Polydiacetylene Liposome Microarray toward Facile Measurement of Platelet Activation in Whole Blood

A novel polydiacetylene-functionalized fibrinogen paper-based biosensor for on-spot and rapid detection of Staphylococcus aureus

Staphylococcus aureus contamination continues to be a harmful foodborne pathogen threatening of human health, and there is a growing need for rapid detection technologies. This study proposed a novel paper biosensor based on a polydiacetylene (PDA) polymer functionalized fibrinogen (Fg) for the detection of S. aureus in food sources. The fluorophore was developed based on the high binding ability of fibrinogen-binding proteins on the surface of S. aureus. This binding caused twisting in the PDA backbone, leading to changes in chromatic and fluorescent. The detection limit of this method was 50.1 CFU/mL for S. aureus-contaminated foodstuffs and 65.0 CFU/mL for the pure S. aureus culture, and the novelty came from its rapidity and selectivity for S. aureus compared to other foodborne bacteria. In summary, the present work provides a rapid detection method for S. aureus detection, which will help in addressing food safety-related issues.

Colorimetric aptasensing of microcystin-LR using DNA-conjugated polydiacetylene

Polydiacetylene (PDA) holds promise as a versatile material for biosensing applications due to its unique optical properties and self-assembly capabilities. In this study, we developed a colorimetric detection biosensor system utilizing PDA and aptamer for the detection of microcystin-LR (MC-LR), a potent hepatotoxin found in cyanobacteria-contaminated environments. The biosensor was constructed by immobilizing MC-LR-specific aptamer on magnetic beads, where the aptamer was hybridized with a urease-labelled complementary DNA (cDNA-urease). Upon binding MC-LR, the aptamer undergoes a conformational change to release cDNA-urease. The released cDNA-urease is subsequently captured by PDA bearing a single-stranded DNA (ssDNA). The enzymatic reaction triggers a distinctive color transition of PDA from blue to red. The results demonstrate exceptional sensitivity, with a linear detection range of 5-100 ng/mL and a limit of detection as low as 1 ng/mL. The practicability of the colorimetric method was demonstrated by detecting different levels of MC-LR in spiked water samples. The recoveries ranged from 77.3 to 102% and the color change, visible to the naked eye, underscores the practical utility for on-site applications. Selectivity for MC-LR over other microcystin variants (MC-RR and MC-YR) was confirmed. The colorimetric detection platform capitalizes on the properties of PDA and nucleic acid, offering a robust method for detecting small molecules with potential applications in environmental monitoring and public health.

Polydiacetylene Liposome-Based Dual-Output Optical Sensor for ppb Level Detection of Dopamine in Solution and Solid Phases

Dopamine (DA), a neurotransmitter, plays a crucial role in regulating motor functions and emotions and can serve as a marker for several diseases. In this study, we report a highly sensitive polydiacetylenes (PDA)-based dual-output sensor for dopamine detection in both solution and solid phases that was developed by modifying PDA liposomes with boronic acid groups at the termini. This sensor exploits the high affinity between the catechol residue of dopamine and the -B(OH)2 group of the PDA-based probe (PDA-PhBA) to form boronate ester bonds, causing a stress-induced blue-to-red color change along with a steady increase in fluorescence response at λmax 622 nm. The PDA-PhBA-based sensor displays high sensitivity toward dopamine with low limit of detection of 6.2 ppb in colorimetric analysis and 0.6 ppb in fluorimetric measurements, demonstrating its dual optical output ability. The sensor works well for adrenaline, another catecholamine, with similar efficacy. Its practical applicability was validated by the successful recovery of trace level dopamine in blood serum and real water samples. Additionally, immobilizing PDA-PhBA liposomes in sodium alginate produced PDA beads for the solid-phase detection of dopamine with an limit of detection (LOD) of 59 nM (9.0 ppb) in colorimetric detection using a smartphone for capturing images and ImageJ software for analysis.

A highly sensitive fluorescence biosensor for aflatoxins B1 detection based on polydiacetylene liposomes combined with exonuclease III-assisted recycling amplification

A fluorescence biosensor for determination of aflatoxin B1 (AFB1) based on polydiacetylene (PDA) liposomes and exonuclease III (EXO III)-assisted recycling amplification was developed. The AFB1 aptamer partially hybridizes with complementary DNA (cDNA), which is released upon recognition of AFB1 by the aptamer. Subsequently, the cDNA hybridizes with hairpin H to form double-stranded DNA that undergoes digestion by EXO III, resulting in the cyclic release of cDNA and generation of capture DNA for further reaction. The capture DNA then hybridizes with probe modified on PDA liposomes, leading to aggregation of liposomes and subsequent fluorescence production. This strategy exhibited a limit of detection of 0.18 ng/mL within the linear range 1-100 ng/mL with a determination coefficient > 0.99. The recovery ranged from 92.81 to 106.45%, with relative standard deviations (RSD) between 1.73 and 4.26%, for corn, brown rice, peanut butter, and wheat samples. The stability, accuracy, and specificity of the method demonstrated the applicability for real sample analysis.

Detection of dopamine levels using a polydiacetylene liposomal aequorin bioluminescent device with octadecylboronic acid

The development of an easy-to-use and rapid method for the determination of dopamine levels is desirable for the diagnosis of neurological conditions, such as Parkinson's disease, which are characterized by low levels of dopamine. Herein, a polydiacetylene liposomal aequorin bioluminescent device (PLABD) containing octadecylboronic acid (OBA) as a recognition material (PLABD-OBA) was prepared for the determination of dopamine concentrations in aqueous solution. The bioluminescent signals of the photoprotein aequorin in PLABD-OBA increased according to increasing dopamine concentrations. The calibration curve showed good linearity over a dopamine concentration range of 70-700 µM (r = 0.918), with a detection limit of 7.5 µM. The addition of other catecholamines to the PLABD-OBA resulted in low bioluminescent signals of aequorin. Because the physiological levels of dopamine are generally 0.001-1.0 µM, this system had insufficient sensitivity for the clinical monitoring of dopamine levels. However, the PLABD-OBA developed herein is an easy-to-use and rapid analytical method that is specific for dopamine.

Dual Friction Force/Fluorescence Microscopy

Friction force microscopy (FFM) is a mode of atomic force microscopy (AFM) that quantifies both normal and horizontal forces against substrates. Recent improvement in its accuracy at nanonewton ranges and the possibility of combining AFM with fluorescence microscopy enabled the simultaneous characterization by FFM and fluorescence microscopy. This Tutorial describes the operation principle of the dual friction force/fluorescence microscopy setup and highlights its emerging applications in mechanochromic materials.

Colorimetric Detection of HER2-Overexpressing-Cancer-Derived Exosomes in Mouse Urine Using Magnetic-Polydiacetylene Nanoparticles

Breast cancer (BC) is a major global health problem, with ≈20-25% of patients overexpressing human epidermal growth factor receptor 2 (HER2), an aggressive marker, yet access to early detection and treatment varies across countries. A low-cost, equipment-free, and easy-to-use polydiacetylene (PDA)-based colorimetric sensor is developed for HER2-overexpressing cancer detection, designed for use in low- and middle-income countries (LMICs). PDA nanoparticles are first prepared through thin-film hydration. Subsequently, hydrophilic magnetic nanoparticles and HER2 antibodies are sequentially conjugated to them. The synthesized HER2-MPDA can be concentrated and separated by a magnetic field while inheriting the optical characteristics of PDA. The specific binding of HER2 antibody in HER2-MPDA to HER2 receptor in HER2-overexpressing exosomes causes a blue-to-red color change by altering the molecular structure of the PDA backbone. This colorimetric sensor can simultaneously separate and detect HER2-overexpressing exosomes. HER2-MPDA can detect HER2-overexpressing exosomes in the culture medium of HER2-overexpressing BC cells and in mouse urine samples from a HER2-overexpressing BC mouse model. It can selectively isolate and detect only HER2-overexpressing exosomes through magnetic separation, and its detection limit is found to be 8.5 × 108  particles mL-1 . This colorimetric sensor can be used for point-of-care diagnosis of HER2-overexpressing BC in LMICs.

Temperature-Controlled Pathway Complexity in Self-Assembly of Perylene Diimide-Polydiacetylene Supramolecule

Self-assembly process represents one of the most powerful and efficient methods for designing functional nanomaterials. For generating optimal functional materials, understanding the pathway complexity during self-assembly is essential, which involves the aggregation of molecules into thermodynamically or kinetically favored pathways. Herein, a functional perylene diimide (PDI) derivative by introducing diacetylene (DA) chains (PDI-DA) is designed. Temperature control pathway complexity with the evolution of distinct morphology for the kinetic and thermodynamic product of PDI-DA is investigated in detail. A facile strategy of UV-induced polymerization is adopted to trap and capture metastable kinetic intermediates to understand the self-assembly mechanism. PDI-DA showed two kinetic intermediates having the morphology of nanosheets and nanoparticles before transforming into the thermodynamic product having fibrous morphology. Spectroscopic studies revealed the existence of distinct H- and J-aggregates for kinetic and thermodynamic products respectively. The polymerized fibrous PDI-DA displayed reversible switching between J-aggregate and H-aggregate.

Amplifying the Sensitivity of Polydiacetylene Sensors: The Dummy Molecule Approach

There is an increasing need for fast and accurate assessment of various health conditions, where polydiacetylenes (PDA), having unique stress-sensitive optical properties, have great potential. When the conjugated backbone of PDA is disturbed by steric repulsion between the receptor-target complexes formed at the PDA surface via specific recognition events, the bandgap of PDA increases and produces color change and fluorescent emission as a dual sensory signal. However, this detection mechanism suggests an intrinsic sensitivity limit of PDA platform because unless adjacent receptors are occupied by target molecules no signal is anticipated. A novel approach to improve the sensitivity and limit of detection of PDA sensors has been developed by preoccupying the surface of PDA liposomes with an optimized amount of artificial target molecules named as dummy molecules. The sensitivity and limit of detection (LOD) showed large improvement by the surface-bound dummy molecules. In addition, the dummy strategy was synergically integrated with another sensitivity enhancing method with a different working mechanism in a PDA sensor for Neomycin detection. When optimized, the LOD of the PDA sensor was improved to 7 nM from 80 nM of the control and the signal intensity increased consistently throughout the entire tested concentration range of the target Neomycin. Finally, the general applicability of the dummy strategy to other target molecules was successfully confirmed by implementing the dummy strategy in a PDA sensor for Surfactin detection.