Polymeric functionalization of mesoporous silica nanoparticles: Biomedical insights

Mesoporous silica nanoparticles (MSNs) endowed with polymer coatings present a versatile platform, offering notable advantages such as targeted, pH-controlled, and stimuli-responsive drug delivery. Surface functionalization, particularly through amine and carboxyl modification, enhances their suitability for polymerization, thereby augmenting their versatility and applicability. This review delves into the diverse therapeutic realms benefiting from polymer-coated MSNs, including photodynamic therapy (PDT), photothermal therapy (PTT), chemotherapy, RNA delivery, wound healing, tissue engineering, food packaging, and neurodegenerative disorder treatment. The multifaceted potential of polymer-coated MSNs underscores their significance as a focal point for future research endeavors and clinical applications. A comprehensive analysis of various polymers and biopolymers, such as polydopamine, chitosan, polyethylene glycol, polycaprolactone, alginate, gelatin, albumin, and others, is conducted to elucidate their advantages, benefits, and utilization across biomedical disciplines. Furthermore, this review extends its scope beyond polymerization and biomedical applications to encompass topics such as surface functionalization, chemical modification of MSNs, recent patents in the MSN domain, and the toxicity associated with MSN polymerization. Additionally, a brief discourse on green polymers is also included in review, highlighting their potential for fostering a sustainable future.

Optimized Epigallocatechin Gallate Delivery and Adipogenesis Inhibition through Fluorescent Mesoporous Nanocarriers

Epigallocatechin gallate (EGCG), a naturally occurring compound known for its multiple health benefits including antioxidant, anti-inflammatory, cancer preventive, and weight management effects, faces challenges due to its inherent instability and limited bioavailability. To address these limitations, our study pioneers an investigation into the unique behavior of EGCG, revealing its degradation into epicatechin (EGC) and gallic acid (GA) during the drug delivery process. In this research, we use fluorescent mesoporous silica nanoparticles (FMSNs) as a sophisticated delivery system for EGCG. This innovative approach aims to not only enhance the stability of EGCG but also regulate its sustained release dynamics to enable prolonged cellular activity. To comprehensively evaluate our novel delivery strategy, we performed assays to assess both the antioxidant potential and its impact on lipid inhibition using Oil Red O. The results not only underscore the potential of FMSN-based nanocarriers for efficient EGCG delivery but also reveal groundbreaking insights into its enzymatic degradation, a previously unexplored facet. This research substantially advances our understanding of EGCG's behavior during delivery and offers a promising avenue for improving its therapeutic efficacy and expanding its applications in health management.

Ion and Molecular Sieving With Ultrathin Polydopamine Nanomembranes

In contrast to biological cell membranes, it is still a major challenge for synthetic membranes to efficiently separate ions and small molecules due to their similar sizes in the sub-nanometer range. Inspired by biological ion channels with their unique channel wall chemistry that facilitates ion sieving by ion-channel interactions, the first free-standing, ultrathin (10-17 nm) nanomembranes composed entirely of polydopamine (PDA) are reported here as ion and molecular sieves. These nanomembranes are obtained via an easily scalable electropolymerization strategy and provide nanochannels with various amine and phenolic hydroxyl groups that offer a favorable chemical environment for ion-channel electrostatic and hydrogen bond interactions. They exhibit remarkable selectivity for monovalent ions over multivalent ions and larger species with K+/Mg2+ of ≈4.2, K+/[Fe(CN)6]3- of ≈10.3, and K+/Rhodamine B of ≈273.0 in a pressure-driven process, as well as cyclic reversible pH-responsive gating properties. Infrared spectra reveal hydrogen bond formation between hydrated multivalent ions and PDA, which prevents the transport of multivalent ions and facilitates high selectivity. Chemically rich, free-standing, and pH-responsive PDA nanomembranes with specific interaction sites are proposed as customizable high-performance sieves for a wide range of challenging separation requirements.

Controlled Quercetin Release by Fluorescent Mesoporous Nanocarriers for Effective Anti-Adipogenesis

Introduction

Quercetin (QUER), a flavonoid abundant in fruits and vegetables, is emerging as a promising alternative therapeutic agent for obesity treatment due to its antioxidant and anti-adipogenic properties. However, the clinical application of QUER is limited by its poor solubility, low bioavailability, and potential toxicity at high doses. To address these challenges, this study aims to develop an advanced drug delivery system using fluorescent mesoporous silica nanoparticles (FMSNs) coated with polydopamine (PDA) for the efficient and sustained delivery of QUER to inhibit adipogenesis.

Methods

The research included the synthesis of PDA-coated FMSNs for encapsulation of QUER, characterization of their mesoporous structures, and systematic investigation of the release behavior of QUER. The DPPH assay was used to evaluate the sustained radical scavenging potential. Concentration-dependent effects on 3T3-L1 cell proliferation, cellular uptake and adipogenesis inhibition were investigated.

Results

PDA-coated FMSNs exhibited well-aligned mesoporous structures. The DPPH assay confirmed the sustained radical scavenging potential, with FMSNs-QUER@PDA showing 53.92 ± 3.48% inhibition at 72 h, which was higher than FMSNs-QUER (44.66 ± 0.57%) and free QUER (43.37 ± 5.04%). Concentration-dependent effects on 3T3-L1 cells highlighted the enhanced efficacy of PDA-coated FMSNs for cellular uptake, with a 1.5-fold increase compared to uncoated FMSNs. Adipogenesis inhibition was also improved, with relative lipid accumulation of 44.6 ± 4.6%, 37.3 ± 4.6%, and 36.5 ± 7.3% at 2.5, 5, and 10 μM QUER concentrations, respectively.

Conclusion

The study successfully developed a tailored drug delivery system, emphasizing sustained QUER release and enhanced therapeutic effects. FMSNs, especially when coated with PDA, exhibit promising properties for efficient QUER delivery, providing a comprehensive approach that integrates advanced drug delivery technology and therapeutic efficacy.

Magnetically actuated pandanus fruit-like nanorobots for enhanced pH-stimulated drug release and targeted biofilm elimination in wound healing

Conventional antibiotic treatment struggles to eliminate biofilms in wounds due to the formation compact barrier. Herein, we fabricate magnetic pandanus fruit-like nanorobots (NRs) that function as drug carriers while exhibit excellent maneuverability for enhanced antibacterial tasks. Specifically, zeolitic imidazolate framework-8 (ZIF-8) is self-assembled on the surface of Fe3O4 nanoparticles, loaded with a small quantity of ciprofloxacin, and covered with a layer of polydopamine (PDA). Energized by external magnetic fields, the NRs (F@Z/C/P) are steered in defined direction to penetrate the infection tissues, and effectively arrive targeted areas for pH stimulated drug release and near-infrared triggered phototherapy, contributing to an antibacterial rate of >99.9 %. The Zn2+ in ZIF-8 and the catechol group in PDA form catechol-ZIF-8-drug structures, which effectively reduce drug release by 11 % in high pH environments and promote rapid drug release by 14 % in low pH environments compared to NRs without PDA. Additionally, F@Z/C/P can remove the biofilms and bacteria in Staphylococcus aureus infected wounds, and eventually be discharged from the infected site after treatment, leading to faster healing with an intact epidermis and minimal harm to surrounding tissues and organs. The study provides a promising strategy for tackling biofilm-associated infections in vivo through the use of multi-functional NRs.

Electropolymerization of Polydopamine at Electrode-Supported Insulating Mesoporous Films

Bioinspired, stimuli-responsive, polymer-functionalized mesoporous films are promising platforms for precisely regulating nanopore transport toward applications in water management, iontronics, catalysis, sensing, drug delivery, or energy conversion. Nanopore technologies still require new, facile, and effective nanopore functionalization with multi- and stimuli-responsive polymers to reach these complicated application targets. In recent years, zwitterionic and multifunctional polydopamine (PDA) films deposited on planar surfaces by electropolymerization have helped surfaces respond to various external stimuli such as light, temperature, moisture, and pH. However, PDA has not been used to functionalize nanoporous films, where the PDA-coating could locally regulate the ionic nanopore transport. This study investigates the electropolymerization of homogeneous thin PDA films to functionalize nanopores of mesoporous silica films. We investigate the effect of different mesoporous film structures and the number of electropolymerization cycles on the presence of PDA at mesopores and mesoporous film surfaces. Our spectroscopic, microscopic, and electrochemical analysis reveals that the amount and location (pores and surface) of deposited PDA at mesoporous films is related to the combination of the number of electropolymerization cycles and the mesoporous film thickness and pore size. In view of the application of the proposed PDA-functionalized mesoporous films in areas requiring ion transport control, we studied the ion nanopore transport of the films by cyclic voltammetry. We realized that the amount of PDA in the nanopores helps to limit the overall ionic transport, while the pH-dependent transport mechanism of pristine silica films remains unchanged. It was found that (i) the pH-dependent deprotonation of PDA and silica walls and (ii) the insulation of the indium-tin oxide (ITO) surface by increasing the amount of PDA within the mesoporous silica film affect the ionic nanopore transport.

Nanocomposite chitosan dressing incorporating polydopamine‑copper Janus nanoparticle

This research aims to introduce a new wound dressing with antibacterial and anti-inflammatory properties made from chitosan and copper-containing Janus nanoparticles (JNPs). The JNPs were synthesized by attaching copper to PDA nanospheres, which were then embedded in Chitosan at different concentrations. The resulting spherical JNPs had a mean size of 208 ± 96 nm, and EDX mapping showed successful adhesion of Cu2+ ions to PDA nanospheres with a total Cu2+ content of 16.5 wt%. The samples exhibited interconnected porous structures, increasing JNPs concentration resulting in larger pore size and higher porosity. The addition of JNPs to 10 % (Ch-JNP 10) resulted in the highest strength, young modulus, and crystallinity, while a reverse trend was observed at higher JNPs content. JNPs improve the antibacterial activity of chitosan-based dressing, especially against E. coli. All samples were biocompatible and did not exhibit any cytotoxic effects. Ch-JNP10 had higher cellular density, confluency, and collagen secretion than other samples. The in vivo study demonstrated that Ch-JNP10 induced epithelialization and oriented collagen fiber formation while reducing inflammation. Overall, Ch-JNP10 may be a potential wound dressing for chronic wounds.

Functionalized nanohybrids with rod shape for improved chemo-phototherapeutic effect against cancer by sequentially generating singlet oxygen and carbon dioxide bubbles

The application of hybrid nanocarriers is expected to play an active role in improving treatment of chemotherapy and phototherapy. Herein, a nanohybrid with a core of mesoporous silica nanorods and shell of folate-functionalized zeolite imidazole framework (ZIF-8/FA) was synthesized via polydopamine (PDA)-mediated integration. A chemotherapeutic drug (DOX), bubble generator (NH4HCO3, ABC), and photosensitive agent (ICG) were simultaneously loaded into the delivery system to construct smart ZIF-8/FA-coated mesoporous silica nanorods (IDa-PRMSs@ZF). We found that ICG endowed the designed delivery system with a moderate photothermal conversion efficiency of 26.06% and the capacity to release 1O2. The produced hyperthermia caused ABC to decompose and further generate carbon dioxide bubbles, thereby facilitating DOX release, sequentially. Importantly, the underlying mechanism was also investigated using mathematical kinetic modeling. The tumor inhibition rate of IDa-PRMSs@ZF under NIR irradiation reached 83.8%. This study provides a promising strategy based on rod-shaped nanohybrids for effective combination antitumor therapy.

Construction of a biomimetic core-shell PDA@Lac bioreactor from intracellular laccase as a nano-confined biocatalyst for decolorization

Enzymes immobilized on the surface of the carriers are difficult to maintain their conformation and high activity due to the influence of the external harsh environments. A biomimetic core-shell PDA@Lac bioreactor was constructed by depositing polydopamine (PDA) on the surface of the recombinant Escherichia coli with CotA laccase gene, and releasing intracellular laccase into the PDA shell using ultrasound to break the cell wall of the bacteria. The bioreactor provided a nano-confined environment for the laccase and accelerated the mass and electron transfer in the volume-confined space, with a 2.77-fold increase in Km compared with the free laccase. Since there was no barrier of the cell wall, the crystal violet dye can enter the bioreactor to participate in the enzymatic reaction. As a result, PDA@Lac achieved excellent decolorization performance even without ABTS as an electron mediator. Moreover, the cytoplasmic solution retained in the PDA shell promoted the enzyme's tolerance to pH, temperature and harsh environments. In addition to PDA encapsulation, carbonyl and -NH₂ groups of PDA were bound covalently with -NH₂ and -COOH on the laccase in the PDA@Lac, resulting in an extremely high laccase loading of 817.59 mg/g. Also, the relative activity of the bioreactor maintained approximately 75% after 10 cycles of reuse. In addition, the protection of the PDA shell increased the resistance of laccase to UV irradiation. This work provides a novel method of laccase immobilization for application in wastewater treatment.

Folic Acid Adjustive Polydopamine Organic Nanoparticles Based Fluorescent Probe for the Selective Detection of Mercury Ions

Polydopamine fluorescent organic nanomaterials present unique physicochemical and biological properties, which have great potential application in bio-imaging and chemical sensors. Here, folic acid (FA) adjustive polydopamine (PDA) fluorescent organic nanoparticles (FA-PDA FONs) were prepared by a facile one-pot self-polymerization strategy using dopamine (DA) and FA as precursors under mild conditions. The as-prepared FA-PDA FONs had an average size of 1.9 ± 0.3 nm in diameter with great aqueous dispersibility, and the FA-PDA FONs solution exhibit intense blue fluorescence under 365 nm UV lamp, and the quantum yield is ~8.27%. The FA-PDA FONs could be stable in a relatively wide pH range and high ionic strength salt solution, and the fluorescence intensities are constant. More importantly, here we developed a method for rapidly selective and sensitive detection of mercury ions (Hg²⁺) within 10 s using FA-PDA FONs based probe, the fluorescence intensities of FA-PDA FONs presented a great linear relationship to Hg²⁺ concentration, the linear range and limit of detection (LOD) were 0-18 µM and 0.18 µM, respectively. Furthermore, the feasibility of the developed Hg²⁺ sensor was verified by determination of Hg²⁺ in mineral water and tap water samples with satisfactory results.

Emulsion-oriented assembly for Janus double-spherical mesoporous nanoparticles as biological logic gates

The ability of Janus nanoparticles to establish biological logic systems has been widely exploited, yet conventional non/uni-porous Janus nanoparticles are unable to fully mimic biological communications. Here we demonstrate an emulsion-oriented assembly approach for the fabrication of highly uniform Janus double-spherical MSN&mPDA (MSN, mesoporous silica nanoparticle; mPDA, mesoporous polydopamine) nanoparticles. The delicate Janus nanoparticle possesses a spherical MSN with a diameter of ~150 nm and an mPDA hemisphere with a diameter of ~120 nm. In addition, the mesopore size in the MSN compartment is tunable from ~3 to ~25 nm, while those in the mPDA compartments range from ~5 to ~50 nm. Due to the different chemical properties and mesopore sizes in the two compartments, we achieve selective loading of guests in different compartments, and successfully establish single-particle-level biological logic gates. The dual-mesoporous structure enables consecutive valve-opening and matter-releasing reactions within one single nanoparticle, facilitating the design of single-particle-level logic systems.

Biofouling-Resistant Ultrafiltration Membranes via Codeposition of Dopamine and Cetyltrimethylammonium Bromide with Retained Size Selectivity and Water Flux

Biofouling is a serious problem in ultrafiltration (UF) membrane applications. Modifying the surface of membranes with low molecular weight, commercially available antibacterial chemistries is an excellent strategy to mitigate biofouling. Herein, we report a new strategy to impart antibacterial and anti-biofouling behavior without changing the support membrane's size selectivity and pure water permeance (PWP). To this end, a strong antibacterial agent, cetyltrimethylammonium bromide (CTAB), was codeposited with dopamine onto commercial polyethersulfone (PES) UF membranes in the presence of nitrogen (N₂) gas backflow. The PWP and pore size of the support membrane did not change with codeposition, confirming the benefit of N₂ backflow in mitigating the solution intrusion phenomenon. X-ray photoelectron spectroscopy (XPS), surface ζ potentials, and contact angle measurements confirmed the successful codeposition of polydopamine (PDA) and CTAB onto the membrane. Among three different CTAB concentrations systematically investigated, the membrane functionalized with CTAB at the critical micelle concentration (CMC) provided the best anti-biofouling activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and retained its surface ζ potential after being stored in 1 M NaCl (pH = 6.8) for 3 months. Our results demonstrate the potential of using a facile, one-step approach to modify commercial UF membranes without compromising their pore size or flux, while simultaneously endowing antibacterial activity.

Polymeric Membrane Marine Sensors with a Regenerable Antibiofouling Coating Based on Surface Modification of a Dual-Functionalized Magnetic Composite

Environmentally compatible polymeric membrane marine sensors with excellent antiadhesive and antibacterial properties have recently been developed. However, the regeneration abilities of these sensors after fouling have rarely been investigated. Herein, a novel strategy for preparation of a regenerable antibiofouling coating via surface modification of a dual-functionalized magnetic composite is proposed. A zwitterionic polymer (i.e., poly(sulfobetaine methacrylate)) and a quaternary ammonium compound (i.e., 3-trimethoxysilylpropyl octadecyldimethyl ammonium chloride) are coated on the surface of Fe₃O₄ microspheres for antiadhesion and bacterial inactivation, respectively. The antifouling magnetic composite can readily be modified on the sensor's surface via the magnetically assisted self-assembly technology. Using a polymeric membrane calcium ion-selective electrode as a model sensor, the protection layer-coated electrode shows the markedly improved antibiofouling activities as compared to the unmodified sensor. More importantly, by altering the direction of the external magnetic field, the antifouling coating can easily be removed after fouling along with the removal of the adsorbed bacterial cells from the electrode's surface, which is followed by re-modifying a fresh coating for regeneration of the antifouling electrode. The proposed methodology for fabrication of a regenerable antibiofouling coating is promising to improve the durability of a marine sensor.

Charge-controllable mussel-inspired magnetic nanocomposites for selective dye adsorption and separation

Magnetic polydopamine (PDA) nanocomposites were prepared with a facile and sustainable synthetic method. The as-synthesized polymer-based hybrid composites inherited the intrinsic adhesiveness contributed by catechol and amino moieties of PDA as well as the magnetic property of Fe₃O₄. With the unique properties of PDA, the surface charges of Fe₃O₄@PDA could be easily tuned by pH for smart adsorption-desorption behaviors. Four commercially available dyestuffs including crystal violet, rhodamine B, direct blue 71 and orange G with different structures and surface charges in solution were selected to investigate the adsorption ability and universality of Fe₃O₄@PDA in wastewater treatment. It was found that the nanocomposites could successfully adsorb these cationic and anionic dyes under suitable pH conditions. This confirmed the ability of the nanoadsorbents for the removal of common textile dyes. The dispersed magnetic nanoadsorbents also demonstrated the ease of collection from dye mixtures, and the possibility of reusing them for several cycles. Selective dye separation was found to be achievable via simple charge control without large consumption of organic solvent and energy. These bio-inspired nanocomposite adsorbents have shown high potential in wastewater treatment and selective recovery of dye waste, especially for wastewater containing ionic dyes.

Designing electrospun fiber platforms for efficient delivery of genetic material and genome editing tools

Electrospun fibers are versatile biomaterial platforms with great potential to support regeneration. Electrospun fiber characteristics such as fiber diameter, degree of alignment, rate of degradation, and surface chemistry enable the creation of unique, tunable scaffolds for various drug or gene delivery applications. The delivery of genetic material and genome editing tools via viral and non-viral vectors are approaches to control cellular protein production. However, immunogenicity, off-target effects, and low delivery efficiencies slow the progression of gene delivery strategies to clinical settings. The delivery of genetic material from electrospun fibers overcomes such limitations by allowing for localized, tunable delivery of genetic material. However, the process of electrospinning is harsh, and care must be taken to retain genetic material bioactivity. This review presents an up-to-date summary of strategies to incorporate genetic material onto or within electrospun fiber platforms to improve delivery efficiency and enhance the regenerative potential of electrospun fibers for various tissue engineering applications.

Insight into the influence of the polymerization time of polydopamine nanoparticles on their size, surface properties and nanomedical applications

In the last decade, novel strategies to synthesize polydopamine nanoparticles (PDA NPs) have been continuously developed owing to useful applications of this synthetic melanin analog in nanotechnology.

Polydopamine coated gold nano blackbodies for tumor-selective spatial thermal damage during plasmonic photothermal cancer therapy

Plasmonic photothermal therapy (PPTT), which involves nanoparticles and near-infrared radiation (NIR) to generate confined heat, is a potential technique for selective thermal damage of cancerous tissue. Herein, tumor-selective spatial damage characteristics during polydopamine (PDA) coated gold nano blackbodies (AuNBs) mediated PPTT is investigated through a tumortissue mimicking phantom. The spatial temperatures during PPTT were measured within the phantom mimicking the optical scattering of superficial invasive ductal carcinoma (injected with AuNBs) surrounded by a region without AuNBs. The phantom was irradiated using broadband NIR radiation (754-816 nm), and spatial temperatures were measured using thermocouples and an infrared thermal camera. The obtained results demonstrate that the tumor region's temperature was elevated to >50°C in about 2.5 minutes and was maintained thereafter for about 6 minutes, which is well sufficient for the thermal ablation of the tumor. While for the region surrounding the tumor, a temperature of about 40-44°C was attained, which is within safe limits for the said exposure duration. Overall, this study demonstrates that for the considered experimental parameters and tumor dimensions, heat-based thermal damage could be confined to the nanoparticle embedded tumor region while maintaining the safe temperature levels for the surrounding region, i.e., 2 mm beyond the tumor boundary.

Broad-Spectrum Reactive Oxygen Species Scavenging and Activated Macrophage-Targeting Microparticles Ameliorate Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a refractory chronic inflammatory disease. An excessively high level of reactive oxygen species (ROS) in the colon is one of the characteristics and pathogenic factors of IBD. Therefore, scavenging excessive ROS is a feasible method to treat IBD. Because ROS include many types of species, scavenging a single kind of ROS is not enough to reduce the ROS level and cure IBD effectively. Herein, broad-spectrum ROS scavenging and activated macrophage-targeting microparticles (MPs) are successfully fabricated by coprecipitation of catalase (CAT) and bovine serum albumin into a MnCO₃ template followed by deposition of polydopamine (PDA), assembly of targeting molecules on the surface, and finally removal of MnCO₃. The CAT content of MPs is about 34.1%. The obtained MPs can effectively scavenge the broad spectrum of ROS and retain 88% of the radical scavenging activity even after the treatment of simulated gastric fluid. The surface-modified dextran sulfate endows MPs with the targeting ability toward activated macrophages, achieving a better therapeutic effect. The MPs with components mostly derived from natural substances exhibit good biocompatibility and can show excellent ROS scavenging ability in cell experiments. In animal experiments, oral administration of a proper dosage of MPs can substantially mitigate colonic inflammation, as evidenced by disease activity index scores reduced by ∼40%, reduced body weight loss, and the production of typical proinflammatory cytokines in the inflammatory colon. This kind of MP can also be utilized for the treatment of other inflammatory diseases.

Ultrathin Polydopamine-Graphene Oxide Hybrid Coatings on Polymer Filters with Improved Filtration Performance and Functionalities

Thin polymer fiber mats, in particular those made of nonwoven polypropylene (PP) fibers, are extensively used for medical and industrial filtration. The recent pandemic has increased the demand for the fabrication of protective masks. The nonwoven PP filter has limitations in filtration efficiency and lacks advanced functionalities. Here, we propose a simple, effective, and low-cost method to functionalize PP filters and endow antimicrobial and photothermal properties. Our approach is based on the deposition of an ultrathin hybrid coating composed of graphene oxide (GO) and polydopamine on the surface of PP filters by spray-coating. The complementary properties and synergic effects of GO and polydopamine in the ultrathin coating improved the filtration efficiency of the PP filter by 20% with little change in pressure drop. Single component coatings did not result in similar improvements in performance. The ultrathin coating also makes the surface of the filter more hydrophilic with negative charges. The photothermal property of GO enables a rapid temperature increase of the surface-coated filter upon light irradiation for easy sterilization. Furthermore, cationic polymer brushes can be grafted to the ultrathin hybrid coating, which adds the highly desired antimicrobial property to the PP filters for their more effective protection against microorganisms.

Highly Selective Adsorption and Desorption of Charged Molecules in Three-Dimensional Networks of Polydopamine-Modified Carbon Nanotube Sponges

We investigated the selective adsorption and desorption behaviors of charged molecules (calcein, brilliant green, and methylene blue) dissolved in water using polydopamine-modified carbon nanotube (CNT) sponges. Porous CNT sponges (CNTSs) as a scaffold for the selective adsorption and desorption of aqueous molecules were fabricated by using a chemical vapor deposition technique. To improve the hydrophilicity of porous CNTS and to control the adsorption and desorption of aqueous molecules, CNT sidewalls were decorated with a hydrophilic polydopamine layer through noncovalent interactions between CNT sidewalls and polydopamine. After this noncovalent chemical modification, the water contact angle of CNTS was close to 0, and the aqueous solution can rapidly infiltrate the three-dimensional (3D) networks of polydopamine-modified CNTS (Pdop-CNTS). The incorporation of pH-responsive polydopamine in CNTS showed an evident advantage of adsorbing positively charged molecules over a pH range of 10.5-4. In aqueous solutions with pH value of ≤3, Pdop-CNTS selectively adsorbed negatively charged molecules. Aqueous molecules carrying net charges were successfully separated from mixture solutions. Moreover, charged calcein and methylene blue molecules adsorbed on the 3D networks of Pdop-CNTS were selectively desorbed from Pdop-CNTS by tuning the pH value of the desorption solution.

Colloidal Stability and Cytotoxicity of Polydopamine-Conjugated Gold Nanorods against Prostate Cancer Cell Lines

Prostate cancer is one of the most common cancers in men. Cell invasion is an important step in the process of cancer metastasis. Herein, gold nanorods (GNRs) and polyethylene glycol (PEG)-coated GNRs were conjugated with polydopamine (PDA). The PDA-nanoconjugates demonstrated excellent colloidal stability upon lyophilization and dispersion in cell culture media with or without the addition of fetal bovine albumin (FBS), compared to unconjugated GNRs. PDA-nanoconjugates exhibited a considerable cytotoxicity against DU-145 and PC3 prostate cancer cell lines over a concentration range of 48 μg/mL-12 μg/mL, while they were biocompatible over a concentration range of 3.0 μg/mL-0.185 μg/mL. Furthermore, PDA-nanoconjugates demonstrated possible anti-invasion activity towards prostate cancer cell lines, particularly DU-145 cell line, by reducing cell migration and cell adhesion properties. The PDA-nanoconjugates could be considered a promising nano-platform toward cancer treatment by reducing the invasion activity; it could also be considered a drug delivery system for chemotherapeutic agents.

Human small intestine cancer cell membrane-camouflaged quercetin-melanin for antibacterial and antitumor activity

E. coli has become an important factor that can lead to cancer because of its ability to cause diverse intestinal changes. Nano-polymer materials provide ideal drug delivery systems for preparing antibacterial and anti-cancer drugs because of their unique structure, easy modification, and high drug loading. The modified natural melanin has the potential to be an excellent nano-carrier. By improving the water-solubility and biocompatibility of the loaded natural drug quercetin, the antibacterial effect of quercetin can be fully played. Here, natural melanin was extracted from frozen squid to synthesize carrier polydopamine (PDA) nanoparticles, and the natural drug quercetin (Q) was modified on the surface of PDA by π-π bond and covalent bond action to produce melanin-quercetin (PDA-Q). We also developed human small intestinal cancer cells (HIC) membrane-camouflaged melanin-Quercetin (PDA-Q) nanoparticles as an anti-cancer platform in vivo. The potential bacteriostatic mechanism was likely driven by the penetration of PDA-Q in E. coli cells, damaging the integrity of the membranes of E. coli and inducing cell death. The mice wound experiment and bacteremia model experiment revealed that C@PDA-Q had a strong inhibitory effect on E. coli in vivo. In addition, the results of the in vitro tumor test also revealed that C@PDA-Q had strong anti-tumor activity against HIC cells of human small intestinal cancer, and the IC50 value was 12.3 ± 0.7 μg/ml, which was slightly better than that for cisplatin. As both melanin nanoparticles and HIC membrane are natural biomaterials, the synthesized C@PDA-Q nano-polymer material shows great potential for use in anti-cancer nano-drug loading.

Polydopamine-Assisted Two-Dimensional Molybdenum Disulfide (MoS2)-Modified PES Tight Ultrafiltration Mixed-Matrix Membranes: Enhanced Dye Separation Performance

Tight ultrafiltration (TUF) membranes with high performance have attracted more and more attention in the separation of organic molecules. To improve membrane performance, some methods such as interface polymerization have been applied. However, these approaches have complex operation procedures. In this study, a polydopamine (PDA) modified MoS₂ (MoS₂@PDA) blending polyethersulfone (PES) membrane with smaller pore size and excellent selectivity was fabricated by a simple phase inversion method. The molecular weight cut-off (MWCO) of as-prepared MoS₂@PDA mixed matrix membranes (MMMs) changes, and the effective separation of dye molecules in MoS₂@PDA MMMs with different concentrations were obtained. The addition amount of MoS₂@PDA increased from 0 to 4.5 wt %, resulting in a series of membranes with the MWCO values of 7402.29, 7007.89, 5803.58, 5589.50, 6632.77, and 6664.55 Da. The MWCO of the membrane M3 (3.0 wt %) was the lowest, the pore size was defined as 2.62 nm, and the pure water flux was 42.0 L m⁻² h⁻¹ bar⁻¹. The rejection of Chromotrope 2B (C2B), Reactive Blue 4 (RB4), and Janus Green B (JGB) in aqueous solution with different concentrations of dyes was better than that of unmodified membrane. The separation effect of M3 and M0 on JGB at different pH values was also investigated. The rejection rate of M3 to JGB was higher than M0 at different pH ranges from 3 to 11. The rejection of M3 was 98.17–99.88%. When pH was 11, the rejection of membranes decreased with the extension of separation time. Specifically, at 180 min, the rejection of M0 and M3 dropped to 77.59% and 88.61%, respectively. In addition, the membrane had a very low retention of salt ions, Nacl 1.58%, Na₂SO₄ 10.52%, MgSO₄ 4.64%, and MgCl₂ 1.55%, reflecting the potential for separating salts and dyes of MoS₂@PDA/PES MMMs.

Mesoporous Polydopamine Nanoparticles Attenuate Morphine Tolerance in Neuropathic Pain Rats by Inhibition of Oxidative Stress and Restoration of the Endogenous Antioxidant System

Oxidative stress resulting from reactive oxygen species (ROS) is known to play a key role in numerous neurological disorders, including neuropathic pain. Morphine is one of the commonly used opioids for pain management. However, long-term administration of morphine results in morphine antinociceptive tolerance (MAT) through elevation of ROS and suppression of natural antioxidant defense mechanisms. Recently, mesoporous polydopamine (MPDA) nanoparticles (NPS) have been known to possess strong antioxidant properties. We speculated that morphine delivery through an antioxidant nanocarrier might be a reasonable strategy to alleviate MAT. MPDAs showed a high drug loading efficiency of ∼50%, which was much higher than conventional NPS. Spectral and in vitro studies suggest a superior ROS scavenging ability of NPS. Results from a rat neuropathic pain model demonstrate that MPDA-loaded morphine (MPDA@Mor) is efficient in minimizing MAT with prolonged analgesic effect and suppression of pro-inflammatory cytokines. Additionally, serum levels of liver enzymes and levels of endogenous antioxidants were measured in the liver. Treatment with free morphine resulted in elevated levels of liver enzymes and significantly lowered the activities of endogenous antioxidant enzymes in comparison with the control and MPDA@Mor-treated group. Histopathological examination of the liver revealed that MPDA@Mor can significantly reduce the hepatotoxic effects of morphine. Taken together, our current work will provide an important insight into the development of safe and effective nano-antioxidant platforms for neuropathic pain management.

Supramolecular-interaction-mediated aggregation of anticarcinogens on triformyl cholic acid-functionalized Fe3O4 nanoparticles and their dual-targeting treatment for liver cancer

Herein, triformyl cholic acid-modified Fe₃O₄ nanoparticles (TCA-MNPs) were first constructed and developed as a novel drug carrier, possessing a high loading capacity, and the synergistic targeted therapy of hepatoma cells in vitro and in vivo.

Stimuli-responsive polydopamine-based smart materials

This review provides in-depth insight into the structural engineering of PDA-based materials to enhance their responsive feature and the use of them in construction of PDA-based stimuli-responsive smart materials.

Polydopamine-based nanomaterials and their potentials in advanced drug delivery and therapy

Polydopamine (PDA) has shown great potentials in biomedical fields due largely to its unique physicochemical properties, including high photothermal transfer efficiency, excellent drug binding capacity, versatile adhesion ability, sensitive pH responsibility and great biocompatibility and biodegradability. These properties confer PDA-based nanoparticles the potentials either as the drug carriers for advanced drug delivery or as the bioactive agents for photothermal therapy, imaging and biosensing. This review aims to provide a comprehensive understanding of PDA, its polymerization mechanisms and the potentials of PDA-based nano-systems in treating various diseases, including cancer, diabetes, inflammation, bacterial infection and Parkinson's disease. In addition, the concerns of PDA in biomedical use are also discussed.

A multifunctional dual-shell magnetic nanocomposite with near-infrared light response for synergistic chemo-thermal tumor therapy

The synergistic tumor therapy in single nanoplatform has always been the goal for high efficacy tumor treatment while still remains great challenge. This paper reports a versatile nanotheranostic platform enlisting magnetic iron oxide nanoparticles, polydopamine (PDA), gold nanocages (Au nanocage) and metal organic framework (MOF, MIL101-NH₂ ) in order to achieve synergistic chemothermal tumor therapy both in vitro and in vivo. The prepared magnetic photothermal nanoparticles (MPNPs) exhibit high drug loading capacity (31.34 mg/g), superior photo-thermal capacity (11.5°C enhancement in 180 s), low bio-toxicity, good magnetic resonance with a low dosage of 22 μg/g, as well as high antitumor efficacy in vivo. Such a novel and multifunctional nanoplatform is expected to find promising applications in target tumor synergistic therapy.

Polydopamine nanoparticles-assisted impedimetric sensor towards label-free lung cancer cell detection

Polydopamine nanoparticles (PDA NPs), among nature-inspired building materials, show special functions for biomedical systems and exploring PDA derived nanostructures for future developments is a fast growing field. Herein, we demonstrated the first evaluation of the PDA NPs for the electrochemical determination of lung cancer cells. In the presented study, PDA NPs were synthesized in a mild and cost-effective fashion by self-polymerization of dopamine in an alkaline environment. The structural and chemical characterizations clearly demonstrated the formation of PDA NPs with controllable size (130 nm), hence applied as a suitable material to functionalize the pencil graphite electrode (PGE) surface to construct a cytosensing nanoprobe. The ability of the developed sensor (PDA NPs/PGE) for label-free electrochemical A-549 lung cancer cells detection was investigated. The designed PDA NPs based cytosensor exhibited good biocompatibility and sensitivity for impedimetric diagnosis of A-549 cells in a wide linear range (1.0 × 10²-1.0 × 10⁵ cells mL^-1) with low detection limit (25 cells mL^-1). Furthermore, the developed bioassay has great potential as liquid biopsy for early cancer detection.

Surface modification of polypropylene membrane for the removal of iodine using polydopamine chemistry

The development of stable and effective iodine removal systems would be highly desirable in addressing environmental issues relevant to water contamination. In the present research, a novel iodine adsorbent was synthesized by self-polymerization of dopamine (PDA) onto inert polypropylene (PP) membrane. This PP/PDA membrane was thoroughly characterized and its susrface propeties was analyzed by various analytical techniques indcluding field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH), contact angle, and surface free energy measurement. The PP/PDA membranes were subsequently used for batchwise removal of iodine at different temperatures (25-70 °C), pH (2-7), and surface areas (1-10 cm²) to understand the underlying adsorption phenomena and to estimate the membrane capacity for iodine uptake. The increase in temperature and pH both led to higher adsorption of iodine. The present approach showed a removal efficiency of over 75% for iodine using 10 cm² PP/PDA membrane (18.87 m² g^-1) within 2 h at moderate temperatures (∼50 °C) and pH > 4, about 15 fold compared to the PP control membrane. The adsorption kinetics and isotherms were well fitted to the pseudo-second-order kinetic and Langmuir isotherm models (R² > 0.99). This adsorbent can be recycled and reused at least six times with stable iodine adsorption. These findings were attributed to the homogenous monolayer adsorption of the iodide on the surface due to the presence of catechol and amine groups in the PP/PDA membrane. This study proposes an efficient adsorbent for iodine removal.

Bioinspired polydopamine nanoparticles: synthesis, nanomechanical properties, and efficient PEGylation strategy

Polydopamine (PDA) is a bioinspired fascinating polymer which is considered nowadays as a material of choice for designing drug delivery nanosystems. Indeed, PDA exhibits multiple interesting features including simple preparation protocols, biocompatibility, simple functionalization procedures, free radicals scavenging and photothermal/photoacoustic properties. However, because of its heterogeneous structure, clear procedures about PDA nanoparticles synthesis and PEGylation with well-defined and reproducible physicochemical properties such as size, shape and nanomechanics are still needed. In this work, we established tightly controlled experimental conditions to synthesize PDA nanoparticles with well-defined size and yield. This allowed us to identify the factors that affect the most these two parameters and to construct surface response plots with accurate predictive values of size and yield. The nanomechanical properties of PDA NPs exhibiting different sizes have been studied with AFM nanoindentation experiments. Our results demonstrated for the first time that the elasticity of PDA NPs was decreasing with their size. This could be explained by the higher geometric packing order of the stacked oligomeric fractions inside the core of the biggest PDA NPs. Next, in order to determine the best PEGylation experimental conditions of PDA NPs using thiol-terminated PEG that allow grafting the highest polymer density with proteins repelling properties, we have first optimized the PEGylation strategy on PDA films. By using a combination of QCM-D and AFM experiments, we could demonstrate that efficient PEGylation of PDA films could be done even at low PEG concentration but in the presence of NaCl which exerts a salting out effect on PEG chains improving thus the grafting density. Finally, we transposed these experimental conditions to PDA NPs and we could synthesize PEGylated PDA NPs exhibiting high stability in physiological conditions as revealed by FTIR and DLS experiments respectively.

Development of Polydopamine Forward Osmosis Membranes with Low Reverse Salt Flux

Application of forward osmosis (FO) is limited due to membrane fouling and, most importantly, high reverse salt fluxes that deteriorate the concentrated product. Polydopamine (PDA) is a widely used, easily applicable, hydrophilic, adhesive antifouling coating. Among the coating parameters, surprisingly, the effect of PDA coating temperature on the membrane properties has not been well studied. Polyethersulfone (PES) 30 kDa ultrafiltration membranes were PDA-coated with varying dopamine concentrations (0.5-3 g/L) and coating temperatures (4-55 °C). The quality of the applied coating has been determined by surface properties, water permeability and reverse salt flux using a 1.2 M MgSO₄ draw solution. The coating thickness increased both with the dopamine concentration and coating temperature, the latter having a remarkably stronger effect resulting in a higher PDA deposition speed and smaller PDA aggregates. In dead‑end stirred cell, the membranes coated at 55 °C with 2.0 g/L dopamine showed NaCl and MgSO₄ retentions of 41% and 93%, respectively. In crossflow FO, a low reverse MgSO₄ flux (0.34 g/m²·h) was found making a very low specific reverse salt flux (J_s/J_w) of 0.08 g/L, which outperformed the commercial CTA FO membranes, showing the strong benefit of high temperature PDA-coated PES membranes to assure high quality products.

Mahon P, Yu A. Polydopamine Nanosphere with In-Situ Loaded Gentamicin and Its Antimicrobial Activity

The mussel inspired polydopamine has acquired great relevance in the field of nanomedicines, owing to its incredible physicochemical properties. Polydopamine nanoparticles (PDA NPs) due to their low cytotoxicity, high biocompatibility and ready biodegradation have already been widely investigated in various drug delivery, chemotherapeutic, and diagnostic applications. In addition, owing to its highly reactive nature, it possesses a very high capability for loading drugs and chemotherapeutics. Therefore, the loading efficiency of PDA NPs for an antibiotic i.e., gentamicin (G) has been investigated in this work. For this purpose, an in-situ polymerization method was studied to load the drug into PDA NPs using variable drug: monomer ratios. Scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) confirmed the successful loading of drug within PDA NPs, mainly via hydrogen bonding between the amine groups of gentamicin and the hydroxyl groups of PDA. The loading amount was quantified by liquid chromatography-mass spectrometry (LC-MS) and the highest percentage loading capacity was achieved for G-PDA prepared with drug to monomer ratio of 1:1. Moreover, the gentamicin loaded PDA NPs were tested in a preliminary antibacterial evaluation using the broth microdilution method against both Gram-(+) Staphylococcus aureus and Gram-(-) Pseudomonas aeruginosa microorganisms. The highest loaded G-PDA sample exhibited the lowest minimum inhibitory concentration and minimum bactericidal concentration values. The developed gentamicin loaded PDA is very promising for long term drug release and treating various microbial infections.

Polydopamine-based surface modification of hemoglobin particles for stability enhancement of oxygen carriers

Templated assembly techniques have been extensively used to develop various types of hemoglobin (Hb) loaded particles with improved performance. However, several instability issues must still be solved, including Hb exposure, enhanced Hb auto-oxidation, and the relatively weak binding of Hb to cross-linkers. Herein, to meet the stability requirements for novel hemoglobin-based oxygen carriers (HBOCs), hemoglobin-polydopamine particles (Hb-PDA) were fabricated using a mild process that combines the co-precipitation of Hb and an inorganic template with the spontaneous adhesion of PDA. The Hb-PDA showed uniform size distribution, chemical integrity of both Hb and PDA, high biocompatibility, and robust oxygen delivery. Our results demonstrated that the use of polydopamine as a biocompatible coating material reduced Hb leakage from the particles under both static and flow conditions, thus mitigating the toxicity associated with free Hb and strengthening the stability of Hb particles. In addition, Hb-PDA reduced HUVEC (Human Umbilical Vein Cells) oxidative injury and scavenged 85% of the available hydroxyl radicals, exhibiting its potential to act as an antioxidant for encapsulated Hb. Hb-PDA therefore shows significant promise as a cell-like structurally and functionally stable HBOCs.

Fabrication of Polydopamine-Based Curcumin Nanoparticles for Chemical Stability and pH-Responsive Delivery

Polydopamine (PDA) possesses high aqueous dispersibility, strong optical absorption, and a zwitterionic property, which give it multitudes of advantages to coat light-sensitive hydrophobic curcumin (Cur) for pH-responsive release. However, PDA is formed in alkaline conditions, which hinders its potential application for alkali-sensitive curcumin coating. Here, we developed a method to prepare PDA-coated Cur nanoparticles (NPs), which reduced chemical degradation of Cur in alkaline conditions. Encapsulation efficiency and loading capacity decreased to 73.69% and 51.80%, as the time for dopamine polymerization went on. PDA could protect Cur from light-induced degradation in powder and solution forms. Controlled release and pH-responsive delivery of PDA-coated Cur were observed under stomach and intestinal conditions compared to free Cur, which resulted from the coverage and thickness of the PDA shell and the electrostatic attraction between PDA and Cur. PDA-coated Cur NPs could be a promising way for the application of Cur in the beverage and food industry.

Fabrication and release behavior of nitrapyrin Microcapsules: Using modified melamine-formaldehyde resin as shell material

As a commonly used nitrification inhibitor, nitrapyrin can significantly improve the utilization of nitrogen in soils. However, the effectiveness of the traditional dosage form of nitrapyrin is reduced by soil adsorption. In this study, nitrapyrin was encapsulated into a melamine-formaldehyde resin microcapsule with good dispersion and release behavior using an in situ polymerization method. The nitrapyrin microcapsules were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and particle-size analysis. The results indicated that the microcapsules had a spherical-shell structure, a uniform morphology with nanoscale micropores on the surface, and a decent nitrapyrin loading content (67.19%). Tests revealed that the release behavior of the nitrapyrin microcapsules was outstanding and conformed to the double-release kinetic model. These results of this study indicate that the nitrapyrin microcapsules can be applied as nitrification inhibitors with beneficial environmental effects and high efficacy.

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

Migration patterns of humpback whales have been monitored using 316L stainless steel (SS) satellite telemetry tags. The potential for tissue infection and necrosis is increased if the bacteria, naturally a part of the diverse microbiome on the skin of humpback whales, can adhere to and colonize the surface of the tags. Polydopamine (pDA) has the potential to prevent the adhesion of one of the most prevalent bacterial strains on the surface of the skin of cetaceans (Psychrobacter) through the release of hydrogen peroxide. The release of hydrogen peroxide from the pDA coatings (40-100 μM) has the ability to induce a bacteriostatic response in E. coli, a commonly used bacteria strain in antimicrobial studies and potentially P. cryohalolentis, a common humpback associated bacteria. The H₂O₂ dose required to induce bacteriostatic conditions in E. coli is approximately 60 μM and in P. cryohalolentis is 100 μM. Bacterial adhesion on the surface of pDA coated SS coupons was measured first using E. coli. The coating successfully prevented adhesion of E. coli on the surface of SS coupons under certain conditions (60% reduction, p < 0.05) but the same was not seen with P. cryohalolentis. When coating conditions were altered (an increase in pH and temperature) the adhesion of P. cryohalolentis was reduced (80% reduction, p < 0.001). Overall, the pDA coatings have the capacity to generate varying amounts of hydrogen peroxide by altering the coating conditions and have the ability to reduce bacterial adhesion on the surface of satellite telemetry tags, and therefore the potential to increase tag functional service lifetime.

Polydopamine Coating of Glucan Particles Increases Uptake into Peyer's Patches

Glucan particles (GPs) are hollow, porous 3-4 μm microspheres derived from the cell walls of Baker's yeast (Saccharomyces cerevisiae). The β-1,3-D glucan outer shell of GPs provides for receptor-mediated uptake by phagocytic cells expressing β-glucan receptors. GPs have been used for efficient encapsulation of different types of payloads (DNA, siRNA, proteins, antigens, small molecules), and these payloads have been delivered in vivo by a variety of routes including oral delivery. It is known that GPs are transported across the intestinal epithelium by Peyer's patch M-cells and accumulate in a subset of CD11c+Langerin-positive dendritic cells (DC) in the subepithelial dome (SED). An increase in GP uptake in the intestinal epithelium is needed to improve our efforts to develop GPs for oral delivery of therapeutics and vaccines. In this Article, we report that polydopamine coating of GPs (PDA-GPs) increases transepithelial uptake. Synthesis of PDA-GPs was optimized to allow for encapsulation of payloads inside the hollow cavity of GPs. PDA-GPs and GP controls were orally administered to mice, and PDA-GPs showed a 42% increased uptake in SED phagocytes. PDA-GP uptake by SED phagocytes in control and M-cell-depleted mice demonstrated both M-cell-dependent and -independent mechanisms. In future studies, we will evaluate PDA-GPs for oral vaccine delivery and the use of PDA-functional groups for secondary surface derivatization to generate particles with ligands targeting other intestinal epithelium cell-surface receptors.

Polymer brush based fluorescent immunosensor for direct monitoring of interleukin-1β in rat blood

A sandwich immunosensor was successfully developed for monitoring of interleukin-1β (IL-1β) in rat whole blood. The substrate stainless steel (SS) was first coated with a polydopamine layer and subsequently grafted with poly(ethylene glycol) methacrylate brushes, onto which a sandwich immunosensor was modified for detection of IL-1β. The device has been successfully applied for monitoring of IL-1β with a limit of detection of 4.7 pg mL^-1, and a linear detection range of 12.5-200 pg mL^-1. Good specificity and selectivity for monitoring of IL-1β in rat macrophage secretion were achieved. Furthermore, this device was validated by detection of IL-1β in rat whole blood samples with greater concentrations observed in obese rats compared to control, and strong positive correlation between concentrations of IL-1β and blood glucose. These results suggest this device is feasible for direct detection of target analytes in biological samples.