Robust Nanoparticle-DNA Conjugates Based on Mussel-Inspired Polydopamine Coating for Cell Imaging and Tailored Self-Assembly

Mg2+-promoted high-efficiency DNA conjugation on polydopamine surfaces for aptamer-based ochratoxin A detection

BACKGROUND

Surface immobilization of DNA is the foundation of a broad range of applications in biosensing and specific DNA extraction. Polydopamine (PDA) coatings can serve as intermediate layers to immobilize amino- or thiol-labelled molecules, including DNA, onto various materials through Michael addition and/or Schiff base reactions. However, the conjugation efficiency is limited by electrostatic repulsion between negatively charged DNA and PDA. Recently, it has been reported that polyvalent metal ions (such as Mg2+ and Ca2+) can mediate the adsorption of DNA on PDA surfaces. Inspired by this, in this work we aimed to exploit polyvalent metal ions to facilitate the conjugation of DNA on PDA.

RESULTS

Mg2+ was used to promote the conjugation of amino-terminated DNA complementary to ochratoxin A (OTA) aptamer (cDNA-NH2) on PDA-coated magnetic nanoparticles (Fe3O4@PDA). After the reaction, the unlinked cDNA-NH2 adsorbed on Fe3O4@PDA mediated by Mg2+ was removed with EDTA. In the presence of 20 mM Mg2+, the amount of covalently linked cDNA-NH2 increased approximately 11-fold compared to that in the absence of Mg2+. The resulting Fe3O4@PDA@cDNA conjugates exhibited superior hybridization capacity towards OTA aptamers, minimal nonspecific adsorption, and excellent chemical stability. The conjugates combined with fluorophore-labelled aptamers were employed for OTA detection, achieving a limit of detection (LOD) of 2.77 ng mL-1. To demonstrate versatility, this conjugation method was extended to Ca2+-promoted conjugation of cDNA-NH2 on Fe3O4@PDA nanoparticles and Mg2+-promoted conjugation of cDNA-NH2 on PDA-coated 96-well plates.

SIGNIFICANCE

The conjugation efficiency of DNA on PDA was significantly improved with the assistance of polyvalent metal ions (Mg2+ and Ca2+), providing a facile and efficient method for DNA immobilization. Due to the substrate-independent adhesion property of PDA, this method demonstrates versatility in DNA surface modification and holds great potential for applications in target extraction, biosensing, and other fields.

Polydopamine-based plasmonic nanocomposites: rational designs and applications

Taking advantage of its adhesive nature and chemical reactivity, polydopamine (PDA) has recently been integrated with plasmonic nanoparticles to yield unprecedented hybrid nanostructures. With advanced architectures and optical properties, PDA-based plasmonic nanocomposites have showcased their potential in a wide spectrum of plasmon-driven applications, ranging from catalysis and chemical sensing, to drug delivery and photothermal therapy. The rational design of PDA-based plasmonic nanocomposites entails different material features of PDA and necessitates a thorough understanding of the sophisticated PDA chemistry; yet, there is still a lack of a systematic review on their fabrication strategies, plasmonic properties, and applications. In this Highlight review, five representative types of PDA-based plasmonic nanocomposites will be featured. Specifically, their design principles, synthetic strategies, and optical behaviors will be elucidated with an emphasis on the irreplaceable roles of PDA in the synthetic mechanisms. Together, their essential functions in diverse applications will be outlined. Lastly, existing challenges and outlooks on the rational design and assembly of next-generation PDA-based plasmonic nanocomposites will be presented. This Highlight review aims to provide synthetic insights and hints to inspire and aid researchers to innovate PDA-based plasmonic nanocomposites.

Facile Fabrication of Energetic Nanocomposite Materials by Polydopamine

Polydopamine-based materials have been widely investigated for incorporation in energetic nanocomposites due to their outstanding adherence. However, these materials are often prepared in alkaline environments, which negatively affects Al nanoparticles. In this study, a one-pot assembly was devised for the preparation of a polydopamine-based Al/CuO energetic nanocomposite material (Al/PDA/CuO) in a neutral environment. The CuO and Al nanoparticles of the Al/PDA/CuO nanothermite were uniformly dispersed and closely combined. Consequently, the Al/PDA/CuO nanothermite was able to release more heat (2069.7 J/g) than physically mixed Al/CuO (1438.9 J/g). Furthermore, the universality of using polydopamine in the assembly of different types of energetic nanocomposite materials was verified, including an organic energetic material-nanothermit (HMX/PDA/Al/CuO nanothermite) and an inorganic oxidant-metal nanocatalyst (AP/PDA/Fe2O3). This study provides a promising route for the preparation of polydopamine-based energetic nanocomposites in neutral aqueous solutions.

Biofunctionalization of HMX with Peptides via Polydopamine Crosslinking for Assembling an HMX@Al@CuO Nanoenergetic Composite

Biological approaches for the synthesis of a hybrid explosive-nanothermite energetic composite have attracted greater scientific attention because of their advantages, including their moderate reactions and the absence of secondary pollution. In this study, a simple technique was developed to fabricate a hybrid explosive-nanothermite energetic composite based on a peptide and a mussel-inspired surface modification. Polydopamine (PDA) was easily imprinted onto the HMX, where it maintained its reactivity and was capable of reacting with a specific peptide used to introduce Al and CuO NPs to the surface of the HMX via specific recognition. The hybrid explosive-nanothermite energetic composites were characterized using differential scanning calorimetry (TG-DSC), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy(XPS), and a fluorescence microscope. A thermal analysis was utilized to investigate the energy-release properties of the materials. The HMX@Al@CuO, which benefitted from an enhanced interfacial contact in comparison with the physically mixed sample (HMX-Al-CuO), demonstrated a 41% lower HMX activation energy.

Phenolic-enabled nanotechnology: versatile particle engineering for biomedicine

Phenolics are ubiquitous in nature and have gained immense research attention because of their unique physiochemical properties and widespread industrial use. In recent decades, their accessibility, versatile reactivity, and relative biocompatibility have catalysed research in phenolic-enabled nanotechnology (PEN) particularly for biomedical applications which have been a major benefactor of this emergence, as largely demonstrated by polydopamine and polyphenols. Therefore, it is imperative to overveiw the fundamental mechanisms and synthetic strategies of PEN for state-of-the-art biomedical applications and provide a timely and comprehensive summary. In this review, we will focus on the principles and strategies involved in PEN and summarize the use of the PEN synthetic toolkit for particle engineering and the bottom-up synthesis of nanohybrid materials. Specifically, we will discuss the attractive forces between phenolics and complementary structural motifs in confined particle systems to synthesize high-quality products with controllable size, shape, composition, as well as surface chemistry and function. Additionally, phenolic's numerous applications in biosensing, bioimaging, and disease treatment will be highlighted. This review aims to provide guidelines for new scientists in the field and serve as an up-to-date compilation of what has been achieved in this area, while offering expert perspectives on PEN's use in translational research.

Spherical Nucleic Acid Mediated Functionalization of Polydopamine-Coated Nanoparticles for Selective DNA Extraction and Detection

Magnetic nanoparticles have been widely used for the separation of biomolecules for biological applications due to the mild and efficient separation process. In previous studies, core-shell magnetic nanoparticles (NPs) were designed for DNA extraction without much sequence specificity. In this work, to achieve highly selective DNA extraction, we designed a core-shell magnetic structure by coating polydopamine (PDA) on Fe₃O₄ NPs. Without divalent metal ions, PDA does not adsorb DNA at neutral pH. The Fe₃O₄@PDA NPs were then functionalized with spherical nucleic acids (SNA) to provide a high density of probe DNA. Fe₃O₄@PDA@SNA was also compared with when a linear SH-DNA was covalently attached to the NPs surface, showing a higher density of the probe SNA than SH-DNA can be loaded on the NPs in a remarkably shorter time. Nonspecific DNA extraction was thoroughly inhibited by both probes. DNA extraction by the Fe₃O₄@PDA@SNA was more effective as well as 5-fold faster than by the Fe₃O₄@PDA@SH-DNA, probably due to the favorable standing conformation of DNA strands in SNA. Moreover, extraction by Fe₃O₄@PDA@SNA showed high robustness in fetal bovine serum, and the same design can be used for selective detection of DNA. Finally, the method was also demonstrated on silica NPs and WS₂ nanosheets for coating with PDA and SNA. Altogether, our findings revealed an interesting and general surface modification strategy using PDA@SNA conjugates for sequence-specific DNA extraction.

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.

Biomimetic Nanopillar-Based Biosensor for Label-Free Detection of Influenza A Virus

Since the first emergence of influenza viruses, they have caused the flu seasonally worldwide. Precise detection of influenza viruses is required to prevent the spreading of the disease. Herein, we developed an optical biosensor using peptide-immobilized nanopillar structures for the label-free detection of influenza viruses. The spin-on-glass nanopillar structures were fabricated by nanoimprint lithography. A sialic acid-mimic peptide, which can specifically bind to hemagglutinin on the surface of the influenza virus, was immobilized onto the nanopillars via polymerized dopamine. The constructed nanopillar sensor enabled us to detect influenza A viruses in the range of 10³-10⁵ plaque-forming units through simple measurements of reflectance. Our findings suggest that biomimetic modification of nanopillar structures can be an alternative method for the immunodiagnosis of influenza viruses.

Transition Metal-Mediated DNA Adsorption on Polydopamine Nanoparticles

Polydopamine (PDA) is a widely used universal coating for a broad range of materials. Interfacing PDA with various biomolecules, such as DNA, is critical for applications such as sensing, intracellular delivery, and material fabrication. Because of the negative surface charge of PDA at neutral pH, electrostatic repulsion exists between PDA and DNA. In previous studies, modified DNA or low pH was used to overcome this repulsion for DNA adsorption. More recently, divalent Ca²⁺ was found to bridge DNA and PDA. Herein, we studied four transition metals (Mn²⁺, Co²⁺, Zn²⁺, and Ni²⁺) and compared their efficiencies with Ca²⁺ for promoting DNA adsorption. These transition metals induced a more efficient and tighter DNA binding compared to Ca²⁺. In all these cases, the DNA phosphate backbone played a dominant role in adsorption, although DNA bases might also interact with strong binding metals such as Ni²⁺. Moreover, when the adsorption affinity was stronger, sensing was more selective to complementary DNA. Finally, aging of PDA appeared to be detrimental for DNA adsorption, which could be due to further oxidation of PDA. We showed that using Zn²⁺ or Ni²⁺ could considerably relieve the aging effect, while storing PDA at 4 °C could slow down aging.

A Self-Assembled Plasmonic Substrate for Enhanced Fluorescence Resonance Energy Transfer

Fluorescence resonance energy transfer (FRET) has found widespread uses in biosensing, molecular imaging, and light harvesting. Plasmonic metal nanostructures offer the possibility of engineering photonic environment of specific fluorophores to enhance the FRET efficiency. However, the potential of plasmonic nanostructures to enable tailored FRET enhancement on planar substrates remains largely unrealized, which are of considerable interest for high-performance on-surface bioassays and photovoltaics. The main challenge lies in the necessitated concurrent control over the spectral properties of plasmonic substrates to match that of fluorophores and the fluorophore-substrate spacing. Here, a self-assembled plasmonic substrate based on polydopamine (PDA)-coated plasmonic nanocrystals is developed to effectively address this challenge. The PDA coating not only drives interfacial self-assembly of the nanocrystals to form closely packed arrays with customized optical properties, but also can serve as a tailored nanoscale spacer between the fluorophores and plasmonic nanocrystals, which collectively lead to optimized fluorescence enhancement. The biocompatible plasmonic substrate that allows convenient bioconjugation imparted by PDA has afforded improved FRET efficiency in DNA microarray assay and FRET imaging of live cells. It is envisioned that the self-assembled plasmonic substrates can be readily integrated into fluorescence-based platforms for diverse biomedical and photoconversion applications.

Gap-enhanced Raman tags: fabrication, optical properties, and theranostic applications

Gap-enhanced Raman tags (GERTs) are emerging probes of surface-enhanced Raman scattering (SERS) spectroscopy that have found promising analytical, bioimaging, and theranostic applications. Because of their internal location, Raman reporter molecules are protected from unwanted external environments and particle aggregation and demonstrate superior SERS responses owing to the strongly enhanced electromagnetic fields in the gaps between metal core-shell structures. In this review, we discuss recent progress in the synthesis, simulation, and experimental studies of the optical properties and biomedical applications of novel spherically symmetrical and anisotropic GERTs fabricated with common plasmonic metals—gold (Au) and silver (Ag). Our discussion is focused on the design and synthetic strategies that ensure the optimal parameters and highest enhancement factors of GERTs for sensing and theranostics. In particular, we consider various core-shell structures with build-in nanogaps to explain why they would benefit the plasmonic GERTs as a superior SERS tag and how this would help future research in clinical analytics and therapeutics.

Multicomponent Plasmonic Nanoparticles: From Heterostructured Nanoparticles to Colloidal Composite Nanostructures

Plasmonic nanostructures possessing unique and versatile optoelectronic properties have been vastly investigated over the past decade. However, the full potential of plasmonic nanostructure has not yet been fully exploited, particularly with single-component homogeneous structures with monotonic properties, and the addition of new components for making multicomponent nanoparticles may lead to new-yet-unexpected or improved properties. Here we define the term "multi-component nanoparticles" as hybrid structures composed of two or more condensed nanoscale domains with distinctive material compositions, shapes, or sizes. We reviewed and discussed the designing principles and synthetic strategies to efficiently combine multiple components to form hybrid nanoparticles with a new or improved plasmonic functionality. In particular, it has been quite challenging to precisely synthesize widely diverse multicomponent plasmonic structures, limiting realization of the full potential of plasmonic heterostructures. To address this challenge, several synthetic approaches have been reported to form a variety of different multicomponent plasmonic nanoparticles, mainly based on heterogeneous nucleation, atomic replacements, adsorption on supports, and biomolecule-mediated assemblies. In addition, the unique and synergistic features of multicomponent plasmonic nanoparticles, such as combination of pristine material properties, finely tuned plasmon resonance and coupling, enhanced light-matter interactions, geometry-induced polarization, and plasmon-induced energy and charge transfer across the heterointerface, were reported. In this review, we comprehensively summarize the latest advances on state-of-art synthetic strategies, unique properties, and promising applications of multicomponent plasmonic nanoparticles. These plasmonic nanoparticles including heterostructured nanoparticles and composite nanostructures are prepared by direct synthesis and physical force- or biomolecule-mediated assembly, which hold tremendous potential for plasmon-mediated energy transfer, magnetic plasmonics, metamolecules, and nanobiotechnology.

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.

Functional Macromolecule-Enabled Colloidal Synthesis: From Nanoparticle Engineering to Multifunctionality

The synthesis of well-defined inorganic colloidal nanostructures using functional macromolecules is an enabling technology that offers the possibility of fine-tuning the physicochemical properties of nanomaterials and has contributed to a broad range of practical applications. The utilization of functional reactive polymers and their colloidal assemblies leads to a high level of control over structural parameters of inorganic nanoparticles that are not easily accessible by conventional methods based on small-molecule ligands. Recent advances in polymerization techniques for synthetic polymers and newly exploited functions of natural biomacromolecules have opened up new avenues to monodisperse and multifunctional nanostructures consisting of integrated components with distinct chemistries but complementary properties. Here, the evolution of colloidal synthesis of inorganic nanoparticles is revisited. Then, the new developments of colloidal synthesis enabled by functional macromolecules and practical applications associated with the resulting optical, catalytic, and structural properties of colloidal nanostructures are summarized. Finally, a perspective on new and promising pathways to novel colloidal nanostructures built upon the continuous development of polymer chemistry, colloidal science, and nanochemistry is provided.

Polydopamine Coating as a Scaffold for Ring-Opening Chemistry To Functionalize Gold Nanoparticles

Gold nanoparticles (GNPs) are promising nanomaterials for various biomedical applications owing to their remarkable optical properties and biocompatibility. However, their interfacial properties require modification for practical use in such applications. Herein, a simple method for modifying the surface of GNPs with polydopamine (PDA) to serve as a scaffold for the subsequent polymerization of hyperbranched polyglycerol (HPG) is reported. GNPs were first coated with PDA (GNP-PDA), and then ring-opening chemistry was used at this interface to modify GNP-PDA with HPG (GNP-PDA-HPG). The produced GNP-PDA-HPG shows not only excellent dispersibility in a salt-containing solution but also strong resistance to aggregation in high- and low-pH solutions, even after 10 days. Moreover, we demonstrate a one-pot method for functionalizing GNP-PDA with HPG and either COOH or trimethylammonium. Finally, we conjugated the trimethylammonium-functionalized GNP-PDA-HPG with fluorescent nanodiamonds to investigate the photothermal ability of the functional GNPs.

Multifunctional Fe3O4@Polydopamine@DNA-Fueled Molecular Machine for Magnetically Targeted Intracellular Zn2+ Imaging and Fluorescence/MRI Guided Photodynamic-Photothermal Therapy

For the precise treatment of tumors, it is necessary to develop a theranostic nanoplatform that has both diagnostic and therapeutic functions. In this article, we designed a new theranostic probe for fluorescence imaging of Zn²⁺ and fluorescence/MRI guided magnetically targeted photodynamic-photothermal therapy. The fluorescence imaging of Zn²⁺ was based on an endogenous ATP-driven DNA nanomachine that could perform repetitive stand displacement reaction. It modifies all units on a single PDA/Fe₃O₄ nanoparticle containing a hairpin-locked initiated strand activated by a target molecule in cells, a two-stranded fuel DNA triggered by ATP, and a two-stranded DNA track responding to an initiated strand and fuel DNA. After entering the cell, the intracellular target Zn²⁺ initiates the nanomachine via an autocatalytic cleavage reaction, and the machine programmatically and gradually runs on the assembled DNA track via fuel DNA driving and the intramolecular toehold-mediated stand displacement reaction. The Fe₃O₄ core first exhibits magnetic targeting, increasing the ability of nanoparticles to enter tumor cells at the tumor site. The Fe₃O₄ could also be employed as a powerful magnetic resonance imaging (MRI) contrast agent and guided therapy. Using 808 nm laser and 635 nm laser irradiation together at the tumor site, the PDA nanoshell produced an excellent photothermal effect and the TMPyP4 molecules entering the cell generated reactive oxygen species, followed by cell damage. A series of reliable experiments suggested that the Fe₃O₄@PDA@DNA nanoprobe showed superior fluorescence specificity, MRI, a remarkable photothermal/photodynamic therapy effect, and favorable biocompatibility. This theranostic nanoplatform offered a split-new insight into tumor fluorescence and MRI diagnosis as well as effective tumor therapy.

Molecular Engineering of Functional Nucleic Acid Nanomaterials toward In Vivo Applications

Recent advances in nanotechnology and engineering have generated many nanomaterials with unique physical and chemical properties. Over the past decade, numerous nanomaterials are introduced into many research areas, such as sensors for environmental monitoring, food safety, point-of-care diagnostics, and as transducers for solar energy transfer. Meanwhile, functional nucleic acids (FNAs), including nucleic acid enzymes, aptamers, and aptazymes, have attracted major attention from the biomedical community due to their unique target recognition and catalytic properties. Benefiting from the recent progress of molecular engineering strategies, the physicochemical properties of nanomaterials are endowed by the target recognition and catalytic activity of FNAs in the presence of a target analyte, resulting in numerous smart nanoprobes for diverse applications including intracellular imaging, drug delivery, in vivo imaging, and tumor therapy. This progress report focuses on the recent advances in designing and engineering FNA-based nanomaterials, highlighting the functional outcomes toward in vivo applications. The challenges and opportunities for the future translation of FNA-based nanomaterials into clinical applications are also discussed.

Morphological Diversity, Protein Adsorption, and Cellular Uptake of Polydopamine-Coated Gold Nanoparticles

Polydopamine (PDA)-coated nanoparticles are adhesive bionanomaterials widely utilized in intracellular applications, yet how their adhesiveness affects their colloidal stability and their interactions with serum proteins and mammalian cells remain unclear. In this work, we systematically investigate the combined effects of dopamine (DA) concentration and polymerization time (both reaction parameters spanning 2 orders of magnitude) on the morphological diversity of PDA-coated nanoparticles by coating PDA onto gold nanoparticle cores. Independent of the DA concentration, Au@PDA NPs remain largely aggregated upon several hours of limited polymerization; interestingly, extended polymerization for 2 days or longer yield randomly aggregated NPs, nearly monodisperse NPs, or worm-like NP chains in the ascending order of DA concentration. Upon exposure to serum proteins, the specific type of proteins adsorbed to the Au@PDA NPs strongly depends upon the DA concentration. As DA concentration increases, less albumin and more hemoglobin subunits adhere. Moreover, cellular uptake is a strong function of polymerization time. Serum-stabilized Au@PDA NPs prepared by limited polymerization enter Neuro-2a and HeLa cancer cells more abundantly than those prepared by extended polymerization. Our data underscore the importance of DA concentration and polymerization time for tuning the morphology and degree of intracellular delivery of PDA-coated nanostructures.

Mitochondria-Targeting Polydopamine Nanocomposites as Chemophotothermal Therapeutics for Cancer

Mitochondria play a key role in a variety of physiological processes, and mitochondria-targeting drug delivery is helpful and effective in cancer therapy. Rhodamine123 (Rhod123) and Doxorubicin (Dox) are not new chemical molecules, and they both can inhibit the growth of cancerous cells. Here, we combine these two "old" chemicals with polydopamine nanoparticles (PDA NPs) to strengthen the antitumor effect with the aid of near-infrared irradiation. PDA NPs carry these two chemicals tightly by hydrogen bonds and π-π stacking besides chemical bonds. The better antitumor profile of PDA-Rhod-Dox comes from the mitochondria-targeting delivery, which decreases ATP in living cells, causing apoptosis of cancerous cells effectively and inhibiting the growth of tumors in mice. The synergistic effect of PDA, Rhod123, and Dox improves the treatment effect of conventional chemotherapy drugs.

Recent Trends in Mussel-Inspired Catechol-Containing Polymers (A Review)

Syntheses and applications of mussel-inspired polymeric materials have gained a foothold in research in recent years. Mussel-inspired chemistry coupled to Michael addition and Schiff’s base reactions was the key success for this intensive research. Unequivocally, The basic building brick of these materials is catechol-containing moiety, namely, 3,4-dihydroxyphenyl-L-alanine (L-DOPA or DOPA) and dopamine (DA). These catechol-based units within the chemical structure of the material ensure chiefly its adhesive characteristic to adherends of different natures. The newly-made catechol-bearing polymeric materials exhibit unique features, implying their importance in several uses and applications. Technology advent is being advantaged with these holdfast mussel protein-like materials. This review sheds light into the recent advances of such mussel-inspired materials for their adhesion capacity to several substrata of different natures, and for their applications mainly in antifouling coatings and nanoparticles technology.

Multifunctional Surface Modification of Nanodiamonds Based on Dopamine Polymerization

Surface functionalization of nanodiamonds (NDs), which is of great interest in advanced material and therapeutic applications, requires the immobilization of functional species, such as nucleic acids, bioprobes, drugs, and metal nanoparticles, onto NDs' surfaces to form stable nanoconjugates. However, it is still challenging to modify the surface of NDs due to the complexity of their surface chemistry and the low density of each functional group on the surfaces of NDs. In this work, we demonstrate a general applicable surface functionalization approach for the preparation of ND-based core-shell nanoconjugates using dopamine polymerization. By taking advantage of the universal adhesion and versatile reactivity of polydopamine, we have effectively conjugated DNA and silver nanoparticles onto NDs. Moreover, the catalytic activity of ND-supported silver nanoparticle was characterized by the reduction of 4-nitrophenol, and the addressability of NDs was tested through DNA hybridization that formed satellite ND-gold nanorod conjugation. This simple and robust method we have presented may significantly improve the capability for attaching various functionalities onto NDs and open up new platforms for applications of NDs.

Optimized polydopamine coating and DNA conjugation onto gold nanorods for single nanoparticle bioaffinity measurements

The formation of a stable polydopamine layer on a nanorod surface depends on the underlying chemistry and optimization enables the formation of packed ssDNA monolayers for bioaffinity applications.

Ultrasensitive electrochemical determination of metronidazole based on polydopamine/carboxylic multi-walled carbon nanotubes nanocomposites modified GCE

An ultrasensitive electrochemical sensor based on polydopamine/carboxylic multi-walled carbon nanotubes (MWCNTs−COOH) nanocomposites modified glassy carbon electrode (GCE) was presented in this work, which has been developed for highly selective and highly sensitive determination of an antimicrobial drug, metronidazole. The preparation of polydopamine/MWCNTs–COOH nanocomposites/GCE sensor is simple and possesses high reproducible, where polydopamine can be coated on the surface of MWCNTs–COOH via a simple electropolymerization process. Under optimized conditions, the proposed sensor showed ultrasensitive determination for metronidazole with a wide linear detection range from 5 to 5000 µmol/dm³ and a low detection limit of 0.25 µmol/dm³ (S/N = 3). Moreover, the proposed sensor has been successfully applied for the quantitative determination of metronidazole in real drug samples. This work may provide a novel and effective analytical platform for determination of metronidazole in application of real pharmaceutical and biological samples analysis.

Cost effective surface functionalization of gold nanoparticles with a mixed DNA and PEG monolayer for nanotechnology applications

We report a cost effective and generally applicable method for co-functionalization of gold nanoparticles with a mixed DNA and PEG polymer layer.

Polydopamine-Enabled Approach toward Tailored Plasmonic Nanogapped Nanoparticles: From Nanogap Engineering to Multifunctionality

We present a platform strategy that offers diverse flexibility in tailoring the structure and properties of core-shell plasmonic nanoparticles with built-in nanogaps. Our results have demonstrated that polydopamine serves multiple concerted functions as a nanoscale spacer to afford controllable nanogap sizes, a redox-active coating to promote metal shell growth, and a reactive scaffold to exclusively lock molecular probes inside the nanogap for surface-enhanced Raman scattering (SERS). More interestingly, the universal adhesion of polydopamine on diverse colloidal substrates allows for customized synthesis of multishell plasmonic nanogapped nanoparticles (NNPs) and multifunctional hybrid NNPs containing different cores (i.e., magnetic nanoparticles), which are not readily accessible by conventional methods. Internally coupled plasmonic NNPs with broadly tunable spectroscopic properties, highly active SERS, and multifunctionality hold great promise for emerging fields, such as sensing, optoelectronics, and theranostics, as demonstrated by the ultrasensitive SERS detection and efficient photothermal killing of food-borne pathogens here.