A remote-controlled generation of gold@polydopamine (core@shell) nanoparticles via physical-chemical stimuli of polydopamine/gold composites

Surface Modification of Polydopamine Particles with Polyethyleneimine Brushes for Enhanced Stability and Reduced Fragmentation

Polydopamine (Pdop) particles possess unique properties but suffer from inherent instability in aqueous environments due to the gradual release of Pdop fragments. This study demonstrated the successful enhancement of the stability and reduction in fragmentation in Pdop particles through surface engineering strategies. Specifically, we investigated the effects of polyelectrolyte multilayer (PEM) coating and polyelectrolyte (PE) brush grafting. Our results showed that PE brush grafting, particularly with long-chain polyethyleneimine (PEI), was more effective in suppressing Pdop fragment release compared to PEM coating. The L-PEI grafted Pdop particles (2.28 chains/nm2) exhibited remarkable stability across a wide pH range (3-9), with inhibition rates exceeding 90% in most cases, reaching 93% at pH 5. Furthermore, a direct correlation between PEI grafting density (0.64 to 2.28 chains/nm2) and inhibition rate was observed, with higher densities yielding greater stability. These findings offer a promising approach for stabilizing Pdop particles for diverse applications.

Amphiphilic Magnetic Particles Dispersed in Water and Oil for the Removal of Hydrophilic and Hydrophobic Microplastics

The study explores the synthesis and versatile properties of amphiphilic magnetic particles (AMPs) achieved through sequential coatings. Modulating the hydrophobic content in the synthesis process allows for the formation of hydrophilic, amphiphilic, and hydrophobic magnetic particles, with stable AMPs synthesis achieved at a ratio of hydrophilic to hydrophobic portions of approximately 71 to 29%. These AMPs exhibited outstanding dispersion in both oil and water within an oil/water mixture. Polyethylenimine in the AMP primarily enhances the removal of hydrophilic microparticles and facilitates dispersion in water. On the other hand, octadecylamine is specifically designed for the effective elimination of hydrophobic microparticles and their dispersion in oil. AMPs demonstrated effective removal capabilities for both hydrophilic and hydrophobic microparticles in water as well as hydrophobic microparticles in 100% oil. Our approach is also suited for eliminating hydrophobic microparticles dispersed in small quantities of oil floating on large bodies of water in real-world situations.

Magnetic Iron Oxide Nanoneedles with Hierarchical Structure for Controllable Catalytic Activity of 4-Nitrophenol Reduction

Catalyst systems with high catalytic activity and sustainability are highly desirable. Here, we report a design for catalytic composites with a hierarchical structure in which polydopamine (PD), multi-metallic nanocatalysts and iron oxide nanoneedles are successively deposited on a magnetic core. PD layers with various thicknesses are coated onto the magnetic core and serve as a template by which to take up multi-metallic nanocatalysts such as Au, Ag and Pt nanoparticles. The iron oxide nanoneedles act as spacers, preventing the nanocomposite from aggregating and increasing the surface area of the composite. The distinctive structures of the controllable template, the multi-metallic catalysts and needle-like layers enable the rapid migration of reactive ionic species and enhance catalytic ability via the synergistic effect of the multi-metallic nanocatalysts and iron oxide nanoneedles. Moreover, due to the strong magnetic property of the catalytic nanocomposites, they can be easily recovered with an external magnet and reused. Our hierarchical nanocomposites for recyclable nanocatalysts provide a new design concept for highly efficient catalysts.

Technical and engineering considerations for designing therapeutics and delivery systems

The newly-emerged pathological conditions and increased rates of drug resistance necessitate application of the state-of-the-art technologies for accelerated discovery of the therapeutic candidates and obtaining comprehensive knowledge about their targets, action mechanisms, and interactions within the body including those between the receptors and drugs. Using the physics- and chemistry-based modern techniques for theranostic purposes, preparing smart carriers, local delivery of genes or drugs, and enhancing pharmaceutical bioavailability could be of great value against the hard-to-treat diseases and growing drug resistance. Besides the artificial intelligence- and quantum-based techniques, crystal engineering capable of designing new molecules with appropriate characteristics, improving the stability and bioavailability of poorly soluble drugs, and efficient carrier development could play a crucial role in manufacturing efficient pharmaceuticals and reducing the adverse events. In this context, identifying the structures and behaviors of crystals and predicting their characteristics are of great value. Electron diffraction by accelerated analysis of the chemicals and sensitivity to charge alterations, electromechanical tools for controlled delivery of therapeutics, mechatronics via fabrication of multi-functional smart products including the organ-on-chip devices for healthcare applications, and optomechatronics by overcoming the limitations of conventional biomedical techniques could address the unmet biomedical requirements and facilitate development of more effective theranostics with improved outcomes.

Molecular Dynamics Simulations of Polydopamine Nanosphere's Structure Based on Experimental Evidence

In this work, we show how to obtain internal monodispersed gold nanoparticles inside polydopamine (PDA) nanospheres that are also externally decorated with gold. The number of internal nanoparticles is affected by the size of the PDA nanosphere used, and the lower limit in the number of gold nanoparticles in the center of decorated nanospheres, one single gold nanoparticle, has been reached. In addition, extensive molecular dynamics simulations of PDA nanospheres based on four different chemical motifs, in the presence of water and with different sizes, have been performed to gain insight into the arrangements capable of accommodating cavities. In particular, PDA nanospheres based on pyranoacridinotrione (PYR) units provide good agreement with the experimental attainment of internal metal nanoparticles. In these, the stacking of PYR units leads to a particular morphology, with large portions of space occupied by the solvent, that would explain the observed formation of gold nanoparticles inside the PDA nanosphere.

Novel Trends in Hydrogel Development for Biomedical Applications: A Review

Nowadays, there are still numerous challenges for well-known biomedical applications, such as tissue engineering (TE), wound healing and controlled drug delivery, which must be faced and solved. Hydrogels have been proposed as excellent candidates for these applications, as they have promising properties for the mentioned applications, including biocompatibility, biodegradability, great absorption capacity and tunable mechanical properties. However, depending on the material or the manufacturing method, the resulting hydrogel may not be up to the specific task for which it is designed, thus there are different approaches proposed to enhance hydrogel performance for the requirements of the application in question. The main purpose of this review article was to summarize the most recent trends of hydrogel technology, going through the most used polymeric materials and the most popular hydrogel synthesis methods in recent years, including different strategies of enhancing hydrogels’ properties, such as cross-linking and the manufacture of composite hydrogels. In addition, the secondary objective of this review was to briefly discuss other novel applications of hydrogels that have been proposed in the past few years which have drawn a lot of attention.

Facile fabrication and nanoscale assembly of polydopamine-functionalized, flexible chitosan films

Substrates that are simultaneously thin, strong, optically transparent, and biocompatible have diverse applications in a range of fundamental and applied fields. While nature-derived materials offer advantages of sustainability and inherent biocompatibility compared to synthetic polymers, their brittleness and swelling, as well as surface charge and chemical functionalization non-conducive to cell growth, can hinder widespread application. In this work, we discuss the fabrication and systematic characterization of polydopamine-coated chitosan thin films. Chitosan is a widely used, partially deacetylated form of chitin, derived from crustaceans and arthropods. Polydopamine (PDA) is derived from chemistries mimicking mussel foot adhesive proteins. A facile dip-coating process of thin and flexible, uncrosslinked chitosan films in aqueous dopamine solutions leads to dramatic changes in physical and chemical properties. We show how the PDA forms time-dependent assemblies on the film surfaces, affecting surface roughness, hydrophilicity, and mechanical strength. Coating the surface for even a few seconds provides functional changes to the films. Our results shows that the optimal coating time is on the order of few hours, whereby the films are optically transparent with excellent extensibility and Young’s modulus, while further coating reduces the benefits of this surface coating. These materials are biocompatible, serving as substrates for cell adhesion and growth while maintaining good viability. Overall, these findings give insight to the effects of PDA assembly on surfaces, and illustrate how a simple, quick, and robust bioinspired coating process can prime substrates for biomedical applications such as tissue engineering, biosensing, and wound healing.

The significance of bioengineered nanoplatforms against SARS-CoV-2: From detection to genome editing

COVID-19 outbreak can impose serious negative impacts on the infrastructures of societies including the healthcare systems. Despite the increasing research efforts, false positive or negative results that may be associated with serologic or even RT-PCR tests, inappropriate or variable immune response, and high rates of mutations in coronavirus may negatively affect virus detection process and effectiveness of the vaccines or drugs in development. Nanotechnology-based research attempts via developing state-of-the-art techniques such as nanomechatronics ones and advanced materials including the sensors for detecting the pathogen loads at very low concentrations or site-specific delivery of therapeutics, and real-time protections against the pandemic outbreaks by nanorobots can provide outstanding biomedical breakthroughs. Considering the unique characteristics of pathogens particularly the newly-emerged ones and avoiding the exaggerated optimism or simplistic views on the prophylactic and therapeutic approaches including the one-size-fits-all ones or presenting multiple medications that may be associated with synergistic toxicities rather than enhanced efficiencies might pave the way towards the development of more appropriate treatment strategies with reduced safety concerns. This paper highlights the significance of nanoplatforms against the viral disorders and their capabilities of genome editing that may facilitate taking more appropriate measures against SARS-CoV-2.

Nanotheranostics against COVID-19: From multivalent to immune-targeted materials

Destructive impacts of COVID-19 pandemic worldwide necessitates taking more appropriate measures for mitigating virus spread and development of the effective theranostic agents. In general, high heterogeneity of viruses is a major challenging issue towards the development of effective antiviral agents. Regarding the coronavirus, its high mutation rates can negatively affect virus detection process or the efficiency of drugs and vaccines in development or induce drug resistance. Bioengineered nanomaterials with suitable physicochemical characteristics for site-specific therapeutic delivery, highly-sensitive nanobiosensors for detection of very low virus concentration, and real-time protections using the nanorobots can provide roadmaps towards the imminent breakthroughs in theranostics of a variety of diseases including the COVID-19. Besides revolutionizing the classical disinfection procedures, state-of-the-art nanotechnology-based approaches enable providing the analytical tools for accelerated monitoring of coronavirus and associated biomarkers or drug delivery towards the pulmonary system or other affected organs. Multivalent nanomaterials capable of interaction with multivalent pathogens including the viruses could be suitable candidates for viral detection and prevention of further infections. Besides the inactivation or destruction of the virus, functionalized nanoparticles capable of modulating patient's immune response might be of great significance for attenuating the exaggerated inflammatory reactions or development of the effective nanovaccines and medications against the virus pandemics including the COVID-19.

Metallic Nanoparticle-Decorated Polydopamine Thin Films and Their Cell Proliferation Characteristics

Plasmonic metal nanoparticle (NP)-decorated thin films of biobased and biocompatible polymers provide significant opportunities in various biomedical applications. Inspired from the adhesive proteins of the marine mussels, polydopamine (PDA) serves as a versatile, biocompatible, and simple thin-film material and enhances cell growth and proliferation. Herein, we report the fabrication of the gold NPs (AuNPs) or silver NPs (AgNPs)-deposited thin films of PDA and their employment in cell growth and proliferation. PDA thin film with its numerous functional groups enabled well-controlled adsorption of NPs. The number density of NPs was manipulated simply by tuning the deposition time. Cell viability test for human lung cancer (A549) and human colon cancer (CaCO2) cell lines indicated that a thin layer of PDA film remarkably enhanced the cell growth and proliferation. The lower number density of NPs for the 24 h of the culture time resulted in a higher proliferation rate. However, the increase in both the number density of NPs and culture time led to a decrease in cell growth.

Metal-Containing Polydopamine Nanomaterials: Catalysis, Energy, and Theranostics

Polydopamine (PDA) is a major type of artificial melanin material with many interesting properties such as antioxidant activity, free-radical scavenging, high photothermal conversion efficiency, and strong metal-ion chelation. The high affinity of PDA to a wide range of metals/metal ions has offered a new class of functional metal-containing polydopamine (MPDA) nanomaterials with promising functions and extensive applications. Understanding and controlling the metal coordination environment is vital to achieve desirable functions for which such materials can be exploited. MPDA nanomaterials with metal/metal ions as the active functions are reviewed, including their synthesis and metal coordination environment and their applications in catalysis, batteries, solar cells, capacitors, medical imaging, cancer therapy, antifouling, and antibacterial coating. The current trends, limitations, and future directions of this area are also explored.

Controllable synthesis of mussel-inspired catechol-formaldehyde resin microspheres and their silver-based nanohybrids for catalytic and antibacterial applications

Size-controlled CFR microspheres and their silver-based nanohybrids were constructed and the nanohybrids display high catalytic reduction activity and antibacterial properties.

Synthesis of Spiked Plasmonic Nanorods with an Interior Nanogap for Quantitative Surface-Enhanced Raman Scattering Analysis

Realizing quantitative surface-enhanced Raman scattering (SERS) analysis is extremely helpful and challenging. Here, we utilize a facile method to synthesize spiked plasmonic nanorods with an interior gap. The Raman signal from the molecules embedded in the gap can be dramatically enhanced, leading to strong, stable, and reproducible SERS signals that can be used as an internal reference for quantitative SERS analysis. We demonstrate that the rough exterior surface has a good performance in enhancing the Raman signal of polycyclic aromatic hydrocarbon molecules adsorbed on the surface. The result shows that this method is applicable for a large range of analyte concentrations and there is an excellent linear relationship between the SERS intensity ratio and the analyte concentration (0.5-100 μM).

Recent progress in the biomedical applications of polydopamine nanostructures

Polydopamine is a dark brown-black insoluble biopolymer produced by autoxidation of dopamine. Although its structure and polymerization mechanism have not been fully understood, there has been a rapid growth in the synthesis and applications of polydopamine nanostructures in biomedical fields such as drug delivery, photothermal therapy, bone and tissue engineering, and cell adhesion and patterning, as well as antimicrobial applications. This article is dedicated to reviewing some of the recent polydopamine developments in these biomedical fields. Firstly, the polymerization mechanism is introduced with a discussion of the factors that influence the polymerization process. The discussion is followed by the introduction of various forms of polydopamine nanostructures and their recent applications in biomedical fields, especially in drug delivery. Finally, the review is summarized followed by brief comments on the future prospects of polydopamine.

Evolution and molecular mechanism of PitAs in iron transport of Streptococcus species

Iron is an essential element for almost all bacteria. The iron ATP-binding cassette (ABC) transporters located on the cell membrane affects bacterial virulence and infection. Although a variety of Fe³⁺-transporters have been found in bacteria, their evolutionary processes are rarely studied. Pneumococcal iron ABC transporter (PitA), a highly conserved Fe³⁺-transporter in most pathogenic bacteria, influences the capsule formation and virulence of bacteria. However, multiple sequence alignment revealed that PitA is expressed in four different variants in bacteria, and the structural complexity of these variants increases progressively. To more efficiently import Fe³⁺ ions into bacterial cells, bacteria have evolved a fused PitA from two separately expressed PitA-1 (SPD_0227) and PitA-2 (SPD_0226) proteins. Further biochemical characterization indicated that both PitA-1 and PitA-2 have weaker Fe³⁺-binding ability than their protein complex. More importantly, Glutathione S-Transferase (GST) pull-down and isothermal titration calorimetry (ITC) detection showed that PitA-1 and PitA-2 interact with each other via Tyr111-Leu37, Asn112-Gln38, Asn103-Leu33, and Asn103-Thr34. Further molecular dynamics (MD) simulations demonstrated that this interaction in full-length PitA is stronger than that in the two individual proteins. Deletion of PitA family genes could lead to decrease in the ability of iron acquisition and of adhesion and invasion of S. pneumoniae. Our study revealed the evolving state and molecular mechanism of Fe³⁺-transporter PitAs in bacteria and provided important information for understanding the iron transportation mechanism in bacteria and designing new antibacterial drugs.

Polyelectrolyte Brush-Grafted Polydopamine-Based Catalysts with Enhanced Catalytic Activity and Stability

Three types of surface treatments, namely, polyethyleneimine (PEI) coating, short PEI (S-PEI) grafting, and long PEI (L-PEI) grafting, were performed on polydopamine (Pdop)-based catalysts to enhance their catalytic activity and stability. Brush-grafted catalysts were prepared by the stepwise synthesis of Au and short (or long) PEI brushes on Pdop particles (PdopP/Au/S- or L-PEI grafting). PEI-coated Pdop-based catalysts (PdopP/Au/PEI coating) were also prepared as non-brush-grafted catalysts. Among the surface-treated PdopP/Au catalysts, the brush-grafted catalysts (S-PEI and L-PEI grafting) exhibited excellent and stable catalytic performance because the brush grafting enabled the protection of the catalysts against harsh conditions, effective transfer of reactants to the catalysts, and confinement of reactants around the catalysts. The brush-grafted catalysts could also more effectively decompose larger dyes than the non-brush-grafted catalysts. The process-to-effectiveness of PEI coating is the best because the release of Pdop from PdopP/Au was moderately inhibited by the presence of only one layer of PEI coating on the PdopP/Au. Thus, this approach could be an alternative method to enhance the stability of PdopP/Au catalysts.