Fast Preparation of Polydopamine Nanoparticles Catalyzed by Fe2+/H2O2 for Visible Sensitive Smartphone-Enabled Cytosensing

Multifunctional nanoparticles for enhanced sonodynamic-chemodynamic immunotherapy with glutathione depletion

Aim: This study aimed to develop a sonodynamic-chemodynamic nanoparticle functioning on glutathione depletion in tumor immunotherapy. Materials & methods: The liposome-encapsulated 2,2-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride (AIPH) and copper-cysteine nanoparticles, AIPH/Cu-Cys@Lipo, were synthesized with a one-pot method. 4T1 cells were injected into female BALB/c mice for modeling. Results: AIPH/Cu-Cys@Lipo was well synthesized. It generated alkyl radicals upon ultrasound stimulation. AIPH/Cu-Cys@Lipo promoted the generation of -OH via a Fenton-like reaction. Both in vitro and in vivo experiments verified that AIPH/Cu-Cys@Lipo significantly inhibited tumor development by decreasing mitochondrial membrane potential, activating CD4+ and CD8+ T cells and promoting the expression of IL-2 and TNF-α. Conclusion: AIPH/Cu-Cys@Lipo provides high-quality strategies for safe and effective tumor immunotherapy.

Smartphone-based pH responsive 3-channel colorimetric biosensor for non-enzymatic multi-antibiotic residues

Antibiotic residues in animal-derived food pose a risk to food safety and human health. Here, a smartphone-based pH-responsive 3-channel colorimetric biosensor is constructed for rapid detection of non-enzymatic multi-antibiotic residues in milk. In this system, a magnetic separation and enrichment approach is designed to specifically capture different antibiotic residues in complex environment. Indicators loaded on polydopamine-silver nanoparticles with excellently pH responsive visualization properties are utilized to ensure the high sensitivity of detection system. Moreover, smartphones are introduced to fulfill the demand for portable and on-site inspection of practical applications. It achieves simultaneous detection of oxytetracycline, kanamycin and streptomycin in the linear range of 1-105 pg/mL with detection limits of 0.085, 0.168, and 0.307 pg/mL, respectively. The practicality of the reported multi-antibiotic residues detection system is successfully demonstrated and evaluated challenging milk samples. Therefore, this system demonstrates the wide applications in multi-antibiotic residue analysis and food safety guarantee.

Engineering of Adhesion at Metal-Poly(lactic acid) Interfaces by Poly(dopamine): The Effect of the Annealing Temperature

Control over adhesion at interfaces from strong bonding to release between thermoplastic polymers (TPs) and metal oxides is highly significant for polymer composites. In this work, we showcase a simple and inexpensive method to tune adhesion between a TP of growing interest, poly(lactic acid) (PLA), and two commercial metal alloys, based on titanium and stainless steel. This is realized by coating titanium and stainless steel wires with polydopamine (PDA), thermally treating them under vacuum at temperatures ranging from 25 to 250 °C, and then comolding them with PLA to form pullout specimens for adhesion tests. Pullout results indicate that PDA coatings treated at low temperatures up to a given threshold significantly improve adhesion between PLA and the metals. Conversely, at higher PDA annealing temperatures beyond the threshold, interfacial bonding gradually declines. The excellent control over interfacial adhesion is attributed to the thermally induced transformation of PDA. In this work, we show using thermogravimetric analysis, X-ray photoelectron spectroscopy, Fourier transform infrared, and ¹³C solid-state NMR that the extent of the thermal transformation is dependent on the annealing temperature. By selecting the annealing temperature, we vary the concentration of primary amine and hydroxyl groups in PDA, which influences adhesion at the metal/PLA interface. We believe that these findings contribute to optimizing and broadening the applications of PDA in composite materials.

Functional Micro-/Nanostructures in Agrofood Science: Precise Inspection, Hazard Elimination, and Potential Health Risks

Nanotechnology, biotechniques, and chemical engineering have arisen as new trends with significant impacts on agrofood science development. Advanced analytical techniques with high sensitivity, specificity, and automation based on micro-/nanomaterials for food hazard elimination have become leading research hotspots in agrofood science. Research progress in micro-/nanomaterials has provided a solid theoretical basis and technical support to solve problems in the industry. However, the rapid development of micro-/nanostructures has also raised concerns regarding potential risks to human health. This review presents the latest advances in the precise inspection and elimination of food hazards from micro-/nanomaterials and discusses the potential threats to human health posed by nanomaterials. The theoretical reference was provided for the application trend of micro-/nanomaterials in the field of agrofood science in the future.

Colorimetric nano-beacon and magnetic separation-based rapid and visual assay for gram-negative bacteria

Food-borne diseases caused by pathogenic bacteria are one of the serious factors affecting human health. However, the most commonly used detection methods for pathogenic bacteria not only require expensive instruments, but also take a long time due to the complicated and cumbersome detection process. Therefore, the development of a fast, simple, and low-cost detection method for pathogenic bacteria is crucial for food safety and human health. In this work, based on the high binding ability of antimicrobial peptide (AMP) and polymyxin B (PMB) to bacteria, combined with magnetic separation technology, a new enzyme-free colorimetric strategy was constructed to achieve visual detection of Gram-negative bacteria in complex samples. The sensor system was divided into the following two parts: a colorimetric signal amplification nanoprobe, which was modified with AMP to enable effective binding of the colorimetric probe to the surface of bacteria, and a PMB-modified magnetic nanobead (MNB), which was used as the capture and enrichment unit of Gram-negative bacteria, as a result of which PMB could effectively distinguish Gram-negative bacteria from Gram-positive bacteria. Under optimized conditions, the detection limit of the method for Gram-negative bacteria (e.g. E. coli (G^-)) was as low as 10 CFU/mL, and it was successfully applied to complex real samples. In addition, the developed colorimetric sensor offered advantages, such as fast response, less time consumption, high sensitivity, and low cost. It can be expected to become a new diagnostic tool for on-site detection of pathogenic bacteria in remote areas.

Novel colorimetric aptasensor based on MOF-derived materials and its applications for organophosphorus pesticides determination

For the visual detection of four organophosphorus pesticides (OPs), a colorimetric aptasensor was developed based on aptamer-mediated bimetallic metal-organic frameworks (MOFs) nano-polymers. Fe-Co magnetic nanoparticles (MNPs) and Fe-N-C nanozymes were prepared based on pyrolytic reaction, and were labeled with broad spectrum aptamers and complementary chains of organophosphorus pesticides respectively. The hybridization of aptamers and complementary chains led to the formation of nano-polymers. In the presence of target pesticides, they competed with complementary chains for aptamers on Fe-Co MNPs, resulting in a large number of Fe-N-C nanozymes signal labels being released into the supernatant. Fe-N-C nanozymes showed similar activity to peroxidase and catalyzed the 3,3',5,5'-tetramethylbenzidine-hydrogen peroxide (TMB-H₂O₂) color system to turn the solution blue-green under mild conditions. The magnetic probes had good selectivity and sensitivity, and were easily separated by magnetic absorption. The sensor functioned well under optimal conditions, demonstrating good stability and specificity for four pesticides: phorate, profenofos, isocarbophos and omethoate, and the detection limits of four pesticides were as low as 0.16 ng/mL, 0.16 ng/mL, 0.03 ng/mL and 1.6 ng/mL respectively, and the recovery rate of OPs residue in vegetable samples was satisfactory. The work described here provided a simple, rapid and sensitive way to construct a biosensor.

Bioinspired, Ultra-fast Polymerization of Dopamine Under Mild Conditions

Spontaneous oxidative polymerization of dopamine (DA) has been widely exploited as a facile and versatile method for surface modification. However, the reaction is very slow and only occurs in alkaline solutions, which severely limit its applications. Herein we report that the reaction can be dramatically accelerated by using Fe²⁺ as catalyst. While it takes hours and days using conventional method, the Fe²⁺ -catalyzed reaction finishes almost immediately at pH 7.0. In addition, under the catalysis of Fe²⁺ , the reaction can occur at a pH down to 4.0. The fast Fe²⁺ -catalyzed polymerization of DA leads to fast deposition of polydopamine (PDA) coating, thus allowing fast surface modification and textile dyeing. The Fe²⁺ -catalyzed reaction also allows spatial control over the PDA deposition. The fast, simple and mild surface modification method developed here will find applications in numerous fields. This article is protected by copyright. All rights reserved.

Engineering 2D Cu-composed metal-organic framework nanosheets for augmented nanocatalytic tumor therapy

The engineered nanoformulation that can be activated by intracellular tumor microenvironment, including acidic pH, overexpressed H₂O₂, and high concentration of glutathione (GSH), features high efficacy to eradicate tumor cells with the intrinsic specificity and therapeutic biosafety. However, the relatively slow reaction rate of traditional Fe²⁺-mediated Fenton reaction induces the low production amount of reactive oxygen species (ROS) and subsequently the limited therapeutic outcome against tumors. Here, we established Cu (II)-based two-dimensional (2D) metal–organic framework (MOF) nanosheets as a distinct chemoreactive nanocatalyst for GSH-triggered and H₂O₂-augmented chemodynamic therapy (CDT), depending on the “AND” logic gate, for significant tumor suppression. After internalization by tumor cells, the MOF catalytic nanosheets reacted with local GSH for inducing GSH consumption and reducing the Cu²⁺ into Cu⁺. Subsequently, abundant hydroxyl radicals (·OH) generation was achieved via Cu⁺-mediated Fenton-like catalytic reaction. The dual effects of ·OH production and GSH depletion thus enhanced ROS production and accumulation in tumor cells, leading to significant cellular apoptosis and tumor inhibition, which was systematically demonstrated in both 4T1 and MDA-MB-231 tumor models. Therefore, GSH and H₂O₂, serve as an “AND” logic gate to trigger the Cu⁺-mediated Fenton-like reaction and reduce GSH level for augmented CDT with high therapeutic specificity and efficacy, thus inducing cellular apoptosis primarily through ferroptosis at the RNA sequence level.

Optical cytosensors for the detection of circulating tumour cells

Blood analysis is an established approach to monitor various diseases, ranging from heart defects and diabetes to cancer. Among various tumor markers in the blood, circulating tumor cells (CTCs) have received increasing attention due to the fact that they originate directly from the tumors. Capturing and detecting CTCs represents a promising approach in cancer diagnostics and clinical management of cancers. CTCs in blood progress to self-seeding a tumour or initiating a new lesion mass. Cytosensors are biosensors intended to identify CTCs in a blood sample of cancer patients and provide information about the cancer status. Herein, we firstly discuss different detection methods of state-of-the-art optical cytosensors, including colorimetry, fluorescence, surface plasmon resonance, photoelectrochemistry and electrochemiluminescence. Then we review the significant advances made in implementing biorecognition elements and nanomaterials for the detection of cancer cells. Despite great progress in optical cytosensors, and their integration with smartphones, they have still only been explored to prototype stages. Much more effort is needed to fulfil their potential in modern cancer diagnostics and in monitoring the state of disease for cancer patients.

CRISPR-Cas12a-regulated DNA adsorption and metallization on MXenes as enhanced enzyme mimics for sensitive colorimetric detection of hepatitis B virus DNA

Hepatitis B virus (HBV) infection is closely associated with the high risk of evolving into human hepatitis diseases including chronic hepatitis, liver fibrosis and cirrhosis, as well as hepatoma. Although various methods have been developed for HBV DNA detection, most of them either rely on expensive instruments or laborious procedures involving professional personnel. In this study, we for the first time established the CRISPR-Cas12a based colorimetric biosensor for target HBV detection by utilizing probe DNA regulation of the catalytic behaviors of Mxene-probe DNA-Ag/Pt nanohybrids. In the presence of HBV target, the Cas12a trans-cleavage activity could be efficiently activated to degrade the DNA probes, which led to the inhibition of DNA metallization and enzyme activity enhancer DNA adsorbed on Mxene, resulting in significantly reduced catalytic activity. The Mxene-probe DNA-Ag/Pt nanohybrids exhibited excellent sensitivity and specificity with subpicomolar detection limits, as well as good accuracy and stability for the determination of target HBV DNA in human serum samples. Moreover, this colorimetric sensing strategy could be integrated with the smartphone platform to allow the visible sensitive detection of target DNA. Taken together, the proposed colorimetric method provides a novel approach for HBV DNA diagnosis, especially suitable for the high endemic, developing countries with limited instrumental and medical supports.

Recent Advances in a Polydopamine-Mediated Antimicrobial Adhesion System

The drug resistance developed by bacteria during antibiotic treatment has been a call to action for researchers and scientists across the globe, as bacteria and fungi develop ever increasing resistance to current drugs. Innovative antimicrobial/antibacterial materials and coatings to combat such infections have become a priority, as many infections are caused by indwelling implants (e.g., catheters) as well as improving postsurgical function and outcomes. Pathogenic microorganisms that can exist either in planktonic form or as biofilms in water-carrying pipelines are one of the sources responsible for causing water-borne infections. To combat this, researchers have developed nanotextured surfaces with bactericidal properties mirroring the topographical features of some natural antibacterial materials. Protein-based adhesives, secreted by marine mussels, contain a catecholic amino acid, 3,4-dihydroxyphenylalanine (DOPA), which, in the presence of lysine amino acid, empowers with the ability to anchor them to various surfaces in both wet and saline habitats. Inspired by these features, a novel coating material derived from a catechol derivative, dopamine, known as polydopamine (PDA), has been designed and developed with the ability to adhere to almost all kinds of substrates. Looking at the immense potential of PDA, this review article offers an overview of the recent growth in the field of PDA and its derivatives, especially focusing the promising applications as antibacterial nanocoatings and discussing various antimicrobial mechanisms including reactive oxygen species-mediated antimicrobial properties.

Copper peroxide/ZIF-8 self-producing H2O2 triggered cascade reaction for amperometric immunoassay of carbohydrate antigen 19-9

Generally, H₂O₂ is frequently adopted to improve analysis capabilities of various detection systems. However, the addition of H₂O₂ with relatively higher concentration can lower the bioactivity of antibodies or antigens and the sensing interface stability in most peroxidase and peroxidase-like immunosensors. In order to solve these issues, we designed a novel copper peroxide/ZIF-8 immunoprobe that can self-produce H₂O₂ to trigger a cascade reaction for the sensitive detection of carbohydrate antigen 19-9. Specifically, CP/ZIF-8 plays a key role as a "signal switch" in the immunosensor. In the presence of HCl, the structures of ZIF-8 and copper peroxide can be broken, producing Cu²⁺ and H₂O₂ and a subsequent Fenton-type reaction that generates •OH. The resulting •OH can induce the decomposition of 3-aminobenzeneboronic acid/poly (vinyl alcohol) (PVA) film on the electrode. Although the immunosensor initially showed little current signal due to the poor conductivity pf ZIF-8 and PVA, the current signal was significantly amplified by a HCl-triggered cascade reaction. Under optimal conditions, the immunosensor displayed a wide linear range from 0.0001 to 100 U mL^-1 with an ultralow limit of detection of 53.5 μU mL^-1 (S/N = 3) for carbohydrate antigen 19-9. Considering these advantages, namely self-producing H₂O₂ and easy operation, this strategy paves a new way to design other novel sensors.

Immunomodulation-Enhanced Nanozyme-Based Tumor Catalytic Therapy

Nanozyme-based tumor catalytic therapy has attracted widespread attention in recent years. However, its therapeutic outcomes are diminished by many factors in the tumor microenvironment (TME), such as insufficient endogenous hydrogen peroxide (H₂ O₂ ) concentration, hypoxia, and immunosuppressive microenvironment. Herein, an immunomodulation-enhanced nanozyme-based tumor catalytic therapy strategy is first proposed to achieve the synergism between nanozymes and TME regulation. TGF-β inhibitor (TI)-loaded PEGylated iron manganese silicate nanoparticles (IMSN) (named as IMSN-PEG-TI) are constructed to trigger the therapeutic modality. The results show that IMSN nanozyme exhibits both intrinsic peroxidase-like and catalase-like activities under acidic TME, which can decompose H₂ O₂ into hydroxyl radicals (•OH) and oxygen (O₂ ), respectively. Besides, it is demonstrated that both IMSN and TI can regulate the tumor immune microenvironment, resulting in macrophage polarization from M2 to M1, and thus inducing the regeneration of H₂ O₂ , which can promote catalytic activities of IMSN nanozyme. The potent antitumor effect of IMSN-PEG-TI is proved by in vitro multicellular tumor spheroids (MCTS) and in vivo CT26-tumor-bearing mice models. It is believed that the immunomodulation-enhanced nanozyme-based tumor treatment strategy is a promising tool to kill cancer cells.

Dual-mode immunoassay system based on glucose oxidase-triggered Fenton reaction for qualitative and quantitative detection of danofloxacin in milk

In this study, a novel colorimetric and fluorescent dual-mode ELISA based on glucose oxidase (GOx)-triggered Fenton reaction was developed for the qualitative and quantitative detection of danofloxacin (DAN). In this system, streptavidin-linked biotinylated anti-DAN-monoclonal antibody (SA-Bio-mAb) and biotinylated GOx (Bio-GOx) form the immune complex mAb-Bio-SA-Bio-GOx. In the absence of DAN, the mAb-Bio-SA-Bio-GOx would be immobilized by combining with coated DAN-BSA and catalyzed glucose to generate H₂O₂. The Fenton reaction between H₂O₂ and Fe²⁺ generated hydroxyl radicals, which oxidized the o-phenylenediamine to 2,3-diamino-phenazine. A dual-signal immunoassay with colorimetry and fluorescence as the signal readout was established. In the presence of DAN, DAN and DAN-BSA competed with Bio-mAb, decreasing the connection between immune complexes and DAN-BSA and finally resulting in lower signal of colorimetry and fluorescence. Under optimal conditions, the limit of detection of the fluorescence immunoassay was 0.337 ng/mL and was 5.24-fold lower than that of traditional ELISA. The colorimetric immunoassay cut-off value was 30 ng/mL in milk. The average recoveries of the method for milk samples that are spiked with different concentrations of DAN were 91.1 to 128.3%, with a coefficient of variation of 0.7 to 8.2%. These results of the method exhibited good agreement with those of liquid chromatography-tandem mass spectrometry system (LC-MS/MS) method. In brief, this work provides an improved screening strategy with high sensitivity and accuracy for the qualitative or quantitative detection of DAN in milk monitoring.

Polydopamine-PEG-Folic Acid Conjugate Film Engineered TiO2 Nanotube Arrays for Photoelectrochemical Sensing of Folate Binding Protein

Serum-soluble folate binding protein (FBP) is an important tumor marker, and the development of a simple biosensing method is highly needed. In this work, a photoelectrochemical (PEC) biosensor for the detection of FBP was proposed based on the construction of an antifouling interface and the unique ligand-protein recognition. The PEC sensing platform was prepared by the biomimetic polydopamine (PDA) coating on TiO₂ nanotubes arrays (NTAs). A significant PEC enhancement effect was obtained due to the macroporous structures. Excellent antifouling performance was achieved by conjugation of amino-group-terminated 8-arm poly(ethylene glycol) (PEG). The incorporation of folic acid (FA) retains the antifouling property and shows recognition abilities toward FBP. The fabricated PEC biosensor shows good analytical performance. The combination of ligand-protein recognition and a PEC antifouling interface provides a good consideration for the development of FBP biosensors.

Colorimetric biosensing of glucose in human serum based on the intrinsic oxidase activity of hollow MnO2 nanoparticles

Hollow MnO₂ nanoparticles with excellent oxidase-like activity for the sensitive and selective detection of glucose in human serum.

Antibacterial Activity Against Methicillin-Resistant Staphylococcus aureus of Colloidal Polydopamine Prepared by Carbon Dot Stimulated Polymerization of Dopamine

A simple one-step process for the polymerization of dopamine has been developed using nitrogen-doped carbon dots (N@C–dots) as the sole initiator. The synthesized amorphous polydopamine (PDA)-doped N@C–dots (PDA–N@C–dots composite) exhibited a negative charge of –39 mV with particle sizes ranging from 200 to 1700 nm. The stable colloidal solution was active against methicillin-resistant Staphylococcus aureus (MRSA), a Gram-negative bacterium. The strong adhesion of the polymer to the bacterial membrane resulted in a limited diffusion of nutrients and wastes in and out of the cell cytosol, which is a generic mechanism to trigger cell death. Another possible route is the autoxidation of the catechol moiety of PDA to form quinone and release reactive oxygen species (ROS) such as superoxide radicle and hydrogen peroxide, two well-known ROS with antimicrobial properties against both Gram-negative and Gram-positive bacteria.

Recent advances in melanin-like nanomaterials in biomedical applications: a mini review

BACKGROUND

Melanins are a group of biopigments in microorganisms that generate a wide range of colorants. Due to their multifunctionality, including ultraviolet protection, radical scavenging, and photothermal conversion, in addition to their intrinsic biocompatibility, natural melanins and synthetic melanin-like nanomaterials have been suggested as novel nano-bio platforms in biomedical applications.

MAIN BODY

Recent approaches in the synthesis of melanin-like nanomaterials and their biomedical applications have briefly been reviewed. Melanin-like nanomaterials have been suggested as endogenous chromophores for photoacoustic imaging and radical scavengers for the treatment of inflammatory diseases. The photothermal conversion ability of these materials under near-infrared irradiation allows hyperthermia-mediated cancer treatments, and their intrinsic fluorescence can be an indicator in biosensing applications. Furthermore, catechol-rich melanin and melanin-like nanomaterials possess a versatile affinity for various functional organic and inorganic additives, allowing the design of multifunctional hybrid nanomaterials that expand their range of applications in bioimaging, therapy, theranostics, and biosensing.

CONCLUSION

Melanin-like natural and synthetic nanomaterials have emerged; however, the under-elucidated chemical structures of these materials are still a major obstacle to the construction of novel nanomaterials through bottom-up approaches and tuning the material properties at the molecular level. Further advancements in melanin-based medical applications can be achieved with the incorporation of next-generation chemical and molecular analytical tools.

Mobilizing Breast Cancer Prevention Research Through Smartphone Apps: A Systematic Review of the Literature

Background: Breast cancer rates have been increasing worldwide, particularly among young women, suggesting important interactions between genes and health behaviors. At the same time, mobile technology, including smartphones applications (apps), has emerged as a new tool for delivering healthcare and health-related services. As of 2018, there were nearly 600 publicly available breast cancer apps designed to provide disease and treatment information, to manage disease, and to raise overall awareness. However, the extent to which apps are incorporated into breast cancer prevention research is unknown. Therefore, the objective of this review was to determine how mobile applications are being used for breast cancer prevention among women across the cancer control continuum. Methods: Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched PubMed and Web of Science Core Collection databases using the keywords breast cancer, smartphone, mobile application, and phone app. Full-length journal articles available in English that addressed the research question were included. We categorized articles by prevention type (primary, secondary, and tertiary) and phase of research (protocol, development, feasibility, pilot, measurement, and effectiveness), and identified common themes and gaps. Results: Our search yielded 82 studies (69 unique) that used apps in breast cancer prevention research across 20 countries. Approximately half of the named apps were publicly available. The majority (73%) of studies targeted tertiary prevention; 15% targeted secondary and 13% targeted primary prevention. Apps were used across all phases of research with the predominant phase being feasibility in tertiary prevention (34%), effectiveness in secondary prevention (63%), and development (30%) and effectiveness (30%) in primary prevention. Common uses included assessing outcomes relevant to clinical care coordination, quality of life, increasing self-efficacy and screening behaviors, and tracking and managing health behaviors. Conclusions: We identified the following gaps: few effectiveness studies in tertiary prevention, minimal use of apps for breast cancer etiology or early detection, and few interventions in those at average risk of breast cancer. These findings suggest that while mobile apps can inform breast cancer prevention across the continuum, more work is needed to incorporate apps into primary prevention.

Polydopamine -aminoglycoside nanoconjugates: Synthesis, characterization, antimicrobial evaluation and cytocompatibility

Development of nanoparticle- and self-assembled nanomaterial-based therapeutics has become a rapidly growing area in the field of nanotechnology. One of the natural compounds, dopamine, presents as a neurotransmitter in the human brain serving as a messenger and deals with the behavioural responses, has provided an ideal platform through self-polymerization under aerobic conditions leading to the formation of a beneficial organic biopolymer, polydopamine (PDA). This polymer provides sufficient reactive functionalities, which can further be use to attach amine- or thiol-containing ligands to obtain conjugates. In the present study, self-polymerized polydopamine nanoparticles have been synthesized and tethered to aminoglycosides (AGs: Gentamicin, Kanamycin and Neomycin) through amino moieties to obtain PDA-AG nanoconjugates. These nanoconjugates are characterized by physicochemical techniques and evaluated for their antimicrobial potency against various bacterial strains including resistant ones. Simultaneously, cytocompatibility was also assessed for PDA-AG nanoconjugates. Of these three nanoconjugates (PDA-Gentamicin, PDA-Kanamycin and PDA-Neomycin), PDA-Kanamycin (PDA-K) nanoconjugate exhibited the highest activity against potent pathogens, least toxicity in human embryonic kidney (HEK 293) cells and intense toxic effects on human glioblastoma (U87) cells. Together, these results advocate the promising potential of these nanoconjugates to be used as potent antimicrobials in future applications.

pH-responsive allochroic nanoparticles for the multicolor detection of breast cancer biomarkers

Estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2) are the three crucial biomarkers for the clinical diagnosis of breast cancer. Sensitive and precise detection of ER, PR, and HER2 is of great significance for the diagnosis of breast cancer. Herein, through a simple solvent-induced self-assembly process, the self-carried allochroic nanoparticles were prepared by using some hydrophobic pH indicator molecules for allochroic NPs-linked immunosorbent assay (named ALISA) of ER, PR, and HER2, respectively. Meanwhile, the introduction of bovine serum albumin (BSA) and antibody (Ab) enhanced the dispersity of the self-assembled nanoparticles as signal tags. Since the ultra-high loading and high-efficiency release of pH indicators, the ALISA exhibitssatisfactory selectivity and sensitivity, which demonstrated the great potential in the early diagnosis and postoperative monitoring of breast cancers. Furthermore, the smartphone was introduced to combine with the ALISA for point-of-care testing, indicating the high feasibility in practical applications.

Fe-N-C Single-Atom Nanozymes for the Intracellular Hydrogen Peroxide Detection

Recently, in situ detection of hydrogen peroxide (H₂O₂) generated from live cells have caused tremendous attention, because it is of great significance in the control of multiple biological processes. Herein, Fe-N-C single-atom nanozymes (Fe-N-C SAzymes) with intrinsic peroxidase-like activity were successfully prepared via high-temperature calcination using FeCl₂, glucose, and dicyandiamide as precursors. The Fe-N-C SAzymes with FeN_x as active sites were similar to natural metalloproteases, which can specifically enhance the peroxidase-like activity rather than oxidase-like activity. Accordingly, owing to the excellent catalytic efficiency of the Fe-N-C SAzymes, colorimetric biosensing of H₂O₂ in vitro was performed via a typical 3,3',5,5'-tetramethylbenzidine induced an allochroic reaction, demonstrating the satisfactory specificity and sensitivity. With regard to the practical application, in situ detection of H₂O₂ generated from the Hela cells by the Fe-N-C SAzymes was also performed, which can expand the applications of the newborn SAzymes.

Polydopamine Nanoparticles Prepared Using Redox-Active Transition Metals

Autoxidation of dopamine to polydopamine by dissolved oxygen is a slow process that requires highly alkaline conditions. Polydopamine can be formed rapidly also in mildly acidic and neutral solutions by using redox-active transition-metal ions. We present a comparative study of polydopamine nanoparticles formed by autoxidation and aerobic or anaerobic oxidation in the presence of Ce(IV), Fe(III), Cu(II), and Mn(VII). The UV-vis spectra of the purified nanoparticles are similar, and dopaminechrome is an early intermediate species. At low pH, Cu(II) requires the presence of oxygen and chloride ions to produce polydopamine at a reasonable rate. The changes in dispersibility and surface charge take place at around pH 4, which indicates the presence of ionizable groups, especially carboxylic acids, on their surface. X-ray photoelectron spectroscopy shows the presence of three different classes of carbons, and the carbonyl/carboxylate carbons amount to 5-15 atom %. The N 1s spectra show the presence of protonated free amino groups, suggesting that these groups may interact with the π-electrons of the intact aromatic dihydroxyindole moieties, especially in the metal-induced samples. The autoxidized and Mn(VII)-induced samples do not contain metals, but the metal content is 1-2 atom % in samples prepared with Ce(IV) or Cu(II), and ca. 20 atom % in polydopamine prepared in the presence of Fe(III). These differences in the metal content can be explained by the oxidation and complexation properties of the metals using the general model developed. In addition, the nitrogen content is lower in the metal-induced samples. All of the metal oxidants studied can be used to rapidly prepare polydopamine at room temperature, but the possible influence of the metal content and nitrogen loss should be taken into account.

An acid-responsive all-in-one signal amplification strategy for the ultrasensitive prostate-specific antigen detection

A one-pot strategy for the preparation of all-in-one signal tags for the colorimetric immunoassay of prostate-specific antigen.