Development and Characterization of an Antimicrobial Polydopamine Coating for Conservation of Humpback Whales

Photothermal nanozymes to self-augment combination cancer therapy by dual-glutathione depletion and hyperthermia/acidity-activated hydroxyl radical generation

Chemodynamic therapy (CDT) has emerged as a promising strategy for tumor treatment. Nevertheless, the low Fenton catalytic efficiency and the high concentration of glutathione (GSH) in cancer cells largely decline antitumor efficacy of CDT. To self-augment antitumor effect of the CDT by combining with photothermal therapy (PTT), the unique photothermal nanozymes that doubly depleted GSH, and generated massive hydroxyl radicals (·OH) in the hyperthermia/acidity-activated manner were developed. Through the coordination of Fe3+ ions with PEGylated chitosan (PEG-CS)-modified polydopamine (PDA) nanoparticles, the attained Fe3+@PEG-CS/PDA nanozymes showed outstanding colloidal stability, photothermal conversion efficiency and acidity-triggered Fe3+ release. By GSH-mediated valence states transition of Fe3+ ions and Michael reaction between GSH and quinone-rich PDA, the nanozymes sufficiently executed dual depletion of GSH with the elevated temperature.Under mimic tumor acidity and near-infrared (NIR) irradiation condition, the endocytosed nanozymes effectively converted intracellular H2O2 into toxic ·OH upon amplified Fenton reaction, thereby potently killing 4T1 cancer cells and RAW 264.7 cells. Importantly, the nanozymes prominently suppressed 4T1 tumor growth in vivo and metastasis of cancer cells by CDT/PTT combination therapy without significant systemic toxicity. Our study provides novel visions in design of therapeutic nanozymes with great clinical translational prospect for tumor treatment.

Photocatalytic and Photothermal Antimicrobial Mussel-Inspired Nanocomposites for Biomedical Applications

Bacterial infection has traditionally been treated with antibiotics, but their overuse is leading to the development of antibiotic resistance. This may be mitigated by alternative approaches to prevent or treat bacterial infections without utilization of antibiotics. Among the alternatives is the use of photo-responsive antimicrobial nanoparticles and/or nanocomposites, which present unique properties activated by light. In this study, we explored the combined use of titanium oxide and polydopamine to create nanoparticles with photocatalytic and photothermal antibacterial properties triggered by visible or near-infrared light. Furthermore, as a proof-of-concept, these photo-responsive nanoparticles were combined with mussel-inspired catechol-modified hyaluronic acid hydrogels to form novel light-driven antibacterial nanocomposites. The materials were challenged with models of Gram-negative and Gram-positive bacteria. For visible light, the average percentage killed (PK) was 94.6 for E. coli and 92.3 for S. aureus. For near-infrared light, PK for E. coli reported 52.8 and 99.2 for S. aureus. These results confirm the exciting potential of these nanocomposites to prevent the development of antibiotic resistance and also to open the door for further studies to optimize their composition in order to increase their bactericidal efficacy for biomedical applications.

Activity-enhanced DNAzyme for design of label-free copper(II) biosensor

Metal ion-driven, DNA-cleaving DNAzymes are characterised by high selectivity and specificity. However, their use for metal ion sensing remains largely unexplored due to long reaction times and poor reaction yields relative to RNA-cleaving DNAzymes and other sensing strategies. Herein we present a study demonstrating a significant rate enhancement of a copper-selective DNA cleaving DNAzyme by both polydopamine (PDA) and gold (Au) nanoparticles (NPs). PDA NPs enhance the reaction through the production of hydrogen peroxide, while for AuNPs the enhancement is aided by the presence of citrate surface moeities, both of which drive the oxidative cleavage of the substrate. A 50-fold enhancement for PDA NPs makes the combination of PDA and DNAzyme suitable for a practical application as a sensitive biosensor for Cu(II) ions. Using DNAzyme deposition onto a gold electrode followed by Polydopamine Assisted DNA Immobilisation (PADI), we achieve a cost-effective, label-free and fast (within 15 min) electrochemical biosensor with a limit of detection of 180 nmol (11 ppm), thus opening a route for the rational design of a new generation of hybrid DNAzyme-based biosensors.

Ultra-stable CsPbBr3@PbBrOH nanorods for fluorescence labeling application based on methylimidazole-assisted synthesis

The extension application of perovskites in aqueous media such as bioassays requires the development of a water-stable perovskite with a simple preparation process and low cost. However, the degradation of perovskites in aqueous solution is still a thorny problem. Here, we develop a methylimidazole-assisted two-step synthesis protocol to prepare CsPbBr₃@PbBrOH nanorods with superior water stability and remarkable optical properties at room temperature. The synergy of 2-methylimidazole (2-MIM), an N-donor ligand, with water can not only facilitate CsPbBr₃ formation and suppress CsPb₂Br₅ or Cs₄PbBr₆ formation, but also promote the formation of a PbBrOH shell capping CsPbBr₃. 2-MIM is ionized into 2-MIM^- in DMF and 2-MIM⁺ in water. They passivated the surface defects and changed the crystallization environment, leading to water-stable CsPbBr₃@PbBrOH. The obtained CsPbBr₃@PbBrOH nanorods can still maintain 91% PL intensity after being stored in water for more than 2 months. Furthermore, the CsPbBr₃@PbBrOH nanorods show excellent stability in polar solvents, water, and phosphate buffer solution in a wide pH range, as well as better thermal and irradiation stability. In addition, the CsPbBr₃@PbBrOH nanorods are further functionalized with polydopamine (PDA) for biomolecular immobilization and immunoassay studies. The resulting assay shows a detection limit of 0.003 ng mL^-1 for IgG detection, illustrating important progress towards expanding fluorescence labeling application of perovskite nanomaterials for immunoassays.

A universal coating strategy for inhibiting the growth of bacteria on materials surfaces

The development of a versatile antibacterial coating, irrespective of material characteristics, is greatly attractive but still a challenge. In this work, mussel-inspired dopamine-modified sodium alginate (SA-DA) was successfully synthesized as the adhesion layer, and antibacterial coatings on three types of substrates, namely cotton fabric, aluminum sheet, and polyurethane membrane, were constructed through the layer-by-layer (LbL) deposition of polyhexamethylene guanidine and sodium alginate. Among the coated materials, the coated cotton fabric was systematically characterized, and the results showed that it still exhibited ideal hydrophilicity, and its liquid absorption capacity increased with an increase in the coating layers. The growth of Escherichia coli and Staphylococcus aureus was notably inhibited on the coated cotton fabric, and 10 coating bilayers achieved 100% inhibition of bacterial growth within 10 min. Furthermore, an ideal antibacterial ability maintained after 10 cycles of antibacterial trials or 50 washing or soaping cycles. In vitro evaluation of the hemostatic effect indicated that the coated cotton fabric could promote blood clotting by concentrating the components of blood and activating the platelets, and no significant hemolysis and cytotoxicity were observed in the coated cotton fabric. Moreover, the coated aluminum and polyurethane film also displayed an obvious antibacterial effect, which proved that the constructed coating could successfully adhere to the metal and polymer surfaces. Therefore, this work provided a proper way for the progress of a current antibacterial coating tactics for different substrate surfaces.

A two-step bioluminescence assay for optimizing antibacterial coating of hollow-fiber membranes with polydopamine in an integrative approach

Pure-water filtration membranes are often fouled by bacterial biofilms. Antibacterial coatings for preventing biofilm formation on such membranes should not rely on leaching of inhibiting compounds but should only be effective on surface contact. Certified assays for antibacterial coatings do not sufficiently exclude leaching effects and involve nutrient-rich cultivation media that do not correspond to conditions in pure-water systems. In this study, a two-step bioluminescence assay was developed for optimizing an antibacterial coating of PES/PVP ultrafiltration hollow-fiber membranes with a polydopamine as a sustainable, bio-inspired material for preventing bacterial biofilm formation. In the first step, leaching of the antimicrobial coating was analyzed by a bioluminescence assay with supernatants generated by washing coated membranes. In the second step, bioluminescence of bacterial biofilms on coated and uncoated membranes was measured using a nutrient-poor medium resembling site-specific conditions. Based on this bioluminescence assay, an optimized protocol for the coating process could be established by acidic polymerization of dopamine using 2 g/L sodium periodate and 4 g/L dopamine at 40 °C for 20 min reaction time. With coatings produced in this way, bioluminescence was reduced on coated membranes only while the corresponding supernatants exhibited no inhibitory effects.

Mussel Inspired Chemistry and Bacteria Derived Polymers for Oral Mucosal Adhesion and Drug Delivery

Ulceration of the oral mucosa is common, can arise at any age and as a consequence of the pain lessens enjoyment and quality of life. Current treatment options often involve the use of topical corticosteroids with poor drug delivery systems and inadequate contact time. In order to achieve local controlled delivery to the lesion with optimal adhesion, we utilized a simple polydopamine chemistry technique inspired by mussels to replicate their adhesive functionality. This was coupled with production of a group of naturally produced polymers, known as polyhydroxyalkanoates (PHA) as the delivery system. Initial work focused on the synthesis of PHA using Pseudomonas mendocina CH50; once synthesized and extracted from the bacteria, the PHAs were solvent processed into films. Polydopamine coating was subsequently achieved by immersing the solvent cast film in a polymerized dopamine solution. Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy confirmed functionalization of the PHA films via the presence of amine groups. Further characterization of the samples was carried out via surface energy measurements and Scanning Electron Microscopy (SEM) micrographs for surface topography. An adhesion test via reverse compression testing directly assessed adhesive properties and revealed an increase in polydopamine coated samples. To further identify the effect of surface coating, LIVE/DEAD imaging and Alamar Blue metabolic activity evaluated attachment and proliferation of fibroblasts on the biofilm surfaces, with higher cell growth in favor of the coated samples. Finally, in vivo biocompatibility was investigated in a rat model where the polydopamine coated PHA showed less inflammatory response over time compared to uncoated samples with sign of neovascularization. In conclusion, this simple mussel inspired polydopamine chemistry introduces a step change in bio-surface functionalization and holds great promise for the treatment of oral conditions.

Catechol-Based Antimicrobial Polymers

Catechol is a key constituent in mussel adhesive proteins and is responsible for strong adhesive property and crosslinking formation. Plant-based polyphenols are also capable of chemical interactions similar to those of catechol and are inherently antimicrobial. This review reports a series of catechol-based antimicrobial polymers classified according to their antimicrobial mechanisms. Catechol is utilized as a surface anchoring group for adhering monomers and polymers of known antimicrobial properties onto various types of surfaces. Additionally, catechol's ability to form strong complexes with metal ions and nanoparticles was utilized to sequester these antimicrobial agents into coatings and polymer matrices. During catechol oxidation, reactive oxygen species (ROS) is generated as a byproduct, and the use of the generated ROS for antimicrobial applications was also introduced. Finally, polymers that utilized the innate antimicrobial property of halogenated catechols and polyphenols were reviewed.

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.

Fabrication and Characterization of Calcium-Phosphate Lipid System for Potential Dental Application

Lipid has been widely studied as a vehicle and loading vector, but there have been no reports of any such related application in the dental field. The purpose of this research was to fabricate and characterize a nano-size calcium-phosphate lipid (CL) system as a potential vehicle in dental regeneration study, wherein the biocompatibility with dental pulp stem cells (DPSCs) was evaluated. The effect of CL on DPSCs proliferation was analyzed by a CCK-8 assay, and the anti-inflammatory effect was investigated by quantitative polymerase chain reaction (qPCR). Moreover, the effect of CL on odontogenic differentiation of inflamed DPSCs (iDPSCs) was studied by Alizarin red staining, tissue-non-specific alkaline phosphatase (TNAP) staining, qPCR, and western blot analyses. The results of this study showed that CL did not affect the proliferation of DPSCs, it down-regulated the inflammatory-associated markers (IL-1β, IL-6, TNF-α, COX-2) of DPSCs treated with Escherichia coli lipopolysaccharide (LPS), and enhanced the in-vitro odontogenic differentiation potential of iDPSCs. This novel biomaterial has a broad application prospect for its bioactivity and flexible physical property, and thus represents a promising pulpal regeneration material.