Photodynamic therapy, priming and optical imaging: Potential co-conspirators in treatment design and optimization - a Thomas Dougherty Award for Excellence in PDT paper

Photodynamic priming modulates cellular ATP levels to overcome P-glycoprotein-mediated drug efflux in chemoresistant triple-negative breast cancer

P-glycoprotein (P-gp, ABCB1) is a well-researched ATP-binding cassette (ABC) drug efflux transporter linked to the development of cancer multidrug resistance (MDR). Despite extensive studies, approved therapies to safely inhibit P-gp in clinical settings are lacking, necessitating innovative strategies beyond conventional inhibitors or antibodies to reverse MDR. Photodynamic therapy is a globally approved cancer treatment that uses targeted, harmless red light to activate non-toxic photosensitizers, confining its cytotoxic photochemical effects to disease sites while sparing healthy tissues. This study demonstrates that photodynamic priming (PDP), a sub-cytotoxic photodynamic therapy process, can inhibit P-gp function by modulating cellular respiration and ATP levels in light accessible regions. Using chemoresistant (VBL-MDA-MB-231) and chemosensitive (MDA-MB-231) triple-negative breast cancer cell lines, we showed that PDP decreases mitochondrial membrane potential by 54.4% ± 30.4 and reduces mitochondrial ATP production rates by 94.9% ± 3.46. Flow cytometry studies showed PDP can effectively improve the retention of P-gp substrates (calcein) by up to 228.4% ± 156.3 in chemoresistant VBL-MDA-MB-231 cells, but not in chemosensitive MDA-MB-231 cells. Further analysis revealed that PDP did not alter the cell surface expression level of P-gp in VBL-MDA-MB-231 cells. These findings indicate that PDP can reduce cellular ATP below the levels that is required for the function of P-gp and improve intracellular substrate retention. We propose that PDP in combination with chemotherapy drugs, might improve the efficacy of chemotherapy and overcome cancer MDR.

Minocycline and photodynamic priming significantly improve chemotherapy efficacy in heterotypic spheroids of pancreatic ductal adenocarcinoma

The prognosis for patients with advanced-stage pancreatic ductal adenocarcinoma (PDAC) remains dismal. It is generally accepted that combination cancer therapies offer the most promise, such as Folforinox, despite their associated high toxicity. This study addresses the issue of chemoresistance by introducing a complementary dual priming approach to attenuate the DNA repair mechanism and to improve the efficacy of a type 1 topoisomerase (Top1) inhibitor. The result is a regimen that integrates drug-repurposing and nanotechnology using 3 clinically relevant FDA-approved agents (1) Top1 inhibitor (irinotecan) at subcytotoxic doses (2) benzoporphyrin derivative (BPD) as a photoactive molecule for photodynamic priming (PDP) to improve the delivery of irinotecan within the cancer cell and (3) minocycline priming (MNP) to modulate DNA repair enzyme Tdp1 (tyrosyl-DNA phosphodiesterase) activity. We demonstrate in heterotypic 3D cancer models that incorporate cancer cells and pancreatic cancer-associated fibroblasts that simultaneous targeting of Tdp1 and Top1 were significantly more effective by employing MNP and photoactivatable multi-inhibitor liposomes encapsulating BPD and irinotecan compared to monotherapies or a cocktail of dual or triple-agents. These data are encouraging and warrant further work in appropriate animal models to evolve improved therapeutic regimens.

Exceptional anticancer photodynamic properties of [1,4-Bis(3,6,9,12-Tetraoxatridec-1-yloxy)phthalocyaninato]zinc(II)

Phthalocyanines have been described as effective photosensitizers for photodynamic therapy and are therefore, being studied for their biomedical applications. The metalation of photosensitizers can improve their photodynamic therapy potential. Here, we focus on the biological properties of [1,4-Bis(3,6,9,12-Tetraoxatridec-1-yloxy)phthalocyaninato]zinc(II) (ZnPc(αEG4)2) and demonstrate its exceptional anticancer activity upon light stimulation to kill preferentially cancer cells with a start of efficiency at 10 pM. Indeed, in this work we highlighted the high selectivity of ZnPc(αEG4)2 for cancer cells compared with healthy ones and we establish its mechanism of action, enabling us to conclude that ZnPc(αEG4)2 could be a powerful tool for cancer therapy.

Shedding Light on Chemoresistance: The Perspective of Photodynamic Therapy in Cancer Management

The persistent failure of standard chemotherapy underscores the urgent need for innovative and targeted approaches in cancer treatment. Photodynamic therapy (PDT) has emerged as a promising photochemistry-based approach to address chemoresistance in cancer regimens. PDT not only induces cell death but also primes surviving cells, enhancing their susceptibility to subsequent therapies. This review explores the principles of PDT and discusses the concept of photodynamic priming (PDP), which augments the effectiveness of treatments like chemotherapy. Furthermore, the integration of nanotechnology for precise drug delivery at the right time and location and PDT optimization are examined. Ultimately, this study highlights the potential and limitations of PDT and PDP in cancer treatment paradigms, offering insights into future clinical applications.

Dual-Function Antibody Conjugate-Enabled Photoimmunotherapy Complements Fluorescence and Photoacoustic Imaging of Head and Neck Cancer Spheroids

Several molecular-targeted imaging and therapeutic agents are in clinical trials for image-guided surgery and photoimmunotherapy (PIT) for head and neck cancers. In this context, we have previously reported the development, characterization, and specificity of a dual-function antibody conjugate (DFAC) for multimodal imaging and photoimmunotherapy (PIT) of EGFR-overexpressing cancer cells. The DFAC reported previously and used in the present study comprises an EGFR-targeted antibody, cetuximab, conjugated to benzoporphyrin derivative (BPD) for fluorescence imaging and PIT and a Si-centered naphthalocyanine dye for photoacoustic imaging. We report here the evaluation and performance of DFAC in detecting microscopic cancer spheroids by fluorescence and photoacoustic imaging along with their treatment by PIT. We demonstrate that while fluorescence imaging can detect spheroids with volumes greater than 0.049 mm3, photoacoustic imaging-based detection was possible even for the smallest spheroids (0.01 mm3) developed in the study. When subjected to PIT, the spheroids showed a dose-dependent response, with smaller spheroids (0.01 and 0.018 mm3) showing a complete response with no recurrence when treated with 100 J/cm2. Together our results demonstrate the complementary imaging and treatment capacity of DFAC. This potentially enables fluorescence imaging to assess the presence of tumor on a macroscopic scale, followed by photoacoustic imaging for delineating tumor margins guiding surgical resection and elimination of any residual microscopic disease by PIT, in a single intraoperative setting.

Theranostic imaging and multimodal photodynamic therapy and immunotherapy using the mTOR signaling pathway

Tumor metastases are considered the leading cause of cancer-associated deaths. While clinically applied drugs have demonstrated to efficiently remove the primary tumor, metastases remain poorly accessible. To overcome this limitation, herein, the development of a theranostic nanomaterial by incorporating a chromophore for imaging and a photosensitizer for treatment of metastatic tumor sites is presented. The mechanism of action reveals that the nanoparticles are able to intervene by local generation of cellular damage through photodynamic therapy as well as by systemic induction of an immune response by immunotherapy upon inhibition of the mTOR signaling pathway which is of crucial importance for tumor onset, progression and metastatic spreading. The nanomaterial is able to strongly reduce the volume of the primary tumor as well as eradicates tumor metastases in a metastatic breast cancer and a multi-drug resistant patient-derived hepatocellular carcinoma models in female mice.

Test method for evaluating the photocytotoxic potential of fluorescence imaging products

Various fluorescence imaging agents are currently under clinical studies. Despite significant benefits, phototoxicity is a barrier to the clinical translation of fluorophores. Current regulatory guidelines on medication-based phototoxicity focus on skin effects during sun exposure. However, with systemic and local administration of fluorophores and targeted illumination, there is now possibility of photochemical damage to deeper tissues during intraoperative imaging procedures. Hence, independent knowledge regarding phototoxicity is required to facilitate the development of fluorescence imaging products. Previously, we studied a cell-free assay for initial screening of reactive molecular species generation from fluorophores. The current work addresses a safety test method based on cell viability as an adjunct and a comparator with the cell-free assay. Our goal is to modify and implement an approach based on the in vitro 3T3 neutral red uptake assay of the Organization for Economic Co-Operation and Development Test Guideline 432 (OECD TG432) to evaluate the photocytotoxicity of clinically relevant fluorophores. These included indocyanine green (ICG), proflavine, methylene blue (MB), and IRDye800, as well as control photosensitizers, benzoporphyrin derivative (BPD) and rose bengal (RB). We performed measurements at agent concentrations and illumination parameters used for clinic imaging. Our results aligned with prior studies, indicating photocytotoxicity in RB and BPD and an absence of reactivity for ICG and IRDye800. DNA interactive agents, proflavine and MB, exhibited drug/light dose-response curves like photosensitizers. This study provides evidence and insights into practices useful for testing the photochemical safety of fluorescence imaging products.

Prospects and Challenges of Synergistic Effect of Fluorescent Carbon Dots, Liposomes and Nanoliposomes for Theragnostic Applications

The future of molecular-level therapy, efficient medical diagnosis, and drug delivery relies on the effective theragnostic function which can be achieved by the synergistic effect of fluorescent carbon dots (FCDs) liposomes (L) and nanoliposomes. FCDs act as the excipient navigation agent while liposomes play the role of the problem-solving agent, thus the term "theragnostic" would describe the effect of LFCDs properly. Liposomes and FCDs share some excellent at-tributes such as being nontoxic and biodegradable and they can represent a potent delivery system for pharmaceutical compounds. They enhance the therapeutic efficacy of drugs via stabilizing the encapsulated material by circumventing barriers to cellular and tissue uptake. These agents facilitate long-term drug biodistribution to the intended locations of action while eliminating systemic side effects. This manuscript reviews recent progress with liposomes, nanoliposomes (collectively known as lipid vesicles) and fluorescent carbon dots, by exploring their key characteristics, applications, characterization, performance, and challenges. An extensive and intensive understanding of the synergistic interaction between liposomes and FCDs sets out a new research pathway to an efficient and theragnostic / theranostic drug delivery and targeting diseases such as cancer.

Photomodulation Approaches to Overcome Antimicrobial Resistance

Photopharmacology is an approach that aims to be an alternative to classical chemotherapy. Herein, the different classes of photoswitches and photocleavage compounds and their biological applications are described. Proteolysis targeting chimeras (PROTACs) containing azobenzene moieties (PHOTACs) and photocleavable protecting groups (photocaged PROTACs) are also mentioned. Furthermore, porphyrins are referenced as successful photoactive compounds in a clinical context, such as in the photodynamic therapy of tumours as well as preventing antimicrobial resistance, namely in bacteria. Porphyrins combining photoswitches and photocleavage systems are highlighted, taking advantage of both photopharmacology and photodynamic action. Finally, porphyrins with antibacterial activity are described, taking advantage of the synergistic effect of photodynamic treatment and antibiotic therapy to overcome bacterial resistance.

Combination of Two Photosensitisers in Anticancer, Antimicrobial and Upconversion Photodynamic Therapy

Photodynamic therapy (PDT) is a special form of phototherapy in which oxygen is needed, in addition to light and a drug called a photosensitiser (PS), to create cytotoxic species that can destroy cancer cells and various pathogens. PDT is often used in combination with other antitumor and antimicrobial therapies to sensitise cells to other agents, minimise the risk of resistance and improve overall outcomes. Furthermore, the aim of combining two photosensitising agents in PDT is to overcome the shortcomings of the monotherapeutic approach and the limitations of individual agents, as well as to achieve synergistic or additive effects, which allows the administration of PSs in lower concentrations, consequently reducing dark toxicity and preventing skin photosensitivity. The most common strategies in anticancer PDT use two PSs to combine the targeting of different organelles and cell-death mechanisms and, in addition to cancer cells, simultaneously target tumour vasculature and induce immune responses. The use of PDT with upconversion nanoparticles is a promising approach to the treatment of deep tissues and the goal of using two PSs is to improve drug loading and singlet oxygen production. In antimicrobial PDT, two PSs are often combined to generate various reactive oxygen species through both Type I and Type II processes.

BODIPY-Based Photothermal Agents with Excellent Phototoxic Indices for Cancer Treatment

Here, we report six novel, easily accessible BODIPY-based agents for cancer treatment. In contrast to established photodynamic therapy (PDT) agents, these BODIPY-based compounds show additional photothermal activity and their cytotoxicity is not dependent on the generation of reactive oxygen species (ROS). The agents show high photocytotoxicity upon irradiation with light and low dark toxicity in different cancer cell lines in 2D culture as well as in 3D multicellular tumor spheroids (MCTSs). The ratio of dark to light toxicity (phototoxic index, PI) of these agents reaches striking values exceeding 830,000 after irradiation with energetically low doses of light at 630 nm. The oxygen-dependent mechanism of action (MOA) of established photosensitizers (PSs) hampers effective clinical deployment of these agents. Under hypoxic conditions (0.2% O₂), which are known to limit the efficiency of conventional PSs in solid tumors, photocytotoxicity was induced at the same concentration levels, indicating an oxygen-independent photothermal MOA. With a PI exceeding 360,000 under hypoxic conditions, both PI values are the highest reported to date. We anticipate that small molecule agents with a photothermal MOA, such as the BODIPY-based compounds reported in this work, may overcome this barrier and provide a new avenue to cancer therapy.

Spotlight on Photoactivatable Liposomes beyond Drug Delivery: An Enabler of Multitargeting of Molecular Pathways

The potential of photoactivating certain molecules, photosensitizers (PS), resulting in photochemical processes, has long been realized in the form of photodynamic therapy (PDT) for the management of several cancerous and noncancerous pathologies. With an improved understanding of the photoactivation process and its broader implications, efforts are being made to exploit the various facets of photoactivation, PDT, and the associated phenomenon of photodynamic priming in enhancing treatment outcomes, specifically in cancer therapeutics. The parallel emergence of nanomedicine, specifically liposome-based nanoformulations, and the convergence of the two fields of liposome-based drug delivery and PDT have led to the development of unique hybrid systems, which combine the exciting features of liposomes with adequate complementation through the photoactivation process. While initially liposomes carrying photosensitizers (PSs) were developed for enhancing the pharmacokinetics and the general applicability of PSs, more recently, PS-loaded liposomes, apart from their utility in PDT, have found several applications including enhanced targeting of drugs, coloading multiple therapeutic agents to enhance synergistic effects, imaging, priming, triggering drug release, and facilitating the escape of therapeutic agents from the endolysosomal complex. This review discusses the design strategies, potential, and unique attributes of these hybrid systems, with not only photoactivation as an attribute but also the ability to encapsulate multiple agents for imaging, biomodulation, priming, and therapy referred to as photoactivatable multiagent/inhibitor liposomes (PMILS) and their targeted versions─targeted PMILS (TPMILS). While liposomes have formed their own niche in nanotechnology and nanomedicine with several clinically approved formulations, we try to highlight how using PS-loaded liposomes could address some of the limitations and concerns usually associated with liposomes to overcome them and enhance their preclinical and clinical utility in the future.

Remediating Desmoplasia with EGFR-Targeted Photoactivable Multi-Inhibitor Liposomes Doubles Overall Survival in Pancreatic Cancer

Desmoplasia is characteristic of pancreatic ductal adenocarcinoma (PDAC), which exhibits 5-year survival rates of 3%. Desmoplasia presents physical and biochemical barriers that contribute to treatment resistance, yet depleting the stroma alone is unsuccessful and even detrimental to patient outcomes. This study is the first demonstration of targeted photoactivable multi-inhibitor liposomes (TPMILs) that induce both photodynamic and chemotherapeutic tumor insult, while simultaneously remediating desmoplasia in orthotopic PDAC. TPMILs targeted with cetuximab (anti-EGFR mAb) contain lipidated benzoporphyrin derivative (BPD-PC) photosensitizer and irinotecan. The desmoplastic tumors comprise human PDAC cells and patient-derived cancer-associated fibroblasts. Upon photoactivation, the TPMILs induce 90% tumor growth inhibition at only 8.1% of the patient equivalent dose of nanoliposomal irinotecan (nal-IRI). Without EGFR targeting, PMIL photoactivation is ineffective. TPMIL photoactivation is also sixfold more effective at inhibiting tumor growth than a cocktail of Visudyne-photodynamic therapy (PDT) and nal-IRI, and also doubles survival and extends progression-free survival by greater than fivefold. Second harmonic generation imaging reveals that TPMIL photoactivation reduces collagen density by >90% and increases collagen nonalignment by >103 -fold. Collagen nonalignment correlates with a reduction in tumor burden and survival. This single-construct phototoxic, chemotherapeutic, and desmoplasia-remediating regimen offers unprecedented opportunities to substantially extend survival in patients with otherwise dismal prognoses.

Photoimmunotherapy Retains Its Anti-Tumor Efficacy with Increasing Stromal Content in Heterotypic Pancreatic Cancer Spheroids

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease characterized by increased levels of desmoplasia that contribute to reduced drug delivery and poor treatment outcomes. In PDAC, the stromal content can account for up to 90% of the total tumor volume. The complex interplay between stromal components, including pancreatic cancer-associated fibroblasts (PCAFs), and PDAC cells in the tumor microenvironment has a significant impact on the prognoses and thus needs to be recapitulated in vitro when evaluating various treatment strategies. This study is a systematic evaluation of photodynamic therapy (PDT) in 3D heterotypic coculture models of PDAC with varying ratios of patient-derived PCAFs that simulate heterogeneous PDAC tumors with increasing stromal content. The efficacy of antibody-targeted PDT (photoimmunotherapy; PIT) using cetuximab (a clinically approved anti-EGFR antibody) photoimmunoconjugates (PICs) of a benzoporphyrin derivative (BPD) is contrasted with that of liposomal BPD (Visudyne), which is currently in clinical trials for PDT of PDAC. We demonstrate that both Visudyne-PDT and PIT were effective in heterotypic PDAC 3D spheroids with a low stromal content. However, as the stromal content increases above 50% in the 3D spheroids, the efficacy of Visudyne-PDT is reduced by up to 10-fold, while PIT retains its efficacy. PIT was found to be 10-, 19-, and 14-fold more phototoxic in spheroids with 50, 75, and 90% PCAFs, respectively, as compared to Visudyne-PDT. This marked difference in efficacy is attributed to the ability of PICs to penetrate and distribute homogeneously within spheroids with a higher stromal content and the mechanistically different modes of action of the two formulations. This study thus demonstrates how the stromal content in PDAC spheroids directly impacts their responsiveness to PDT and proposes PIT to be a highly suited treatment option for desmoplastic tumors with particularly high degrees of stromal content.

Towards Photodynamic Image-Guided Surgery of Head and Neck Tumors: Photodynamic Priming Improves Delivery and Diagnostic Accuracy of Cetuximab-IRDye800CW

Fluorescence image-guided surgery (IGS) using antibody conjugates of the fluorophore IRDye800CW have revolutionized the surgical debulking of tumors. Cetuximab, an anti-epidermal growth factor receptor (EGFR) monoclonal antibody, conjugated to IRDye800CW (Cet-IRDye800) is the first molecular targeted antibody probe to be used for IGS in head and neck cancer patients. In addition to surgical debulking, Cetuximab-targeted photodynamic therapy (photoimmunotherapy; PIT) is emerging in the clinic as a powerful modality for head and neck tumor photodestruction. A plethora of other photoactivable agents are also in clinical trials for photodynamic-based therapies of head and neck cancer. Considering the vascular and stromal modulating effects of sub-therapeutic photodynamic therapy, namely photodynamic priming (PDP), this study explores the potential synergy between PDP and IGS for a novel photodynamic image-guided surgery (P-IGS) strategy. To the best of our knowledge, this is the first demonstration that PDP of the tumor microenvironment can augment the tumor delivery of full-length antibodies, namely Cet-IRDye800. In this study, we demonstrate a proof-of-concept that PDP primes orthotopic FaDu human head and neck tumors in mice for P-IGS by increasing the delivery of Cet-IRDye800 by up to 138.6%, by expediting its interstitial accumulation by 10.5-fold, and by increasing its fractional tumor coverage by 49.5% at 1 h following Cet-IRDye800 administration. Importantly, PDP improves the diagnostic accuracy of tumor detection by up to 264.2% with respect to vicinal salivary glands at 1 h. As such, PDP provides a time-to-surgery benefit by reducing the time to plateau 10-fold from 25.7 h to 2.5 h. We therefore propose that a pre-operative PDP regimen can expedite and augment the accuracy of IGS-mediated surgical debulking of head and neck tumors and reduce the time-to-IGS. Furthermore, this P-IGS regimen, can also enable a forward-looking post-operative protocol for the photodestruction of unresectable microscopic disease in the surgical bed. Beyond this scope, the role of PDP in the homogenous delivery of diagnostic, theranostic and therapeutic antibodies in solid tumors is of considerable significance to the wider community.

Intraligand Excited States Turn a Ruthenium Oligothiophene Complex into a Light-Triggered Ubertoxin with Anticancer Effects in Extreme Hypoxia

Ru(II) complexes that undergo photosubstitution reactions from triplet metal-centered (³MC) excited states are of interest in photochemotherapy (PCT) due to their potential to produce cytotoxic effects in hypoxia. Dual-action systems that incorporate this stoichiometric mode to complement the oxygen-dependent photosensitization pathways that define photodynamic therapy (PDT) are poised to maintain antitumor activity regardless of the oxygenation status. Herein, we examine the way in which these two pathways influence photocytotoxicity in normoxia and in hypoxia using the [Ru(dmp)₂(IP-nT)]²⁺ series (where dmp = 2,9-dimethyl-1,10-phenanthroline and IP-nT = imidazo[4,5-f][1,10]phenanthroline tethered to n = 0-4 thiophene rings) to switch the dominant excited state from the metal-based ³MC state in the case of Ru-phen-Ru-1T to the ligand-based ³ILCT state for Ru-3T and Ru-4T. Ru-phen-Ru-1T, having dominant ³MC states and the largest photosubstitution quantum yields, are inactive in both normoxia and hypoxia. Ru-3T and Ru-4T, with dominant ³IL/³ILCT states and long triplet lifetimes (τ_TA = 20-25 μs), have the poorest photosubstitution quantum yields, yet are extremely active. In the best instances, Ru-4T exhibit attomolar phototoxicity toward SKMEL28 cells in normoxia and picomolar in hypoxia, with phototherapeutic index values in normoxia of 10⁵-10¹² and 10³-10⁶ in hypoxia. While maximizing excited-state deactivation through photodissociative ³MC states did not result in bonafide dual-action PDT/PCT agents, the study has produced the most potent photosensitizer we know of to date. The extraordinary photosensitizing capacity of Ru-3T and Ru-4T may stem from a combination of very efficient ¹O₂ production and possibly complementary type I pathways via ³ILCT excited states.

Recent advances in noble metal complex based photodynamic therapy

Photodynamic therapy (PDT) utilizes light-activated photosensitizers (PSs) to generate toxic species for therapeutics. It has become an emerging solution for cancer treatment because of its specific spatiotemporal selectivity and minimal invasiveness. Noble metal (Ru, Ir and Pt) complexes are of increasing interest as photosensitizers for their excellent photophysical, photochemical, and photobiological properties. In this review, we highlight recent advancements in the development of noble metal complex photosensitizers for PDT during the last 5 years. We will summarize the design strategies of noble metal complexes for efficient and precise PDT, including increasing the light penetration depth, reducing the oxygen-dependent nature and improving target ability. Finally, we summarize recent efforts for the development of noble-based PSs and discuss the limitations of such PSs in clinical application and future perspectives in this field, such as the combination of PDT with other treatment modalities.

Dissecting extracellular and intracellular distribution of nanoparticles and their contribution to therapeutic response by monochromatic ratiometric imaging

Efficient delivery of payload to intracellular targets has been identified as the central principle for nanomedicine development, while the extracellular targets are equally important for cancer treatment. Notably, the contribution of extracellularly distributed nanoparticles to therapeutic outcome is far from being understood. Herein, we develop a pH/light dual-responsive monochromatic ratiometric imaging nanoparticle (MRIN), which functions through sequentially lighting up the intracellular and extracellular fluorescence signals by acidic endocytic pH and near-infrared light. Enabled by MRIN nanotechnology, we accurately quantify the extracellular and intracellular distribution of nanoparticles in several tumor models, which account for 65–80% and 20–35% of total tumor exposure, respectively. Given that the majority of nanoparticles are trapped in extracellular regions, we successfully dissect the contribution of extracellularly distributed nanophotosensitizer to therapeutic efficacy, thereby maximize the treatment outcome. Our study provides key strategies to precisely quantify nanocarrier microdistribtion and engineer multifunctional nanomedicines for efficient theranostics.

Detailed quantification of nanoparticle distribution in tumor tissues can provide the prediction of drug delivery efficacy and therapeutic outcome. Here the authors develop a pH/light dual responsive monochromatic ratiometric-imaging nanoparticle which can quantify extracellular and intracellular nanoparticle distribution in several tumor models.

Clinical evaluation of a mobile, low-cost system for fluorescence guided photodynamic therapy of early oral cancer in India

BACKGROUND

Morbidity and mortality due to oral cancer in India are exacerbated by a lack of access to effective treatments amongst medically underserved populations. We developed a user-friendly low-cost, portable fibre-coupled LED system for photodynamic therapy (PDT) of early oral lesions, using a smartphone fluorescence imaging device for treatment guidance, and 3D printed fibreoptic attachments for ergonomic intraoral light delivery.

METHODS

30 patients with T₁N₀M₀ buccal mucosal cancer were recruited from the JN Medical College clinics, Aligarh, and rural screening camps. Tumour limits were defined by external ultrasound (US), white light photos and increased tumour fluorescence after oral administration of the photosensitising agent ALA (60 mg/kg, divided doses), monitored by a smartphone fluorescence imaging device. 100 J/cm² LED light (635 nm peak) was delivered followed by repeat fluorescence to assess photobleaching. US and biopsy were repeated after 7-17 days. This trial is registered with ClinicalTrials.gov, NCT03638622, and the study has been completed.

FINDINGS

There were no significant complications or discomfort. No sedation was required. No residual disease was detected in 22 out of 30 patients who completed the study (26 of 34 lesions, 76% complete tumour response, 50 weeks median follow-up) with up to 7.2 mm depth of necrosis. Treatment failures were attributed to large tumour size and/or inadequate light delivery (documented by limited photobleaching). Moderately differentiated lesions were more responsive than well-differentiated cancers.

INTERPRETATION

This simple and low-cost adaptation of fluorescenceguided PDT is effective for treatment of early-stage malignant oral lesions and may have implications in global health.

Dual Function Antibody Conjugates for Multimodal Imaging and Photoimmunotherapy of Cancer Cells

Precision imaging, utilizing molecular targeted agents, is an important tool in cancer diagnostics and guiding therapies. While there are limitations associated with single mode imaging probes, multimodal molecular imaging probes enabling target visualization through complementary imaging technologies provides an attractive alternative. However, there are several challenges associated with designing molecular probes carrying contrast agents for complementary multimodal imaging. Here, we propose a dual function antibody conjugate (DFAC) comprising an FDA approved photosensitizer Benzoporphyrin derivative (BPD) and a naphthalocyanine-based photoacoustic dye (SiNc(OH)) for multimodal infrared (IR) imaging. While fluorescence imaging, through BPD, provides sensitivity, complementing it with photoacoustic imaging, through SiNc(OH), provides a depth-resolved spatial resolution much beyond the optical diffusion limits of fluorescence measurements. Through a series of in vitro experiments, we demonstrate the development and utilization of DFACs for multimodal imaging and photodynamic treatment of squamous cell carcinoma (A431) cell line. The proposed DFACs have potential use in precision imaging applications such as guiding tumor resection surgeries and photodynamic treatment of residual microscopic disease thereby minimizing local recurrence. The data demonstrated in this study merits further investigation for its preclinical and clinical translation.

Combined Fluorescence and Optoacoustic Imaging for Monitoring Treatments against CT26 Tumors with Photoactivatable Liposomes

The newly developed multimodal imaging system combining raster-scan optoacoustic (OA) microscopy and fluorescence (FL) wide-field imaging was used for characterizing the tumor vascular structure with 38/50 μm axial/transverse resolution and assessment of photosensitizer fluorescence kinetics during treatment with novel theranostic agents. A multifunctional photoactivatable multi-inhibitor liposomal (PMILs) nano platform was engineered here, containing a clinically approved photosensitizer, Benzoporphyrin derivative (BPD) in the bilayer, and topoisomerase I inhibitor, Irinotecan (IRI) in its inner core, for a synergetic therapeutic impact. The optimized PMIL was anionic, with the hydrodynamic diameter of 131.6 ± 2.1 nm and polydispersity index (PDI) of 0.05 ± 0.01, and the zeta potential between -14.9 ± 1.04 to -16.9 ± 0.92 mV. In the in vivo studies on BALB/c mice with CT26 tumors were performed to evaluate PMILs' therapeutic efficacy. PMILs demonstrated the best inhibitory effect of 97% on tumor growth compared to the treatment with BPD-PC containing liposomes (PALs), 81%, or IRI containing liposomes (L-[IRI]) alone, 50%. This confirms the release of IRI within the tumor cells upon PMILs triggering by NIR light, which is additionally illustrated by FL monitoring demonstrating enhancement of drug accumulation in tumor initiated by PDT in 24 h after the treatment. OA monitoring revealed the largest alterations of the tumor vascular structure in the PMILs treated mice as compared to BPD-PC or IRI treated mice. The results were further corroborated with histological data that also showed a 5-fold higher percentage of hemorrhages in PMIL treated mice compared to the control groups. Overall, these results suggest that multifunctional PMILs simultaneously delivering PDT and chemotherapy agents along with OA and FL multi-modal imaging offers an efficient and personalized image-guided platform to improve cancer treatment outcomes.

Combination of tetrapyridylporphyrins and arene ruthenium(II) complexes to treat synovial sarcoma by photodynamic therapy

Four tetrapyridylporphyrin and four dipyridylporphyrin arene ruthenium complexes have been synthesized and characterized. In these complexes, the porphyrin core is either metal-free or occupied by zinc, and the arene ligand of the arene ruthenium units are either the standard methyl-isopropyl-benzene ([Formula: see text]cymene) or the less common phenylpropanol (PhPrOH) derivative. The porphyrin derivatives are coordinated to four arene ruthenium units or only two, in accordance with the number of pyridyl substituents at the periphery of the porphyrins, 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (TPyP) and 5,15-diphenyl-10,20-di(pyridin-4-yl)porphyrin (DPhDPyP). All eight complexes were evaluated as anticancer agents on synovial sarcoma cells, in the presence and absence of light, suggesting that both the arene ligand and the porphyrin core substituent can play a crucial role in fine-tuning the photodynamic activity of such organometallic photosensitizers.

Targeting X box-binding protein-1 (XBP1) enhances the sensitivity of HOS osteosarcoma cells to pyropheophorbide- α methyl ester-mediated photodynamic therapy

Photodynamic therapy (PDT), utilizes a photochemical reaction between photosensitizer and light to cause cancer death by generating reactive oxygen species (ROS). X-box binding protein 1 (XBP1), a downstream product of the IRE1α-XBP1 pathway, regulates diverse target genes, including various proto-oncogenes and its overexpression was closely related to the occurrence and progression of malignant tumors. The present study was performed to explore the role of XBP1 in human osteosarcoma HOS cells treated with pyropheophorbide-α methyl ester (MPPα)-mediated photodynamic therapy (PDT) (MPPα-PDT) and its potential mechanisms. The protein IRE1α and XBP1 increased with a time-dependent manner after MPPα-PDT treated, which indicated that MPPα-PDT induced the activation of the IRE1α-XBP1 pathway in HOS cells. Besides, MPPα-PDT treated alone or combined with XBP1 knockdown could both restrain the cell viability, but the latter one has more notable effect, which indicated that XBP1 knockdown may enhance the cell inhibitory effect by MPPα-PDT. Simultaneously, the apoptotic rate measured by flow cytometry (FCM) was increased surprisedly and the expression of apoptosis proteins was increased when knockdown XBP1 under the MPPα-PDT. In addition, antioxidant-related proteins such as the Catalase and SOD1 protein levels decreased, while the intracellular ROS content increased in HOS cells when knockdown XBP1 under the MPPα-PDT. These results suggested that the mechanism of XBP1 mediating resistance in HOS cells might be related to the expression of antioxidant molecules. In summary, this study found that the IRE1α-XBP1 pathway was activated in HOS cells after MPPα-PDT treated, and furthermore, XBP1 knockdown could decrease HOS cell viability through apoptosis and enhance the anti-tumor effect of MPPα-PDT remarkably in the meantime, which related to the regulation of oxidation-antioxidant system.

Dramatic Reduction of Distant Pancreatic Metastases Using Local Light Activation of Verteporfin with Nab-Paclitaxel

Despite substantial drug development efforts, pancreatic adenocarcinoma (PDAC) remains a difficult disease to treat, and surgical resection is the only potentially curative option. Unfortunately, 80% of patients are ineligible for surgery due to the presence of invasive disease and/or distant metastases at the time of diagnosis. Treatment strategies geared towards reclassifying these patients as surgical candidates by reducing metastatic burden represents the most promising approach to improve long-term survival. We describe a photodynamic therapy (PDT) based approach that, in combination with the first-line chemotherapeutic nab-paclitaxel, effectively addresses distant metastases in three separate orthotopic PDAC models in immunodeficient mice. In addition to effectively controlling local tumor growth, PDT plus nab-paclitaxel primes the tumor to elicit systemic effects and reduce or abrogate metastases. This combination dramatically inhibits (up to 100%) the eventual development of metastases in models of early stage PDAC, and completely eliminates metastasis in 55% of animals with already established distant disease in late-stage models. Our findings suggest that this light activation process initiates local biological and/or physiological changes within the tumor microenvironment that can be leveraged to treat both localized and distant disease, and potentially reclassify patients with previously inoperable disease as surgical candidates.

Nanoparticle-Mediated Delivery Systems in Photodynamic Therapy of Colorectal Cancer

Colorectal cancer (CRC) involving a malignant tumour remains one of the greatest contributing causes of fatal mortality and has become the third globally ranked malignancy in terms of cancer-associated deaths. Conventional CRC treatment approaches such as surgery, radiation, and chemotherapy are the most utilized approaches to treat this disease. However, they are limited by low selectivity and systemic toxicity, so they cannot completely eradicate this disease. Photodynamic therapy (PDT) is an emerging therapeutic modality that exerts selective cytotoxicity to cancerous cells through the activation of photosensitizers (PSs) under light irradiation to produce cytotoxic reactive oxygen species (ROS), which then cause cancer cell death. Cumulative research findings have highlighted the significant role of traditional PDT in CRC treatment; however, the therapeutic efficacy of the classical PDT strategy is restricted due to skin photosensitivity, poor cancerous tissue specificity, and limited penetration of light. The application of nanoparticles in PDT can mitigate some of these shortcomings and enhance the targeting ability of PS in order to effectively use PDT against CRC as well as to reduce systemic side effects. Although 2D culture models are widely used in cancer research, they have some limitations. Therefore, 3D models in CRC PDT, particularly multicellular tumour spheroids (MCTS), have attracted researchers. This review summarizes several photosensitizers that are currently used in CRC PDT and gives an overview of recent advances in nanoparticle application for enhanced CRC PDT. In addition, the progress of 3D-model applications in CRC PDT is discussed.

Recent Strategies to Develop Innovative Photosensitizers for Enhanced Photodynamic Therapy

This review presents a robust strategy to design photosensitizers (PSs) for various species. Photodynamic therapy (PDT) is a photochemical-based treatment approach that involves the use of light combined with a light-activated chemical, referred to as a PS. Attractively, PDT is one of the alternatives to conventional cancer treatment due to its noninvasive nature, high cure rates, and low side effects. PSs play an important factor in photoinduced reactive oxygen species (ROS) generation. Although the concept of photosensitizer-based photodynamic therapy has been widely adopted for clinical trials and bioimaging, until now, to our surprise, there has been no relevant review article on rational designs of organic PSs for PDT. Furthermore, most of published review articles in PDT focused on nanomaterials and nanotechnology based on traditional PSs. Therefore, this review aimed at reporting recent strategies to develop innovative organic photosensitizers for enhanced photodynamic therapy, with each example described in detail instead of providing only a general overview, as is typically done in previous reviews of PDT, to provide intuitive, vivid, and specific insights to the readers.

Diverse host-associated fungal systems as a dynamic source of novel bioactive anthraquinones in drug discovery: Current status and future perspectives

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Diversity and distribution of host-living fungi producing AQs in the terrestrial ecosystem are assembled.

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AQs biosynthesis and their SAR are elucidated to guide the approaches in novel drugs design and development.

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Several examples of true endophytic fungi producing AQs like their different host plants have been reported as interesting alternative sources of drugs.

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The review recapitulates the novel AQs with rare chemical skeleton that could open future venues for investigation of their biological activities.

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Lichens are assembled as unique source of several bioactive classes of AQs.

Background

Despite, a large number of bioactive anthraquinones (AQs) isolated from host-living fungi, only plant-derived AQs were introduced in the global consumer markets. Host-living fungi represents renewable and extendible resources of diversified metabolites to be exploited for bioactives production. Unique classes of AQs from fungi include halogenated and steroidal AQs, and absent from planta are of potential to explore for biological activity against urging diseases such as cancer and multidrug-resistant pathogens. The structural diversity of fungal AQs, monomers, dimers, trimers, halogenated, etc… results in a vast range of pharmacological activities.

Aim of review

The current study capitalizes on uncovering the diversity and distribution of host-living fungal systems producing AQs in different terrestrial ecosystems ranging from plant endophytes, lichens, animals and insects. Furthermore, the potential bioactivities of fungal derived AQs i.e., antibacterial, antifungal, antiviral (anti-HIV), anticancer, antioxidant, diuretic and laxative activities are assembled in relation to their structure activity relationship (SAR). Analyzing for structure–activity relationship among fungal AQs may facilitate bioengineering of more potential analogues. Withal, elucidation of AQs biosynthetic pathways in fungi is discussed from different fungal hosts to open up new possibilities for potential biotechnological applications. Such comprehensive review unravels terrestrial host-living fungal systems as a treasure trove in drug discovery, in addition to future perspectives and trends for their exploitation in pharmaceutical industries.

Key Scientific Concepts of Review

Such comprehensive review unravels terrestrialhost-living fungal systems as a treasure trove in drug discovery, in addition to future perspectives and trends for their exploitation in pharmaceutical industries.

Photodynamic Priming Improves the Anti-Migratory Activity of Prostaglandin E Receptor 4 Antagonist in Cancer Cells In Vitro

The combination of photodynamic agents and biological inhibitors is rapidly gaining attention for its promise and approval in treating advanced cancer. The activity of photodynamic treatment is mainly governed by the formation of reactive oxygen species upon light activation of photosensitizers. Exposure to reactive oxygen species above a threshold dose can induce cellular damage and cancer cell death, while the surviving cancer cells are "photodynamically primed", or sensitized, to respond better to other drugs and biological treatments. Here, we report a new combination regimen of photodynamic priming (PDP) and prostaglandin E2 receptor 4 (EP4) inhibition that reduces the migration and invasion of two human ovarian cancer cell lines (OVCAR-5 and CAOV3) in vitro. PDP is achieved by red light activation of the FDA-approved photosensitizer, benzoporphyrin derivative (BPD), or a chemical conjugate composed of the BPD linked to cetuximab, an anti-epithelial growth factor receptor (EGFR) antibody. Immunoblotting data identify co-inhibition of EGFR, cAMP-response element binding protein (CREB), and extracellular signal-regulated kinase 1/2 (ERK1/2) as key in the signaling cascades modulated by the combination of EGFR-targeted PDP and EP4 inhibition. This study provides valuable insights into the development of a molecular-targeted photochemical strategy to improve the anti-metastatic effects of EP4 receptor antagonists.

Cetuximab-Ag2S quantum dots for fluorescence imaging and highly effective combination of ALA-based photodynamic/chemo-therapy of colorectal cancer cells

Colorectal cancer (CRC) has a poor prognosis and urgently needs better therapeutic approaches. 5-Aminolevulinic acid (ALA) induced protoporphyrin IX (PpIX) based photodynamic therapy (PDT) is already used in the clinic for several cancers but not yet well investigated for CRC. Currently, systemic administration of ALA offers a limited degree of tumour selectivity, except for intracranial tumours, limiting its wider use in the clinic. The combination of effective ALA-PDT and chemotherapy may provide a promising alternative approach for CRC treatment. Herein, theranostic Ag₂S quantum dots (AS-2MPA) optically trackable in near-infrared (NIR), conjugated with endothelial growth factor receptor (EGFR) targeting Cetuximab (Cet) and loaded with ALA for PDT monotherapy or ALA/5-fluorouracil (5FU) for the combination therapy are proposed for enhanced treatment of EGFR(+) CRC. AS-2MPA-Cet exhibited excellent targeting of the high EGFR expressing cells and showed a strong intracellular signal for NIR optical detection in a comparative study performed on SW480, HCT116, and HT29 cells, which exhibit high, medium and low EGFR expression, respectively. Targeting provided enhanced uptake of the ALA loaded nanoparticles by strong EGFR expressing cells and formation of higher levels of PpIX. Cells also differ in their efficiency to convert ALA to PpIX, and SW480 was the best, followed by HT29, while HCT116 was determined as unsuitable for ALA-PDT. The therapeutic efficacy was evaluated in 2D cell cultures and 3D spheroids of SW480 and HT29 cells using AS-2MPA with either electrostatically loaded, hydrazone or amide linked ALA to achieve different levels of pH or enzyme sensitive release. Most effective phototoxicity was observed in SW480 cells using AS-2MPA-ALA-electrostatic-Cet due to enhanced uptake of the particles, fast ALA release and effective ALA-to-PpIX conversion. Targeted delivery reduced the effective ALA concentration significantly which was further reduced with codelivery of 5FU. Delivery of ALA via covalent linkages was also effective for PDT, but required a longer incubation time for the release of ALA in therapeutic doses. Phototoxicity was correlated with high levels of reactive oxygen species (ROS) and apoptotic/necrotic cell death. Hence, both AS-2MPA-ALA-Cet based PDT and AS-2MPA-ALA-Cet-5FU based chemo/PDT combination therapy coupled with strong NIR tracking of the nanoparticles demonstrate an exceptional therapeutic effect on CRC cells and excellent potential for synergistic multistage tumour targeting therapy.

Design and Synthesis of New PEGylated Polydopamine-Based Nanoconstructs Bearing ROS-Responsive Linkers and a Photosensitizer for Bimodal Photothermal and Photodynamic Therapies against Cancer

Polydopamine (PDA) nanoparticles (NPs) have recently acquired considerable attention for the development of nanoplatforms with multifunctional properties including photothermal (PTT) and photodynamic (PDT) activities. In addition to their high PTT performance, they can be easily conjugated to different types of photosensitizers (PSs) to acquire PDT activity. However, because of PDA free-radical scavenging properties, grafting the PSs directly to PDA surfaces may lead to an inefficient PDT outcome. Thus, the present work aims at synthesizing and characterizing a new PEGylated PDA-based nanoplatform with bifunctional PTT and PDT properties, which allows bimodal cancer therapy with the possibility to release the PS on demand in a spatiotemporal fashion. To do so, PDA NPs with a well-defined size and shape were prepared by the auto-oxidative self-polymerization process of dopamine hydrochloride in mild alkaline solution. The impact of the size on the PTT conversion efficiency was then determined. This allowed us to choose the optimal PDA NP size for PTT applications. Next, PDA NPs were decorated with SH-PEG polymers that bear at their extremity a thioketal reactive oxygen species-cleavable linker coupled to trisulfonated-tetraphenylporphyrin (TPPS₃) chosen as a hydrophilic PS. The grafting efficiency of PS-conjugated PEG on PDA was demonstrated in situ using a quartz crystal microbalance with dissipation monitoring. In addition, the photoinduced release of the PS was demonstrated by ¹H NMR. Finally, PTT/PDT bimodal therapy was assessed in vitro on human squamous esophageal cells by illuminating the PDA NPs at two different wavelengths, which showed the strong synergistic effect of combining PTT and PDT within this nanoplatform.

Photodynamic Therapy: A Compendium of Latest Reviews

Photodynamic therapy (PDT) is a promising therapy against cancer. Even though it has been investigated for more than 100 years, scientific publications have grown exponentially in the last two decades. For this reason, we present a brief compendium of reviews of the last two decades classified under different topics, namely, overviews, reviews about specific cancers, and meta-analyses of photosensitisers, PDT mechanisms, dosimetry, and light sources. The key issues and main conclusions are summarized, including ways and means to improve therapy and outcomes. Due to the broad scope of this work and it being the first time that a compendium of the latest reviews has been performed for PDT, it may be of interest to a wide audience.

Photodynamic priming with triple-receptor targeted nanoconjugates that trigger T cell-mediated immune responses in a 3D in vitro heterocellular model of pancreatic cancer

Photodynamic priming (PDP), a collateral effect of photodynamic therapy, can transiently alter the tumor microenvironment (TME) beyond the cytotoxic zone. Studies have demonstrated that PDP increases tumor permeability and modulates immune-stimulatory effects by inducing immunogenic cell death, via the release of damage-associated molecular patterns and tumor-associated antigens. Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest of cancers with a stubborn immunosuppressive TME and a dense stroma, representing a challenge for current molecular targeted therapies often involving macromolecules. We, therefore, tested the hypothesis that PDP's TME modulation will enable targeted therapy and result in immune stimulation. Using triple-receptor-targeted photoimmuno-nanoconjugate (TR-PINs)-mediated PDP, targeting epidermal growth factor receptor, transferrin receptor, and human epidermal growth factor receptor 2 we show light dose-dependent TR-PINs mediated cytotoxicity inhuman PDA Ccells (MIAPaCa-2),co-cultured with human pancreatic cancer-associated fibroblasts (PCAFs) in spheroids. Furthermore, TR-PINs induced the expression of heat shock proteins (Hsp60, Hsp70), Calreticulin, and high mobility group box 1 in a light dose and time-dependent manner.TR-PINs-mediated T cell activation was observed in co-cultures of immune cells with the MIA PaCa-2-PCAF spheroids. Both CD4⁺ T and CD8⁺ T cells showed light dose and time-dependant antitumor reactivity by upregulating degranulation marker CD107a and interferon-gamma post-PDP. Substantial tumor cell death in immune cell-spheroid co-cultures by day 3 shows the augmentation by antitumor T cell activation and their ability to recognize tumors for a light dose-dependent kill. These data confirm enhanced destruction of heterogeneous pancreatic spheroids mediated by PDP-induced phototoxicity, TME modulation and increased immunogenicity with targeted nanoconstructs.

OPD (Online Plasmodium Diagnosis): An ALA-PpIX based functional assay to predict active malaria

BACKGROUND

Malaria kills one child every 30 seconds reaching up to 3000 children a day. The mosquito borne malarial parasite invades the blood stream and hijacks red blood cells (RBCs). One of the medical successes of the 20^th century was development of malaria diagnostic tests. However, poor specificity and sensitivity along with the inability of these assays to distinguish active malarial infections has put the management scheme in jeopardy.

AIM

To develop an in-vitro functional assay to predict active malarial infections.

METHODS

Plasmodium falciparum (3D7) parasites were incubated with delta-aminolevulinic acid (ALA) for 7 h and imaged using a confocal microscope for protoporphyrin IX (PpIX) fluorescence. Similarly, PpIX was extracted, and fluorescence was estimated by fluorimetry.

RESULTS

Imaging showed that the falciparum-infected RBCs fluoresced while the non-infected cells did not. Moreover, fluorimetry showed fluorescent peaks only in actively infected RBCs.

CONCLUSIONS

ALA was only taken up by infected RBCs. When the parasites were loaded with ALA, they fluoresced. These proof-of-concept results demonstrate the first functional assay to detect/diagnose active malaria.

REAP (Rapid Elimination of Active Plasmodium): A photodynamic strategy exploiting intrinsic kinetics of the parasite to combat severe malaria

Plasmodium falciparum, the causative organism of Malaria is a mosquito-borne parasitic disease which infects red blood cells (RBCs), where it multiplies rapidly and goes through different stages of its life cycle. When the parasite load exceeds >3% in the blood, malaria transforms into severe malaria which requires immediate attention as death occurs within hours to days. The increase in people traveling to malaria-endemic areas and resistance/partial resistance to most known antimalarial drugs has put the current management scheme in jeopardy. To improve the patient outcome at this point, the physician may opt to perform exchange transfusions from another individual as an adjunct therapy to reduce parasitized RBCs, but the strategy has many drawbacks, including chances of infection. These limitations can be mitigated if the patient's own blood is withdrawn/extracted, sterilized from the parasitic load and then re-transfused almost similar to what is done in extracorporeal blood treatment for sepsis, poisoning and graft versus host disease. Thus, in the present study a light-based photochemical approach, Photodynamic Therapy (PDT) built on delta-aminolevulinic acid-protoporphyrin IX (ALA-PpIX) synthesis is exploited. This modality was effective at destruction of both resistant and susceptible strains of parasites, including at a high load mimicking severe drug resistant malaria. The current findings have set the stage for concept of an ALA-PpIX based PDT platform, "the REAP (Rapid Elimination of Active Plasmodium) strategy". This approach provides an additional tool towards the defense against multi-drug resistant severe malaria, and other intracellular blood pathogens, dependent on heme-synthesis.

Improving the photodynamic therapy of pyropheophorbide a through the combination of hypoxia-sensitive molecule and infrared light-excited d-TiO2−X nanoparticles

Photodynamic therapy (PDT) involving the generation of cytotoxic reactive oxygen species under light in the presence of sufficient oxygen has been widely used in diagnosing and treating cancer. However, the ubiquitous hypoxia in many solid tumors due to their abnormal proliferation and vascularization has greatly compromised the therapeutic effect. We have designed and prepared a tumor therapeutic nanoplatform for improving PDT based on defective TiO[Formula: see text] (d-TiO[Formula: see text] with the consideration that the continuous PDT would cause hypoxic tumor microenvironment (HTM) in which many hypoxia-sensitive drugs might be activated to exert the antitumor activities. The inorganic d-TiO[Formula: see text] nanoparticles (NPs) were firstly prepared and then modified by APTES to obtain the mesoporous d-TiO[Formula: see text]@SiO2NPs. The organic photosensitizer pyropheophorbide-a (PPa) and hypoxic-sensitive agent 6-aminoflavone (AF) were then adsorbed in the mesoporous SiO2, followed by further hydrophilic PEGylation to improve the biocompatibility. Defective d-TiO[Formula: see text] and the PPa could simultaneously consume oxygen after light excitation, while the resulted HTM was utilized to activate the hypoxic-sensitive agent 6-aminoflavone (AF) to trigger anti-cancer effect. The prepared d-TiO[Formula: see text]@SiO2/PPa/AF@PEG NPs were stable in normal physiological environment, and could continuously release PPa and AF under slightly acidic conditions. The in vitro experiments against cancer cells suggested that the combination of PPa and AF displayed significantly enhanced antitumor activities than that of monotherapy. Therefore, this research offered a potential application for 6-aminoflavone in PDT-induced hypoxia to improve the antitumor effects.

Photosensitizer-Functionalized Nanocomposites for Light-Activated Cancer Theranostics

Photosensitizers (PSs) have received significant attention recently in cancer treatment due to its theranostic capability for imaging and phototherapy. These PSs are highly responsive to light source of a suitable wavelength for image-guided cancer therapy from generated singlet oxygen and/or thermal heat. Various organic dye PSs show tremendous attenuation of tumor cells during cancer treatment. Among them, porphyrin and chlorophyll-based ultraviolet-visible (UV-Vis) dyes are employed for photodynamic therapy (PDT) by reactive oxygen species (ROS) and free radicals generated with 400-700 nm laser lights, which have poor tissue penetration depth. To enhance the efficacy of PDT, other light sources such as red light laser and X-ray have been suggested; nonetheless, it is still a challenging task to improve the light penetration depth for deep tumor treatment. To overcome this deficiency, near infrared (NIR) (700-900 nm) PSs, indocyanine green (ICG), and its derivatives like IR780, IR806 and IR820, have been introduced for imaging and phototherapy. These NIR PSs have been used in various cancer treatment modality by combining photothermal therapy (PTT) and/or PDT with chemotherapy or immunotherapy. In this review, we will focus on the use of different PSs showing photothermal/photodynamic response to UV-Vis or NIR-Vis light. The emphasis is a comprehensive review of recent smart design of PS-loaded nanocomposites for targeted delivery of PSs in light-activated combination cancer therapy.

Antimicrobial Photodynamic Inactivation Using Topical and Superhydrophobic Sensitizer Techniques: A Perspective from Diffusion in Biofilms†

This review describes nanoparticle and dye diffusion in bacterial biofilms in the context of antimicrobial photodynamic inactivation (aPDI). aPDI requires the diffusion of a photosensitizer (Sens) into the biofilm and subsequent photoactivation of oxygen for the generation of reactive oxygen species (ROS) that inactivate microbes. Molecular diffusion in biofilms has been long investigated, whereas this review is intended to draw a logical link between diffusion in biofilms and ROS, a combination that leads to the current state of aPDI and superhydrophobic aPDI (SH-aPDI). This review should be of interest to photochemists, photobiologists and researchers in material and antimicrobial sciences as is ties together conventional aPDI with the emerging subject of SH-aPDI.

Subtherapeutic Photodynamic Treatment Facilitates Tumor Nanomedicine Delivery and Overcomes Desmoplasia

Limited tumor nanoparticle accumulation remains one of the main challenges in cancer nanomedicine. Here, we demonstrate that subtherapeutic photodynamic priming (PDP) enhances the accumulation of nanoparticles in subcutaneous murine prostate tumors ∼3-5-times without inducing cell death, vascular destruction, or tumor growth delay. We also found that PDP resulted in an ∼2-times decrease in tumor collagen content as well as a significant reduction of extracellular matrix density in the subendothelial zone. Enhanced nanoparticle accumulation combined with the reduced extravascular barriers improved therapeutic efficacy in the absence of off-target toxicity, wherein 5 mg/kg of Doxil with PDP was equally effective in delaying tumor growth as 15 mg/kg of Doxil. Overall, this study demonstrates the potential of PDP to enhance tumor nanomedicine accumulation and alleviate tumor desmoplasia without causing cell death or vascular destruction, highlighting the utility of PDP as a minimally invasive priming strategy that can improve therapeutic outcomes in desmoplastic tumors.