Photoinduced Dynamics and Toxicity of a Cancer Drug in Proximity of Inorganic Nanoparticles under Visible Light

Unraveling an Ultrafast Electron Transport Mechanism in a Photocatalytic "Micromachine" for Their Potential Light Harvesting Applications

Following the seminal discovery of Richard Feynman, several micromachines have been made that are capable of several applications, such as solar energy harvesting, remediation of environmental pollution, etc. Here we have synthesized a nanohybrid combining TiO₂ nanoparticle and light harvesting robust organic molecule RK1 (2-cyano-3-(4-(7-(5-(4-(diphenylamino)phenyl)-4-octylthiophen-2-yl)benzo[c][1,2,5] thiadiazol-4-yl)phenyl) acrylic acid) as a model micromachine having solar light harvesting ability potential for application in photocatalysis, preparation of solar active devices, etc. Detailed structural characterization, including High Resolution Transmission Electronic Microscopy (HRTEM) and Fourier-transform infrared spectroscopy (FTIR), has been performed on the nanohybrid. We have studied the excited-state ultrafast dynamics of the efficient push-pull dye RK1 in solution, on mesoporous semiconductor nanoparticles, and in insulator nanoparticles by streak camera (resolution of the order of 500 fs). The dynamics of such photosensitizers in polar solvents have been reported, and it has been observed that completely different dynamics occur when they are attached to the surface of the semiconductor/insulator nanosurface. A femtosecond-resolved fast electron transfer has been reported when photosensitizer RK1 has been attached to the surface of the semiconductor nanoparticle, which in turn plays a crucial role in the development of an efficient light harvesting material. The generation of reactive oxygen species as a result of femtosecond-resolved photoinduced electron injection in the aqueous medium is also investigated in order to explore the possibility of redox-active micromachines, which are found to be crucial for efficient and enhanced photocatalysis.

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.

ROS triggered local delivery of stealth exosomes to tumors for enhanced chemo/photodynamic therapy

BACKGROUND

Exosomes are recognized as effective platforms for targeted delivery for their high physicochemical stability and biocompatibility. However, most of the exosomes are inevitably and rapidly cleared by mononuclear phagocytic system (MPS) during cancer therapy. How to engineer exosome to enhance the delivery efficiency is being intensively explored. In this study, we have constructed mPEG2000-TK-CP05 decorated exosomes as effective delivery platforms to achieve enhanced photodynamic/chemical cancer therapy.

RESULTS

Exosomes were coated with CP05-TK-mPEG2000, in which CP05 is a peptide with high affinity to exosomal CD63 and TK could be cleaved by ROS. The resulted exosomes, namely stealth Exo, were electroporated to load RB (photosensitizer Rose Bengal) and Dox (Doxorubicin). We verified that the Stealth Exo@RB (Stealth Exo additionally loaded with RB) could escape MPS while accumulate in the tumor region efficiently in the xenograft model when laser irradiation conducted locally. Additionally, we revealed that the Stealth Exo serves as an efficient platform for Dox delivery. Dox, together with the RB mediated photodynamic therapy induce tumor cell damage synergistically in the tumor region. Moreover, the proposed switchable stealth exosomes minimized the dose of toxic Dox and thus allowed robust tumor immune response.

CONCLUSIONS

Our results indicated that the proposed Stealth Exo greatly improves both the accessibility and efficiency of drug delivery, with minimal chemical or genetic engineering. The proposed Stealth Exo serve as a promising and powerful drug delivery nanoplatform in cancer treatment.

Inorganic-Organic Synergy in Nano-hybrids makes a New Class of Drug with Targeted Delivery: Glutamate Functionalization of Iron Nanoparticles for Potential Bone Marrow Delivery and X-ray Dynamic Therapy

Abstract:

The direct delivery of therapeutic molecules is generally inefficient and has several problems. Hence, nano medicines with targeted and controlled delivery applications have been an exciting field of research for the past decade. In this regard, the adjustable properties of inorganic nanoparticles like particle size distribution, ability to change the targeting ligand to have a higher affinity towards the pathologic cell, and controlled delivery properties have made it indispensable for targeted drug delivery applications. Changing the ligand on the surface of the inorganic nanoparticle can direct different therapeutic molecules to different organs like the liver, spleen, kidney, bone, and even brain. However, while the other targeted nano medicines are well-reported targeting of therapeutics to bone marrow cells is sparse in the literature. Hence, the administration of therapeutics for bone-related disorders like bone metastases leads to several problems like severe systemic toxicity and suboptimal efficacy. In this direction, we have shown our successful effort to functionalise a model inorganic nanoparticle (Fe2O3) by glutamate ligand which is reported to have a high affinity towards the NMDA receptors of the bone cells. We have performed spectroscopic studies to characterize the nano-hybrid. We have shown that the cargo or the Fe2O3 nanoparticle possesses the ability to generate photo-induced reactive oxygen species (ROS), thereby leading to a therapeutic opportunity for bone metastases. In addition, the nanoparticle also possesses the ability to generate enhanced ROS on X-ray irradiation, which may provide a new strategy for bone metastases and cancer therapy. Also, this paper reviews the advancement in the drug delivery applications of inorganic nanoparticles and highlights the crosstalk between the inorganic nanoparticles with the conjugated targeting ligand for efficient delivery applications.

Dual Sensitization via Electron and Energy Harvesting in a Nanohybrid for Improvement of Therapeutic Efficacy

We demonstrate experimental evidence of the effect of surface plasmon resonance of noble metal nanoparticles (NPs) on the activity of a well-known biomedicinal drug in the proximity of a semiconductor having a wide band gap for enhanced photodynamic therapy (PDT) efficacy. We have chosen riboflavin (Rf) (or vitamin B₂) as a model photosensitizer, attached with ZnO NPs and further attached with gold (Au) NP-decorated ZnO to increase the efficiency. The synthesized nanohybrids are characterized with the help of different microscopic, optical spectroscopic, and density functional theory (DFT)-based techniques. The DFT and time-dependent DFT-based calculations validate the experimental findings. A detailed ultrafast spectroscopic study has been carried out further to study the excited-state charge dynamics in the interface of the nanohybrids. The occurrence of a Förster resonance energy transfer (FRET) between Rf and Au has been found to be the key reason for the increased efficiency in the Rf-ZnO-Au nanohybrid over the Rf-ZnO one. The dipolar coupling between Au and Rf in the Rf-ZnO-Au nanohybrid further facilitates the generation of reactive oxygen species (ROS) in comparison to Rf-ZnO under blue-light irradiation. The greater efficiency in ROS generation by the Rf-ZnO-Au nanohybrid has been utilized for antimicrobial action against methicillin-resistant S. aureus (MRSA). Overall, the present study highlights the dual sensitization for achieving enhanced electron injection efficiency in the Rf-ZnO-Au nanohybrid in order to use it as an antibacterial agent that could be translated in PDT.

pH-Triggered nanoreactors as oxidative stress amplifiers for combating multidrug-resistant biofilms

Developing radical oxygen species (ROS)-generating nanoreactors as new "antibiotics" is a promising strategy for the treatment of multidrug-resistant (MDR) biofilm infections. Herein, we designed and fabricated silver nanoparticle-decorated calcium peroxide (CaO2) nanoreactors (CPA) for combating MDR biofilms. CPA could locally boost ROS production as oxidative stress amplifiers in a pH-triggered and self-catalytic manner in acidic biofilms, where H2O2 was released by the hydrolysis of CaO2 and sequentially catalyzed by Ag NPs in situ to generate O2˙-, thereby efficiently disrupting mature biofilms and killing bacteria.

Non-Polymeric Nanogels as Versatile Nanocarriers: Intracellular Transport of the Photosensitizers Rose Bengal and Hypericin for Photodynamic Therapy

The use of nanocarriers for intracellular transport of actives has been extensively studied in recent years and represents a central area of nanomedicine. The main novelty of this paper lies on the use of nanogels formed by a low-molecular-weight gelator (1). Here, non-polymeric, molecular nanogels are successfully used for intracellular transport of two photodynamic therapy (PDT) agents, Rose Bengal (RB) and hypericin (HYP). The two photosensitizers (PSs) exhibit different drawbacks for their use in clinical applications. HYP is poorly water-soluble, while the cellular uptake of RB is hindered due to its dianionic character at physiological pH values. Additionally, both PSs tend to aggregate precluding an effective PDT. Despite the different nature of these PSs, nanogels from gelator 1 provide, in both cases, an efficient intracellular transport into human colon adenocarcinoma cells (HT-29) and a notably improved PDT efficiency, as assessed by confocal laser scanning microscopy and flow cytometry. Furthermore, no significant dark toxicity of the nanogels is observed, supporting the biocompatibility of the delivery system. The developed nanogels are highly reproducible due to their non-polymeric nature, and their synthesis is easily scaled up. The results presented here thus confirm the potential of molecular nanogels as valuable nanocarriers, capable of entrapping both hydrophobic and hydrophilic actives, for PDT of cancer.

Nanoscale ZnO-based photosensitizers for photodynamic therapy

Due to the ability to induce the generation of reactive oxygen species (ROS) under light irradiation, ZnO nanoparticles show great potential in photodynamic therapy (PDT). Photo-triggered ROS production by ZnO nanoparticles and the resulting phototoxicity are efficient in killing cancer cells. This review highlights the recent exciting progress on the nanoscale ZnO-based photosensitizers (PSs) for PDT. Both the semplice ZnO nanoparticles as the PSs and the various chemicals (organic PS, dopant, metal and chemotherapeutic drugs) modified ZnO nanoparticles as the PSs show good ROS generation efficiency. The productive rate of ROS, the wavelength of exciting lights, and the therapeutic effect can be altered by doping different chemicals into ZnO nanoparticles at will. Additionally, we give some outlook on the design and functionalization of next-generation ZnO nanoparticles for more effective anti-cancer applications.

Wide bandgap semiconductor-based novel nanohybrid for potential antibacterial activity: ultrafast spectroscopy and computational studies

The properties of nanomaterials generated by external stimuli are considered an innovative and promising replacement for the annihilation of bacterial infectious diseases.

Enhanced Water Stability and Photoresponsivity in Metal-Organic Framework (MOF): A Potential Tool to Combat Drug-resistant Bacteria

In this work, we have successfully synthesized a bimetallic (Zinc and Cobalt) Zeolitic Imidazolate Framework (Zn50Co50-ZIF), a class in a wider microporous Metal-Organic Framework (MOF) family. The synthesized nanostructures maintain both water stability like ZIF-8 (solely Zn containing) and charge transfer electronic band in the visible optical spectrum as ZIF-67 (solely Co containing). Crystal structure from XRD, high resolution transmission electron microscopy (HRTEM) followed by elemental mapping (EDAX) confirm structural stability and omnipresence of the metal atoms (Zn and Co) across the nanomaterial with equal proportion. Existence of charge transfer state consistent with ZIF67 and intact ultrafast excited state dynamics of the imidazolate moiety in both ZIF-8 and ZIF-67, is evidenced from steady state and time resolved optical spectroscopy. The thermal and aqueous stabilities of Zn50Co50-ZIF are found to be better than ZIF-67 but comparable to ZIF-8 as evidenced by solubility, scanning electron microscopy (SEM) and XRD studies of the material in water. We have evaluated the photoinduced ROS generation by the mixed ZIF employing dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay. We have also explored the potentiality of the synthesized material for the alternate remediation of methicillin resistant Staphylococcus aureus (MRSA) infection through the photoinduced reactive oxygen species (ROS) generation and methylene blue (MB) degradation kinetics.

Novel one pot synthesis and spectroscopic characterization of a folate-Mn3O4 nanohybrid for potential photodynamic therapeutic application

Treatment of cancer using nanoparticles made of inorganic and metallic compounds has been increasingly used, owing to their novel intrinsic physical properties and their potential to interact with specific cellular sites, thereby significantly reducing severe secondary effects. In this study, we report a facile strategy for synthesis of folate capped Mn₃O₄ nanoparticles (FA-Mn₃O₄ NPs) with high colloidal stability in aqueous media using a hydrothermal method for potential application in photodynamic therapy (PDT) of cancer. The capping of FA to Mn₃O₄ NPs was confirmed using various spectroscopic techniques. In adenocarcinomic human alveolar basal epithelial cells (A549), the nanohybrid synthesised with a combination of FA and Mn₃O₄ shows remarkable PDT activity via intracellular ROS generation (singlet oxygen). As established by a DNA fragmentation assay and fluorescence studies, the nanohybrid can cause significant nuclear DNA damage by light induced enhanced ROS generation. In the assessment of Bax, Bcl2 provides strong evidence of apoptotic cellular death. Cumulatively, the outcomes of this study suggest that these newly synthesized FA-Mn₃O₄ NPs can specifically destroy cells with overexpressed folate receptors, thereby providing a solution in the journey of cancer eradication.

Folate capped Mn₃O₄ nanoparticles can be used in PDT for specifically destroying folate receptor-overexpressing cancer cells through photo induced free radical damage.

NIR-Light-Active ZnO-Based Nanohybrids for Bacterial Biofilm Treatment

Nanomaterials with antimicrobial properties triggered by external stimuli appear to be a promising and innovative substitute for the destruction of antibiotic-resistant superbugs as they can induce multiple disruptions in the cellular mechanism. This study demonstrates the use of squaraine (SQ) dye as the photosensitive material, activated in the near-infrared tissue-transparent therapeutic window. The dye has been covalently attached to the ZnO nanoparticle surface, forming ZnO-SQ nanohybrids. The formation of the nanohybrids is confirmed using Fourier transform infrared and other optical spectroscopic methods. The photoinduced interfacial electron transfer process (as confirmed using the time-resolved fluorescence technique) from the excited state of SQ to the conduction band of ZnO is responsible for the greater reactive oxygen species (ROS) generation ability of the nanohybrid. The production of photoactivated ROS (especially singlet oxygen species) by ZnO-SQ provides remarkable antimicrobial action against clinically significant Staphylococcus aureus. Detailed investigations suggest synergistic involvement of cell membrane disruption and nanoparticle internalization followed by photoinduced intracellular ROS generation, which result in an unprecedented 95% bacterial killing activity by the nanohybrid. Moreover, the efficacy of the nanohybrid for disruption of bacterial biofilms has been examined. The electron microscopic images suggest significant bacterial cell death following structural alteration and reduced adherence property of the biofilms. Nanodimension-driven greater internalization of ZnO-SQ followed by an improved dissolution of ZnO in an acidic environment of the biofilm as well as red-light-driven interfacial charge separation and ROS generation improves the efficacy of the material for biofilm destruction. An artificial medical implant mimicking titanium sheets coated with ZnO-SQ depicts light-triggered disruption in the adherence property of matured biofilms. The cytotoxicity and hemolysis assays show inherent biocompatibility of the photoactive nanohybrid. This study is notably promising for the treatment of life-threatening drug-resistant infections and eradication of biofilms formed within artificial implants.

Sensitized ZnO nanorod assemblies to detect heavy metal contaminated phytomedicines: spectroscopic and simulation studies

The immense pharmacological relevance of the herbal medicine curcumin including anti-cancer and anti-Alzheimer effects, suggests it to be a superior alternative to synthesised drugs. The diverse functionalities with minimal side effects intensify the use of curcumin not only as a dietary supplement but also as a therapeutic agent. Besides all this effectiveness, some recent literature reported the presence of deleterious heavy metal contaminants from various sources in curcumin leading to potential health hazards. In this regard, we attempt to fabricate ZnO based nanoprobes to detect metal conjugated curcumin. We have synthesized and structurally characterized the ZnO nanorods (NR). Three samples namely curcumin (pure), Zn-curcumin (non-toxic metal attached to curcumin) and Hg-curcumin (toxic heavy metal attached to curcumin) were prepared for consideration. The samples were electrochemically deposited onto ZnO surfaces and the attachment was confirmed by cyclic voltammetry experiments. Moreover, to confirm a molecular level interaction picosecond-resolved PL-quenching of ZnO NR due to Förster Resonance Energy Transfer (FRET) from donor ZnO NR to the acceptor curcumin moieties was employed. The attachment proximity of ZnO NR and curcumin moieties depends on the size of metals. First principles analysis suggests a variance of attachment sites and heavy metal Hg conjugated curcumin binds through a peripheral hydroxy group to NR. We fabricated a facile photovoltaic device consisting of ZnO NR as the working electrode with Pt counter electrode and iodide-triiodide as the electrolyte. The trend in photocurrent under visible light illumination suggests an enhancement in the case of heavy metal ions due to long range interaction and greater accumulation of charge at the active electrode. Our results provide a detailed physical insight into interfacial processes that are crucial for detecting heavy-metal attached phytomedicines and are thus expected to find vast application as sensors for the detection of selective metal contaminants.

Influence of Nanotoxicity on Human Health and Environment: The Alternative Strategies

Currently, nanotechnology revolutionizing both scientific and industrial community due to their applications in the fields of medicine, environmental protection, energy, and space exploration. Despite of the evident benefits of nanoparticles, there are still open questions about the influence of these nanoparticles on human health and environment. This is one of the critical issues that have to be addressed in the near future, before massive production of nanomaterials. Manufactured nanoparticles, which are finding ever-increasing applications in industry and consumer products fall into the category of emerging contaminants with ecological and toxicological effects on populations, communities and ecosystems. The existing experimental knowledge gave evidence that inhaled nanoparticles are less efficiently separated than larger particles by the macrophage clearance mechanisms and these nanoparticles are known to translocate through the lymphatic, circulatory and nervous systems to many tissues and organs, including the brain. In this review we highlight adverse impacts of nanoparticles on human and the environment with special emphasis on green nanoscience as a sustainable alternative.

Essential Dynamics of an Effective Phototherapeutic Drug in a Nanoscopic Delivery Vehicle: Psoralen in Ethosomes for Biofilm Treatment

Appropriate localization of a drug and its structure/functional integrity in a delivery agent essentially dictates the efficacy of the vehicle and the medicinal activity of the drug. In the case of a phototherapeutic drug, its photoinduced dynamics becomes an added parameter. Here, we have explored the photoinduced dynamical events of a model phototherapeutic drug psoralen (PSO) in a potential delivery vehicle called an ethosome. Dynamic light scattering confirms the structural integrity of the ethosome vehicle after the encapsulation of PSO. Steady state and picosecond resolved polarization gated spectroscopy, including the well-known strategy of solvation and Förster resonance energy transfer, reveal the localization of the drug in the vehicle and the environment in the proximity of PSO. We have also investigated the efficacy of drug delivery to various individual bacteria (Gram-negative: Escherichia coli; Gram-positive: Staphylococcus aureus) and bacterial biofilms. Our optical and electron microscopic studies reveal a significant reduction in bacterial survival (∼70%) and the destruction of bacterial adherence following a change in the morphology of the biofilms after phototherapy. Our studies are expected to find relevance in the formulation of drug delivery agents in several skin diseases and biofilm formation in artificial implants.

A novel nanohybrid for cancer theranostics: folate sensitized Fe2O3 nanoparticles for colorectal cancer diagnosis and photodynamic therapy

Organic-inorganic nanohybrids are becoming popular for their potential biological applications, including diagnosis and treatment of cancerous cells. The motive of this study is to synthesise a nanohybrid for the diagnosis and therapy of colorectal cancer. Here we have developed a facile and cost-effective synthesis of folic acid (FA) templated Fe₂O₃ nanoparticles with excellent colloidal stability in water using a hydrothermal method for the theranostics applications. The attachment of FA to Fe₂O₃ was confirmed using various spectroscopic techniques including FTIR and picosecond resolved fluorescence studies. The nanohybrid (FA-Fe₂O₃) is a combination of two nontoxic ingredients FA and Fe₂O₃, showing remarkable photodynamic therapeutic (PDT) activity in human colorectal carcinoma cell lines (HCT 116) via generation of intracellular ROS. The light induced enhanced ROS activity of the nanohybrid causes significant nuclear DNA damage, as confirmed from the comet assay. Assessment of p53, Bax, Bcl2, cytochrome c (cyt c) protein expression and caspase 9/3 activity provides vivid evidence for cell death via an apoptotic pathway. In vitro magnetic resonance imaging (MRI) experiments in folate receptor (FR) overexpressed cancer cells (HCT 116) and FR deficient human embryonic kidney cells (HEK 293) reveal the target specificity of the nanohybrid towards cancer cells, and are thus pronounced MRI contrasting agents for the diagnosis of colorectal cancer.

Citrate functionalized Mn3O4 in nanotherapy of hepatic fibrosis by oral administration

Aim:

To test the potential of orally administered citrate functionalized Mn₃O₄ nanoparticles (C-Mn₃O₄ NPs) as a therapeutic agent against hepatic fibrosis and associated chronic liver diseases.

Materials & methods:

C-Mn₃O₄ NPs were synthesized and the pH dependent antioxidant mechanism was characterized by in vitro studies. CCl₄ intoxicated mice were orally treated with C-Mn₃O₄ NPs to test its in vivo antioxidant and antifibrotic ability.

Results:

We demonstrated ultrahigh efficacy of the C-Mn₃O₄ NPs in treatment of chronic liver diseases such as hepatic fibrosis and cirrhosis in mice compared with conventional medicine silymarin without any toxicological implications.

Conclusion:

These findings may pave the way for practical clinical use of the NPs as safe medication of chronic liver diseases associated with fibrosis and cirrhosis in human subjects.

Hepatic fibrosis is a common response to chronic liver injury from a number of causes including alcohol, toxin, and persistent viral and helminthic infections, which may ultimately lead to hepatic carcinoma. Although billions of people are affected throughout the world, there is no drug available for treatment of this chronic disease. Here, in a preclinical study, we have shown that oral administration of citrate functionalized Mn₃O₄ nanoparticles can effectively reduce the extent of liver fibrosis in mice. We have also predicted the underlying therapeutic mechanism that involves mitochondria and antioxidant systems of the body.

Allosteric Inhibitory Molecular Recognition of a Photochromic Dye by a Digestive Enzyme: Dihydroindolizine makes α-chymotrypsin Photo-responsive

The structural-functional regulation of enzymes by the administration of an external stimulus such as light could create photo-switches that exhibit unique biotechnological applications. However, molecular recognition of small ligands is a central phenomenon involved in all biological processes. We demonstrate herein that the molecular recognition of a photochromic ligand, dihydroindolizine (DHI), by serine protease α-chymotrypsin (CHT) leads to the photo-control of enzymatic activity. We synthesized and optically characterized the photochromic DHI. Light-induced reversible pyrroline ring opening and a consequent thermal back reaction via 1,5-electrocyclization are responsible for the photochromic behavior. Furthermore, DHI inhibits the enzymatic activity of CHT in a photo-controlled manner. Simultaneous binding of the well-known inhibitors 4-nitrophenyl anthranilate (NPA) or proflavin (PF) in the presence of DHI displays spectral overlap between the emission of CHT-NPA or CHT-PF with the respective absorption of cis or trans DHI. The results suggest an opportunity to explore the binding site of DHI using Förster resonance energy transfer (FRET). Moreover, to more specifically evaluate the DHI binding interactions, we employed molecular docking calculations, which suggested binding near the hydrophobic site of Cys-1-Cys-122 residues. Variations in the electrostatic interactions of the two conformers of DHI adopt unfavorable conformations, leading to the allosteric inhibition of enzymatic activity.

Multi-angle fluorometer technique for the determination of absorption and scattering coefficients of subwavelength nanoparticles

A thorough analysis of the resonance light scattering (RLS) technique for quantitative scattering measurements of subwavelength nanoparticles is reported. The systematic error associated with using a measurement at a single angle to represent all of the scattered light is investigated. In-depth analysis of the reference material was performed to identify and minimize the error associated with the reference material. Semiconductor ZnO nanobullets and spherical Au nanoparticles of various sizes were used to verify the approach. A simple and inexpensive modification to standard fluorometers is demonstrated using a glass prism allowing scattering measurements in the slightly forward and backwards directions. This allows quantification of the systematic error associated with RLS which is consistently overlooked.