Polydopamine Nanoparticles for Combined Chemo- and Photothermal Cancer Therapy

Functionalized Polydopamine Nanoparticles: A Promising Drug Delivery Platform for the Treatment of Tuberculosis

Tuberculosis (TB) is considered a major infectious disease by the World Health Organization. The WHO estimates that there are 1.8 million TB deaths, and 10.4 million new cases of the disease reported yearly. While there are conventional therapies for TB, they have drawbacks such as a lengthy pill regimen, rigorous scheduling, and protracted treatment duration, which can result in strains of the disease that are multidrug-resistant (MDR) and extensively drug-resistant (XDR). Future TB control is at risk due to the emergence of MDR strains. This worry has made the hunt for a successful remedy necessary. One biomedical innovation has been the application of nanotechnology, which offers a fresh avenue of treating TB. Such nanotechnology approach includes Polydopamine (PDA) nanoparticles which have demonstrated the ability to reduce these difficulties. In recent times, PDA, which is an intriguing bioinspired polymer, has become a material of choice for designing drug delivery nano-systems. In fact, PDA nanoparticles show several intriguing characteristics, such as easy manufacturing approach, biocompatibility, the ability to scavenge free radicals, and photothermal and photoacoustic features. It is easily functionalized to promote blood circulation, cellular absorption, and drug release, among other functions. As a result, this review has examined the various PDA functionalization techniques aimed at overcoming MDR and enhancing TB treatment.

Quantification of Cisplatin Encapsulated in Nanomedicine: An Overview

Cisplatin, which kills cancer cells mainly through DNA crosslinking, has been widely used as a first-line chemotherapeutic agent although it also causes severe side effects. To improve anticancer outcomes, various types of cisplatin-based nanomedicines have been developed, either through direct incorporation or coordination of cisplatin within nanoparticles (NPs). During the formulation and characterization of cisplatin-loaded NPs, quantitative determination of cisplatin is crucial for both clinically used and newly developed NPs. While NPs facilitate cisplatin delivery, the use of different nanomaterials inevitably complicates its determination and increases the cost of quantification. Currently, there is still a significant demand for an accurate, simple, and cost-effective method to determine cisplatin in NPs, which would facilitate the screening and quality control of cisplatin-based nanomedicines. This review aims to discuss the main strategies for quantifying cisplatin, following a summary of the main types of cisplatin-loaded NPs. Application examples of cisplatin determination in NPs are provided, and the key features of each quantification strategy are compared. In addition, NP-based electrochemical sensors are included as an emerging approach for characterizing cisplatin loaded in NPs. Rational selection of an appropriate cisplatin determination method for NPs according to the quantification principle and specific drug-delivery settings is highly recommended.

Melanin/melanin-like nanoparticles in tumor photothermal and targeted therapies

Melanin is a pigment found in nature that has good photothermal conversion qualities as well as stability, adaptability, and ease of manufacture. In addition to displaying the inherent properties of melanin, melanin/melanin-like nanoparticles (NPs) also have strong dispersion stability, excellent biocompatibility and biodegradability. Melanin/melanin-like NPs have been extensively studied for tumor therapy due to their unique photothermal properties and ability to target tumor cells. They have demonstrated particular promise in photothermal therapy of cancers. Using photothermal conversion materials to create a thermal effect by light irradiation, photothermal therapy (PTT) is a therapeutic approach that kills tumor cells locally. In this paper, we firstly review the preparation methods and physicochemical properties of melanin/melanin-like NPs, and then systematically and in-depth describe the recent advances of melanin/melanin-like NPs, especially synthetic polydopamine (PDA) melanin, in oncology applications, mainly focusing on tumor photothermal and targeted therapies. In addition, we summarize the advantages of melanin/melanin-like NPs in improving the efficacy of photothermal therapy, reducing toxic side effects, and enhancing tumor targeting, and discuss the current challenges and future directions.

Chemotherapeutics-Loaded Poly(Dopamine) Core-Shell Nanoparticles for Breast Cancer Treatment

Chemophotothermal therapy is an emerging treatment of metastatic and drug-resistant cancer anomalies. Among various photothermal agents tested, poly(dopamine) provides an excellent biocompatible alternative that can be used to develop novel drug delivery carriers for cancer treatment. This study explores the synthesis of starch-encapsulated, poly(dopamine)-coated core-shell nanoparticles in a one-pot synthesis approach and by surfactant-free approach. The nanoparticles produced are embellished with polymeric stealth coatings and are tested for their physiologic stability, photothermal properties, and drug delivery in metastatic triple-negative breast cancer cell (TNBC) lines. Our results indicate that stealth polymer-coated nanoparticles exhibit superior colloidal stability under physiologic conditions, and are excellent photothermal agents, as determined by the increase in temperature of solution in the presence of nanoparticles, upon laser irradiation. The chemotherapeutic drug-loaded nanoparticles also showed concentration-dependent toxicities in TNBC and in a brain metastatic cell line. SIGNIFICANCE STATEMENT: This study develops, for the first time, biocompatible core-shell nanoparticles in a template-free approach that can serve as a drug delivery carrier and as photothermal agents for cancer treatment.

Melanin-Ce6-loaded polydopamine nanoparticles-based enhanced phototherapy for B16 melanoma cancer cells

Melanoma is one of the most aggressive and lethal types of cancer owing to its metastatic propensity and chemoresistance property. An alternative therapeutic option is photodynamic and photothermal therapies (PDT/PTT), which employ near-infrared (NIR) light to generate heat and reactive oxygen species (ROS). As per previous reports, Melanin (Mel), and its synthetic analogs (i.e. polydopamine nanoparticles) can induce NIR light-mediated heat energy, thereby selectively targeting and ameliorating cancer cells. Similarly, chlorin e6 (Ce6) also has high ROS generation ability and antitumor activity against various types of cancer. Based on this tenet, In the current study, we have encapsulated Mel-Ce6 in a polydopamine (PDA) nanocarrier (MCP NPs) synthesized by the oxidation polymerization method. The hydrodynamic diameter of the synthesized spherical MCP NPs was 139 ± 10 nm. The MCP NPs, upon irradiation with NIR 690 nm laser for 6 min, showed photothermal efficacy of more than 50 °C. Moreover, the red fluorescence in the MCP NPs due to Ce6 can be leveraged for diagnostic purposes. Further, the MCP NPs exhibited considerable biocompatibility with the L929 cell line and exerted nearly 70% ROS-mediated cytotoxicity on the B16 melanoma cell line after the laser irradiation. Thus, the prepared MCP NPs could be a promising theranostic agent for treating the B16 melanoma cancer.

The Induction of Combined Hyperthermal Ablation Effect of Irreversible Electroporation with Polydopamine Nanoparticle-Coated Electrodes

Irreversible electroporation (IRE) is a prominent non-thermal ablation method widely employed in clinical settings for the focal ablation therapy of solid tumors. Utilizing high-voltage, short-duration electric pulses, IRE induces perforation defects in the cell membrane, leading to apoptotic cell death. Despite the promise of irreversible electroporation (IRE) in clinical applications, it faces challenges concerning the coverage of target tissues for ablation, particularly when compared to other thermal ablation therapies such as radiofrequency ablation, microwave ablation, and cryoablation. This study aims to investigate the induced hyperthermal effect of IRE by applying a polydopamine nanoparticle (Dopa NP) coating on the electrode. We hypothesize that the induced hyperthermal effect enhances the therapeutic efficacy of IRE for cancer ablation. First, we observed the hyperthermal effect of IRE using Dopa NP-coated electrodes in hydrogel phantom models and then moved to in vivo models. In particular, in in vivo animal studies, the IRE treatment of rabbit hepatic lobes with Dopa NP-coated electrodes exhibited a two-fold higher increase in temperature (ΔT) compared to non-coated electrodes. Through a comprehensive analysis, we found that IRE treatment with Dopa NP-coated electrodes displayed the typical histological signatures of hyperthermal ablation, including the disruption of the hepatic cord and lobular structure, as well as the infiltration of erythrocytes. These findings unequivocally highlight the combined efficacy of IRE with Dopa NPs for electroporation and the hyperthermal ablation of target cancer tissues.

ON/OFF based synergetic plasmonic photothermal drug release approach through core-satellite like mussel-inspired polydopamine nanoparticles

One of the studies on new drug delivery and release systems that has increased in recent years is the study using plasmonic nanoparticles. In this study, polydopamine nanoparticles (PDOP NPs), which contribute to photothermal drug release by near infrared radiation (NIR), were decorated with gold nanoparticles (AuNPs) to utilize their plasmonic properties, and a core-satellite-like system was formed. With this approach, epirubicin (EPI)-loaded PDOP NPs were prepared by utilizing the plasmonic properties of AuNPs. Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) methods were used to evaluate the structural properties of these particles. The release behavior of the prepared structures in acidic (pH 5.0) and neutral (pH 7.4) environments based on the ON/OFF approach was also examined. The biocompatibility properties of the particles were evaluated on mouse fibroblast (L929) and anticancer activities on neuroblastoma (SH-SY5Y) cells. The effects of prepared EPI-loaded particles and laser-controlled drug release on ROS production, genotoxicity, and apoptosis were also investigated in SH-SY5Y cells. With the calculated combination index (CI) value, it was shown that the activity of EPI-loaded AuNP@PDOP NPs increased synergistically with the ON/OFF-based approach. The developed combination approach is considered to be remarkable and promising for further evaluation before clinical use.

Light-responsive polymeric nanoparticles for retinal drug delivery: design cues, challenges and future perspectives

A multitude of sight-threatening retinal diseases, affecting hundreds of millions around the globe, lack effective pharmacological treatments due to ocular barriers and common drug delivery limitations. Polymeric nanoparticles (PNPs) are versatile drug carriers with sustained drug release profiles and tunable physicochemical properties which have been explored for ocular drug delivery to both anterior and posterior ocular tissues. PNPs can incorporate a wide range of drugs and overcome the challenges of conventional retinal drug delivery. Moreover, PNPs can be engineered to respond to specific stimuli such as ultraviolet, visible, or near-infrared light, and allow precise spatiotemporal control of the drug release, enabling tailored treatment regimens and reducing the number of required administrations. The objective of this study is to emphasize the therapeutic potential of light-triggered drug-loaded polymeric nanoparticles to treat retinal diseases through an exploration of ocular pathologies, challenges in drug delivery, current production methodologies and recent applications. Despite challenges, light-responsive PNPs hold the promise of substantially enhancing the treatment landscape for ocular diseases, aiming for an improved quality of life for patients.

Vinorelbine-loaded multifunctional magnetic nanoparticles as anticancer drug delivery systems: synthesis, characterization, and in vitro release study

In this study, a multifunctional therapeutic agent combining chemotherapy and photothermal therapy on a single platform has been developed in the form of vinorelbine-loaded polydopamine-coated iron oxide nanoparticles. Vinorelbine (VNB) is loaded on the surface of iron oxide nanoparticles produced by a solvothermal technique after coating with polydopamine (PDA) with varying weight ratios as a result of dopamine polymerisation and covalent bonding of thiol-polyethylene glycol (SH-PEG). The VNB/PDA/Fe3O4 nanoparticles have a saturation magnetisation value of 60.40 emu/g in vibrating sample magnetometry, which proves their magnetisation. Vinorelbine, which is used as an effective cancer therapy agent, is included in the nanocomposite structure, and in vitro drug release studies under different pH conditions (pH 5.5 and 7.4) and photothermal activity at 808 nm NIR laser irradiation are investigated. The comprehensive integration of precise multifunctional nanoparticles design, magnetic response, and controlled drug release with photothermal effect brings a different perspective to advanced cancer treatment research.

Synthesis of Taxifolin-Loaded Polydopamine for Chemo-Photothermal-Synergistic Therapy of Ovarian Cancer

Chemotherapy is a well-established method for treating cancer, but it has limited effectiveness due to its high dosage and harmful side effects. To address this issue, researchers have explored the use of photothermal agent nanoparticles as carriers for precise drug release in vivo. In this study, three different sizes of polydopamine nanoparticles (PDA-1, PDA-2, and PDA-3) were synthesized and evaluated. PDA-2 was selected for its optimal size, encapsulation rate, and drug loading rate. The release of the drug from PDA-2@TAX was tested at different pH and NIR laser irradiation levels. The results showed that PDA-2@TAX released more readily in an acidic environment and exhibited a high photothermal conversion efficiency when exposed to an 808 nm laser. In vitro experiments on ovarian cancer cells demonstrated that PDA-2@TAX effectively inhibited cell proliferation, highlighting its potential for synergistic chemotherapy-photothermal treatment.

Antigen-Capturing Dendritic-Cell-Targeting Nanoparticles for Enhanced Tumor Immunotherapy Based on Photothermal-Therapy-Induced In Situ Vaccination

In situ vaccines have revolutionized immunotherapy as they can stimulate tumor-specific immune responses, with the cancer being the antigen source. However, the heterogeneity of tumor antigens and insufficient dendritic cells (DCs) activation result in low cancer immunogenicity and hence poor vaccine response. Herein, a new in situ vaccine composed of acid-responsive liposome-coated polydopamine (PDA) nanoparticles modified with mannose and loaded with resiquimod (R848) is designed to promote the efficacy of immunotherapy. The in situ vaccine can actively target the tumor site based on the decomposition of the liposome, while the PDA nanoparticles promote photothermal therapy and capture the immunogenic cell-death-induced tumor-associated antigens based on the adsorption effect of dopamine-mimetic mussels. The PDA nanoparticles, which are modified with a mannose ligand, target the DCs and release R848 for activated antigen presentation. As a result, the in situ vaccine not only effectively activates the maturation of the DCs but also significantly enhances their effect on cytotoxic T lymphocyte cells. Furthermore, the vaccine effectively inhibits the distant recurrence and metastasis of tumors via long-term immune memory effects. Therefore, the in situ vaccine provides a potential strategy for improving the efficacy of cancer immunotherapy.

Polydopamine Nanomaterials for Overcoming Current Challenges in Cancer Treatment

In efforts to overcome current challenges in cancer treatment, multifunctional nanoparticles are attracting growing interest, including nanoparticles made with polydopamine (PDA). PDA is a nature-inspired polymer with a dark brown color. It has excellent biocompatibility and is biodegradable, offering a range of extraordinary inherent advantages. These include excellent drug loading capability, photothermal conversion efficiency, and adhesive properties. Though the mechanism of dopamine polymerization remains unclear, PDA has demonstrated exceptional flexibility in engineering desired morphology and size, easy and straightforward functionalization, etc. Moreover, it offers enormous potential for designing multifunctional nanomaterials for innovative approaches in cancer treatment. The aim of this work is to review studies on PDA, where the potential to develop multifunctional nanomaterials with applications in photothermal therapy has been demonstrated. Future prospects of PDA for developing applications in enhancing radiotherapy and/or immunotherapy, including for image-guided drug delivery to boost therapeutic efficacy and minimal side effects, are presented.

Doxorubicin-Loaded Fungal-Carboxymethyl Chitosan Functionalized Polydopamine Nanoparticles for Photothermal Cancer Therapy

In this work, we synthesized doxorubicin-loaded fungal-carboxymethyl chitosan (FC) functionalized polydopamine (Dox@FCPDA) nanoparticles for improved anticancer activity via photothermal drug release. The photothermal properties revealed that the FCPDA nanoparticles with a concentration of 400 µg/mL produced a temperature of about 61.1 °C at 2 W/cm² laser illumination, which is more beneficial for cancer cells. Due to the hydrophilic FC biopolymer, the Dox was successfully encapsulated into FCPDA nanoparticles via electrostatic interactions and pi-pi stacking. The maximum drug loading and encapsulation efficiency were calculated to be 19.3% and 80.2%, respectively. The Dox@FCPDA nanoparticles exhibited improved anticancer activity on HePG2 cancer cells when exposed to an NIR laser (800 nm, 2 W/cm²). Furthermore, the Dox@FCPDA nanoparticles also improved cellular uptake with HepG2 cells. Therefore, functionalizing FC biopolymer with PDA nanoparticles is more beneficial for drug and photothermal dual therapeutic properties for cancer therapy.

Applications of polydopaminic nanomaterials in mucosal drug delivery

Polydopamine (PDA) is a biopolymer with unique physicochemical properties, including free-radical scavenging, high photothermal conversion efficiency, biocompatibility, biodegradability, excellent fluorescent and theranostic capacity due to their abundant surface chemistry. Thus, PDA is used for a myriad of applications including drug delivery, biosensing, imaging and cancer therapy. Recent reports present a new functionality of PDA as a coating nanomaterial, with major implications in mucosal drug delivery applications, particularly muco-adhesion and muco-penetration. However, this application has received minimal traction in the literature. In this review, we present the physicochemical and functional properties of PDA and highlight its key biomedical applications, especially in cancer therapy. A detailed presentation of the role of PDA as a promising coating material for nanoparticulate carriers intended for mucosal delivery forms the core aspect of the review. Finally, a reflection on key considerations and challenges in the utilizing PDA for mucosal drug delivery, along with the possibilities of translation to clinical studies is expounded.

Cisplatin-loaded metal–phenolic network with photothermal-triggered ROS generation for chemo-photothermal therapy of cancer

Developing multifunctional composites has received widespread attention for cancer treatment. Herein, a metal–phenolic network (MPN)-based composite loading with chemotherapy agents (TAFP) exhibits high anti-tumor therapeutic efficacy via photothermal therapy (PTT), chemo-dynamic therapy (CDT), and chemotherapy. The nanocomposite was formed by mixing the chemotherapeutic drugs (cisplatin, DDP) into the tannic acid (TA) and Fe3+ network (TAFe) to integrate the synergistic effect of PTT, CDT, and chemotherapy. Due to the acidic tumor microenvironment, the active substances could be released with the degradation of the metal–phenolic network, and the released DDP would induce the chemotherapy. More importantly, the released TA under the acidic environment could increase iron bioavailability by converting Fe3+ to Fe2+, which converts hydrogen peroxide (H2O2) to highly toxic hydroxyl radical via the Fenton reaction. Meanwhile, the heat generated from TAFP after near-infrared (NIR) laser irradiation could enhance the therapeutic effect of CDT and chemotherapy. Furthermore, the composite exhibited unique anticancer efficacy in vivo with low toxicity. Collectively, this work may facilitate the development of metal–phenolic network-based photothermal agents for clinic anti-tumor applications.

Melanin-like Nanoparticles as an Alternative to Natural Melanin in Retinal Pigment Epithelium Cells and Their Therapeutic Effects against Age-Related Macular Degeneration

Melanin is a natural pigment that is widely distributed in many parts of the human body, such as the skin and retinal pigment epithelium (RPE) in eyes. In contrast to skin melanin, which is being constantly synthesized by the epidermal melanocytes, melanin in the RPE does not regenerate. Melanin is known to function as a potential radical scavenger and photoprotective agent. However, the protective effects of melanin against oxidative stress decline with increasing age. This phenomenon has been correlated with the pathogenesis of age-related macular degeneration (AMD). To increase the potential antioxidant and photoprotective characteristics of melanin, we designed a therapeutic strategy for replenishment of melanin using PEGylated synthetic melanin-like nanoparticles (MNPs) in the RPE for the treatment of AMD. We performed experiments using AMD-like cellular and mouse models and demonstrated that MNPs are biocompatible and selectively target reactive oxygen species (ROS) with powerful antioxidant properties. MNPs can traffic and accumulate in the RPE and are exclusively located in cytosol, but not the nucleus and mitochondria of the cells, for at least 3 months after a single-dose intravitreal injection. Our findings demonstrate that MNPs are able to substitute for natural melanin in the RPE and suggest the potential efficacy of MNPs as a natural radical scavenger against oxidative stress in ROS-related diseases, such as AMD.

Conquering Cancer Multi-Drug Resistance Using Curcumin and Cisplatin Prodrug-Encapsulated Mesoporous Silica Nanoparticles for Synergistic Chemo- and Photodynamic Therapies

Recently, the development of anti-cancer approaches using different physical or chemical pathways has shifted from monotherapy to synergistic therapy, which can enhance therapeutic effects. As a result, enormous efforts have been devoted to developing various delivery systems encapsulated with dual agents for synergistic effects and to combat cancer cells acquired drug resistance. In this study, we show how to make Institute of Bioengineering and Nanotechnology (IBN)-1-based mesoporous silica nanoparticles (MSNs) for multifunctional drug delivery to overcome drug resistance cancer therapy. Initially, curcumin (Cur)-embedded IBN-1 nanocomposites (IBN-1-Cur) are synthesized in a simple one-pot co-condensation and then immobilized with the prodrug of Cisplatin (CP) on the carboxylate-modified surface (IBN-1-Cur-CP) to achieve photodynamic therapy (PDT) and chemotherapy in one platform, respectively, in the fight against multidrug resistance (MDR) of MES-SA/DX5 cancer cells. The Pluronic F127 triblock copolymer, as the structure-directing agent, in nanoparticles acts as a p-glycoprotein (p-gp) inhibitor. These designed hybrid nanocomposites with excellent structural properties are efficiently internalized by the endocytosis and successfully deliver Cur and CP molecules into the cytosol. Furthermore, the presence of Cur photosensitizer in the nanochannels of MSNs resulted in increased levels of cellular reactive oxygen species (ROS) under light irradiation. Thus, IBN-1-Cur-CP showed excellent anti-cancer therapy in the face of MES-SA/DX5 resistance cancer cells, owing to the synergistic effects of chemo- and photodynamic treatment.

Precisely controlled polydopamine-mediated antibacterial system: mathematical model of polymerization, prediction of antibacterial capacity, and promotion of wound healing

In this work, the polydopamine (PDA)-mediated antibacterial system is synthesized to carry out antimicrobial activities in vitro and in vivo. First, to precisely control the surface modification of nanodiamonds (NDs), a mathematical kinetics model of PDA deposition is established, and the conditions of synthesis reaction are discussed including influencing factors such as the concentrations of dopamine, reaction time, and the kinetic constant k1, which is a function of several variables associated with the reaction temperature, light irradiance (especially at ultraviolet wavelengths), pH value and concentration of dissolved O2 in the solution. A simulated visualization demonstrates that the deposition thickness of PDA is positively correlated with temperature and light irradiance, and PDA is easier to deposit in an alkaline solution and will be terminated if the dissolved O2 is insufficient. Then, the precisely controlled thickness of PDA can control the growth of AgNPs, rendering the intensity of Raman peaks increased and providing a predictable antibacterial effect against E. coli in vitro. An optimized antibacterial hydrogel containing NDs-PDA/Ag is prepared and characterized by the Fourier transform infrared spectroscopy and field emission scanning electron microscopy. Finally, the antibacterial experiments to promote wound healing in vivo are performed, which are verified by pathological and immunohistochemical-stained sections. This work provides a theoretical basis of predicting the PDA-assisted surface modification of NDs, giving a divinable antibacterial effect, and promoting wounds healing in vivo.

IGF1 receptor-targeted black TiO2 nanoprobes for MRI-guided synergetic photothermal-chemotherapy in drug resistant pancreatic tumor

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest malignant tumors with features of matrix barrier caused poor drug permeability, and susceptibility to drug resistance. Herein, a PDAC and its stromal cell dual-targeted photothermal-chemotherapy strategy is explored to loosen the matrix and reverse drug resistance. To achieve this goal, black TiO2-Gd nanocomposites were conjugated with insulin like growth factor 1 (IGF1), and loaded with gemcitabine (GEM) to construct bTiO2-Gd-IGF1-GEM nanoprobes. In vitro results show that under 808 nm near-infrared irradiation, killing effect of the nanoprobes on drug-resistant MIA PaCa-2 cell is 3.3 times than that of GEM alone. In vivo experiments indicate the synergetic photothermal-chemotherapy not only loosens fibrous matrix of pancreatic tumor model, but also dramatically inhibits tumor growth, and almost completely eradicates the tumor after 12 days of treatment. In addition, relaxation rate of the nanoprobes is 8.2 times than commercial contrast agent Magnevist, therefore boosts the signal of magnetic resonance imaging in pancreatic tumor. In conclusion, our results reinforce that the prepared nanoprobes are promising to break matrix barrier and overcome drug resistance in PDAC.

Investigation of Gentamicin Release from Polydopamine Nanoparticles

Polydopamine (PDA), being highly reactive in nature, has acquired great attention in multi-disciplinary fields. Owing to its fascinating properties, including its biocompatible, non-toxic and readily bio-degradative nature, we investigated the drug loading and release behavior, using an aminoglycoside antibiotic gentamicin (G) as a model drug. The gentamicin was loaded into the PDA nanoparticles (NPs) via an in situ polymerization method. The release kinetics of the gentamicin was then studied in pH 3, 5 and 7.4. Two batches with varied gentamicin loadings, G-PDA NPs 1:1 (with approx. 84.1% loaded gentamicin) and G-PDA NPs 0.6:1 (with approx. 72.7% loaded gentamicin), were studied. The drug release data were analyzed by LC–MS. The PDA showed good stability in terms of gentamicin release at alkaline pH over a period of seven days. The negative surface charge of PDA at pH 7.4 makes a strong bond with gentamicin, hence preventing its release from the PDA NPs. However, at pH 5 and 3, the amine groups of PDA are more prone towards protonation, making PDA positively charged, hence the repulsive forces caused the gentamicin to detach and release from the G-PDA NPs. Consequently, approx. 40% and 55% drug release were observed at pH 5 and 3, respectively, from the G-PDA NPs 1:1. However, the drug released from G-PDA NPs 0.6:1 was found to be one half as compared to the G-PDA NPs 1:1, which is obvious to the concentration gradient. These findings suggested that the in situ loading method for gentamicin could provide drug release over a period of seven days, hence defending the drug’s efficacy and safety challenges. Furthermore, two kinetic models, namely the Ritger–Peppas and Higuchi models, were implemented to determine the drug release kinetics. Curve fitting analysis supported our findings for the drug release kinetics which are followed by PDA structural changes in response to pH.

Construction of Double-Shelled Hollow Ag2S@Polydopamine Nanocomposites for Fluorescence-Guided, Dual Stimuli-Responsive Drug Delivery and Photothermal Therapy

The design and preparation of multifunctional drug carriers for combined photothermal–chemotherapy of cancer have attracted extensive attention over the past few decades. However, the development of simple-structured stimuli-responsive theranostic agents as both photothermal agents and chemotherapeutic agents remains a big challenge. Herein, a novel double-shelled nanocarrier composed of hollow Ag₂S (HAg₂S) nanospheres and a mesoporous polydopamine (MPDA) exterior shell was fabricated through a facile process. Notably, HAg₂S possesses both fluorescence and photothermal properties. MPDA acts as a drug carrier and photothermal agent. Meanwhile, the cavity structure between HAg₂S and MPDA provides more space for drug loading. The nanocarrier presents a high drug loading rate of 23.4%. It exhibits an apparent pH-responsive DOX release property due to the acidic sensitivity of PDA. In addition, the release of DOX is promoted under NIR irradiation, which is attributed to the heating action generated by the photothermal effect of HAg₂S and MPDA. The cytotoxicity test shows that the nanocarriers possess good biocompatibility. Compared with single photothermal therapy or chemotherapy, the combined treatment represents a synergistic effect with higher therapeutic efficacy. In addition, the nanocarriers exhibit excellent fluorescence imaging capability and can target HepG2 cells. These simple-structured smart nanocarriers have a great potential for fluorescence-mediated combination cancer therapy.

Electroless deposition of copper nanoparticles integrates polydopamine coating on reverse osmosis membranes for efficient biofouling mitigation

In this study, highly antimicrobial CuNPs were integrated into a hydrophilic polydopamine (PDA) coating and immobilized on a RO TFC membrane via a mild and facile reduction approach to form a stable and durable dual-functional layer. Based on the XDLVO analysis, the introduction of PDA increased the membrane-foulant total interaction energy (ΔG_mwf) to 14.13 mJ/m², resulting in improved anti-adhesive properties as demonstrated by a 37% decrease in BSA adsorption for the modified membranes. The well dispersed and high loadings of CuNPs induced by PDA conferred strong bacterial toxicity to the modified membranes, reducing the viability of E. coli by 76%. Furthermore, the presence of catechol groups on PDA favors the formation of covalent bond with CuNPs, thus prolonging the durability of the copper-based anti-biofouling membranes. The combination of PDA coating and CuNPs functionalization imparts the membrane with simultaneous anti-adhesive and anti-microbial properties, leading to a substantial reduction in biofouling propensity in dynamic biofouling experiments. Specifically, the flux decline due to biofouling observed for the modified membranes significantly decreased from 65% to 39%, and biofilm thickness and TOC biomass were 58%, and 55% lower, respectively. This study provides a facile and versatile strategy to construct high performance RO membranes with excellent anti-biofouling functionality.

Amyloid Protein-Biofunctionalized Polydopamine Nanoparticles Demonstrate Minimal Plasma Protein Fouling and Efficient Photothermal Therapy

Polydopamine (PDA) shows great application potential in photothermal therapy (PTT) of tumors due to its excellent photothermal performance. However, PDA rich in a large number of catechin structures, with strong adhesion, can readily attach to plasma proteins in blood to form protein corona, which greatly hinders the transfer efficiency to tumors and reduces the bioavailability. In this paper, a simple, rapid phase-transitioned albumin biomimetic nanocorona (TBSA) is used for the surface camouflage of PDA nanoparticles for minimal plasma protein fouling and efficient PTT. TBSA coating is formed by the BSA-derived amyloid through the hydrophobic aggregation near the isoelectric point and the rupture of disulfide bonds by tris(2-carboxyethyl) phosphine. The stable PDA@TBSA complexes are formed by camouflaging TBSA onto the surface of PDA through hydrophobic, electrostatic, and covalent binding between TBSA and PDA, which showed excellent anti-plasma protein adsorption properties profited from the surface charge of PDA@TBSA approaching equilibrium and the surface passivation of BSA. The plasma protein thickness of the PDA@TBSA surface is 6 times lower than that of PDA at adsorption saturation. In vitro and in vivo experiments have revealed that PDA@TBSA has an excellent photothermal antitumor effect compared to PDA. Both PDA and PDA@TBSA treatment plus 808 nm laser irradiation result in more than 70% inhibition on tumor cell proliferation. In addition, PDA@TBSA does not cause a significant inflammatory response and tissue damage. Taken together, the TBSA coating endows PDA with low-fouling functions in blood and improves the residence time of PDA in blood and enrichment in the tumor tissue. This work offers a novel and efficient strategy for the design of functional nanosystems exploiting the speciality of the biomolecular corona formation around nanomaterials.

Polydopamine-Bi2WO6-Decorated Gauzes as Dual-Functional Membranes for Solar Steam Generation and Photocatalytic Degradation Applications

The dual-functional Bi2WO6/polydopamine (PDA)-modified gauze membrane has been developed for applications in photocatalytic degradation and solar steam generation. Two types of membrane were prepared by changing the growth sequence of Bi2WO6 nanomaterials and PDA on gauze substrates. The spatial distribution of Bi2WO6 and polydopamine has a great influence on light absorption, photocatalytic degradation, and solar steam generation performances. Bi2WO6 photocatalysts can absorb short-wavelength light for the photocatalytic decoloration of organic dyes. The photothermal polydopamine can convert light into heat for water evaporation. Besides, the gauze substrate provides water transport channels to facilitate water evaporation. The morphology, surface chemistry, and optical properties of Bi2WO6-PDA modified gauzes were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and diffuse reflectance spectra. The photothermal properties, wetting properties, and solar steam generation rates of the composite films were also studied. Degradation of 96% of indigo carmine was achieved after being irradiated for 120 min in the presence of G/PDA/BWNP. The water evaporation rates of the G/BWP/PDA sample under the irradiation of an Xe lamp (light intensity = 1000 W/m2) reached 1.94 kg·m-2·h-1.

Photothermally responsive Pickering emulsions stabilised by polydopamine nanobowls

Pickering emulsions with stimuli responsive properties have attracted mounting research attention owing to their potential for on-demand destabilisation of emulsions. However, a combination of biocompatibility and long-term stability are essential to efficiently apply such systems in biomedical applications, and this remains a significant challenge. To address current limitations, here we report the formation of photothermally responsive oil-in-water (o/w) Pickering emulsions fabricated using biocompatible stabilisers and showing prolonged stability. For the first time, we explore polydopamine (PDA) bowl-shaped mesoporous nanoparticles (PDA nanobowls) as a Pickering stabiliser without any surface modification or other stabiliser present. As-prepared PDA nanobowl-stabilised Pickering emulsions are shown to be pH responsive, and more significantly show high photothermal efficiency under near-infrared illumination due the incorporation of PDA into the system, which has remarkable photothermal response. These biocompatible, photothermally responsive o/w Pickering emulsion systems show potential in controlled drug release applications stimulated by NIR illumination.

Poly(2-ethyl-2-oxazoline) functionalized reduced graphene oxide: Optimization of the reduction process using dopamine and application in cancer photothermal therapy

The high near infrared (NIR) absorption displayed by reduced graphene oxide (rGO) nanostructures renders them a great potential for application in cancer photothermal therapy. However, the production of this material often relies on the use of hydrazine as a reductant, leading to poor biocompatibility and environmental-related issues. In addition, to improve rGO colloidal stability, this material has been functionalized with poly(ethylene glycol). However, recent studies have reported the immunogenicity of poly(ethylene glycol)-based coatings. In this work, the production of rGO, by using dopamine as the reducing agent, was optimized considering the size distribution and NIR absorption of the attained materials. The obtained results unveiled that the rGO produced by using a 1:5 graphene oxide:dopamine weight ratio and a reaction time of 4 h (termed as DOPA-rGO) displayed the highest NIR absorption while retaining its nanometric size distribution. Subsequently, the DOPA-rGO was functionalized with thiol-terminated poly(2-ethyl-2-oxazoline) (P-DOPA-rGO), revealing suitable physicochemical features, colloidal stability and cytocompatibility. When irradiated with NIR light, the P-DOPA-rGO could produce a temperature increase (ΔT) of 36 °C (75 μg/mL; 808 nm, 1.7 W/cm², 5 min). The photothermal therapy mediated by P-DOPA-rGO was capable of ablating breast cancer cells monolayers (viability < 3%) and could reduce heterotypic breast cancer spheroids' viability to just 30%. Overall, P-DOPA-rGO holds a great potential for application in breast cancer photothermal therapy.

Design and Synthesis of New PEGylated Polydopamine-Based Nanoconstructs Bearing ROS-Responsive Linkers and a Photosensitizer for Bimodal Photothermal and Photodynamic Therapies against Cancer

Polydopamine (PDA) nanoparticles (NPs) have recently acquired considerable attention for the development of nanoplatforms with multifunctional properties including photothermal (PTT) and photodynamic (PDT) activities. In addition to their high PTT performance, they can be easily conjugated to different types of photosensitizers (PSs) to acquire PDT activity. However, because of PDA free-radical scavenging properties, grafting the PSs directly to PDA surfaces may lead to an inefficient PDT outcome. Thus, the present work aims at synthesizing and characterizing a new PEGylated PDA-based nanoplatform with bifunctional PTT and PDT properties, which allows bimodal cancer therapy with the possibility to release the PS on demand in a spatiotemporal fashion. To do so, PDA NPs with a well-defined size and shape were prepared by the auto-oxidative self-polymerization process of dopamine hydrochloride in mild alkaline solution. The impact of the size on the PTT conversion efficiency was then determined. This allowed us to choose the optimal PDA NP size for PTT applications. Next, PDA NPs were decorated with SH-PEG polymers that bear at their extremity a thioketal reactive oxygen species-cleavable linker coupled to trisulfonated-tetraphenylporphyrin (TPPS₃) chosen as a hydrophilic PS. The grafting efficiency of PS-conjugated PEG on PDA was demonstrated in situ using a quartz crystal microbalance with dissipation monitoring. In addition, the photoinduced release of the PS was demonstrated by ¹H NMR. Finally, PTT/PDT bimodal therapy was assessed in vitro on human squamous esophageal cells by illuminating the PDA NPs at two different wavelengths, which showed the strong synergistic effect of combining PTT and PDT within this nanoplatform.

TPGS-Galactose-Modified Polydopamine Co-delivery Nanoparticles of Nitric Oxide Donor and Doxorubicin for Targeted Chemo-Photothermal Therapy against Drug-Resistant Hepatocellular Carcinoma

The lack of cancer cell specificity and the occurrence of multidrug resistance (MDR) are two major obstacles in the treatment of hepatocellular carcinoma (HCC). To tackle these challenges, a novel nanoparticle (NP)-based drug delivery system (DDS) with a core/shell structure consisted of d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS)-galactose (Gal)/polydopamine (PDA) is fabricated. The NP is loaded with doxorubicin (DOX) and a nitric oxide (NO) donor N,N'-di-sec-butyl-N,N'-dinitroso-1,4-phenylenediamine (BNN) sensitive to heat to afford NO-DOX@PDA-TPGS-Gal. The unique binding of Gal to asialoglycoprotein receptor (ASGPR) and the pH-sensitive degradation of NP ensure the targeted transportation of NP into liver cells and the release of DOX in HCC cells. The near-infrared (NIR) light further facilitates DOX release and initiates NO generation from BNN due to the photothermal property of PDA. In addition to the cytotoxicity contributed by DOX, NO, and heat, TPGS and NO act as MDR reversal agents to inhibit P-glycoprotein (P-gp)-related efflux of DOX by HepG2/ADR cells. The combined chemo-photothermal therapy (chemo-PTT) by NO-DOX@PDA-TPGS-Gal thus shows potent anti-cancer activity against drug-resistant HCC cells in vitro and in vivo and significantly prolongs the life span of drug-resistant tumor-bearing mice. The present work provides a useful strategy for highly targeted and MDR reversal treatment of HCC.

Hollow mesoporous polydopamine nanospheres: synthesis, biocompatibility and drug delivery

Various polydopamine (PDA) nanospheres were synthesized by utilizing triblock copolymer Pluronic F127 and 1,3,5-trimethylbenzene (TMB) as soft templates. Precise morphology control of polydopamine nanospheres was realized from solid polydopamine nanospheres to hollow polydopamine nanospheres, mesoporous polydopamine nanospheres and hollow mesoporous polydopamine nanospheres (H-MPDANSs) by adjusting the weight ratio of TMB to F127. The inner diameter of the prepared H-MPDANSs can be controlled in the range of 50-100 nm, and the outer diameter is about 180 nm. Furthermore, the thickness of hollow mesoporous spherical shell can be adjusted by changing the amount of dopamine (DA). The H-MPDANSs have good biocompatibility, excellent photothermal properties, high drug loading capacity, and outstanding sustainable drug release properties. In addition, both NIR laser irradiation and acid pH can facilitate the controlled release of doxorubicin (DOX) from H-MPDANSs@DOX.

Nanoplatforms for Targeted Stimuli-Responsive Drug Delivery: A Review of Platform Materials and Stimuli-Responsive Release and Targeting Mechanisms

To achieve the promise of stimuli-responsive drug delivery systems for the treatment of cancer, they should (1) avoid premature clearance; (2) accumulate in tumors and undergo endocytosis by cancer cells; and (3) exhibit appropriate stimuli-responsive release of the payload. It is challenging to address all of these requirements simultaneously. However, the numerous proof-of-concept studies addressing one or more of these requirements reported every year have dramatically expanded the toolbox available for the design of drug delivery systems. This review highlights recent advances in the targeting and stimuli-responsiveness of drug delivery systems. It begins with a discussion of nanocarrier types and an overview of the factors influencing nanocarrier biodistribution. On-demand release strategies and their application to each type of nanocarrier are reviewed, including both endogenous and exogenous stimuli. Recent developments in stimuli-responsive targeting strategies are also discussed. The remaining challenges and prospective solutions in the field are discussed throughout the review, which is intended to assist researchers in overcoming interdisciplinary knowledge barriers and increase the speed of development. This review presents a nanocarrier-based drug delivery systems toolbox that enables the application of techniques across platforms and inspires researchers with interdisciplinary information to boost the development of multifunctional therapeutic nanoplatforms for cancer therapy.

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.

One-pot, self-catalyzed synthesis of self-adherent hydrogels for photo-thermal, antimicrobial wound treatment

Self-adhering hydrogels are promising materials to be employed as wound dressings, because they can be used for wound healing without the necessity of additional stitching. However, micro-organisms can easily adhere to these hydrogels as well, which usually causes wound infections. Therefore, adhesive hydrogels are often combined with antibiotics. However, this introduces a risk of drug resistance, cytotoxicity and poor cell affinity. Consequently, recently, there has been great interest in developing non-antibiotic, antibacterial adhesive hydrogels. In this article, we present a simple one-pot synthesis procedure to prepare self-adhesive hydrogels composed of poly(acrylamide) (PAM), naturally derived chitosan (CS) and tannic acid/ferric ion chelates (TA@Fe³⁺). TA@Fe³⁺ enables self-catalysis of the polymerization reaction. In addition, due to its near infrared (NIR) photothermal responsiveness, TA@Fe³⁺ allows for eliminating the bacterial activity with up to 91.6% and 94.7% effectivity against Escherichia coli and Staphylococcus aureus, respectively. Mechanical and adhesion testing shows that the hydrogels are tough as well as flexible and will adhere repeatedly to many types of biological tissues, which can be attributed to the combination of physical and chemical bonding between TA@Fe³⁺ and PAM and CS, respectively. Moreover, in vitro and in vivo tests indicate that the NIR photothermally active hydrogel can effectively prevent bacterial infection and accelerate tissue regeneration, which demonstrates that these hydrogels are promising functional materials for wound healing applications.

Thermo-resistance of ESKAPE-panel pathogens, eradication and growth prevention of an infectious biofilm by photothermal, polydopamine-nanoparticles in vitro

Nanotechnology offers many novel infection-control strategies that may help prevent and treat antimicrobial-resistant bacterial infections. Here, we synthesized polydopamine, photothermal-nanoparticles (PDA-NPs) without further surface-functionalization to evaluate their potential with respect to biofilm-control. Most ESKAPE-panel pathogens in suspension with photothermal-nanoparticles showed three- to four-log-unit reductions upon Near-Infra-Red (NIR)-irradiation, but for enterococci only less than two-log unit reduction was observed. Exposure of existing Staphylococcus aureus biofilms to photothermal-nanoparticles followed by NIR-irradiation did not significantly kill biofilm-inhabitants. This indicates that the biofilm mode of growth poses a barrier to penetration of photothermal-nanoparticles, yielding dissipation of heat to the biofilm-surrounding rather than in its interior. Staphylococcal biofilm-growth in the presence of photothermal-nanoparticles could be significantly prevented after NIR-irradiation because PDA-NPs were incorporated in the biofilm and heat dissipated inside it. Thus, unmodified photothermal nanoparticles have potential for prophylactic infection-control, but data also constitute a warning for possible development of thermo-resistance in infectious pathogens.

Magnetite Nanoparticles and Spheres for Chemo- and Photothermal Therapy of Hepatocellular Carcinoma in vitro

Introduction

We present a multimodal nanoplatforms for the treatment of hepatocellular carcinoma (HCC) in vitro. The nanoplatforms are based on polydopamine (PDA)-coated magnetite nanoparticles (NPs) and spheres (sMAG) with PAMAM dendrimers and functionalized with NHS-PEG-Mal (N-hydroxysuccinimide–polyethylene glycol–maleimide) linker, which allows their functionalization with a folic acid derivative. The nanomaterials bearing a folic acid-targeting moiety show high efficiency in killing cancer cells in the dual chemo- and photothermal therapy (CT-PTT) of the liver cancer cells in comparison to modalities performed separately.

Materials and Methods

All materials are characterized in detail with transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, zeta potential and magnetic measurements. Also, photothermal properties were determined under irradiation of nanoparticles with laser beam of 2 W/cm². The nontoxicity of nanoparticles with doxorubicin and without was checked by WST and LIVE/DEAD assay. Those tests were also used to evaluate materials bearing folic acid and anticancer drug in combined chemo- and photothermal therapy of HCC. Further, the generation of reactive oxygen species profile was also evaluated using flow cytometry test.

Results

Both NPs and sMAG showed high photothermal properties. Nevertheless, the higher photothermal response was found for magnetic spheres. Materials of concentration above 10 µg/mL reveal that their activity was comparable to free doxorubicin. It is worth highlighting that a functionalized magnetic sphere with DOXO more strongly affected the HepG2 cells than smaller functionalized nanoparticles with DOXO in the performed chemotherapy. This can be attributed to the larger size of particles and a different method of drug distribution. In the further stage, both materials were assessed in combined chemo- and photothermal therapy (CT-PTT) which revealed that magnetic spheres were also more effective in this modality than smaller nanoparticles.

Conclusion

Here, we present two types of nanomaterials (nanoparticles and spheres) based on polydopamine and PAMAM dendrimers g.5.0 functionalized with NHS-PEG-Mal linker terminated with folic acid for in vitro hepatocellular carcinoma treatment. The obtained materials can serve as efficient agents for dual chemo- and photothermal therapy of HCC. We also proved that PDA-coated magnetic spheres were more efficient in therapies based on near-infrared irradiation because determined cell viabilities for those materials are lower than for the same concentrations of nanomaterials based on small magnetic nanoparticles.

Strategies for Using Polydopamine to Induce Biomineralization of Hydroxyapatite on Implant Materials for Bone Tissue Engineering

In the field of tissue engineering, there are several issues to consider when designing biomaterials for implants, including cellular interaction, good biocompatibility, and biochemical activity. Biomimetic mineralization has gained considerable attention as an emerging approach for the synthesis of biocompatible materials with complex shapes, categorized organization, controlled shape, and size in aqueous environments. Understanding biomineralization strategies could enhance opportunities for novel biomimetic mineralization approaches. In this regard, mussel-inspired biomaterials have recently attracted many researchers due to appealing features, such as strong adhesive properties on moist surfaces, improved cell adhesion, and immobilization of bioactive molecules via catechol chemistry. This molecular designed approach has been a key point in combining new functionalities into accessible biomaterials for biomedical applications. Polydopamine (PDA) has emerged as a promising material for biomaterial functionalization, considering its simple molecular structure, independence of target materials, cell interactions for adhesion, and robust reactivity for resulting functionalization. In this review, we highlight the strategies for using PDA to induce the biomineralization of hydroxyapatite (HA) on the surface of various implant materials with good mechanical strength and corrosion resistance. We also discuss the interactions between the PDA-HA coating, and several cell types that are intricate in many biomedical applications, involving bone defect repair, bone regeneration, cell attachment, and antibacterial activity.

Polydopamine-Incorporated Nanoformulations for Biomedical Applications

Polydopamine (PDA), a pigment in natural melanin, has attracted considerable attention because of its excellent optical properties, extraordinary adhesion, and good biocompatibility, which make it a promising material for application in energy, environmental, and biomedical fields. In this review, PDA-incorporated nanoformulations are focused for biomedical applications such as drug delivery, bioimaging, and tumor therapy. First, the recent advances in PDA-incorporated nanoformulations for drug delivery are discussed. Further, their application in boimaging, such as fluorescence imaging, photothermal imaging, and photoacoustic imaging, is reviewed. Next, their therapeutic applications, including chemotherapy, photodynamic therapy, photothermal therapy, and synergistic therapy are discussed. Finally, other biomedical applications of PDA-incorporated nanoformulations such as biosensing and clinical diagnosis are briefly presented. Finally, the biomedical applications of PDA-incorporated nanoformulations along with their prospects are summarized.

Bowl-Shaped Polydopamine Nanocapsules: Control of Morphology via Template-Free Synthesis

Synthesis of hollow polydopamine bowl-shaped nanoparticles (nanobowls), as small as 80 nm in diameter, via a one-pot template-free rapid method is reported. Addition of dopamine to a solution of 0.606 mg/mL tris(hydroxymethyl)aminomethane in an ethanol/water mixed solvent resulted in the formation of hollow spherical nanocapsules within 2 h. At longer reaction times, the formation of conventional solid nanospheres dominated the reaction. The wall thickness of the nanocapsules increased with increasing dopamine concentration in the reaction medium. Wall thickness was also influenced by oxygen availability during the reaction. Nanocapsules with thin walls were prone to collapse. When dried, over 90% of the nanocapsules with wall thickness on the order of 11 nm collapsed. Also, the degree of collapse of individual nanoparticles changed from complete to partial to no collapse as the wall thickness was increased. Varying the ethanol content affected the cavity size and overall dimension of the nanocapsules produced but did not result in a significant change to the wall thickness. A mechanism describing the formation of the nanocapsules and their subsequent collapse into nanobowls is presented. The shape-tunable nanobowls prepared through this green, rapid, and affordable method are expected to have applications in the biomedical, electrochemical, and catalytic fields.

Eradicating Infecting Bacteria while Maintaining Tissue Integration on Photothermal Nanoparticle-Coated Titanium Surfaces

Photothermal nanoparticles locally release heat when irradiated by near-infrared (NIR). Clinical applications initially involved tumor treatment, but currently extend toward bacterial infection control. Applications toward much smaller, micrometer-sized bacterial infections, however, bear the risk of collateral damage by dissipating heat into tissues surrounding an infection site. This can become a complication when photothermal nanoparticle coatings are clinically applied on biomaterial surfaces requiring tissue integration, such as titanium-made, bone-anchored dental implants. Dental implants can fail due to infection in the pocket formed between the implant screw and the surrounding soft tissue ("peri-implantitis"). We address the hitherto neglected potential complication of collateral tissue damage by evaluating photothermal, polydopamine nanoparticle (PDA-NP) coatings on titanium surfaces in different coculture models. NIR irradiation of PDA-NP-coated (200 μg/cm2) titanium surfaces with adhering Staphylococcus aureus killed staphylococci within an irradiation time window of around 3 min. Alternatively, when covered with human gingival fibroblasts, this irradiation time window maintained surface coverage by fibroblasts. Contaminating staphylococci on PDA-NP-coated titanium surfaces, as can be per-operatively introduced, reduced surface coverage by fibroblasts, and this could be prevented by NIR irradiation for 5 min or longer prior to allowing fibroblasts to adhere and grow. Negative impacts of early postoperative staphylococcal challenges to an existing fibroblast layer covering a coated surface were maximally prevented by 3 min NIR irradiation. Longer irradiation times caused collateral fibroblast damage. Late postoperative staphylococcal challenges to a protective keratinocyte layer covering a fibroblast layer required 10 min NIR irradiation for adverting a staphylococcal challenge. This is longer than foreseen from monoculture studies because of additional heat uptake by the keratinocyte layer. Summarizing, photothermal treatment of biomaterial-associated infection requires precise timing of NIR irradiation to prevent collateral damage to tissues surrounding the infection site.

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.

Melanin-based nanomaterials: The promising nanoplatforms for cancer diagnosis and therapy

Melanin-based nanoplatforms are biocompatible nanomaterials with a variety of unique physicochemical properties such as strong photothermal conversion ability, excellent drug binding capacity, strong metal chelation capacity, high chemical reactivity and versatile adhesion ability. These innate talents not only make melanin-based nanoplatforms be an inborn theranostic nanoagent for photoacoustic imaging-guided photothermal therapy of cancers, but also enable them to be conveniently transferred into cancer-targeting drug delivery systems and multimodality imaging nanoprobes. Due to the intriguing properties, melanin-based nanoplatforms have attracted much attention in investigations of cancer diagnosis and therapy. This review provides an overview of recent research advances in applications of melanin-based nanoplatforms in the fields of cancer diagnosis and therapy including cancer photothermal therapy, anticancer drug delivery, cancer-specific multimodal imaging and theranostics, etc. The remaining challenges and prospects of melanin-based nanoplatforms in biomedical applications are discussed at the end of this review.