Photosensitizer-doped conjugated polymer nanoparticles with high cross-sections for one- and two-photon excitation

Self-Reporting Conjugated Polymer Nanoparticles for Superoxide Generation and Detection

Conjugated polymer nanoparticles (CPNs or Pdots) have become increasingly popular fluorophores for multimodal applications that combine imaging with phototherapeutic effects. Reports of CPNs in photodynamic therapy applications typically focus on their ability to generate singlet oxygen. Alternatively, CPN excited states can interact with oxygen to form superoxide radical anion and a CPN-based hole polaron, both of which can have deleterious effects on fluorescence properties. Here, we demonstrate that CPNs prepared from the common conjugated polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1',3}-thiadiazole)] (PFBT, also known as F8BT) generate superoxide upon irradiation. We use the same CPNs to detect superoxide by doping them with a superoxide-responsive hydrocyanine dye developed by Murthy and co-workers. Superoxide induces off-to-on fluorescence switching by converting quenching hydrocyanine dyes to fluorescent cyanine dyes that act as fluorescence resonance energy transfer (FRET) acceptors for PFBT chromophores. Amplified FRET from the multichromophoric CPNs yields fluorescence signal intensities that are nearly 50 times greater than when the dye is excited directly or over 100 times greater when signal readout is from the CPN channel. The dye loading level governs the maximum amount of superoxide that induces a change in fluorescence properties and also influences the rate of superoxide generation by furnishing competitive excited state deactivation pathways. These results suggest that CPNs can be used to deliver superoxide in applications in which it is desirable and provide a caution for fluorescence-based CPN applications in which superoxide can damage fluorophores.

Nanotechnology for brain tumor imaging and therapy based on π-conjugated materials: state-of-the-art advances and prospects

In contemporary biomedical research, the development of nanotechnology has brought forth numerous possibilities for brain tumor imaging and therapy. Among these, π-conjugated materials have garnered significant attention as a special class of nanomaterials in brain tumor-related studies. With their excellent optical and electronic properties, π-conjugated materials can be tailored in structure and nature to facilitate applications in multimodal imaging, nano-drug delivery, photothermal therapy, and other related fields. This review focuses on presenting the cutting-edge advances and application prospects of π-conjugated materials in brain tumor imaging and therapeutic nanotechnology.

Revolutionizing cancer treatment: nanotechnology-enabled photodynamic therapy and immunotherapy with advanced photosensitizers

Nanotechnology-enhanced photodynamic therapy (PDT) and immunotherapy are emerging as exciting cancer therapeutic methods with significant potential for improving patient outcomes. By combining these approaches, synergistic effects have been observed in preclinical studies, resulting in enhanced immune responses to cancer and the capacity to conquer the immunosuppressive tumor microenvironment (TME). Despite challenges such as addressing treatment limitations and developing personalized cancer treatment strategies, the integration of nanotechnology-enabled PDT and immunotherapy, along with advanced photosensitizers (PSs), represents an exciting new avenue in cancer treatment. Continued research, development, and collaboration among researchers, clinicians, and regulatory agencies are crucial for further advancements and the successful implementation of these promising therapies, ultimately benefiting cancer patients worldwide.

Amplification of Cerenkov luminescence using semiconducting polymers for cancer theranostics

The therapeutic efficacy of photodynamic therapy is limited by the ability of light to penetrate tissues. Due to this limitation, Cerenkov luminescence (CL) from radionuclides has recently been proposed as an alternative light source in a strategy referred to as Cerenkov radiation induced therapy (CRIT). Semiconducting polymer nanoparticles (SPNs) have ideal optical properties, such as large absorption cross-sections and broad absorbance, which can be utilized to harness the relatively weak CL produced by radionuclides. SPNs can be doped with photosensitizers and have nearly 100% energy transfer efficiency by multiple energy transfer mechanisms. Herein, we investigated an optimized photosensitizer doped SPN as a nanosystem to harness and amplify CL for cancer theranostics. We found that semiconducting polymers significantly amplified CL energy transfer efficiency. Bimodal PET and optical imaging studies showed high tumor uptake and retention of the optimized SPNs when administered intravenously or intratumorally. Lastly, we found that photosensitizer doped SPNs have excellent potential as a cancer theranostics nanosystem in an in vivo tumor therapy study. Our study shows that SPNs are ideally suited to harness and amplify CL for cancer theranostics, which may provide a significant advancement for CRIT that are unabated by tissue penetration limits.

Sweet light o' mine: Photothermal and photodynamic inactivation of tenacious pathogens using conjugated polymers

Each year a rising number of infections can not be successfully treated owing to the increasing pandemic of antibiotic resistant pathogens. The global shortage of innovative antibiotics fuels the emergence and spread of drug resistant microbes. Basic research, development, and applications of alternative therapies are urgently needed. Since the 90´s, light-mediated therapies have promised to be the next frontier combating multidrug-resistance microbes. These platforms have demonstrated to be a reliable, rapid, and efficient alternative to eliminate tenacious pathogens while avoiding the emergence of resistance mechanisms. Among the materials showing antimicrobial activity triggered by light, conjugated polymers (CPs) have risen as the most promising option to tackle this complex situation. These materials present outstanding characteristics such as high absorption coefficients, great photostability, easy processability, low cytotoxicity, among others, turning them into a powerful class of photosensitizer (PS)/photothermal agent (PTA) materials. Herein, we summarize and discuss the advances in the field of CPs with applications in photodynamic inactivation and photothermal therapy towards bacteria elimination. Additionally, a section of current challenges and needs in terms of well-defined benchmark experiments and conditions to evaluate the efficiency of phototherapies is presented.

Facile and wide-range size tuning of conjugated polymer nanoparticles for biomedical applications as a fluorescent probe

Conjugated polymer nanoparticles (Pdots) are expected to be novel bioimaging and sensing probes. However, the size tuning required to control biological interactions has not been well established. Herein, we achieved a size-tunable synthesis of Pdots ranging from 30 to 200 nm by controlling the hydrolysis rate of the stabilising agent and evaluated their cellular imaging properties.

Dual-Targeting into the Mitochondria of Cancer Cells for Ratiometric Investigation of the Dynamic Fluctuation of Sulfur Dioxide and Formaldehyde with Two-Photon Integrated Semiconducting Polymer Dots

Mitochondrial sulfur dioxide (SO₂) and formaldehyde (FA) in cancer cells serve as important signal molecules in mediating multiple physiological and pathological activities. Accurate monitoring of the dynamic fluctuation of SO₂ and FA in the mitochondria of cancer cells is important for insight into their relationships and functions in cancer, understanding cancer mechanism, and the role of mitochondrial homeostasis in cancer invasion and metastasis. Herein, a novel integrated two-photon semiconducting polymer dot (BF@Pdots) with dual-targeting (cancer cells and mitochondrial) and dual-emission in green and red regions, which is rationally designed through a four-step engineering strategy by using two newly synthesized functionalized polymers PFNA and FD-PSMA as precursors, has been developed for accurate tracking of the dynamic variation of SO₂ and FA in the mitochondria of cancer cells. The sensing mechanism is on the basis of the fluorescence resonance energy transfer (FRET) process in BF@Pdots tuned by the reversible Michael addition reaction between the sensing-groups and SO₂ (or FA). The integrated BF@Pdots nanoprobes display excellent performances in the accurate detection of the dynamic fluctuation of SO₂ and FA such as precise positioning in the mitochondria of cancer cells, self-calibrating ratiometric, two-photon emission with long wavelength excitation, and fast reversible response. The BF@Pdots nanoprobes are also applied to the ratiometric detection of the dynamic fluctuation of exogenous and endogenous SO₂ and FA in the mitochondria of cancer cells for the first time with satisfactory results. Taken together, this work will provide an attractive way to develop versatile integrated Pdots-based fluorescent probes through flexible molecular engineering for applications in accurate imaging of biomolecules in living systems.

General Strategy to Achieve Color-Tunable Ratiometric Two-Photon Integrated Single Semiconducting Polymer Dot for Imaging Hypochlorous Acid

It is highly desired and challenging to construct integrated (all-in-one) single semiconducting-polymer-derived dot (Pdot) without any postmodification but with desired performances for bioapplications. In this work, eight hypochlorous acid (HClO)-sensitive integrated polymers and corresponding polymer-derived Pdots are designed through molecular engineering to comparatively study their analytical performances for detecting and imaging HClO. The optimized polymers-derived Pdots are obtained through regulating donor-acceptor structure, the content of HClO-sensitive units, and the position of HClO-sensitive units in the polymer backbone. The designed Pdots display distinguished characteristics including multicolours with blue, yellow, and red three primary fluorescence colors, determination mode from single-channel to dual-channel (ratiometric) quantification, ultrafast response, low detection limit, and high selectivity for ClO^- sensing based on specific oxidation of ClO^--sensitive unit 10-methylphenothiazine (PT) accompanied by altering the intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET) processes in Pdots. The prepared integrated Pdots are also applied for two-photon ClO^- imaging in HeLa cells and one- and two-photon ClO^- imaging produced in acute inflammation in mice with satisfactory results. We believe that the present study not only provides excellent integrated fluorescent nanoprobes for ClO^- monitoring in living systems but also extends a general strategy for designing integrated semiconducting polymers and Pdots with desired performances for biological applications.

New Approach in the Application of Conjugated Polymers: The Light-Activated Source of Versatile Singlet Oxygen Molecule

For many years, the research on conjugated polymers (CPs) has been mainly focused on their application in organic electronics. Recent works, however, show that due to the unique optical and photophysical properties of CPs, such as high absorption in UV–Vis or even near-infrared (NIR) region and efficient intra-/intermolecular energy transfer, which can be relatively easily optimized, CPs can be considered as an effective light-activated source of versatile and highly reactive singlet oxygen for medical or catalytic use. The aim of this short review is to present the novel possibilities that lie dormant in those exceptional polymers with the extended system of π-conjugated bonds.

Engineering fluorescent semiconducting polymer nanoparticles for biological applications and beyond

We summarize the recent advances in engineering approaches to obtain functionalized semiconducting polymer nanoparticles (SPNs) for biological applications. The challenges and outlook of fabricating functionalized SPNs are also provided.

Multifunctional system for combined chemodynamic–photodynamic therapy employing the endothelin axis based on conjugated polymer nanoparticles

Most nanomedicines that attack tumors by Reactive Oxygen Species (ROS) based on lipid peroxidation mechanisms require external activation to work.

Stimulus-responsive nanocarriers for targeted drug delivery

Cancer is a multifactorial disease that involves unique tumor microenvironment (TEM) and abnormal organs with complex structures.

Photodynamic Therapy and Immunity: An Update

Dr. Thomas Dougherty and his Oncology Foundation of Buffalo were the first to support my (S.O.G.) research into the effects of photodynamic therapy (PDT) on the host immune system. The small grant I was awarded in 2002 launched my career as an independent researcher; at the time, there were few studies on the importance of the immune response on the efficacy of PDT and no studies demonstrating the ability of PDT to enhance antitumor immunity. Over the last decades, the interest in PDT as an enhancer of antitumor immunity and our understanding of the mechanisms by which PDT enhances antitumor immunity have dramatically increased. In this review article, we look back on the studies that laid the foundation for our understanding and provide an update on current advances and therapies that take advantage of PDT enhancement of immunity.

Ultrastable and Biofunctionalizable Conjugated Polymer Nanoparticles with Encapsulated Iron for Ferroptosis Assisted Chemodynamic Therapy

We report the development of novel tumor-targeted conjugated polymer nanoparticles (CPNPs) carrying iron for chemodynamic therapy (CDT). Tumor cell killing proceeds through ferroptosis, a reactive oxygen species (ROS) mechanism that is not dependent on external activation by, for example, light, as is the case in photodynamic therapy (PDT). The ferroptosis mechanism is also not heavily reliant on oxygen availability and is, therefore, promising for the treatment of hypoxic tumors. In this work, we apply this development to the case study of melanoma, a difficult to treat cancer in advanced stages due to resistance to chemotherapy. The iron-carrying CPNPs reported here are targeted to endothelin-B receptors (EDNRB) through endothelin-3 surface moieties (EDN3-CPNPs). Our results show excellent targeting to tumor cells that overexpress EDNRB, specifically for melanoma and bladder tumor cells. In these cases, efficient cell killing, over 80% at higher doses, was found. Conversely, tumor cells not targeted by the EDN3-CPNPs show little effects of CDT, with tumor cell death under 20% in most cases. The outcomes of our work demonstrate that EDN3-CPNPs enable ferroptosis-assisted CDT and present a new therapeutic avenue for tumor treatment.

Porphyrin-based bridged silsesquioxane nanoparticles for targeted two-photon photodynamic therapy of zebrafish xenografted with human tumor

BACKGROUND

Bridged silsesquioxane nanoparticles (BSNs) recently described represent a new class of nanoparticles exhibiting versatile applications and particularly a strong potential for nanomedicine.

AIMS

In this work, we describe the synthesis of BSNs from an octasilylated functional porphyrin precursor (PORBSNs) efficiently obtained through a click reaction. These innovative and very small-sized nanoparticles were functionalized with PEG and mannose (PORBSNs-mannose) in order to target breast tumors in vivo.

METHODS AND RESULTS

The structure of these nanoparticles is constituted of porphyrins J aggregates that allow two-photon spatiotemporal excitation of the nanoparticles. The therapeutic potential of such photoactivable nanoparticles was first studied in vitro, in human breast cancer cells in culture and then in vivo on zebrafish embryos bearing human tumors. These animal models were intravenously injected with 5 nL of a solution containing PORBSNs-mannose. An hour and half after the injection of photoactivable and targeted nanoparticles, the tumor areas were excited for few seconds with a two-photon beam induced focused laser. We observed strong tumor size decrease, with the involvement of apoptosis pathway activation.

CONCLUSION

We demonstrated the high targeting, imaging, and therapeutic potential of PORBSNs-mannose injected in the blood stream of zebrafish xenografted with human tumors.

Use of Exogenous and Endogenous Photomediators as Efficient ROS Modulation Tools: Results and Perspectives for Therapeutic Purposes

Reactive Oxygen Species (ROS) play an essential dual role in living systems. Healthy levels of ROS modulate several signaling pathways, but at the same time, when they exceed normal physiological amounts, they work in the opposite direction, playing pivotal functions in the pathophysiology of multiple severe medical conditions (i.e., cancer, diabetes, neurodegenerative and cardiovascular diseases, and aging). Therefore, the research for methods to detect their levels via light-sensitive fluorescent probes has been extensively studied over the years. However, this is not the only link between light and ROS. In fact, the modulation of ROS mediated by light has been exploited already for a long time. In this review, we report the state of the art, as well as recent developments, in the field of photostimulation of oxidative stress, from photobiomodulation (PBM) mediated by naturally expressed light-sensitive proteins to the most recent optogenetic approaches, and finally, we describe the main methods of exogenous stimulation, in particular highlighting the new insights based on optically driven ROS modulation mediated by polymeric materials.

The π-π stacking-guided supramolecular self-assembly of nanomedicine for effective delivery of antineoplastic therapies

In traditional nano drug-delivery systems, the complex chemical bonds between drug and carrier often complicate the preparation process and are less prone to rupture upon entry into the target, which is detrimental to the timely release of the drug. The π-π stacking provides us with a promising alternative as it is a weak interaction between the aromatic rings. Since most antitumor drugs are hydrophobic molecules with complex aromatic π-π-conjugated structures, the construction of self-assembly based on π-π stacking between drugs and carriers has the advantage of improving the stability and drug loading capacity as well as the improvement of hydrophilicity and biosafety. This article introduces the recent advances in π-π stacking-guided nano self-assembly for antineoplastic delivery.

Metallated porphyrin-doped conjugated polymer nanoparticles for efficient photodynamic therapy of brain and colorectal tumor cells

Aim: Assess biocompatibility, uptake and photodynamic therapy (PDT) mechanism of metallated porphyrin doped conjugated polymer nanoparticles (CPNs) in human brain and colorectal tumor cells and macrophages. Materials & methods: CPNs were developed employing 9,9-dioctylfluorene-alt-benzothiadiazole, an amphiphilic polymer (PS-PEG-COOH),  and platinum octaethylporphyrin. T98G, SW480 and RAW 264.7 cell lines were exposed to CPNs to assess uptake and intracellular localization. Additionally, a PDT protocol using CPNs was employed for the in vitro killing of cancer and macrophage cell lines. Results & conclusion: CPNs were well incorporated into glioblastoma and macrophage cells with localization in lysosomes. SW480 cells were less efficient incorporating CPNs with localization in the plasma membrane. In all cell lines PDT treatment was efficient inducing oxidative stress that triggered apoptosis.

Therapeutic Considerations and Conjugated Polymer-Based Photosensitizers for Photodynamic Therapy

Conjugated polymers have recently attracted a great deal of attention for applications in photodynamic therapy (PDT) because of their light-harvesting capability, efficient energy transfer, and singlet oxygen generation properties. This review describes recent advances in PDT development, including therapeutic mechanisms of PDT in cancer treatments, light excitation methods, and especially recent advances of conjugated polyelectrolytes and conjugated polymer nanoparticles as photosensitizers. The future direction on PDT and further development of conjugated polymer photosensitizers are discussed. The aim of this review is to stimulate innovative ideas to synthesize a new generation of conjugated polymer photosensitizers and promote their translation to clinical applications of PDT.

Ratiometric Singlet Oxygen Detection in Water Using Acene-Doped Conjugated Polymer Nanoparticles

Although fluorescent probes for the detection of singlet oxygen (1O2) have been an active area of research, most such probes rely upon change in intensity of a single band. Herein, we report a FRET-based, 1O2-sensitive aqueous suspension of conjugated polymer nanoparticles (CPNs) comprising the energy-donating host polymer poly[{9,9-dioctyl-2,7-divinylene-fluorenylene}-alt-co-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}] doped with an energy acceptor, the 1O2-sensitive thienoacene 5,12-bis(4-methoxyphenyl)-2-butyltetraceno[2,3-b]thiophene. Using a phthalocyanine-based sensitizer, IRDye 700DX, our probe shows a rapid, ratiometric response to photosensitized 1O2 in water in both cuvettes and 96-well plates that compares favorably to the commercial 1O2-sensitive dye, singlet oxygen sensor green. The response to irradiation of even nanomolar concentrations of photosensitizer demonstrates the sensitivity of our ratiometric probe.

Light-Induced Translocation of a Conjugated Polyelectrolyte in Cells: From Fluorescent Probe to Anticancer Agent

Dual-functional probes, which not only enable visualization of diseased cells but also induce therapeutic cellular responses, are essential to biological studies. In the current work, a conjugated polyelectrolyte, PPET3-N2, was designed and synthesized as a dual-functional probe. The poly(phenylene ethynylene) terthiophene polymer backbone contributes to the polymer's light-harvesting property to ensure the strong fluorescence as well as photosensitization, whereas quantanary ammonium side chains interact with target organelle for localization. As a fluorescent probe, PPET3-N2 was endocytosed to lysosomes through clathrin-mediated endocytosis (CME) and macropinocytosis (MPC) pathways. Colocalization of the probe with commercial fluorescent lysosome labels confirmed that this probe localized on lysosomes with high specificity and photostability. Real-time monitoring of autolysosome formation in autophagic cells was also demonstrated, providing a viable platform for cell-based screening of autophagy inhibitors. Finally, as a photosensitizer, PPET3-N2 can efficiently generate singlet oxygen in living cells upon irradiation of white light, leading to the destruction of lysosome membrane and release of ROS and lysosomal enzymes in cytoplasma, causing cell death.

Photo-Cross-Linkable Polymer Dots with Stable Sensitizer Loading and Amplified Singlet Oxygen Generation for Photodynamic Therapy

Photodynamic therapy (PDT) is a promising treatment modality for clinical cancer therapy. However, the therapeutic effect of PDT is strongly dependent on the property of photosensitizer. Here, we developed photo-cross-linkable semiconductor polymer dots doped with photosensitizer Chlorin e6 (Ce6) to construct a nanoparticle platform for photodynamic therapy. Photoreactive oxetane groups were attached to the side chains of the semiconductor polymer. After photo-cross-linking reaction, the Ce6-doped Pdots formed an interpenetrated structure to prevent Ce6 leaching out from the Pdot matrix. Spectroscopic characterizations revealed an efficient energy transfer from the polymer to Ce6 molecules, resulting in amplified generation of singlet oxygen. We evaluated the cellular uptake, cytotoxicity, and photodynamic effect of the Pdots in gastric adenocarcinoma cells. In vitro photodynamic experiments indicated that the Ce6-doped Pdots (∼10 μg/mL) effectively killed the cancer cells under low dose of light irradiation (∼60 J/cm²). Furthermore, in vivo photodynamic experiments were carried out in tumor-bearing nude mice, which indicated that the Pdot photosensitizer apparently suppressed the growth of solid tumors. Our results demonstrate that the photo-cross-linkable Pdots doped with photosensitizer are promising for photodynamic cancer treatment.

Targeting Antitumor Immune Response for Enhancing the Efficacy of Photodynamic Therapy of Cancer: Recent Advances and Future Perspectives

Photodynamic therapy (PDT) is a minimally invasive therapeutic strategy for cancer treatment, which can destroy local tumor cells and induce systemic antitumor immune response, whereas, focusing on improving direct cytotoxicity to tumor cells treated by PDT, there is growing interest in developing approaches to further explore the immune stimulatory properties of PDT. In this review we summarize the current knowledge of the innate and adaptive immune responses induced by PDT against tumors, providing evidence showing PDT facilitated-antitumor immunity. Various immunotherapeutic approaches on different cells are reviewed for their effectiveness in improving the treatment efficiency in concert with PDT. Future perspectives are discussed for further enhancing PDT efficiency via intracellular targetable drug delivery as well as optimized experimental model development associated with the study of antitumor immune response.

Amplified Singlet Oxygen Generation in Semiconductor Polymer Dots for Photodynamic Cancer Therapy

This paper described the energy-transfer amplified singlet oxygen generation in semiconductor polymer dots (Pdots) for in vitro and in vivo photodynamic therapy. Hydrophobic photosensitizer tetraphenylporphyrin was facilely doped in the nanoparticles consisting of densely packed semiconductor polymers. Optical characterizations indicated that the fluorescence of Pdots was completely quenched by the photosensitizer, yielding an energy transfer efficiency of nearly 100% and singlet-oxygen generation quantum yield of ∼50%. We evaluated the cellular uptake, dark toxicity, and photodynamic therapy of the Pdot photosensizer in human gastric adenocarcinoma cells. The in vitro studies indicated that cancer cells were efficiently destroyed at very low dose of the Pdots such as 1 μg/mL by using the light dose of 90 J/cm(2), which is considerably less than that in clinical practice. The antitumor effect of the Pdots was further evaluated in vivo with human gastric adenocarcinoma xenografts in Balb/c nude mice, which show that the xenograft tumors were significantly inhibited and eradicated in some cases. Our results indicate the energy transfer amplified Pdot platforms have great therapeutic potential for treating malignant cancers.

Decoration of porphyrin with tetraphenylethene: converting a fluorophore with aggregation-caused quenching to aggregation-induced emission enhancement

A new porphyrin derivative with aggregation-induced emission enhancement was synthesized via tetraphenylethene decoration and it demonstrates bright imaging ability in vitro.

Two-photon excitation nanoparticles for photodynamic therapy

Integration of the two-photon excitation (TPE) technique and nanomaterials to construct TPE nanoparticle-based photosensitizers for PDT is summarized and reviewed.

Photon Harvesting in Sunscreen-Based Functional Nanoparticles

The ultraviolet light component in the solar spectrum is known to cause several harmful effects, such as allergy, skin ageing, and skin cancer. Thus, current research attention has been paid to the design and fundamental understanding of sunscreen-based materials. One of the most abundantly used sunscreen molecules is Avobenzone (AB), which exhibits two tautomers. Here, we highlight the preparation of spherically shaped nanoparticles from the sunscreen molecule AB as well as from sunscreen-molecule-encapsulated polymer nanoparticles in aqueous media and study their fundamental photophysical properties by steady-state and time-resolved spectroscopy. Steady-state studies confirm that the AB molecule is in the keto and enol forms in tetrahydrofuran, whereas the enol form is stable in the case of both AB nanoparticles and AB-encapsulated poly(methyl methacrylate) (PMMA) nanoparticles. Thus, the keto-enol transformation of AB molecules is restricted to a nanoenvironment. An enhancement of photostability in both the nanoparticle and PMMA-encapsulated forms under UV light irradiation is observed. The efficient excited energy transfer (60 %) from AB to porphyrin molecules opens up further prospects in potential applications as light-harvesting systems.

Signal enhancement of sensing nitroaromatics based on highly sensitive polymer dots

A new, rapid, sensitive, selective and portable fluorescence detection method for nitroaromatics based on polymer dots (Pdots) had been successfully developed not only in aqueous media but also in the solid state with test strips. The fluorescence quenching rates were proportional to the concentrations of 2,4,6-trinitrophenol (TNP) in the range of 0.2-20.0 μg mL(-1) and p-nitrophenol (PNP) in the range of 0.05-6.0 μg mL(-1), when Pdots were used as ratiometric fluorescent sensors in aqueous solution. The 3σ limit of detection of PNP reached 18.8 ng mL(-1). Compared with polymer-based detection for nitroaromatics in the organic phase, the signal enhancement effect was initially found when Pdots were used to detect nitroaromatics in the aqueous phase. The mechanism of the interaction between Pdots and nitroaromatics was revealed as an electron transfer phenomenon from the electron-rich chromophoric probe to the electron deficient nitroaromatics. The results indicated that Pdots-based detection was particularly suitable for on-site qualitative detection and quantitative analysis of nitroaromatics.

Erythrocyte membrane-coated NIR-triggered biomimetic nanovectors with programmed delivery for photodynamic therapy of cancer

A new type of photodynamic therapy (PDT) agents using upconversion nanoparticles (UCNPs) with incorporated photosensitizers as the inner core and an erythrocyte membrane (RM) decorated with dual targeting moieties as the cloak is developed. Owing to the endogenous nature of RM, the RM-coating endows the PDT agents with perfect biocompatibility and stealth ability to escape from the entrapment by the reticulo-endothelial system (RES). More importantly, owing to the unique nature of erythrocyte as an oxygen carrier in the blood, the RM outer layer of the agents unequivocally facilitates the permeation of ground-state molecular oxygen ((3)O2) and the singlet oxygen ((1)O2) as compared to the previously developed PDT agents with other types of coating. Another salient feature of the as-prepared PDT platform is the decoration of RM with dual targeting moieties for selective recognition of cancer cells and mitochondrial targeting, respectively. The synergistic effect of RM coating and dual-targeting of such feature-packed agents are investigated in tumor-bearing mice and the improved PDT therapeutic efficacy is confirmed, which is the first paradigm where RM-coated NIR-triggered nanovectors with programmed delivery ability is applied in PDT of tumor in vivo.

Fluorescence resonance energy transfer in a binary organic nanoparticle system and its application

Fluorescent organic nanoparticles have a much better photostability than molecule-based probes. Here, we report a simple strategy to detect chemicals and biomolecules by a binary nanoparticle system based on fluorescence resonance energy transfer (FRET). Poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO, energy donor) and poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV, energy acceptor) are utilized to prepare the binary nanoparticle system through a reprecipitation method. Since the FRET process is strongly distance-dependent, a change in the interparticle distance between the two kinds of nanoparticles after introduction of analytes will alter the FRET efficiency. The response of the binary nanoparticle system to cationic polyelectrolytes was investigated by monitoring the FRET efficiency from PFO to MEH-PPV nanoparticles and the fluorescence color of the nanoparticle solutions. Furthermore, the cationic polyelectrolyte pretreated binary nanoparticle system can be used to detect DNA by desorption of nanoparticles from the polyelectrolyte's chains and the detection concentration can go down to 10(-14) M. Thus, the binary nanoparticle system shows great promise for applications in chemical sensing or biosensing.

Enhanced two-photon fluorescence imaging and therapy of cancer cells via Gold@bridged silsesquioxane nanoparticles

A two-photon photosensitizer with four triethoxysilyl groups is synthesized through the click reaction. This photosensitizer allows the design of bridged silsesquioxane (BS) nanoparticles through a sol-gel process; moreover, gold core BS shells or BS nanoparticles decorated with gold nanospheres are synthesized. An enhancement of the two-photon properties is noted with gold and the nanoparticles are efficient for two-photon imaging and two-photon photodynamic therapy of cancer cells.

Conducting polymer nanoparticles for targeted cancer therapy

Functionalized conducting polymer nanoparticles allow for targeted delivery, tracking by fluorescence bioimaging, and therapeutics through formation of reactive oxygen species.

Pdots nanoparticles load photosensitizers and enhance efficiently their photodynamic effect by FRET

Pdot nanoparticles enhance the photodynamic effect by efficient FRET to the photosensitizer. Thus, production of singlet oxygen is increased and causes irreversible damage to cancer cells.

Two-photon excitation of porphyrin-functionalized porous silicon nanoparticles for photodynamic therapy

Porous silicon nanoparticles (pSiNPs) act as a sensitizer for the 2-photon excitation of a pendant porphyrin using NIR laser light, for imaging and photodynamic therapy. Mannose-functionalized pSiNPs can be vectorized to MCF-7 human breast cancer cells through a mannose receptor-mediated endocytosis mechanism to provide a 3-fold enhancement of the 2-photon PDT effect.

Conjugated-polymer-based energy-transfer systems for antimicrobial and anticancer applications

Conjugated polymers (CPs) attract a lot of attention in sensing, imaging, and biomedical applications because of recent achievements that are highlighted in this Research News article. A brief review of recent progress in the application of CP-based energy-transfer systems in antimicrobial and anticancer treatments is provided. The transfer of excitation energy from CPs to photosensitizers leads to the generation of reactive oxygen species (ROS) that are able to efficiently kill pathogenic microorganisms and cancer cells in the surroundings. Both fluorescence resonance energy transfer (FRET) and bioluminescence energy transfer (BRET) modes are discussed.

Semiconducting polymer encapsulated mesoporous silica particles with conjugated Europium complexes: toward enhanced luminescence under aqueous conditions

Immobilization of lanthanide organic complexes in meso-organized hybrid materials for luminescence applications have attracted immense interest due to the possibility of controlled segregation at the nanoscopic level for novel optical properties. Aimed at enhancing the luminescence intensity and stability of the hybrid materials in aqueous media, we developed polyvinylpyrrolidone (PVP) stabilized, semiconducting polymer (poly(9-vinylcarbazole), PVK) encapsulated mesoporous silica hybrid particles grafted with Europium(III) complexes. Monosilylated β-diketonate ligands (1-(2-naphthoyl)-3,3,3-trifluoroacetonate, NTA) were first co-condensed in the mesoporous silica particles as pendent groups for bridging and anchoring the lanthanide complexes, resulting in particles with an mean diameter of ∼ 450 nm and a bimodal pore size distribution centered at 3.5 and 5.3 nm. PVK was encapsulated on the resulted particles by a solvent-induced surface precipitation process, in order to seal the mesopores and protect Europium ions from luminescence quenching by producing a hydrophobic environment. The obtained polymer encapsulated MSN-EuLC@PVK-PVP particles exhibit significantly higher intrinsic quantum yield (Φ(Ln) = 39%) and longer lifetime (τ(obs) = 0.51 ms), as compared with those without polymer encapsulation. Most importantly, a high luminescence stability was realized when MSN-EuLC@PVK-PVP particles were dispersed in various aqueous media, showing no noticeable quenching effect. The beneficial features and positive attributes of both mesoporous silica and semiconducting polymers as lanthanide-complex host were merged in a single hybrid carrier, opening up the possibility of using these hybrid luminescent materials under complex aqueous conditions such as biological/physiological environments.

Size-dependent property and cell labeling of semiconducting polymer dots

Semiconducting polymer dots (Pdots) represent a new class of fluorescent nanoparticles for biological applications. In this study, we investigated their size-dependent fluorescence and cellular labeling properties. We demonstrate that the polymer conformation in solution phase largely affects the polymer folding and packing during the nanoparticle preparation process, resulting in solution-phase control over the fluorescence properties of semiconducting polymer nanoparticles. The resulting Pdots exhibit apparent size dependent absorption and emission, a characteristic feature of different chain packing behaviors due to the preparation conditions. Single-particle fluorescence imaging was employed to perform a side-by-side comparison on the Pdot brightness, indicating a quadratic dependence of single-particle brightness on particle size. Upon introducing a positively charged dye Nile blue, all the three type of Pdots were quenched very efficiently (Ksv > 1 × 10(7) M(-1)) in an applied quenching process at low dye concentrations, but exhibit apparent difference in quenching efficiency with increasing dye concentration. Furthermore, Pdots of different sizes were used for cell uptake and cellular labeling involving biotin-streptavidin interactions. Fluorescence imaging together with flow cytometry studies clearly showed size dependent labeling brightness. Small-sized Pdots appear to be more effective for immunolabeling of cell surface, whereas medium-sized Pdots exhibit the highest uptake efficiency. This study provides a concrete guidance for selecting appropriate particle size for biological imaging and sensing applications.