Advancements in molecular disassembly of optical probes: a paradigm shift in sensing, bioimaging, and therapeutics

The majority of self-assembled fluorescent dyes suffer from aggregation-caused quenching (ACQ), which detrimentally affects their diagnostic and therapeutic effectiveness. While aggregation-induced emission (AIE) active dyes offer a promising solution to overcome this limitation, they may face significant challenges as the intracellular environment often prevents aggregation, leading to disassembly and posing challenges for AIE fluorogens. Recent progress in signal amplification through the disassembly of ACQ dyes has opened new avenues for creating ultrasensitive optical sensors and enhancing phototherapeutic outcomes. These advances are well-aligned with cutting-edge technologies such as single-molecule microscopy and targeted molecular therapies. This work explores the concept of disaggregation-induced emission (DIE), showcasing the revolutionary capabilities of DIE-based dyes from their design to their application in sensing, bioimaging, disease monitoring, and treatment in both cellular and animal models. Our objective is to provide an in-depth comparison of aggregation versus disaggregation mechanisms, aiming to stimulate further advancements in the design and utilization of ACQ fluorescent dyes through DIE technology. This initiative is poised to catalyze scientific progress across a broad spectrum of disciplines.

A simple protocol for the synthesis of perylene bisimides from perylene tetracarboxylic dianhydride

Perylene bisimides are highly attractive polycyclic aromatic hydrocarbons due to their photostability associated to unique and characteristic photochemical properties. They have been widely used for analytical purposes, despite the hydrophobicity of most of these compounds. The ring substitution pattern plays an important role in fine-tuning the physicochemical properties that govern solubility and aggregation. In this work, a selection of perylene bisimides were prepared from the reaction of perylenetetracarboxylic dianhydride with α-amino acids or primary aliphatic and aromatic amines. These molecules were obtained in good yield by a simple synthetic protocol based on the use of imidazole as a green solvent and avoiding the need for complex purification methods, a major advantage for future applications. Functionalization of the exocyclic substituent can also be performed and was exemplified by the incorporation of the maleimide and anthraquinone moieties.

A Review on Graphene Analytical Sensors for Biomarker-based Detection of Cancer

The engineering of nanoscale materials has broadened the scope of nanotechnology in a restricted functional system. Today, significant priority is given to immediate health diagnosis and monitoring tools for point-of-care testing and patient care. Graphene, as a one-atom carbon compound, has the potential to detect cancer biomarkers and its derivatives. The atom-wide graphene layer specialises in physicochemical characteristics, such as improved electrical and thermal conductivity, optical transparency, and increased chemical and mechanical strength, thus making it the best material for cancer biomarker detection. The outstanding mechanical, electrical, electrochemical, and optical properties of two-dimensional graphene can fulfil the scientific goal of any biosensor development, which is to develop a more compact and portable point-of-care device for quick and early cancer diagnosis. The bio-functionalisation of recognised biomarkers can be improved by oxygenated graphene layers and their composites. The significance of graphene that gleans its missing data for its high expertise to be evaluated, including the variety in surface modification and analytical reports. This review provides critical insights into graphene to inspire research that would address the current and remaining hurdles in cancer diagnosis.

Recent advances of nanocrystals in cancer theranostics

Emerging cancer cases across the globe and treating them with conventional therapies with multiple limitations have been challenging for decades. Novel drug delivery systems and alternative theranostics are required for efficient detection and treatment. Nanocrystals (NCs) have been established as a significant cancer diagnosis and therapeutic tool due to their ability to deliver poorly water-soluble drugs with sustained release, low toxicity, and flexibility in the route of administration, long-term sustainable drug release, and noncomplicated excretion. This review summarizes several therapies of NCs, including anticancer, immunotherapy, radiotherapy, biotheranostics, targeted therapy, photothermal, and photodynamic. Further, different imaging and diagnostics using NCs are mentioned, including imaging, diagnosis through magnetic resonance imaging (MRI), computed tomography (CT), biosensing, and luminescence. In addition, the limitations and potential solutions of NCs in the field of cancer theranostics are discussed. Preclinical and clinical data depicting the importance of NCs in the spotlight of cancer, its current status, future aspects, and challenges are covered in detail.

Rapid detection of hydrogen sulfide in vegetables and monosodium glutamate based on perylene supramolecular aggregates using an indicator displacement assays strategy

Hydrogen sulfide (H₂S) has been clearly identified as a hazardous chemical pollutant that seriously affects food safety and human health. In order to develop a rapid, accurate and efficient H₂S tracking method, this work propose a strategy based on indicator displacement assays (IDA). A water-soluble histidine-modified perylene diimide fluorescent probe was synthesized by a one-step method, and the probe can form supramolecular aggregates in the presence of Cd²⁺. There will be a fluorescence transformation of probe, caused by the change of the state of aggregation and adjusted by various concentration of S^2-, which can achieve the fluorescence detection of S^2-. The limit of detection is as low as 0.41 µmol/L. Particularly worth mentioning is that the probe in this work can be recycled for at least 5 times, which is environmentally friendly and economical. Finally, this method was applied in three kinds of vegetables and monosodium glutamate samples.

Applications of graphene-based electrochemical and optical biosensors in early detection of cancer biomarkers

Graphene is a one-atom-thick carbon compound, which holds promises for detecting cancer biomarkers along with its derivatives. The atom-wide graphene layer is ideal for cancer biomarker detection due to its unique physicochemical properties like increased electrical and thermal conductivity, optical transparency, and enhanced chemical and mechanical strength. The scientific aim of any biosensor is to create a smaller and portable point of care device for easy and early cancer detection; graphene is able to live up to that. Apart from tumour detection, graphene-based biosensors can diagnose many diseases, their biomarkers, and pathogens. Many existing remarkable pieces of research have proven the candidacy of nanoparticles in most cancer biomarkers detection. This article discusses the effectiveness of graphene-based biosensors in different cancer biomarker detection. This article provides a detailed review of graphene and its derivatives that can be used to detect cancer biomarkers with high specificity, sensitivity, and selectivity. We have highlighted the synthesis procedures of graphene and its products and also discussed their significant properties. Furthermore, we provided a detailed overview of the recent studies on cancer biomarker detection using graphene-based biosensors. The different paths to create and modify graphene surfaces for sensory applications have also been highlighted in each section. Finally, we concluded the review by discussing the existing challenges of these biosensors and also highlighted the steps that can be taken to overcome them.

A perylene diimide-based nanoring architecture for exogenous and endogenous ATP detection: biochemical assay for monitoring phosphorylation of glucose

Positively charged amphiphiles hold great significance in supramolecular chemistry due to their good solubility, and physiochemical and molecular recognition properties. Herein, we report the synthesis, characterization and molecular recognition properties of the dicationic amphiphile based on perylene diimide-tyrosine alkyl amide amine (PDI 3). PDI 3 showed the formation of a nanoring architecture in the self-assembled aggregated state (90% H₂O-DMSO mixture) as observed by SEM and TEM studies. The diameter of the nanoring is around 30-50 nm with a height varying from 1 to 2 nm. The self-assembled aggregates of PDI 3 are very sensitive towards nucleoside triphosphates. Upon addition of ATP, PDI 3 showed a decrease in the absorbance and emission intensity at 535 and 580 nm (due to the monomer state), respectively. The lowest detection limit for ATP is 10.8 nM (UV) and 3.06 nM (FI). Upon interaction of ATP with PDI 3, the nanoring morphology transformed into a spherical structure. These changes could be attributed to the formation of ionic self-assembled aggregates between dicationic PDI 3 and negatively charged ATP via electrostatic and H-bonding interactions. The complexation mechanism of PDI 3 and ATP was confirmed by optical, NMR, Job's plot, DLS, SEM and AFM studies. PDI 3 displays low cytotoxicity toward MG-63 cells and can be successfully used for the detection of exogenous and endogenous ATP. The resulting PDI 3 + ATP complex is successfully used as a 'turn-on' biochemical assay for monitoring phosphorylation of glucose.

AIE materials for cancer cell detection, bioimaging and theranostics

AIE materials exhibit weakly emissive or non-emissive properties in dilute solutions while emit powerful fluorescence in the aggregated/solid state. Recently, AIE based materials have gained immense attention due to their multifunctional role in cancer cell detection, bioimaging and cancer theranostics. In this present book chapter, we will highlight recent advancements of AIE materials for different cancer theranostics applications.

A mitochondria-targeting fluorescent sensor for on-off-on response to Cu2+ and ATP in cells and zebrafish

Cupric ion (Cu²⁺) and adenosine triphosphate (ATP) are functionally important in mitochondria and play essential roles in many important biological processes. In this work, a mitochondria-targeting fluorescent molecule Mito-A was used as a probe to detect Cu²⁺ and ATP. The results showed remarkable fluorescence quenching of Mito-A in the presence of Cu²⁺, and then the quenched fluorescence solution gradually recovered due to the ATP binding to Cu²⁺ from the structure of the molecule. Mito-A has high sensitivity to Cu²⁺ and ATP, with limits of detection (LOD) close to 40 nM and 0.43 μM, respectively. Cell imaging experiments showed that Mito-A has good mitochondria-targeting capabilities, and can be successfully employed for imaging Cu²⁺ and ATP in living cells and zebrafish.

Aggregation-driven fluorescence quenching of imidazole-functionalized perylene diimide for urea sensing

Stimuli-responsive self-assembly of functional amphiphilic molecules by specific chemical stimulants is a promising strategy for sensor application. Herein, we demonstrate a fast optical detection of urea in human urine by exploiting bolaform perylene diimide functionalized with imidazoles (PDI-Hm), whose aggregation is induced by urea hydrolysis. The hydroxides produced from the enzymatic urea hydrolysis deprotonate the imidazoles to reduce electrostatic repulsion between PDI-Hm molecules in a HCl-methanol mixture, thereby leading to aggregation and consequent fluorescence quenching. The molecular interaction of PDI-Hm was further scrutinized to understand the aggregation behavior driven by the screening of electrical repulsion. As an optical sensing probe, PDI-Hm displays a prompt response (<1 min) to hydroxide and detection limit of 0.4 mM for urea. PDI-Hm incorporating urease offers considerable selectivity toward urea among various components in human urine. The urea sensing accuracy of this PDI-Hm fluorescence chemosensor is comparable to that of a clinical method, showing 93.4% consistency. Furthermore, the PDI-Hm was fabricated into a gel film allowed for the fast screening of excessive urea in urine.

Near-IR oxime-based solvatochromic perylene diimide probe as a chemosensor for Pd species and Cu2+ ions in water and live cells

A near-IR perylene diimide probe (OPR-PDI) containing an oxime-propargyl hybrid moiety at the bay position, was designed and synthesized for detection of Pd species and Cu²⁺ ions in 90% water, the solid state and MG-63 live cells. The aggregation tendency of OPR-PDI in different polarity solvents transmits solvatochromic and fluorochromic properties to differentiate certain organic solvents. Supramolecular aggregates of OPR-PDI in 90% water act as a dual chemosensor for palladium (Pd) species via de-propargylation or hydrolysis of the Schiff-base and Cu²⁺ ions via complexation with the O/N binding site with a low limit of detection (LOD) of the order of 7.9 × 10^-8 M and 3.4 × 10^-7 M respectively. TLC strips coated with OPR-PDI can be applied for sensing of Pd⁰ and Cu²⁺ ions in the solid state at levels as low as 34.6 ng cm^-2 and 10.5 ng cm^-2. OPR-PDI imprinted TLC strips could be used as paper sheets for writing coloured alphabets using Pd⁰ and Cu²⁺ ions as ink. Moreover, MTT assay showed that OPR-PDI has very low cytotoxicity (IC₅₀ = 230 μM), good permeability, biocompatibility and can be applied for bio-imaging of Pd species and Cu²⁺ ions in MG-63 cells. DFT calculations, and cyclic voltammetric (CV) and NMR titration studies have also been discussed.

Recent Trends of the Bio-Inspired Nanoparticles in Cancer Theranostics

In recent years, various nanomaterials have emerged as an exciting tool in cancer theranostic applications due to their multifunctional property and intrinsic molecular property aiding effective diagnosis, imaging, and successful therapy. However, chemically synthesized nanoparticles have several issues related to the cost, toxicity and effectiveness. In this context, bio-inspired nanoparticles (NPs) held edges over conventionally synthesized nanoparticles due to their low cost, easy synthesis and low toxicity. In this present review article, a detailed overview of the cancer theranostics applications of various bio-inspired has been provided. This includes the recent examples of liposomes, lipid nanoparticles, protein nanoparticles, inorganic nanoparticles, and viral nanoparticles. Finally, challenges and the future scopes of these NPs in cancer therapy and diagnostics applications are highlighted.

Water-Soluble Perylene Diimide for Highly Sensitive and Repeatable Metal Ion Detection with Novel Logic Gate Operation

In this paper, we report a synthesised water soluble perylene derivative, N,N′-di(2-aspartic acid)-perylene-3,4,9,10-tetracarboxylic diimide (PASP), for highly sensitive and repeatable detection of copper (Cu2+) and aluminium ions (Al3+) and novel logic gate operation. In the presence of metal ions, a dramatic decrease in PASP optical intensity was induced based on the strong interaction between terminal carboxy groups and the metal ions. Detection limits of 0.22 and 0.24μM were respectively obtained at physiological pH. The signals could be recovered upon the addition of ethylenediaminetetraacetate (EDTA) and P2O74−, which competed for Cu2+ and Al3+ in the PASP-CuII and PASP-AlIII systems and induced their dissociation as secondary sensors for anions. At least four detection cycles were performed with a high recovery efficiency. Based on these phenomena, a novel three-level logic gate (OR-IMP-OR) was performed for smart signal readout with metal ions (Cu2+ and Al3+) and anions (EDTA and P2O74−) as input signals, and the relative change of optical intensity of PASP as output signal. Furthermore, the prepared PASP molecule also responded sensitively to Cu2+ and Al3+ in 10% diluted serum medium.

A terbium-based metal-organic framework@gold nanoparticle system as a fluorometric probe for aptamer based determination of adenosine triphosphate

This study reports on a method for fluorometric aptasensing of adenosine triphosphate (ATP). It is based on the interaction of dispersed (red) and agglomerated (blue) gold nanoparticles (AuNPs) with a water-dispered terbium(III) based metal-organic framework (Tb-MOF). The dispersed AuNPs quench the emissions of the Tb-MOF, while the aggregated AuNPs have little effect. Under the condition of high salt concentration, the free aptamer against ATP does not stabilize the AuNPs against aggregation. This causes a color change from red to blue and weak quenching of the fluorescence of the Tb-MOF (with peaks at 489 nm and 544 nm after excitation at 290 nm). On addition of ATP, it will be bound by its aptamer to form a complex that is adsorbed on the AuNPs. This protects the AuNPs from salt-induced aggregation and the color (with a peak at 525 nm) remains red. The two fluorescence bands of the Tb-MOF are therefore suppressed by fluorescence resonance energy transfer (FRET) between Tb-MOF and the dispersed AuNPs. Fluorescence drops linearly in the 50 nM to 10 μM ATP concentration range, and the detection limit is 23 nM. ATP analogs such as guanosine triphosphate, uridine triphosphate, cytidine triphosphate, adenosine monophosphate and cyclic adenosine monophosphate have no obvious interference. The method was successfully applied to the determination of ATP in (spiked) human plasma samples and gave satisfactory recoveries. Graphical abstract Schematic of a terbium-based metal-organic framework@gold nanoparticle system as a fluorometric probe for aptamer based determination of adenosine triphosphate. The dispersed gold nanoparticles (AuNPs) quench the fluorescence of the terbium-based metal-organic framework (Tb-MOF), while the aggregated AuNPs have little effect. In the presence of adenosine triphosphate (ATP), the aptamer-ATP complexes provide greater protection towards AuNPs than aptamer alone under high salt condition. Based on this, a novel Tb-MOF@AuNP platform is established for ATP detection.

Simultaneous Detection of Adenosine Triphosphate and Glucose Based on the Cu-Fenton Reaction

Both adenosine triphosphate (ATP) and glucose are important to human health, and their abnormal levels are closely related to angiocardiopathy and hypoglycaemia. Therefore, the simultaneous determination of ATP and glucose with a single test mode is highly desirable for disease diagnostics and early recognition. Herein, a new fluorescence on/off switch sensing platform is developed by carbon nanodots (CNDs) to detect ATP and glucose simultaneously. The fluorescence of CNDs can be quenched by Cu²⁺ and hydrogen peroxide (H₂O₂), due to the formation of hydroxyl radicals (&middot;OH) produced in the Cu-Fenton reaction. Based on the high affinity of Cu²⁺ with ATP, the fluorescence of CNDs will recover effectively after adding ATP. Additionally, glucose can be efficiently catalyzed by glucose oxidase (GOx) to generate H₂O₂, so the platform can also be utilized to analyze glucose. Under optimum conditions, this sensing platform displays excellent sensitivity and the linear ranges are from 0.1 to 7 &mu;M for ATP with a limit of detection (LOD) of 30.2 nM, and from 0.1 to 7 mM for glucose with a LOD 39.8 &mu;M, respectively. Benefiting from the high sensitivity and selectivity, this sensing platform is successfully applied for simultaneous detection of ATP and glucose in human serum samples with satisfactory recoveries.

Electrochemical and optical biosensors for early-stage cancer diagnosis by using graphene and graphene oxide

Conventional instruments for cancer diagnosis including magnetic resonance imaging, computed tomography scan, are expensive and require long-waiting time, whilst the outcomes have not approached to the successful early-stage diagnosis yet. Due to the special properties of graphene-based nanocomposites, e.g., good electrical and thermal conductivity, luminescence, and mechanic flexibility, these ultra-thin two-dimensional nanostructures have been extensively used as platforms for detecting biomolecules and cells. Herein, we discuss the development of two types of graphene and graphene oxide-based biosensors: electrochemical and optical, aimed for tumor detection and early diagnosis of cancer. Moreover, we highlight the challenges of their use as biosensors for cancer detection. Efficient surface modification and suitable bio-conjugation of graphene and graphene oxide is discussed, including key role in improvement of the biocompatibility, and improved performance in terms of selectivity and sensitivity towards the early diagnosis of cancer.

Spiral frameworks constructed by 1,2-phenylene-dioxydiacetic acid as highly sensitive and selective luminescent probes to detect PO43− ions in aqueous solutions

Three novel clubbed photo-luminescent lanthanide 1D coordination polymers, [Ln(L)(NO₃)(H₂O)₂]_n (where Ln is La, Ce, and Pr, respectively, and H₂L = 1,2-phenylenedioxydiacetic acid), were synthesized under hydrothermal conditions.

Carbon dots–quinoline derivative nanocomposite: facile synthesis and application as a “turn-off” fluorescent chemosensor for detection of Cu2+ ions in tap water

In this paper, a novel quinoline derivative: 8-(pyridin-2-ylmethoxy)quinoline-2-carboxylic acid (Q) has been successfully synthesized, then it was coupled with carbon dots (CDs) to synthesize a CDs–Q nanocomposite by a simple and green method.

Coumarinyl thioether Schiff base as a turn-on fluorescent Zn(ii) sensor and the complex as chemosensor for the selective recognition of ATP, along with its application in whole cell imaging

A Zn²⁺ sensor, coumarinyl thioether Schiff base shows the LOD 0.068 μM. The fluorogenic complex, [ZnL] recognizes ATP in presence of other anions and the LOD, 6.7 μM, is the lowest in literature. Ligand is used for fluorescence cell imaging process.

Modulation of Amyloid-β Fibrils into Mature Microrod-Shaped Structure by Histidine Functionalized Water-Soluble Perylene Diimide

Alzheimer's disease (AD) is associated with different types of amyloid peptide aggregates including senile plaques, fibrils, protofibrils, and oligomers. Due to these difficulties, a powerful strategy is needed for the disaggregation of amyloid aggregates by modulating their self-aggregation behavior. Herein, we report a unique approach toward transforming the aggregated amyloidogenic peptides using an amino acid functionalized perylene diimide as a molecular modulator, which is a different nondestructive approach as compared to inhibiting the aggregation of peptides. The histidine functionalized perylenediimide (PDI-HIS) molecule could coassemble with amyloid β (Aβ) peptides via hydrogen bonding that leads to the enhancement in the π-π interactions between Aβ and PDI-HIS moieties. The Thioflavin T (ThT) assay and various spectroscopic and microscopic techniques establish that the PDI-HIS molecules accelerate the Aβ1-40 and the amyloid aggregates in CSF into micro size coassembled structures. These results give rise to a new and unique complementary approach for modulating the biological effects of the aggregates in amyloidogenic peptides.

A turn-on fluorescent pyrene-based chemosensor for Cu(ii) with live cell application

A pyrene-based fluorescent sensor (PHP) was synthesized for Cu(ii) detection.