomedical applications owing to their unique physicochemical properties and surface functionalities. Lately, much effort has been directed towards the development of smart, stimuli-responsive nanocarriers that are capable of releasing their cargos in response to specific stimuli. These intelligent-responsive nanocarriers can be further surface-functionalized so as to achieve active tumor targeting in a sequential manner, which can be simply modulated by the stimuli. By applying this methodological approach, these intelligent-responsive nanocarriers can be directed to different target-specific organs, tissues, or cells and exhibit on-demand controlled drug release that may enhance therapeutic effectiveness and reduce systemic toxicity. Light, an external stimulus, is one of the most promising triggers for use in nanomedicine to stimulate on-demand drug release from nanocarriers. Light-triggered drug release can be achieved through light irradiation at different wavelengths, either in the UV, visible, or even NIR region, depending on the photophysical properties of the photo-responsive molecule embedded in the nanocarrier system, the structural characteristics, and the material composition of the nanocarrier system. In this review, we highlighted the emerging functional role of light in nanocarriers, with an emphasis on light-responsive liposomes and dual-targeted stimuli-responsive liposomes. Moreover, we provided the most up-to-date photo-triggered targeting strategies and mechanisms of light-triggered drug release from liposomes and NIR-responsive nanocarriers. Lastly, we addressed the current challenges, advances, and future perspectives for the deployment of light-responsive liposomes in targeted drug delivery and therapy.