Type I macrophage activator photosensitizer against hypoxic tumors

Photodynamic immunotherapy has emerged as a promising strategy to treat cancer. However, the hypoxic nature of most solid tumors and notoriously immunosuppressive tumor microenvironment could greatly compromise the efficacy of photodynamic immunotherapy. To address this challenge, we rationally synthesized a type I photosensitizer of TPA-DCR nanoparticles (NPs) with aggregation-enhanced reactive oxygen species generation via an oxygen-independent pathway. We demonstrated that the free radicals produced by TPA-DCR NPs could reprogram M0 and M2 macrophages into an anti-tumor state, which is not restricted by the hypoxic conditions. The activated M1 macrophages could further induce the immunogenic cell death of cancer cells by secreting pro-inflammatory cytokines and phagocytosis. In addition, in vivo anti-tumor experiments revealed that the TPA-DCR NPs could further trigger tumor immune response by re-educating tumor-associated macrophages toward M1 phenotype and promoting T cell infiltration. Overall, this work demonstrates the design of type I organic photosensitizers and mechanistic investigation of their superior anti-tumor efficacy. The results will benefit the exploration of advanced strategies to regulate the tumor microenvironment for effective photodynamic immunotherapy against hypoxic tumors.

The photosensitizer-triggered macrophage-mediated photodynamic immunotherapy is reported. The TPA-DCR NPs induce the ICD of hypoxic tumor by generating type I ROS to polarize macrophage, then promote tumor infiltration of T cells.     

Type I photosensitizers based on phosphindole oxide for photodynamic therapy: apoptosis and autophagy induced by endoplasmic reticulum stress

Photodynamic therapy (PDT) is considered a pioneering and effective modality for cancer treatment, but it is still facing challenges of hypoxic tumors. Recently, Type I PDT, as an effective strategy to address this issue, has drawn considerable attention. Few reports are available on the capability for Type I reactive oxygen species (ROS) generation of purely organic photosensitizers (PSs). Herein, we report two new Type I PSs, α-TPA-PIO and β-TPA-PIO, from phosphindole oxide-based isomers with efficient Type I ROS generation abilities. A detailed study on photophysical and photochemical mechanisms is conducted to shed light on the molecular design of PSs based on the Type I mechanism. The in vitro results demonstrate that these two PSs can selectively accumulate in a neutral lipid region, particularly in the endoplasmic reticulum (ER), of cells and efficiently induce ER-stress mediated apoptosis and autophagy in PDT. In vivo models indicate that β-TPA-PIO successfully achieves remarkable tumor ablation. The ROS-based ER stress triggered by β-TPA-PIO-mediated PDT has high potential as a precursor of the immunostimulatory effect for immunotherapy. This work presents a comprehensive protocol for Type I-based purely organic PSs and highlights the significance of considering the working mechanism in the design of PSs for the optimization of cancer treatment protocols.

Phosphindole oxide-based photosensitizers with Type I reactive oxygen species generation ability are developed and used for endoplasmic reticulum stress-mediated photodynamic therapy of tumors.     

Pheophytin Derived Near‐Infrared‐Light Responsive Carbon Dot Assembly as a New Phototheranotic Agent for Bioimaging and Photodynamic Therapy

Carbon dots (CDs), a kind of phototheranostic agent with the capability of simultaneous bioimaging and phototherapy [i.e., photodynamic therapy (PDT) or photothermal therapy (PTT)], have received considerable attention because of their remarkable properties, including flexibility for surface modification, high biocompatibility, low toxicity and photo‐induced activity for malignant tumor cells. Among numerous carbon sources, it has been found that natural biomass are good candidates for the preparation of CD phototheranostic agents. In this study, pheophytin, a type of Mg‐free chlorophyll derivative and also a natural product with low toxicity, was used as a raw carbon source for the synthesis of CDs by using a microwave method. The obtained hydrophobic CDs exhibited a maximum near‐infrared (NIR) emission peak at approximately 680 nm, and high singlet oxygen (¹O₂) generation with a quantum yield of 0.62. The self‐assembled CDs from the as‐prepared CDs with DSPE‐mPEG2000 retained efficient ¹O₂ generation. The obtained carbon dot assembly was not only an efficient fluorescence (FL) imaging agent but also a smart PDT agent. Our studies indicated that the obtained hydrophilic CD assembly holds great potential as a new phototheranostic agent for cancer therapy. This work provides a new route for synthesis of CDs and proposes a readily available candidate for tumor treatment.     

Biocompatible Polymer-Modified Nanoplatform for Ferroptosis-Enhanced Combination Cancer Therapy

Ferroptosis is a novel type of iron-dependent non-apoptotic pathway that regulates cell death and shows unique mechanisms including causing lipid peroxide accumulation, sensitizing drug-resistant cancers, priming immunity by immunogenic cell death, and cooperatively acting with other anticancer modalities for eradicating aggressive malignancies and tumor relapse. Recently, there has been a great deal of effort to design and develop anticancer biocompatible polymeric nanoplatforms including polypeptide and PEGylated ones to achieve effective ferroptosis therapy (FT) and synergistic combination therapies including chemotherapy (CT), photodynamic therapy (PDT), sonodynamic therapy (SDT), photothermal therapy (PTT), gas therapy (GT) including nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S), and immunotherapy (IT). To be noted, the combo therapies such as FT-CT, FT-PTT, FT-GT, and FT-IT are attracting much efforts to fight against intractable and metastatic tumors as they can generate synergistic antitumor effects and immunogenic cell death (ICD) effects or modulate immunosuppressive tumor microenvironments to initiate strong antitumor immunity and memory effects. The polymeric Fenton nano-agents with good biosafety and high anticancer efficacy will provide a guarantee for their applications. In this review, various biocompatible polymer-modified nanoplatforms designed for FT and combo treatments are summarized for anticancer therapies and discussed for potential clinical transitions.     

Biomimetic Cascade Polymer Nanoreactors for Starvation and Photodynamic Cancer Therapy

The selective disruption of nutritional supplements and the metabolic routes of cancer cells offer a promising opportunity for more efficient cancer therapeutics. Herein, a biomimetic cascade polymer nanoreactor (GOx/CAT-NC) was fabricated by encapsulating glucose oxidase (GOx) and catalase (CAT) in a porphyrin polymer nanocapsule for combined starvation and photodynamic anticancer therapy. Internalized by cancer cells, the GOx/CAT-NCs facilitate microenvironmental oxidation by catalyzing endogenous H₂O₂ to form O₂, thereby accelerating intracellular glucose catabolism and enhancing cytotoxic singlet oxygen (¹O₂) production with infrared irradiation. The GOx/CAT-NCs have demonstrated synergistic advantages in long-term starvation therapy and powerful photodynamic therapy (PDT) in cancer treatment, which inhibits tumor cells at more than twice the rate of starvation therapy alone. The biomimetic polymer nanoreactor will further contribute to the advancement of complementary modes of spatiotemporal control of cancer therapy.     

Hitherto-Unexplored Photodynamic Therapy of Ag2S and Enhanced Regulation Based on Polydopamine In Vitro and Vivo

Given their superior penetration depths, photosensitizers with longer absorption wavelengths present broader application prospects in photodynamic therapy (PDT). Herein, Ag₂S quantum dots were discovered, for the first time, to be capable of killing tumor cells through the photodynamic route by near-infrared light irradiation, which means relatively less excitation of the probe compared with traditional photosensitizers absorbing short wavelengths. On modification with polydopamine (PDA), PDA-Ag₂S was obtained, which showed outstanding capacity for inducing reactive oxygen species (increased by 1.69 times). With the addition of PDA, Ag₂S had more opportunities to react with surrounding O₂, which was demonstrated by typical triplet electron spin resonance (ESR) analysis. Furthermore, the PDT effects of Ag₂S and PDA-Ag₂S achieved at longer wavelengths were almost identical to the effects produced at 660 nm, which was proved by studies in vitro. PDA-Ag₂S showed distinctly better therapeutic effects than Ag₂S in experiments in vivo, which further validated the enhanced regulatory effect of PDA. Altogether, a new photosensitizer with longer absorption wavelength was developed by using the hitherto-unexplored photodynamic function of Ag₂S quantum dots, which extended and enhanced the regulatory effect originating from PDA.     

A Mitochondrion-Localized Two-Photon Photosensitizer Generating Carbon Radicals Against Hypoxic Tumors

The efficacy of photodynamic therapy is typically reliant on the local concentration and diffusion of oxygen. Due to the hypoxic microenvironment found in solid tumors, oxygen-independent photosensitizers are in great demand for cancer therapy. We herein report an iridium(III) anthraquinone complex as a mitochondrion-localized carbon-radical initiator. Its emission is turned on under hypoxic conditions after reduction by reductase. Furthermore, its two-photon excitation properties (λ_ex=730 nm) are highly desirable for imaging. Upon irradiation, the reduced form of the complex generates carbon radicals, leading to a loss of mitochondrial membrane potential and cell death (IC₅₀^light=2.1 μm , IC₅₀^dark=58.2 μm , PI=27.7). The efficacy of the complex as a PDT agent was also demonstrated under hypoxic conditions in vivo. To the best of our knowledge, it is the first metal-complex-based theranostic agent which can generate carbon radicals for oxygen-independent two-photon photodynamic therapy.     

Tumor Microenvironment Stimuli-Responsive Fluorescence Imaging and Synergistic Cancer Therapy by Carbon-Dot–Cu2+ Nanoassemblies

A method is developed to fabricate tumor microenvironment (TME) stimuli-responsive nanoplatform for fluorescence (FL) imaging and synergistic cancer therapy via assembling photosensitizer (chlorine e6, Ce6) modified carbon dots (CDs-Ce6) and Cu²⁺. The as-obtained nanoassemblies (named Cu/CC nanoparticles, NPs) exhibit quenched FL and photosensitization due to the aggregation of CDs-Ce6. Their FL imaging and photodynamic therapy (PDT) functions are recovered efficiently once they entering tumor sites by the stimulation of TME. Introducing of Cu²⁺ not only provides extra chemodynamic therapy (CDT) function through reaction with hydrogen peroxide (H₂O₂), but also depletes GSH in tumors by a redox reaction, thus amplifying the intracellular oxidative stress and enhancing the efficacy of reactive oxygen species (ROS) based therapy. Cu/CC NPs can act as a FL imaging guided trimodal synergistic cancer treatment agent by photothermal therapy (PTT), PDT, and thermally amplified CDT.     

CO/light dual-activatable Ru(ii)-conjugated oligomer agent for lysosome-targeted multimodal cancer therapeutics

Stimuli-activatable and subcellular organelle-targeted agents with multimodal therapeutics are urgently desired for highly precise and effective cancer treatment. Herein, a CO/light dual-activatable Ru(ii)-oligo-(thiophene ethynylene) (Ru-OTE) for lysosome-targeted cancer therapy is reported. Ru-OTE is prepared via the coordination-driven self-assembly of a cationic conjugated oligomer (OTE-BN) ligand and a Ru(ii) center. Upon the dual-triggering of internal gaseous signaling molecular CO and external light, Ru-OTE undergoes ligand substitution and releases OTE-BN followed by dramatic fluorescence recovery, which could be used for monitoring drug delivery and imaging guided anticancer treatments. The released OTE-BN selectively accumulates in lysosomes, physically breaking their integrity. Then, the generated cytotoxic singlet oxygen (¹O₂) causes severe lysosome damage, thus leading to cancer cell death via photodynamic therapy (PDT). Meanwhile, the release of the Ru(ii) core also suppresses cancer cell growth as an anticancer metal drug. Its significant anticancer effect is realized via the multimodal therapeutics of physical disruption/PDT/chemotherapy. Importantly, Ru-OTE can be directly photo-activated using a two-photon laser (800 nm) for efficient drug release and near-infrared PDT. Furthermore, Ru-OTE with light irradiation inhibits tumor growth in an MDA-MB-231 breast tumor model with negligible side effects. This study demonstrates that the development of an activatable Ru(ii)-conjugated oligomer potential drug provides a new strategy for effective subcellular organelle-targeted multimodal cancer therapeutics.

The anticancer therapeutics of lysosome disruption/PDT/chemotherapy based on Ru-OTE complex was achieved, which provides a new strategy for developing multimodal and effective stimuli-activatable subcellular organelle-targeted cancer therapeutics.     

Co-delivery of enzymes and photosensitizers via metal-phenolic network capsules for enhanced photodynamic therapy

The intrinsic hypoxic tumor microenvironment and limited accumulation of photosensitizers（PSs） result in unsatisfied efficiency of photodynamic therapy（PDT）.To enhance the PDT efficiency against solid tumors,a functional oxygen self-supplying and PS-delivering nanosystem is fabricated via the combination of catalase（CAT）,chlorin e6（Ce6） and metal-phenolic network（MPN） capsule.It is demonstrated that the CAT encapsulated in the capsules（named CCM capsules） could catalyze the degradation of hydrog...     

Photo-catalytic Staphylococcus aureus inactivation and biofilm destruction with novel bis-tridentate iridium(III) photocatalyst

Bacterial infection is currently a serious challenge globally, causing death of thousands of human beings. New antimicrobial agents with novel mechanism of action are urgently needed. Transition metal complexes have shown great potentials in photodynamic and photocatalytic therapy. Herein, we take full advantage of metal photocatalyst and successfully developed a novel cyclometalated iridium(III) complex (Ir1) with higher biofilm damage efficiency than the clinical antibiotics. Ir1 synergistically generates reactive oxygen species and coenzyme photocatalytic activity with high efficiency under white light irradiation. Combined with these properties, Ir1 exhibited excellent photoinactivation of S. aureus and effectively damaged the biofilm. This work provides a new approach for the development of antibacterial photodynamic therapy.     

Light-dependent Oxygen Consumption in Bacteriochlorophyll-Serine-treated Melanoma Tumors: On-line Determination Using a Tissue-inserted Oxygen Microsensor

Successful application of anticancer therapy, and especially photodynamic therapy (PDT) mediated by type II (PDTII) processes, depends on the oxygen content within the tumor before, during and after treatment. The high consumption of oxygen during type II PDT imposes constraints on therapy strategies. Although rates of oxygen consumption and repletion during PDTII were suggested by theoretical studies, direct measurements have not been reported. Application of a novel oxygen sensor allowed continuous and direct in situ measurements (up to a depth of 8–9 mm from the tumor surface and for several hours) of temporal variations in the oxygen partial pressure (pO₂) during PDT. Highly pigmented M2R mouse melanoma tumors implanted in CD1 nude mice were treated with bacteriochlorophyll-serine (Bchl-Ser; a new photodynamic reagent) and were subjected to fractionated illumination (700 < λ. < 900 nm) at a fluence rate of 12 mW cm^-2. This illumination led to total oxygen depletion with an average consumption rate of 7.2 uAf(O₂) s^-1. Spontaneous reoxygenation (at an average rate of 2.5 µM(O₂)/s) was observed during the following dark period. These rates are in good agreement with theoretical considerations (Foster et al., Radiat. Res. 126, 296,1991 and Henning et al, Radiat. Res. 142, 221, 1995). The observed patterns of oxygen consumption and recovery during prolonged periods of light/dark cycles were interpreted in terms of vasculature damage and sensitizer clearance. The presented data support the previously suggested advantages of fractionated illumination for type II photodynamic processes.     

Synergistic Effects of Metals in a Promising RuII−PtII Assembly for a Combined Anticancer Approach: Theoretical Exploration of the Photophysical Properties

Ru^II?Pt^II complexes are a class of bioactive molecules of interest as anticancer agents that combine a light‐absorbing chromophore with a cisplatin‐like unit. The results of a DFT and TDDFT investigation of a Ru^II complex and its conjugate with a cis‐PtCl₂ moiety reveal that a synergistic effect of the metals makes the assembly a promising multitarget anticancer drug. Inspection of type I and type II photoreactions and spin–orbit coupling computations reveals that the cis‐PtCl₂ moiety improves the photophysical properties of the Ru^II chromophore, ensuring efficient singlet oxygen generation and making the assembly suitable for photodynamic therapy. At the same time, the Ru^II chromophore promotes a new alternative activation mechanism of the Pt^II ligand via a triplet metal‐to‐ligand charge transfer (³M LCT) state, before reaching the biological target. The importance of the supramolecular architecture is accurately derived, opening interesting new perspectives on the use of bimetallic Ru^II?Pt^II assemblies in a combined anticancer approach.     

Nucleus‐Targeted Organoiridium–Albumin Conjugate for Photodynamic Cancer Therapy

An organoiridium–albumin bioconjugate ( Ir1‐HSA ) was synthesized by reaction of a pendant maleimide ligand with human serum albumin. The phosphorescence of Ir1‐HSA was enhanced significantly compared to parent complex Ir1 . The long phosphorescence lifetime and high ¹O₂ quantum yield of Ir1‐HSA are highly favorable properties for photodynamic therapy. Ir1‐HSA mainly accumulated in the nucleus of living cancer cells and showed remarkable photocytotoxicity against a range of cancer cell lines and tumor spheroids (light IC₅₀; 0.8–5 μm , photo‐cytotoxicity index PI=40–60), while remaining non‐toxic to normal cells and normal cell spheroids, even after photo‐irradiation. This nucleus‐targeting organoiridium‐albumin is a strong candidate photosensitizer for anticancer photodynamic therapy.     

Type I Photosensitizer Targeting G-Quadruplex RNA Elicits Augmented Immunity for Cancer Ablation

Type I photodynamic therapy (PDT) represents a promising treatment modality for tumors with intrinsic hypoxia. However, type I photosensitizers (PSs), especially ones with near infrared (NIR) absorption, are limited and their efficacy needs improvement via new targeting tactics. We develop a NIR type I PS by engineering acridinium derived donor-π-acceptor systems. The PS exhibits an exclusive type I PDT mechanism due to effective intersystem crossing and disfavored energy transfer to O₂, and shows selective binding to G-quadruplexes (G4s) via hydrogen bonds identified by a molecular docking study. Moreover, it enables fluorogenic detection of G4s and efficient O₂⋅⁻ production in hypoxic conditions, leading to immunogenic cell death and substantial variations of gene expression in RNA sequencing. Our strategy demonstrates augmented antitumor immunity for effective ablation of immunogenic cold tumor, highlighting its potential of RNA-targeted type I PDT in precision cancer therapy.     

Highly luminescence manganese doped carbon dots

Heteroatom doped carbon dots(CDs) with distinct merits are of great attractions in various fields such as solar cells, catalysis, trace element detection and photothermal therapy. In this work, we successfully synthesized blue-fluorescence and photostability manganese-doped carbon dots(Mn-CDs) with a quantum yield up to 7.5%, which was prepared by a facile one-step hydrothermal method with sodium citrate and manganese chloride. The Mn-CDs is the high mono-dispersity, uniform spherical nanoparticles. The Mn element plays a critical role in achieving a high quantum yield in synthesis of carbon dots, which was confirmed by the structure analysis using XPS and FTIR. Spectroscopic investigations proved that the decent PLQY and luminescence properties of Mn-CDs are due to the heteroatom doped, oxidized carbon-based surface passivation. In addition, the Mn-CDs are demonstrated as promising fluorescent sensors for iron ions with a linear range of 0–500 mmol/L and a detection limit of2.1 nmol/L(turn-off), indicating their great potential as a fluorescent probe for chemical sensing.     

Oxygen-supplied mesoporous carbon nanoparticles for enhanced photothermal/photodynamic synergetic therapy against antibiotic-resistant bacterial infections

Pandemic and epidemic spread of antibiotic-resistant bacterial infections would result in a huge number of fatalities globally. To combat antibiotic-resistant pathogens, new antimicrobial strategies should be explored and developed to confront bacteria without acquiring or increasing drug-resistance. Here, oxygen saturated perfluorohexane (PFH)-loaded mesoporous carbon nanoparticles (CIL@ICG/PFH@O₂) with photothermal therapy (PTT) and enhanced photodynamic therapy (PDT) utility are developed for antibacterial applications. Ionic liquid groups are grafted onto the surface of mesoporous carbon nanoparticles, followed by anion-exchange with the anionic photosensitizer indocyanine green (ICG) and loading oxygen saturated PFH to prepare CIL@ICG/PFH@O₂. These CIL@ICG/PFH@O₂ nanoparticles exhibit effective PTT and enhanced PDT properties simultaneously upon 808 nm light irradiation. In vitro assays demonstrate that CIL@ICG/PFH@O₂ shows a synergistic antibacterial action against antibiotic-resistant pathogens (methicillin-resistant Staphylococcus aureus and kanamycin-resistant Escherichia coli). Moreover, CIL@ICG/PFH@O₂ could effectively kill drug-resistant bacteria in vivo to relieve inflammation and eliminate methicillin-resistant Staphylococcus aureus-wound infection under NIR irradiation, and the released oxygen can increase collagen deposition, epithelial tissue formation and blood vessel formation to promote wound healing while enhancing the PDT effect. This study proposes a platform with enhanced PTT/PDT effects for effective, controlled, and precise treatment of topical drug-resistant bacterial infections.

We report oxygen saturated perfluorohexane (PFH)-loaded mesoporous carbon nanoparticles (CIL@ICG/PFH@O₂) with photothermal therapy (PTT) and enhanced photodynamic therapy (PDT) utility for antibacterial applications.     

Studies on the Photodynamic Mechanism of Tetrapyrrole Compounds by Laser Flash Photolysis

Photodynamic therapy (PDT) is a promising new treatment technique which can potentially destroy unwanted and malignant tissues, such as those of cancer. The photodynamic mechanisms of three tetrapyrrole compounds: Mg‐purpurin‐18, tetra(meso‐chlorophenyl)porphyrin (m‐TCPP) and 2,7,12,18‐tetramethyl‐3,8‐di[(1‐isobutoxyl)‐ ethyl]‐13,17‐bis[3‐di(2‐chloroethyl)aminopropyl]porphyrin (TDBP) in acetonitrile were investigated by 355 nm laser flash photolysis. It was found that after laser flash photolysis (LFP), the excited states of TDBP and Mg‐purpurin‐18 could react with O₂ and ¹O₂ was produced, which proved that TDBP and Mg‐purpurin‐18 took effects through type II mechanism in PDT. This suggested that TDBP and Mg‐purpurin‐18 should be suitable for target tissues containing enough O₂. Mg‐purpurin‐18 has two extra absorptions at 550 and 700 nm, which means it has broad choices of laser wavelength in PDT. It was also found that m‐TCPP could be photoionized when excited with 355 nm laser under N₂‐saturated condition. It could also react with O₂ to produce reactive oxygen species such as superoxide and the peroxide anions, but not ¹O₂. These were known as the Type I mechanism. So m‐TCPP could be used even at low oxygen concentration or more polar environments with good behavior in PDT. From the above studies on the three different tetrapyrrole compounds it could be concluded that the structure of porphin ring takes a main role in PDT. And there was important impact on the photodynamic mechanism for the functional group directly connecting with porphin ring, while little influence for the functional group indirectly connecting with porphin ring. These will be of great value in the discovery of new PDT drugs.     

SENSITIVITY OF ACTIVATED MURINE PERITONEAL MACROPHAGES TO PHOTODYNAMIC KILLING WITH BENZOPORPHYRIN DERIVATIVE

Abstract— This study compared the ability of highly purified resting and activated DBA/2 mouse peritoneal macrophages to survive treatment with the photosensitizer benzoporphyrin derivative (BPD, verteporfin) and light. Culture of macrophages with recombinant murine interferon-γ (rIFN-γ, 100 U/mL) for 72 h imparted a phenotypic and functional activation by dramatically increasing cell surface expression of major histocompatibility complex Class II (Ia) molecules and the formation of nitric oxide. The rIFN-γ-activated macrophages were significantly (P < 0.05) more sensitive (lethal dose to cause a 50% reduction in cell survival, LD₅₀= 14.4 ± 1.1 ng/mL) to photodynamic killing with BPD and light (10 J/cm²) than cells (LD₅₀= 18.2 ± 2.0 ng/mL) cultured in medium alone. In contrast, macrophages treated with different concentrations of bacterial lipopolysaccharide (LPS) were as resistant or more resistant to photodynamic killing than cells cultured in medium alone. No cytotoxic effect of BPD was detected in cultures containing the drug but protected from light. Comparable amounts of BPD were taken up in vitro by unactivated and rIFN-γ-activated macrophages, as detected by flow cytometric analysis. However, cells cultured with LPS (10 μg/mL) took up more BPD than macrophages cultured in medium alone or with rIFN-γ. The DBA/2 P815 mastocytoma cells took up greater amounts of the drug and were subsequently more vulnerable to treatment with BPD and light (LD₅₀= 6.9 ng/mL) than macrophages cultured under any condition. The explanation for the increased vulnerability of rIFN-γ-activated macrophages and the greater resistance of LPS-activated macrophages, relative to medium-cultured macrophages, to photodynamic killing with BPD is uncertain. However, the increased susceptibility of macrophages, activated with the immunomodulatory cytokine IFN-γ, to treatment with BPD and light might indicate how photodynamic therapy could interfere with the development of experimental autoimmune disease, conditions in which activated macrophages are known to be involved.     

Electrochemical Luminescent DNA Sensor Based on Polymerase-assisted Signal Amplification

A novel polymerase-based electrochemical luminescence (ECL) DNA sensor was constructed for messenger RNA (mRNA) detection by cyclic chain displacement polymerization, assisted by target mRNA cycle and quantum dots signal amplification. Firstly, the mercapto-modified capture-type probe DNA (CP) was immobilized on the surface of a magneto-controlled glassy carbon electrode via Au-S bond. After the addition of target mRNA, CP was opened and hybridized with mRNA to form double-stranded DNA (dsDNA). Then polymerase, primer chain (DNA1) and bases were added, which made the primer chain extend to replace the target mRNA. After one amplification cycle, the mRNA chain could open another hairpin in order to carry out next cycle of amplification. Finally, the ECL detection was carried out by adding DNA2 labeled thioglycolic acid-CdTe quantum dots. The amplification of the target mRNA by the addition of polymerase and the signal combined with the quantum dots label greatly improved the sensitivity of the sensor. The results showed that corresponding ECL signal had a good linear relationship with logarithm of target mRNA concentration in the range of 1 × 10^?15 to 1 × 10^?11 M, with a detection limit of 3.4 × 10^?16 M (S/N = 3). Under the optimal conditions, the recoveries of mRNA spiked in human serum sample were from 97.2 % to 102.3 %. This sensor exhibited good selectivity, stability and reproducibility.