An efficient strategy to assemble water soluble histidine-perylene diimide and graphene oxide for the detection of PPi in physiological conditions and in vitro

Biomedical applications of graphene-based nanomaterials: recent progress, challenges, and prospects in highly sensitive biosensors

Graphene-based nanomaterials (graphene, graphene oxide, reduced graphene oxide, graphene quantum dots, graphene-based nanocomposites, etc.) are emerging as an extremely important class of nanomaterials primarily because of their unique and advantageous physical, chemical, biological, and optoelectronic aspects. These features have resulted in uses across diverse areas of scientific research. Among all other applications, they are found to be particularly useful in designing highly sensitive biosensors. Numerous studies have established their efficacy in sensing pathogens and other biomolecules allowing for the rapid diagnosis of various diseases. Considering the growing importance and popularity of graphene-based materials for biosensing applications, this review aims to provide the readers with a summary of the recent progress in the concerned domain and highlights the challenges associated with the synthesis and application of these multifunctional materials.

Chitosan-initiated gold nanoparticles with enhanced fluorescence for unique Fe3+/PPi sensing and photothermal therapy

The design of surface ligands is crucial for ligand-protected gold nanoparticles (AuNPs). Herein, following the principle of green synthesis, environmentally friendly gold nanoparticles (AuNPs@His@CC, AuHC) were fabricated based on dual ligands of histidine and carboxylated chitosan. AuHC showed the advantages of low toxicity, good photoluminescent stability and ideal biocompatibility. Compared with single histidine-coated gold nanoclusters (AuNCs@His, AuH), AuHC presented enhanced fluorescence attributed to the addition of chitosan. The blue-emitting AuHC has a unique response to Fe3+ with detection limits as low as 9.51 nM. Interestingly, the quenched fluorescence of AuHC-Fe3+ system could be restored through the introduction of PPi with a detection limit of 10.6 μM. So an "on-off-on" fluorescence sensing platform was achieved. Apart from good optical properties and sensing, the designed AuHC demonstrated outstanding photothermal conversion efficiency (27.8 %), which made it ideal material for thermal ablation of tumor. To be specific, after laser irradiation (660 nm, 0.78 W cm-2, 10 min) of AuHC, the survival rate of HeLa cells as a tumor cell model decreased to 12.7 %, indicating that AuHC has a significant tumor inhibition effect in vitro. Besides, AuHC also could be a befitting candidate for overcoming drug-resistant tumor cells such as MCF-7/ADR cells. Notably, AuHC can markedly ablate solid tumors in 4T1 tumor-bearing mice after laser irradiation (660 nm, 0.78 W cm-2, 10 min). Hence this work provides insight into the design of multifunctional AuNPs platform for simultaneously integrating the ion sensing and photothermal therapy of cancer.

Perylene diimide-based sensors for multiple analyte sensing (Fe2+/H2S/ dopamine and Hg2+/Fe2+): cell imaging and INH, XOR, and encoder logic

In this report, we present our results on the recognition of multiple analytes using trisubstituted PDI-based chemosensors DNP and DNB in 50% HEPES buffered-CH₃CN solution. Upon the addition of Hg²⁺, DNB showed a decrease and increase in absorbance intensity at 560 and 590 nm, respectively, with a detection limit of 7.17 μM and bleaching of the violet color (de-butynoxy). Similarly, the addition of Fe²⁺ or H₂S to the solution of DNP or DNB resulted in ratiometric changes (A_688nm/A_560nm) with respective detection limits of 185 nM and 27.6 nM for Fe²⁺, respectively, and a color change from violet to green. However, the addition of >37 μM H₂S caused a decrease in absorbance at 688 nm with a concomitant blue shift to 634 nm. Upon the addition of dopamine, the DNP + Fe²⁺ assay showed ratiometric (A_560nm/A_688nm) changes within 10 s along with a color change from green to violet. Moreover, DNP has been successfully used for the exogenous detection of Fe²⁺ in A549 cells. Further, the multiple outputs observed with DNP in the presence of H₂S have been used to construct NOR, XOR, INH and 4-to-2 encoder logic gates and circuits.

Comprehensive Thione-Derived Perylene Diimides and Their Bio-Conjugation for Simultaneous Imaging, Tracking, and Targeted Photodynamic Therapy

In this study, the chromophore 3,4,9,10-perylenetetracarboxylic diimide (PDI) is anchored with phenyl substituents at the imide N site, followed by thionation, yielding a series of thione products 1S-PDI-D, 2S-cis-PDI-D, 2S-trans-PDI-D, 3S-PDI-D, and 4S-PDI-D, respectively, with n = 1, 2, 3, and 4 thione. The photophysical properties are dependent on the number of anchored thiones, where the observed prominent lower-lying absorption is assigned to the S₀ → S₂(ππ*) transition and is red-shifted upon increasing the number of thiones; the lowest-lying excited state is ascribed to a transition-forbidden S₁(nπ*) configuration. All nS-PDIs are non-emissive in solution but reveal an excellent two-photon absorption cross-section of >800 GM. Supported by the femtosecond transient absorption study, the S₁(nπ*) → T₁(ππ*) intersystem crossing (ISC) rate is > 10¹² s^-1, resulting in ∼100% triplet population. The lowest-lying T₁(ππ*) energy is calculated to be in the order of 1S-PDI-D > 2S-cis-PDI-D ∼ 2S-trans-PDI-D > 3S-PDI-D > 4S-PDI-D, where the T₁ energy of 1S-PDI-D (1.10 eV) is higher than that (0.97 eV) of the ¹O₂ ¹Δ_g state. 1S-PDI-D is further modified by either conjugation with peptide FC131 on the two terminal sides, forming 1S-FC131, or linkage with peptide FC131 and cyanine5 dye on each terminal, yielding Cy5-1S-FC131. In vitro experiments show power of 1S-FC131 and Cy5-1S-FC131 in recognizing A549 cells out of other three lung normal cells and effective photodynamic therapy. In vivo, both molecular composites demonstrate outstanding antitumor ability in A549 xenografted tumor mice, where Cy5-1S-FC131 shows superiority of simultaneous fluorescence tracking and targeted photodynamic therapy.

A novel phenolphthalein-based fluorescent chemosensor for pyrophosphate detection via an Al3+ displacement approach in real samples and living cells

Herein, we report a new phenolphthalein appended Schiff base (PASB) as reversible fluorescent sensor for the detection of pyrophosphate (PPi) ions through the metal displacement mechanism. PASB showed sensing exclusively toward Al³⁺ ions in DMF/H₂O (v/v = 1/4, pH 5.5) solution, which resulted in a significant fluorescence enhancement at 540 nm. The 1: 2 binding stoichiometry for the complex formation between PASB and Al³⁺ was confirmed by Job's plot and mass spectroscopic studies. Moreover, a solution of the in situ formed PASB-Al³⁺ complex displayed a high selectivity to PPi. The addition of PPi to PASB-Al³⁺ ensemble significantly quenched its fluorescence. Thus, a dual response was established based on "Off-On-Off" strategy for detection of both Al³⁺ and PPi. The detection limit is 5.86 nM and 26 nM for Al³⁺ and PPi, respectively. On this basis, we use PASB to detect Al³⁺ in food samples. Furthermore, PASB was successfully applicable to detect Al³⁺ and PPi for intracellular imaging in Human liver cancer cells.

Perylene diimide-based treatment and diagnosis of diseases

Integrated treatment using imaging technology to monitor biological processes for the precise treatment and diagnosis of diseases to improve treatment outcomes is becoming a hot topic. Accordingly, perylene diimide (PDI) has excellent photothermal conversion and photostability, which can be used as a good material for disease treatment and diagnosis. Herein, we review the latest research progress on the real-time diagnosis of related diseases based on perylene diimide probes in the aspects of bioimaging, detection of biomarkers and determination of the pH in living cells. Furthermore, perylene diimide-based multifunctional nano-delivery systems are particularly emphasized, showing great therapeutic potential in the field of image-guided combination therapy in tumor therapy. Finally, the great opportunities and challenges still faced by perylene diimide before entering the clinic are comprehensively analyzed.

Review on application of perylene diimide (PDI)-based materials in environment: Pollutant detection and degradation

Environment pollution is getting serious and various poisonous contaminants with chemical durability, biotoxicity and bioaccumulation have been widespreadly discovered in municipal wastewaters and surface water. The detection and removal of pollutants show great significance for the protection of human health and other organisms. Due to its distinctive physical and chemical properties, perylene diimide (PDI) has received widespread attention from different research fields, especially in the area of environment. In this review, a comprehensive summary of the development of PDI-based materials in fluorescence detection and advanced oxidation technology for environment was introduced. Firstly, we chiefly presented the recent progress about the synthesis of PDI and PDI-based nanomaterials. Then, their application in fluorescence detection for environment was presented and categorized, principally including the detection of heavy metal ions, harmful anions and organic contaminants in the environment. In addition, the application of PDI and PDI-based materials in different advanced oxidation technologies for environment, such as photocatalysis, photoelectrocatalysis, Fenton and Fenton-like reaction and persulfate activation, was also summarized. At last, the challenges and future prospects of PDI-based materials in environmental applications were discussed. This review focuses on presenting the practical applications of PDI and PDI-based materials as fluorescent probes or catalysts (especially photocatalysts) in the detection of hazardous substances or catalytic elimination of organic contaminants. The contents are aimed at supplying the researchers with a deeper understanding of PDI and PDI-based materials and encouraging their further development in environmental applications.

Self-Assembling Peptidic Bolaamphiphiles for Biomimetic Applications

Bolaamphiphile, which is a class of amphiphilic molecules, has a unique structure of two hydrophilic head groups at the ends of the hydrophobic center. Peptidic bolaamphiphiles that employ peptides or amino acids as their hydrophilic groups exhibit unique biochemical activities when they self-organize into supramolecular structures, which are not observed in a single molecule. The self-assembled peptidic bolaamphiphiles hold considerable promise for imitating proteins with biochemical activities, such as specific affinity toward heterogeneous substances, a catalytic activity similar to a metalloenzyme, physicochemical activity from harmonized amino acid segments, and the capability to encapsulate genes like a viral vector. These diverse activities give rise to large research interest in biomaterials engineering, along with the synthesis and characterization of the assembled structures. This review aims to address the recent progress in the applications of peptidic bolaamphiphile assemblies whose densely packed peptide motifs on their surface and their stacked hydrophobic centers exhibit unique protein-like activity and designer functionality, respectively.

Copper oxide integrated perylene diimide self-assembled graphitic pencil for robust non-enzymatic dopamine detection

Exploring a robust, extremely sensitive, cost-effective and reliable assay platform for the precise analysis of dopamine (DA) has become a big challenge predominantly at the clinical level. To participate in this quest, herein, we fabricated a perylene diimide (PDI) self-assembled graphitic surface of the graphitic pencil electrode (GPE) anchored copper oxide (CuO). The self-assembled N-rich PDI led to the fast movement of ions by decreasing the bandgap and improved the electron transport kinetics with more exposed catalytic active sites, thus resulting in the robust electrochemical sensing of DA. The designed sensor exhibited good sensitivity (4 μM⁻¹ cm⁻²), high structural stability, repeatability and excellent reproducibility with an RSD value of 2.9%. Moreover, the developed system showed a wide linear range (5 μM to 500 μM) and reliable selectivity even in the presence of co-existing interferants, such as ascorbic acid and uric acid. The fabricated nanohybrid was eventually employed to analyze DA in spiked physiological fluids and provided satisfactory recoveries. The designed PDI-CuO based interface also showed a very low detection limit of 6 nM (S/N = 3), consequently confirming its suitability for clinical and biological applications.

Exploring a robust, extremely sensitive, cost-effective and reliable assay platform for the precise analysis of dopamine (DA) has become a big challenge predominantly at the clinical level.

Restoring the Oxidase-Like Activity of His@AuNCs for the Determination of Alkaline Phosphatase

In this paper, we propose a simple colorimetric method for the sensitive and selective detection of alkaline phosphatase (ALP) activity based on the turn off/turn on oxidase mimic activity of His@AuNCs. His@AuNCs/graphene oxide hybrids (His@AuNCs/GO) were easily obtained using the self-assembly method with poly (diallyldimethylammonium chloride) (PDDA)-coated GO and showed high oxidase-like activity compared with His@AuNCs. We found that the pyrophosphate ion (P₂O₇^4-, PPi) could effectively inhibit the oxidase mimic activity of His@AuNCs/GO, and the hydrolysis of PPi by ALP restored the inhibited activity of His@AuNCs/GO, enabling them to efficiently catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to generate the blue oxidized product oxTMB. The intensity of the color showed a linear dependency with the ALP activity. ALP was detected in the linear range of 0-40 mU/mL with a low detection limit (LOD) of 0.26 mU/mL (S/N = 3). The proposed method is fast, easy, and can be applied to monitor the ALP activity in serum samples accurately and effectively, which suggests its practicability and reliability in the detection of ALP activity in clinical practice.

Perylene Diimide-Based Fluorescent and Colorimetric Sensors for Environmental Detection

Perylene tetracarboxylic diimide (PDI) and its derivatives exhibit excellent thermal, chemical and optical stability, strong electron affinity, strong visible-light absorption and unique fluorescence on/off features. The combination of these features makes PDIs ideal molecular frameworks for development in a broad range of sensors for detecting environmental pollutants such as heavy metal ions (e.g., Cu2+, Cd2+, Hg2+, Pd2+, etc.), inorganic anions (e.g., F-, ClO4-, PO4-, etc.), as well as poisonous organic compounds such as nitriles, amines, nitroaromatics, benzene homologues, etc. In this review, we provide a comprehensive overview of the recent advance in research and development of PDI-based fluorescent sensors, as well as related colorimetric and multi-mode sensor systems, for environmental detection in aqueous, organic or mixed solutions. The molecular design of PDIs and structural optimization of the sensor system (regarding both sensitivity and selectivity) in response to varying analytes are discussed in detail. At the end, a perspective summary is provided covering both the key challenges and potential solutions for the future development of PDI-based optical sensors.

Selective Detection of Pyrophosphate Anions in Aqueous Medium Using Aggregation of Perylene Diimide as a Fluorescent Probe

A water-soluble perylene diimide, aspartic acid-functionalized perylene diimide (APDI), has shown significant sequential "turn-off" and "turn-on" responses toward Cu2+ and inorganic pyrophosphate (PPi), respectively. APDI was found to show selectivity toward Cu2+ and inorganic PPi over adenosine monophosphate, adenosine diphosphate, and adenosine triphosphate. The detection has been studied by absorption and emission spectroscopy techniques. Incorporation of Cu2+ into the solution of APDI results in a distinct quenching of the fluorescence intensity, while there was no spectral change in the presence of other metal ions. The formed APDI-Cu2+ ensemble can turn on its fluorescence signal when PPi is present. The detection of PPi could be traced by looking at the change in color of the solution under the naked eye. No interference was observed from other anions, making the APDI-Cu2+aggregate a highly selective biosensor for PPi.

Recent advances in inorganic nanomaterials for wound-healing applications

The emergence of inorganic nanoparticles has generated considerable expectation for solving various biomedical issues including wound healing and tissue regeneration. This review article highlights the role and recent advancements of inorganic nanoparticles for wound healing and tissue regeneration along with their advantages, clinical status, challenges and future directions.

The Boolean logic tree of molecular self-assembly system based on cobalt oxyhydroxide nanoflakes for three-state logic computation, sensing and imaging of pyrophosphate in living cells and in vivo

Sensing of pyrophosphate (PPi) is helpful to better understand many life processes and diagnose various early-stage diseases. However, many traditional reported methods based on artificial receptors for sensing of PPi exhibit some disadvantages including difficulties in designing appropriate binding sites and complicated multi-step assembly/functionalization. Thus, it is significantly important and a big challenge to know how to use a simple molecular self-assembly or an interaction system to solve the above-mentioned limits to achieve the quantitative analysis of specific substances in the system. Based on the natural connection and similarity (such as stimulus responsiveness) between sensing and logic computing, in this study, the Boolean logic tree of molecular self-assembly system based on the cobalt oxyhydroxide (CoOOH) nanoplatform is constructed and applied to organize and connect "plug and play" molecular events (fluorescent dye, acridine orange and anion, PPi). By using molecules as inputs and the corresponding fluorescence signal as the output, the CoOOH-based molecular self-assembly system can be programmed for three-input fluorescent Boolean logic computation, fluorescent three-state logic computation, detection of PPi (linear range from 50 to 6400 nM with a detection limit of 20 nM) and even for imaging in living cancer cells and in vivo (in systems such as Zebrafish and Carassius auratus). Our approach adds a new dimension for expanding molecular logic computing and sensing systems, which will not only provide more opportunities for developing novel logic computing paradigms, but also be helpful in promoting the development and applications of intelligent molecular computing and sensing systems.

Coordinating Self-Assembly of Copper Perylenetetracarboxylate Nanorods: Selectively Lighting up Normal Cells around Cancerous Ones for Better Cancer Diagnosis

Specific imaging of cancer cells has been well-accepted in cancer diagnosis although it cannot precisely mark the boundary between the normal and cancerous cells and report their mutual influence. We report a nanorod fluorescent probe of copper perylenetetracarbonate (PTC-Cu) that can specifically light up normal cells. In combination with cancer cell imaging, the cocultured normal and cancer cells can be lit up with different colors, offering a clear contrast between the normal and cancer cells when they coexist. Because cancerous cells are only 20-30% in cancer area, this provides a possibility to visibly detect the mutual influence between the cancer and normal cells during therapy. We expect this method is beneficial to better cancer diagnosis and therapy.

Polycondensation of a Perylene Bisimide Derivative and L-Malic Acid as Water-Soluble Conjugates for Fluorescent Labeling of Live Mammalian Cells

Based on simple mixing and polymerization of a hydroxyl-containing derivative of perylene bisimide (PBI) and l-malic acid, here, we demonstrate a new type of dye-polymer conjugate, PBI-poly(α,β-malic acid) (PBI–PMA). Benefiting from the excellent water-solubility of weak polyanionic PMA structure and the high fluorescence of PBI, the PBI-PMA conjugates readily dissolve in water, displaying strong pH-dependent fluorescence with the highest intensity at pH 6. Due to the excellent biocompatibility of PMA, those conjugates showed low cytotoxicity on L929 cells. Using L929 and HeLa cells, we also confirmed that the PBI-PMA-labeled cells display intense fluorescence. Overall, the PBI-PMA conjugate demonstrates high potential as a cell labeling agent with its synthesis ease, good solubility in aqueous medium, low cytotoxicity, and high fluorescence.

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.

Biocompatible nickel-prussian blue@silver nanocomposites show potent antibacterial activities

Aim

Silver nanoparticles have long been used as potent antibacterial agents. However, toxicity concerns of silver nanoparticles have limited their successful clinical applications. Hence, development of silver-based novel biocompatible nanomaterials for antibacterial applications is a challenging task.

Materials & methods

Accordingly, in this work, we synthesized a biocompatible silver-based nanocomposite for antibacterial applications. The nanocompostie was characterized by several analytical techniques. The nanocomposite was further tested for its cytotoxicity in cells, chicken embryo and bacteria.

Results & Conclusion

Herein, we report a simple and cost-effective method for the synthesis of nickel-prussian blue@silver nanocomposites. The nanocomposite is highly stable and shows biocompatibility observed by in vitro assay and by ex vivo chicken embryonic angiogenesis assay. The nanocomposite exhibits profound antibacterial activity toward Gram-negative (Escherichia coli) and Gram-positive (Bacillus subtillus) bacteria. The results altogether suggest the future potential applications of nickel-prussian blue@silver nanocomposite as an antibacterial agent.

Synthesis and deposition of a Tröger’s base polymer on the electrode surface for potentiometric detection of a neuroblastoma tumor marker metabolite

We propose an innovative approach to detect a low molecular weight metabolite of neuroblastoma.