Novel photosensitizer-protein nanoparticles for photodynamic therapy: photophysical characterization and in vitro investigations

F127/chlorin e6-nanomicelles to enhance Ce6 solubility and PDT-efficacy mitigating lung metastasis in melanoma

Photodynamic Therapy (PDT) is a promising paradigm for treating cancer, especially superficial cancers, including skin and oral cancers. However, the effectiveness of PDT is hindered by the hydrophobicity of photosensitizers. Here, chlorin e6 (Ce6), a hydrophobic photosensitizer, was loaded into pluronic F127 micelles to enhance solubility and improve tumor-specific targeting efficiency. The resulting Ce6@F127 Ms demonstrated a significant increase in solubility and singlet oxygen generation (SOG) efficiency in aqueous media compared to free Ce6. The confocal imaging and fluorescence-activated cell sorting (FACS) analysis confirmed the enhanced internalization rate of Ce6@F127 Ms in murine melanoma cell lines (B16F10) and human oral carcinoma cell lines (FaDu). Upon laser irradiation (666 nm), the cellular phototoxicity of Ce6@F127 Ms against B16F10 and FaDu was approximately three times higher than the free Ce6 treatment. The in vivo therapeutic investigations conducted on a murine model of skin cancer demonstrated the ability of Ce6@F127 Ms, when combined with laser treatment, to penetrate solid tumors effectively, which resulted in a significant reduction in tumor volume compared to free Ce6. Further, the Ce6@F127 Ms demonstrated upregulation of TUNEL-positive cells, downregulation of proliferation markers in tumor tissues, and prevention of lung metastasis with insignificant levels of proliferating cells and collagenase, as validated through immunohistochemistry. Subsequent analysis of serum and blood components affirmed the safety and efficacy of Ce6@F127 Ms in mice. Consequently, the developed Ce6@F127 Ms exhibits significant potential for concurrently treating solid tumors and preventing metastasis. The photodynamic formulation holds great clinical translation potential for treating superficial tumors.

Hypoxia alleviating platinum(IV)/chlorin e6-based combination chemotherapeutic-photodynamic nanomedicine for oropharyngeal carcinoma

Hypoxia is an important pathological hallmark of the tumor microenvironment, associated with metabolic alterations, cell proliferation, aggressiveness, metastasis, and therapy resistance in cancers. Hypoxia impedes the outcome of photodynamic therapy (PDT), which is largely dependent on molecular oxygen to generate cytotoxic ¹O₂. Here, a near-infrared light activatable, oxygen-generating nanomicellar PDT-chemotherapy system (mPPCPN Ms) constituted of amphiphilic mPEG-PLA, photosensitizer Ce6, and tetravalent platinum prodrug Pt(IV)-diazide was developed for oral squamous cell carcinoma. The polymer conjugate self-assemble to nanosize (115 ± 2.35 nm) micelles, which, upon irradiation (660 nm laser), activated Ce6, and photodecomposed to produce cytotoxic Pt(II), azidyl radical, and molecular oxygen. The strategically fabricated PDT-chemotherapy produced a strong antitumor response in vitro using oral squamous cell carcinoma and in vivo in oral cancer-xenografted mouse models, revealing its significant potential in chemo-photodynamic combination therapy with the benefit of reversing hypoxia.

Nanotherapeutic Intervention in Photodynamic Therapy for Cancer

The clinical need for photodynamic therapy (PDT) has been growing for several decades. Notably, PDT is often used in oncology to treat a variety of tumors since it is a low-risk therapy with excellent selectivity, does not conflict with other therapies, and may be repeated as necessary. The mechanism of action of PDT is the photoactivation of a particular photosensitizer (PS) in a tumor microenvironment in the presence of oxygen. During PDT, cancer cells produce singlet oxygen (¹O₂) and reactive oxygen species (ROS) upon activation of PSs by irradiation, which efficiently kills the tumor. However, PDT's effectiveness in curing a deep-seated malignancy is constrained by three key reasons: a tumor's inadequate PS accumulation in tumor tissues, a hypoxic core with low oxygen content in solid tumors, and limited depth of light penetration. PDTs are therefore restricted to the management of thin and superficial cancers. With the development of nanotechnology, PDT's ability to penetrate deep tumor tissues and exert desired therapeutic effects has become a reality. However, further advancement in this field of research is necessary to address the challenges with PDT and ameliorate the therapeutic outcome. This review presents an overview of PSs, the mechanism of loading of PSs, nanomedicine-based solutions for enhancing PDT, and their biological applications including chemodynamic therapy, chemo-photodynamic therapy, PDT-electroporation, photodynamic-photothermal (PDT-PTT) therapy, and PDT-immunotherapy. Furthermore, the review discusses the mechanism of ROS generation in PDT advantages and challenges of PSs in PDT.

I, Deniega FM, Delica K, Fernandez K, Lebrilla CB, Manalo MN, Heralde III FM, Completo GCJ, Nacario RC. Biological Assay-Guided Fractionation and Mass Spectrometry-Based Metabolite Profiling of Annona muricata L. Cytotoxic Compounds against Lung Cancer A549 Cell Line

Annona muricata L. (Guyabano) leaves are reported to exhibit anticancer activity against cancer cells. In this study, the ethyl acetate extract from guyabano leaves was purified through column chromatography, and the cytotoxic effects of the semi-purified fractions were evaluated against A549 lung cancer cells using in vitro MTS cytotoxicity and scratch/wound healing assays. Fractions F15-16C and F15-16D exhibited the highest anticancer activity in the MTS assay, with % cytotoxicity values of 99.6% and 99.4%, respectively. The bioactivity of the fractions was also consistent with the results of the scratch/wound healing assay. Moreover, untargeted metabolomics was employed on the semi-purified fractions to determine the putative compounds responsible for the bioactivity. The active fractions were processed using LC-MS/MS analysis with the integration of the following metabolomic tools: MS-DIAL (for data processing), MetaboAnalyst (for data analysis), GNPS (for metabolite annotation), and Cytoscape (for network visualization). Results revealed that the putative compounds with a significant difference between active and inactive fractions in PCA and OPLS-DA models were pheophorbide A and diphenylcyclopropenone.

Importance of Rose Bengal Loaded with Nanoparticles for Anti-Cancer Photodynamic Therapy

Rose Bengal (RB) is a photosensitizer (PS) used in anti-cancer and anti-bacterial photodynamic therapy (PDT). The specific excitation of this PS allows the production of singlet oxygen and oxygen reactive species that kill bacteria and tumor cells. In this review, we summarize the history of the use of RB as a PS coupled by chemical or physical means to nanoparticles (NPs). The studies are divided into PDT and PDT excited by X-rays (X-PDT), and subdivided on the basis of NP type. On the basis of the papers examined, it can be noted that RB used as a PS shows remarkable cytotoxicity under the effect of light, and RB loaded onto NPs is an excellent candidate for nanomedical applications in PDT and X-PDT.

Hydrophobicity Regulates the Cellular Interaction of Cyanine5-Labeled Poly(3-hydroxypropionate)-Based Comb Polymers

An in-depth understanding of the effect of physicochemical properties of nanocarriers on their cellular uptake and fate is crucial for the development of novel delivery systems. In this study, well-defined hydrophobic carboxylated poly(3-hydroxypropionate)-based comb polymers were synthesized. Two oligo(3-hydroxypropionate) (HP_n) of different degrees of polymerization (DP; 5 and 9) bearing α-vinyl end-groups were obtained by an hydrogen transfer polymerization (HTP)-liquid/liquid extraction strategy. 2-Carboxyethyl acrylate (CEA), representing the DP 1 analogue of HP_n, was also included in the study. (Macro)monomers were polymerized via reversible addition-fragmentation chain-transfer (RAFT) polymerization and fully characterized by ¹H NMR spectroscopy and size exclusion chromatography. All polymers were non-hemolytic and non-cytotoxic against NIH/3T3 cells. Detailed cellular association and uptake studies of Cy5-labeled polymers by flow cytometry and confocal laser scanning microscopy (CLSM) revealed that the carboxylated water-soluble PCEA, the polymer with the shortest side chain, efficiently targets mitochondria. However, increasing the side-chain DP led to a change in the intracellular fate. P(HP₅) was trafficked to both mitochondria and lysosomes, while P(HP₉) was exclusively found in lysosomes. Importantly, FLIM-FRET investigation of P(HP₅) provided initial insight into the mitochondria subcompartment location of Cy5-labeled carboxylated polymers. Moreover, intracellular uptake mechanism studies were performed. Blocking scavenger receptors by dextran sulfate or cooling cells to 4 °C significantly affected the cell association of hydrophobic carboxylated polymers with an insignificant response to membrane-potential inhibitors. In contrast, water-soluble carboxylated polymers' cellular association was substantially inhibited in cells treated with compounds depleting the mitochondrial potential (ΔΨ). Overall, this study highlights hydrophobicity as a valuable means to tune the cellular interaction of carboxylated polymers and thus will inform the design of future drug carriers based on Cy5-modified carboxylated polymers.

Determining and unravelling origins of reduced photoinactivation efficacy of bacteria in milk

Bovine mastitis is an endemic disease of dairy cattle that is considered to be one of the most frequent and costly diseases in veterinary medicine. An increase in the incidence of disease results in the increased use of antibiotics, which in turn increases the potential of bacterial resistance. This study aimed to investigate the effectiveness of antimicrobial photodynamic therapy (aPDT) in the treatment of bovine mastitis, as an alternative to systemic antibiotics. To identify the key factors affecting photoinactivation efficacy, realistic experiments in view of the end-use were conducted in milk samples using two different photosensitizers: methylene blue (MB) and silicon (IV) phthalocyanine derivative (SiPc). We explored the effects of divalent ions and fat content on the aPDT outcome and determined influence of different proteins on aPDT efficacy. Levels of bacterial sensitivity to PSs varied depending on the type of bacteria (Gram-positive vs. Gram-negative) and light exposure time. Critical interrelated factors affecting aPDT in milk were identified and an efficient combination of treatment conditions that can lead to a full photodynamic inactivation of bacteria was determined.

Cell-Penetrating Protein/Corrole Nanoparticles

Recent work has highlighted the potential of metallocorroles as versatile platforms for the development of drugs and imaging agents, since the bioavailability, physicochemical properties and therapeutic activity can be dramatically altered by metal ion substitution and/or functional group replacement. Significant advances in cancer treatment and imaging have been reported based on work with a water-soluble bis-sulfonated gallium corrole in both cellular and rodent-based models. We now show that cytotoxicities increase in the order Ga < Fe < Al < Mn < Sb < Au for bis-sulfonated corroles; and, importantly, that they correlate with metallocorrole affinities for very low density lipoprotein (VLDL), the main carrier of lipophilic drugs. As chemotherapeutic potential is predicted to be enhanced by increased lipophilicity, we have developed a novel method for the preparation of cell-penetrating lipophilic metallocorrole/serum-protein nanoparticles (NPs). Cryo-TEM revealed an average core metallocorrole particle size of 32 nm, with protein tendrils extending from the core (conjugate size is ~100 nm). Optical imaging of DU-145 prostate cancer cells treated with corrole NPs (≤100 nM) revealed fast cellular uptake, very slow release, and distribution into the endoplasmic reticulum (ER) and lysosomes. The physical properties of corrole NPs prepared in combination with transferrin and albumin were alike, but the former were internalized to a greater extent by the transferrin-receptor-rich DU-145 cells. Our method of preparation of corrole/protein NPs may be generalizable to many bioactive hydrophobic molecules to enhance their bioavailability and target affinity.

AlPcS4-PDT for gastric cancer therapy using gold nanorod, cationic liposome, and Pluronic® F127 nanomicellar drug carriers

Purpose

As a promising photodynamic therapy (PDT) agent, Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS₄) provides deep penetration into tissue, high quantum yields, good photostability, and low photobleaching. However, its low delivery efficiency and high binding affinity to serum albumin cause its low penetration into cancer cells, further limiting its PDT effect on gastric cancer. In order to improve AlPcS₄/PDT effect, the AlPcS₄ delivery sys tems with different drug carriers were synthesized and investigated.

Materials and methods

Gold nanorods, cationic liposomes, and Pluronic^® F127 nanomicellars were used to formulate the AlPcS₄ delivery systems. The anticancer effect was evaluated by CCK-8 assay and colony formation assay. The delivery efficiency of AlPcS₄ and the binding affinity to serum proteins were determined by fluorescence intensity assay. The apoptosis and necrosis ability, reactive oxygen species and singlet oxygen generation, mitochondrial transmembrane potential and ([Ca²⁺]_i) concentration were further measured to evaluate the mechanism of cell death.

Results

The series of synthesized AlPcS₄ delivery systems with different drug carriers improve the limited PDT effect in varying degrees. In contrast, AlPcS₄ complex with gold nanorods has significant anticancer effects because gold nanorods are not only suitable for AlPcS₄ delivery, but also exhibit enhanced singlet oxygen generation effect and photothermal effect to induce cell death directly. Moreover, AlPcS₄ complex with cationic liposomes shows the potent inhibition effect because of its optimal AlPcS₄ delivery efficiency and ability to block serum albumin. In addition, AlPcS₄ complex with Pluronic F127 exhibits inferior PDT effect but presents lower cytotoxicity, slower dissociation rate, and longer retention time of incorporated drugs; thus, F127–AlPcS₄ is used for prolonged gastric cancer therapy.

Conclusion

The described AlPcS₄ drug delivery systems provide promising agents for gastric cancer therapy.

Photodynamic Therapy

Photodynamic therapy is a clinical technique for the treatment of cancers, microbial infections and other medical conditions by means of light-induced generation of reactive oxygen species using photosensitising drugs. The intrinsic fluorescence of many such drugs make them potential theranostic agents for simultaneous diagnosis and therapy. This chapter reviews the basic chemical and biological aspects of photodynamic therapy with an emphasis on its applications in theranostics. The roles of nanotechnology is highlighted, as well as emerging trends such as photoimmunotherapy, image-guided surgery and light- and singlet-oxygen dosimetry.

Cyclopeptidic photosensitizer prodrugs as proteolytically triggered drug delivery systems of pheophorbide A: part I – self-quenched prodrugs

RAFTs bearing multiple copies of pheophorbide A allow perfectly defined photosensitizer prodrugs.

"One-Pot" Fabrication of Highly Versatile and Biocompatible Poly(vinyl alcohol)-porphyrin-based Nanotheranostics

Nanoparticle-based theranostic agents have emerged as a new paradigm in nanomedicine field for integration of multimodal imaging and therapeutic functions within a single platform. However, the clinical translation of these agents is severely limited by the complexity of fabrication, long-term toxicity of the materials, and unfavorable biodistributions. Here we report an extremely simple and robust approach to develop highly versatile and biocompatible theranostic poly(vinyl alcohol)-porphyrin nanoparticles (PPNs). Through a “one-pot” fabrication process, including the chelation of metal ions and encapsulation of hydrophobic drugs, monodispersenanoparticle could be formed by self-assembly of a very simple and biocompatible building block (poly(vinyl alcohol)-porphyrin conjugate). Using this approach, we could conveniently produce multifunctional PPNs that integrate optical imaging, positron emission tomography (PET), photodynamic therapy (PDT), photothermal therapy (PTT) and drug delivery functions in one formulation. PPNs exhibited unique architecture-dependent fluorescence self-quenching, as well as photodynamic- and photothermal- properties. Near-infrared fluorescence could be amplified upon PPN dissociation, providing feasibility of low-background fluorescence imaging. Doxorubicin (DOX)-loaded PPNs achieved 53 times longer half-life in blood circulation than free DOX. Upon irradiation by near infrared light at a single excitation wavelength, PPNs could be activated to release reactive oxygen species, heat and drugs simultaneously at the tumor sites in mice bearing tumor xenograft, resulting in complete eradication of tumors. Due to their organic compositions, PPNs showed no obvious cytotoxicity in mice via intravenous administration during therapeutic studies. This highly versatile and multifunctional PPN theranostic nanoplatform showed great potential for the integration of multimodal imaging and therapeutic functions towards personalized nanomedicine against cancers.

Synthesis of a poly(ethylene glycol) galloyl sensitizer tip for an 'all-in-one' photodynamic device

This paper describes the synthesis of a specialized silica tip for an optical fiber device capable of delivering all components necessary for photodynamic therapy. Oxygen, light and a cleavable tripolyethylene glycol (PEG)-galloyl pheophorbide sensitizer are simultaneously delivered by the silica tip, where the tip was synthesized in six steps. A comparison of synthetic steps to reach PEGylated sensitizers bound to fluorinated silica and a previously reported Teflon/polyvinyl alcohol (PVA) nanocomposite ( Ghosh, G. et al. J. Phys. Chem. B 2015, 119, 4155- 4164) was made. The hydrolytic stability of the attached PEGs and the extent to which the PEG groups enhance solubility will also be discussed. The new triPEG-galloyl sensitizer has the potential for use in intraoperative pointsource photodynamic therapy which aims for precision treatment of residual disease. Schematic of the synthesis of a photoactive silica surface. It is composed of fluorinated silica connected to a photo-releasable sensitizer with short-chain PEGs.

Unique chlorophylls in picoplankton Prochlorococcus sp. "Physicochemical properties of divinyl chlorophylls, and the discovery of monovinyl chlorophyll b as well as divinyl chlorophyll b in the species Prochlorococcus NIES-2086"

In this review, we introduce our recent studies on divinyl chlorophylls functioning in unique marine picoplankton Prochlorococcus sp. (1) Essential physicochemical properties of divinyl chlorophylls are compared with those of monovinyl chlorophylls; separation by normal-phase and reversed-phase high-performance liquid chromatography with isocratic eluent mode, absorption spectra in four organic solvents, fluorescence information (emission spectra, quantum yields, and life time), circular dichroism spectra, mass spectra, nuclear magnetic resonance spectra, and redox potentials. The presence of a mass difference of 278 in the mass spectra between [M+H]⁺ and the ions indicates the presence of a phytyl tail in all the chlorophylls. (2) Precise high-performance liquid chromatography analyses show divinyl chlorophyll a' and divinyl pheophytin a as the minor key components in four kinds of Prochlorococcus sp.; neither monovinyl chlorophyll a' nor monovinyl pheophytin a is detected, suggesting that the special pair in photosystem I and the primary electron acceptor in photosystem II are not monovinyl but divinyl-type chlorophylls. (3) Only Prochlorococcus sp. NIES-2086 possesses both monovinyl chlorophyll b and divinyl chlorophyll b, while any other monovinyl-type chlorophylls are absent in this strain. Monovinyl chlorophyll b is not detected at all in the other three strains. Prochlorococcus sp. NIES-2086 is the first example that has both monovinyl chlorophyll b as well as divinyl chlorophylls a/b as major chlorophylls.

Photosensitizer-loaded bubble-generating mineralized nanoparticles for ultrasound imaging and photodynamic therapy

In this work, we have developed photosensitizer-loaded bubble-generating calcium carbonate (CaCO₃)-mineralized nanoparticles that have potential for ultrasound imaging (US)-guided photodynamic therapy (PDT) of tumors. A photosensitizer, chlorin e6 (Ce6)-loaded CaCO₃-mineralized nanoparticles (Ce6-BMNs), was prepared using an anionic block copolymer-templated in situ mineralization method. Ce6-BMNs were composed of the Ce6-loaded CaCO₃ core and the hydrated poly(ethylene glycol) (PEG) shell. Ce6-BMNs exhibited excellent stability under serum conditions. Ce6-BMNs showed enhanced echogenic US signals at tumoral acid pH by generating carbon dioxide (CO₂) bubbles. Ce6-BMNs effectively inhibited Ce6 release at physiological pH (7.4). At a tumoral acidic pH (6.4), Ce6 release was accelerated with CO₂ bubble generation due to the dissolution of the CaCO₃ mineral core. Upon irradiation of Ce6-BMN-treated MCF-7 breast cancer cells, the cell viability dramatically decreased with increasing Ce6 concentration. The phototoxicity of the Ce6-BMNs was much higher than that of free Ce6. On the basis of tumoral pH-responsive CO₂ bubble-generation and simultaneous Ce6 release at the target tumor site, these CaCO₃ mineralized nanoparticles can be considered as promising theranostic nanoparticles for US imaging-guided PDT in the field of tumor therapy.

Redox-Responsive Porphyrin-Based Polysilsesquioxane Nanoparticles for Photodynamic Therapy of Cancer Cells

The development of stimulus-responsive photosensitizer delivery systems that carry a high payload of photosensitizers is of great importance in photodynamic therapy. In this study, redox-responsive polysilsesquioxane nanoparticles (PSilQNPs) built by a reverse microemulsion approach using 5,10,15,20-tetrakis(carboxyphenyl) porphyrin (TCPP) silane derivatives as building blocks, were successfully fabricated. The structural properties of TCPP-PSilQNPs were characterized by dynamic light scattering (DLS)/ζ-potential, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The photophysical properties were determined by UV-vis and fluorescence spectroscopy. The quantity of singlet oxygen generated in solution was measured using 1,3-diphenylisobenzofuran. The redox-responsive release of TCPP molecules was successfully demonstrated in solution in the presence of a reducing agent. The internalization of TCPP-PSilQNPs in cancer cells was investigated using laser scanning confocal microscopy. Phototoxicity experiments in vitro showed that the redox-responsive TCPP-PSilQNPs exhibited an improved phototherapeutic effect on cervical cancer cells compared to a non-responsive TCPP-PSilQNP control material.

Drug Carrier for Photodynamic Cancer Therapy

Photodynamic therapy (PDT) is a non-invasive combinatorial therapeutic modality using light, photosensitizer (PS), and oxygen used for the treatment of cancer and other diseases. When PSs in cells are exposed to specific wavelengths of light, they are transformed from the singlet ground state (S₀) to an excited singlet state (S₁-Sn), followed by intersystem crossing to an excited triplet state (T₁). The energy transferred from T₁ to biological substrates and molecular oxygen, via type I and II reactions, generates reactive oxygen species, (¹O₂, H₂O₂, O₂*, HO*), which causes cellular damage that leads to tumor cell death through necrosis or apoptosis. The solubility, selectivity, and targeting of photosensitizers are important factors that must be considered in PDT. Nano-formulating PSs with organic and inorganic nanoparticles poses as potential strategy to satisfy the requirements of an ideal PDT system. In this review, we summarize several organic and inorganic PS carriers that have been studied to enhance the efficacy of photodynamic therapy against cancer.

Ternary graphene quantum dot-polydopamine-Mn3O4 nanoparticles for optical imaging guided photodynamic therapy and T1-weighted magnetic resonance imaging

Imaging-guided therapy, which bridges treatment and diagnosis, plays an important role in overcoming the limitations of classical cancer therapy. To provide a more exact location of the tumor and to reduce side effects to normal tissues, a multifunctional probe was designed to serve as both an imaging agent and a therapeutic agent. Ternary hybrid nanoparticles comprised of visible red-responsive graphene, the T₁-weighted magnetic resonance imaging (MRI) agent Mn₃O₄ and a mussel-inspired linker polydopamine. The conjugation of graphene to Mn₃O₄ through polydopamine enhanced the water solubility of Mn₃O₄, enabling an efficient uptake by cancer cells as well as tumor accumulation when the nanoparticles were intravenously administered into mice. These nanoparticles, when localized at a tumor site, exhibited low cytotoxicity in the dark, while light irradiation of the cancer cells transfected with the nanoparticles resulted in significant phototherapeutic effects, apparently by generating toxic reactive oxygen species. These nanoparticles also allowed excellent T₁-weighted MR imaging in a human lung cancer xenograft model and were successfully used for combined visible red-imaging-guided photodynamic therapy and T₁-weighted MRI.

Enhanced in vitro photocytotoxicity of water-soluble dendritic pheophorbide-a

Photosensitizers can produce highly reactive singlet oxygen with exposure to visible light and are used in photodynamic therapy to treat a variety of tumors. We report on the synthesis of triethylene glycol dendron-conjugated pheophorbide-a5, a novel photosensitizer. The characteristic absorption bands (Soret and Q-bands, λmax = 405 and 670 nm, respectively) of 5 were appeared clearly in aqueous solution, due to the improved water-solubility of the dendron moiety. The value of singlet oxygen quantum yield of 5 (ΦΔ = 0.22) was higher than free pheophorbide-a (ΦΔ = 0.17) as reference in aqueous solution. Compound 5 also exhibited an enhanced in vitro phototoxicity than pheophorbide-a (PhA) in the concentration range of 1.0–5.0 μg/mL: cell viability in cells treated with 5 was reduced by ~20%, indicating a cell death rate of ~80%, while PhA treatment resulted in a cell death rate of only about 10%. These results indicate that 5 will likely be more efficient in PDT applications. Compared with free PhA, compound 5 showed highly enhanced singlet oxygen generation ability and in vitro photocytotoxicity.

Redox-sensitive cross-linking enhances albumin nanoparticle function as delivery system for photodynamic cancer therapy

Photodynamic cancer therapy is still limited in its efficiency because of a lack of targeted methods avoiding non-specific toxicity. To overcome this we developed a system that is solely effective upon cellular uptake and intracellular activation by incorporating redox-sensitive chemistry. We used a nanoprecipitation method to obtain human serum albumin nanoparticles (HSA NP) with a diameter of 295 ± 5 nm and decorated them with the photosensitizer (PS) chlorin e6 (Ce6). The NP were stabilized using a redox-sensitive cross-linker to create a smart drug delivery system that is activated only upon NP disintegration in the reducing intracellular environment. Indeed, our drug delivery NP broke down in an environment emulating the reducing intracellular environment with 10 mM glutathione, but not under extracellular conditions. In contrast, the control cross-linked with glutaraldehyde did not break down in the reducing environment. Upon NP disintegration Ce6 fluorescence doubled as the result of diminished self-quenching. While the Ce6-HSA NP did not produce a significant amount of singlet oxygen upon irradiation, NP disintegration restored singlet oxygen production to about half of the value generated by the free Ce6. In vitro experiments with HeLa cells showed that the smart system was able to kill up to 81% of the cells while the glutaraldehyde cross-linked control only killed 56% of them at a drug concentration of 10 ng/ml. Also, Ce6 immobilization in HSA NP prevented dark toxicity in three different cell lines. For the first time, we demonstrate that it is possible to design a smart NP drug delivery system delivering a PS drug to cancer cells while avoiding toxicity prior to the uptake and irradiation. This finding may provide a means of designing more efficient PDT in cancer treatment.

Recent progress in biomedical applications of Pluronic (PF127): Pharmaceutical perspectives

Most of the administered anti-cancer drugs are hydrophobic in nature and are known to have poor water solubility, short residence time, rapid clearance from the body and systemic side effects. Polymeric-based targeted particulate carrier system has shown to directly deliver the encapsulated anti-cancer drug to the desired site of action and prevent the interaction of encapsulated drug with the normal cells. Pluronic F127 (PF127) has been widely investigated for its broad-range of therodiagnostic applications in biomedical and pharmaceutical sciences, but rapid dissolution in the physiological fluids, short residence time, rapid clearance, and weak mechanical strength are the main shortcomings that are associated with PF127 and have recently been overcome by making various modifications in the structure of PF127 notably through preparation of PF127-based mixed polymeric micelles, PF127-conjugated nanoparticles and PF127-based hydrophobically modified thermogels. In this article, we have briefly discussed the recent studies that have been conducted on various anti-cancer drugs using PF127 as nano-carrier modified with other copolymers and/or conjugated with magnetic nanoparticles. The key findings of these studies demonstrated that the modified form of PF127 can significantly increase the stability of incorporated hydrophobic drugs with enhanced in vitro cytotoxicity and cellular uptake of anti-cancer drugs. Moreover, the modified form of PF127 has also shown its therapeutic potentials as therodiagnostics in various types of tumors and cancers. Hence, it can be concluded that the modified form of PF127 exhibits significant therodiagnostic effects with increased tumor-specific delivery of anti-cancer drugs having minimal toxic effects as compared to PF127 alone and/or other copolymers.

Conjugatable water-soluble Pt(II) and Pd(II) porphyrin complexes: novel nano- and molecular probes for optical oxygen tension measurement in tissue engineering

Measurement of oxygen tension in compressed collagen sheets was performed using matrix-embedded optical oxygen sensors based on platinum(II) and palladium(II) porphyrins supported on polyacrylamide nanoparticles. Bespoke, fully water-soluble, mono-functionalised Pt(II) and Pd(II) porphyrin complexes designed for conjugation under mild conditions were obtained using microwave-assisted metallation. The new sensors display a linear response (1/τ vs. O2) to varying oxygen tension over a biologically relevant range (7.0 × 10(-4) to 2.7 × 10(-1) mM) in aqueous solutions; a behaviour that is maintained following conjugation to polyacrylamide nanoparticles, and following embedding of the nanosensors in compressed collagen sheets, paving the way to innovative approaches for real-time resolution of oxygen gradients throughout 3D matrices useful for tissue regeneration.

Toward a molecular understanding of the photosensitizer-copper interaction for tumor destruction

The aim of this study was to shown that the photosensitizer in photodynamic therapy (PDT) can contribute to the dark toxicity and phototoxicity of the tumor by binding with copper. This binding process can remove the copper from the body, stopping angiogenesis as well as activating the mechanisms of cell death, such as apoptosis and necrosis. In PDT, this coupling may be considered a new route for fighting cancer in addition to those already known which involve reactive oxygen species.

Luminescence spectroscopy of singlet oxygen enables monitoring of oxygen consumption in biological systems consisting of fatty acids

The interaction of singlet oxygen ((1)O2) generated in a photosensitized process with well-known reference photosensitizers Perinaphthenone (PN) and TMPyP is investigated in a model system consisting of fatty acids and the respective exogenous photosensitizer (PS) in solution by direct detection of the luminescence photons of (1)O2 at 1270 nm. Such a model system is a first approach to mimic the complex environment of (1)O2 in a biological cell which consists mainly of water, proteins, sugars and lipids. Firstly, the important issue of oxygen consumption is evaluated which has to be considered during luminescence detection of (1)O2. It is known that the luminescence signal of (1)O2 is dependent on the oxygen concentration of the environment. Cellular components such as lipids represent oxygen consumers due to peroxidation of their unsaturated double bonds. Secondly, the experimental conditions for this model system regarding oxygen consumption are optimized to estimate the rates and rate constants of the coupled system. Thirdly, the triplet decay of the PS can provide more precise information about the actual oxygen concentration close to the PS and can be used, therefore, as a more precise method to determine the oxygen concentration in more complex systems such as a biological cell. The aim is to get a better understanding of photosensitized reactions of (1)O2 with cellular components to further improve methodologies, in particular at a cellular level using luminescence spectroscopy. In conclusion, luminescence detection might be a helpful tool to monitor precisely and promptly changes in oxygen concentration in a complex environment.

Photodynamic nanomedicine in the treatment of solid tumors: perspectives and challenges

Photodynamic therapy (PDT) is a promising treatment strategy where activation of photosensitizer drugs with specific wavelengths of light results in energy transfer cascades that ultimately yield cytotoxic reactive oxygen species which can render apoptotic and necrotic cell death. Without light the photosensitizer drugs are minimally toxic and the photoactivating light itself is non-ionizing. Therefore, harnessing this mechanism in tumors provides a safe and novel way to selectively eradicate tumor with reduced systemic toxicity and side effects on healthy tissues. For successful PDT of solid tumors, it is necessary to ensure tumor-selective delivery of the photosensitizers, as well as, the photoactivating light and to establish dosimetric correlation of light and drug parameters to PDT-induced tumor response. To this end, the nanomedicine approach provides a promising way towards enhanced control of photosensitizer biodistribution and tumor-selective delivery. In addition, refinement of nanoparticle designs can also allow incorporation of imaging agents, light delivery components and dosimetric components. This review aims at describing the current state-of-the-art regarding nanomedicine strategies in PDT, with a comprehensive narrative of the research that has been carried out in vitro and in vivo, with a discussion of the nanoformulation design aspects and a perspective on the promise and challenges of PDT regarding successful translation into clinical application.

Advanced photodynamic agent from chondroitin sulfate/zinc phthalocyanine conjugate

In order to improve the therapeutic effect of zinc phthalocyanines (ZnPc), a photoactive nanodrug was prepared with acetylated chondroitin sulfate (AcCS), utilizing a simple chemical method. AcCS/ZnPc nanodrugs have a unimodal size distribution below 200 nm and a negative surface charge due to AcCS located on the nanodrug surface. In organic solvent such as DMSO or DMF, it has strong fluorescence intensity and generates abundant singlet oxygen. However, in aqueous solvent, AcCS/ZnPc nanodrugs developed a self-organized form which induced reducing fluorescence intensity and singlet oxygen generation. The cellular uptake of the nanodrug was determined using a cell lysis test and confocal microscopy observation. The results indicated that cellular internalization efficiency of the nanodrug was 1.7–2.1 times higher than that of free ZnPc . Also, the phototoxicity of the nanodrug was detected via MTT assay with or without light. Although free ZnPc did not exhibit cytotoxicity in both light and dark condition, the nanodrug exhibited increasing cytotoxicity after irradiation. We therefore suggest that AcCS/ZnPc nanodrugs may have promising applications as new photodynamic agents for the clinical treatment of various tumors.

Shining light on nanotechnology to help repair and regeneration

Phototherapy can be used in two completely different but complementary therapeutic applications. While low level laser (or light) therapy (LLLT) uses red or near-infrared light alone to reduce inflammation, pain and stimulate tissue repair and regeneration, photodynamic therapy (PDT) uses the combination of light plus non-toxic dyes (called photosensitizers) to produce reactive oxygen species that can kill infectious microorganisms and cancer cells or destroy unwanted tissue (neo-vascularization in the choroid, atherosclerotic plaques in the arteries). The recent development of nanotechnology applied to medicine (nanomedicine) has opened a new front of advancement in the field of phototherapy and has provided hope for the development of nanoscale drug delivery platforms for effective killing of pathological cells and to promote repair and regeneration. Despite the well-known beneficial effects of phototherapy and nanomaterials in producing the killing of unwanted cells and promoting repair and regeneration, there are few reports that combine all three elements i.e. phototherapy, nanotechnology and, tissue repair and regeneration. However, these areas in all possible binary combinations have been addressed by many workers. The present review aims at highlighting the combined multi-model applications of phototherapy, nanotechnology and, reparative and regeneration medicine and outlines current strategies, future applications and limitations of nanoscale-assisted phototherapy for the management of cancers, microbial infections and other diseases, and to promote tissue repair and regeneration.

Self-organized nanogel from pullulan/pheophorbide-A conjugate as a macromolecular photodynamic agent

The potential of pullulan(PL)/pheophorbide-A(phA) nanogel (PL/phA) was evaluated as a macromolecular photosensitizer (PS) for photodynamic therapy (PDT). Two samples with different degrees of substitution of phA (PL/phA1 and 2) were synthesized and analyzed by 1H NMR. The mean diameters of self-organized nanogels from PL/phA1 and 2 in aqueous solution were approximately 100 and 160 nm with mono-size distribution, respectively. The changes in nanogel photoactivity such as fluorescence intensity and singlet oxygen (1O2) production were observed in the solvents, dimethyl sulfoxide (DMSO) and phosphate buffered saline (PBS). Although, their photoactivity in DMSO, which cannot form self-organized nanogels, was similar to that of free phA, activities were suppressed in the aqueous solution due to self-quenching between phAs similar to a fluorescence resonance energy transfer (FRET) effect. Moreover, as the nanogels were co-incubated with HeLa cells, the self-quenching effect gradually disappeared as a function of time. Based upon confocal microscopy and cytotoxicity results, we infer that the nanogels were internalized in cancer cells by endocytosis and then degraded by various enzymes in the endosome and lysosome, leading to the restoration of photoactivity. Therefore, the self-organized PL/phA nanogels may be recommended for development of new PDT with minimal unfavorable phototoxic affects.

Targeted albumin-based nanoparticles for delivery of amphipathic drugs

We report the preparation and physical and biological characterization of human serum albumin-based micelles of approximately 30 nm diameter for the delivery of amphipathic drugs, represented by doxorubicin. The micelles were surface conjugated with cyclic RGD peptides to guide selective delivery to cells expressing the α(v)β(3) integrin. Multiple poly(ethylene glycol)s (PEGs) with molecular weight of 3400 Da were used to form a hydrophilic outer layer, with the inner core formed by albumin conjugated with doxorubicin via disulfide bonds. Additional doxorubicin was physically adsorbed into this core to attain a high drug loading capacity, where each albumin was associated with about 50 doxorubicin molecules. The formed micelles were stable in serum but continuously released doxorubicin when incubated with free thiols at concentrations mimicking the intracellular environment. When incubated with human melanoma cells (M21+) that express the α(v)β(3) integrin, higher uptake and longer retention of doxorubicin was observed with the RGD-targeted micelles than in the case of untargeted control micelles or free doxorubicin. Consequently, the RGD-targeted micelles manifested cytotoxicity at lower doses of drug than control micelles or free drug.