Intrinsically Mn2+-Chelated Polydopamine Nanoparticles for Simultaneous Magnetic Resonance Imaging and Photothermal Ablation of Cancer Cells

Isopropanol-promoted DNA extraction by polydopamine functionalized magnetic particles based on metal coordination

High-quality DNA is an important guarantee to start downstream experiments in many biological and medical research areas. Magnetic particle-based DNA extraction methods from blood mainly depend on electrostatic adsorption in a low-pH environment. However, the strong acidic environment can influence the DNA stability. Herein, a polydopamine-functionalized magnetic particle (PDA@Fe3O4)-based protocol was developed for DNA extraction from whole blood samples. In the protocol, Mg2+ and Ca2+ were utilized to bridge the adsorption of DNA by PDA@Fe3O4 via the metal-mediated coordination. Isopropanol was found to efficiently promote DNA adsorption by triggering the change of the conformation of DNA from B-form to more compact A-form. In 50 % isopropanol solution, the DNA adsorption efficiency was nearly 100 % in the presence of 0.5 mM Ca2+ or 1.5 mM Mg2+. The role of metal ions and isopropanol in DNA adsorption was explored. The protocol averts the strong acidic environment and PCR inhibitors, such as high concentrations of salt or polyethylene glycol. It demonstrates superiority in DNA yield (59.13 ± 3.63 ng μL-1) over the commercial kit (27.33 ± 4.98 ng μL-1) and phenol-chloroform methods (37.90 ± 0.47 ng μL-1). In addition, to simplify the operastion, an automated nucleic acid extraction device was designed and fabricated to extract whole genomic DNA from blood. The feasibility of the device was verified by extracting DNA from cattle and pig blood samples. The extracted DNA was successfully applied to discriminate the beef authenticity by a duplex PCR system. The results demonstrate that the DNA extraction protocol and the automated device have great potential in blood samples.

Enhanced n-Type Thermoelectric Properties and Structure Evolution of Carbonized Metal-Coordination Polydopamine

Carbonized polydopamine (cPDA) exhibits a nitrogenous graphite-like structure with n-type semiconductor property. However, the low electrical conductivity and Seebeck coefficient of cPDA cannot meet the needs of flexible thermoelectric devices. In this study, a series of metal ions were coordinated with cPDA to enhance n-type thermoelectric properties. At 300 K, all metal-coordination cPDA (metal-cPDA) samples obtain lower thermal conductivity compared to cPDA. Mn-cPDA exhibits the greatest Seebeck coefficient of -25.94 μV K-1, which is almost six times higher than cPDA. Fe-cPDA shows the best electrical conductivity of 2.45 × 105 S m-1. An optimal power factor (PF) value of 11.93 μW m-1 K-2 is achieved in Ca-cPDA with the enhanced electrical conductivity of 9.5 × 104 S m-1 and Seebeck coefficient of -11.24 μV K-1. Using Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM), we revealed the structural characterization of metal-cPDA. Our results indictate that the different metal ions (Mn2+, Zn2+, Mg2+, Al3+, Ca2+, and Fe3+) exert varying influences on the growth of graphite-like structure within metal-cPDA, which lead to the evolution of electrical conductivity. We observe that the carrier density and carrier mobility depend on both the degree of graphitization and the metal-ion coordination, which work together on electrical conductivity and Seebeck coefficient. These findings and understanding of the thermoelectric properties of PDA-based materials will help to realize high-performance n-type thermoelectric materials for flexible electronic device applications.

Clickable X-ray Nanoprobes for Nanoscopic Bioimaging of Cellular Structures

Synchrotron-based X-ray microscopy (XRM) has garnered widespread attention from researchers due to its high spatial resolution and excellent energy (element) resolution. Existing molecular probes suitable for XRM include immune probes and genetic labeling probes, enabling the precise imaging of various biological targets within cells. However, immune labeling techniques are prone to cross-interference between antigens and antibodies. Genetic labeling technologies have limited systems that allow express markers independently, and moreover, genetically encoded labels based on catalytic polymerization lack a fixed morphology. When applied to cell imaging, this can result in reduced localization accuracy due to the diffusion of labels within the cells. Therefore, both techniques face challenges in simultaneously labeling multiple biotargets within cells and achieving high-precision imaging. In this work, we applied the click reaction and developed a third category of imaging probes suitable for XRM, termed clickable X-ray nanoprobes (Click-XRN). Click-XRN consists of two components: an X-ray-sensitive multicolor imaging module and a particle-size-controllable morphology module. Efficient identification of intra- and extracellular biotargets is achieved through click reactions between the probe and biomolecules. Click-XRN possesses a controllable particle size, and its loading of various metal ions provides distinctive signals for imaging under XRM. Based on this, we optimized the imaging energy of Click-XRN with different particle sizes, enabling single-color and two-color imaging of the cell membrane, cell nucleus, and mitochondria with nanoscale spatial nanometers. Our work provides a potent molecular tool for investigating cellular activities through XRM.

Melanin-Inspired Composite Materials: From Nanoarchitectonics to Applications

Synthetic melanin is a mimic of natural melanin analogue with intriguing properties such as metal-ion chelation, redox activity, adhesion, and broadband absorption. Melanin-inspired composite materials are formulated by assembly of melanin with other types of inorganic and organic components to target, combine, and build up the functionality, far beyond their natural capabilities. Developing efficient and universal methodologies to prepare melanin-based composite materials with unique functionality is vital for their further applications. In this review, we summarize three types of synthetic approaches, predoping, surface engineering, and physical blending, to access various melanin-inspired composite materials with distinctive structure and properties. The applications of melanin-inspired composite materials in free radical scavenging, bioimaging, antifouling, and catalytic applications are also reviewed. This review also concludes current challenges that must be addressed and research opportunities in future studies.

Melanin/melanin-like nanoparticles: As a naturally active platform for imaging-guided disease therapy

The development of biocompatible and efficient nanoplatforms that combine diagnostic and therapeutic functions is of great importance for precise disease treatment. Melanin, an endogenous biopolymer present in living organisms, has attracted increasing attention as a versatile bioinspired functional platform owing to its unique physicochemical properties (e.g., high biocompatibility, strong chelation of metal ions, broadband light absorption, high drug binding properties) and inherent antioxidant, photoprotective, anti-inflammatory, and anti-tumor effects. In this review, the fundamental physicochemical properties and preparation methods of natural melanin and melanin-like nanoparticles were outlined. A systematical description of the recent progress of melanin and melanin-like nanoparticles in single, dual-, and tri-multimodal imaging-guided the visual administration and treatment of osteoarthritis, acute liver injury, acute kidney injury, acute lung injury, brain injury, periodontitis, iron overload, etc. Was then given. Finally, it concluded with a reasoned discussion of current challenges toward clinical translation and future striving directions. Therefore, this comprehensive review provides insight into the current status of melanin and melanin-like nanoparticles research and is expected to optimize the design of novel melanin-based therapeutic platforms and further clinical translation.

Imaging-Guided Photoacoustic Immunotherapy Based on the Polydopamine-Functionalized Black Phosphorus Nanocomposites

Phototherapy has great application prospects in superficial tumors, such as melanoma, esophageal cancer, and breast carcinoma, owing to the advantages of noninvasiveness, high spatiotemporal selectivity, and less side effects. However, classical phototherapies including photodynamic and photothermal therapy still need to settle the bottleneck problems of poor efficacy, inevitable thermal damage, and a high rate of postoperative recurrence. In this study, we developed a nanocomposite with excellent optical properties and immune-stimulating properties, termed PBP@CpG, which was obtained by functionalizing black phosphorus (BP) with polydopamine and further adsorbing CpG. Benefiting from the protection of polydopamine against BP, ideal light absorption, and photoacoustic conversion properties, PBP@CpG not only enables precisely delineation of the tumor region with photoacoustic imaging but also powerfully disrupts the plasma membrane and cytoskeleton of tumor cells with a photoacoustic cavitation effect. In addition, we found that the photoacoustic cavitation effect was also capable of inducing immunogenic cell death and remarkably strengthening the antitumor immune response upon cooperating with immune adjuvant CpG. Therefore, PBP@CpG was expected to provide a promising nanoplatform for optical theranostics and herald a new strategy of photoimmunotherapy based on the photoacoustic cavitation effects and immunostimulatory effect.

Photothermal therapy of copper incorporated nanomaterials for biomedicine

Studies have reported on the significance of copper incorporated nanomaterials (CINMs) in cancer theranostics and tissue regeneration. Given their unique physicochemical properties and tunable nanostructures, CINMs are used in photothermal therapy (PTT) and photothermal-derived combination therapies. They have the potential to overcome the challenges of unsatisfactory efficacy of conventional therapies in an efficient and non-invasive manner. This review summarizes the recent advances in CINMs-based PTT in biomedicine. First, the classification and structure of CINMs are introduced. CINMs-based PTT combination therapy in tumors and PTT guided by multiple imaging modalities are then reviewed. Various representative designs of CINMs-based PTT in bone, skin and other organs are presented. Furthermore, the biosafety of CINMs is discussed. Finally, this analysis delves into the current challenges that researchers face and offers an optimistic outlook on the prospects of clinical translational research in this field. This review aims at elucidating on the applications of CINMs-based PTT and derived combination therapies in biomedicine to encourage future design and clinical translation.

Manganese-Based Nanotheranostics for Magnetic Resonance Imaging-Mediated Precise Cancer Management

Manganese (Mn)-based magnetic resonance imaging (MRI) has become a competitive imaging modality for cancer diagnosis due to its advantages of non-invasiveness, high resolution and excellent biocompatibility. In recent years, a variety of Mn contrast agents based on different material systems have been synthesized, and a series of multi-purpose Mn nanocomposites have also emerged, showing satisfactory relaxation efficiency and MRI performance thus possess the transformation and application value in MRI-synergized cancer diagnosis and treatment. This tutorial review starts from the classification and properties of Mn-based nanomaterials, and then summarizes various preparation and functionalization strategies of nanosized Mn contrast agents, especially focuses on the latest progress of Mn contrast agents in MRI-synergized precise cancer theranostics. In addition, present review also discusses the current clinical transformation obstacles such as unclear molecular mechanisms, potential nanotoxicity, and scale production constraints. This paper provides evidence-based recommendations about the future prospects of multifunctional nanoplatforms, as well as technical guidance and panoramic expectations for the design of clinically meaningful cancer management programs.

Microenvironment responsive nanocomposite hydrogel with NIR photothermal therapy, vascularization and anti-inflammation for diabetic infected wound healing

Bacterial infection, excessive inflammation and damaging blood vessels network are the major factors to delay the healing of diabetic ulcer. At present, most of wound repair materials are passive and can't response to the wound microenvironment, resulting in a low utilization of bioactive substances and hence a poor therapeutic effect. Therefore, it's essential to design an intelligent wound dressing responsive to the wound microenvironment to achieve the release of drugs on-demand on the basis of multifunctionality. In this work, metformin-laden CuPDA NPs composite hydrogel (Met@ CuPDA NPs/HG) was fabricated by dynamic phenylborate bonding of gelatin modified by dopamine (Gel-DA), Cu-loaded polydopamine nanoparticles (CuPDA NPs) with hyaluronic acid modified by phenyl boronate acid (HA-PBA), which possessed good injectability, self-healing, adhesive and DPPH scavenging performance. The slow release of metformin was achieved by the interaction with CuPDA NPs, boric groups (B-N coordination) and the constraint of hydrogel network. Metformin had a pH and glucose responsive release behavior to treat different wound microenvironment intelligently. Moreover, CuPDA NPs endowed the hydrogel excellent photothermal responsiveness to kill bacteria of >95% within 10 min and also the slow release of Cu²⁺ to protect wound from infection for a long time. Met@ CuPDA NPs/HG also recruited cells to a certain direction and promoted vascularization by releasing Cu²⁺. More importantly, Met@CuPDA NPs/HG effectively decreased the inflammation by eliminating ROS and inhibiting the activation of NF-κB pathway. Animal experiments demonstrated that Met@CuPDA NPs/HG significantly promoted wound healing of diabetic SD rats by killing bacteria, inhibiting inflammation, improving angiogenesis and accelerating the deposition of ECM and collagen. Therefore, Met@CuPDA NPs/HG had a great application potential for diabetic wound healing.

Synthesis and characterization of Gd3+-loaded hyaluronic acid-polydopamine nanoparticles as a dual contrast agent for CT and MRI scans

Magnetic resonance imaging and computed tomography (CT) suffer from low contrast sensitivity and potential toxicity of contrast agents. To overcome these limitations, we developed and tested a new class of dual contrast agents based on polydopamine nanoparticles (PDA-NPs) that are functionalized and targeted with hyaluronic acid (HA). These nanoparticles (NPs) are chelated with Gd³⁺ to provide suitable contrast. The targeted NPs were characterized through ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), infrared Fourier transform (FTIR), and dynamic light scattering (DLS). The cytotoxicity was investigated on HEK293 cells using an MTT assay. The contrast property of synthesized Gd³⁺/PDA/HA was compared with Barium sulfate and Dotarem, as commercial contrast agents (CAs) for CT and MRI, respectively. The results illustrated that synthesized PDA-NPs have a spherical morphology and an average diameter of 72 nm. A distinct absorption peak around 280 nm in the UV-vis spectrum reported the self-polymerization of PDA-NPs. The HA coating on PDA-NPs was revealed through a shift in the FTIR peak of C=O from 1618 cm^-1 to 1635 cm^-1. The Gd³⁺ adsorption on PDA/HA-NPs was confirmed using an adsorption isotherm assay. The developed CA showed low in vitro toxicity (up to 158.98 µM), and created a similar contrast in MRI and CT when compared to the commercial agents. The r₁ value for PDA/HA/Gd³⁺ (6.5 (mg/ml)^-1 s^-1) was more than Dotarem (5.6 (mg/ml)^-1 s^-1) and the results of the hemolysis test showed that at concentrations of 2, 4, 6, and 10 mg/ml, the hemolysis rate of red blood cells is very low. Additionally, the results demonstrated that PDA/HA/Gd³⁺ could better target the CD₄₄⁺-expressing cancer cells than PDA/Gd³⁺. Thus, it can be concluded that lower doses of developed CA are needed to achieve similar contrast of Dotarem, and the developed CA has no safety concerns in terms of hemolysis. The stability of PDA/HA/Gd³⁺ has also been evaluated by ICP-OES, zeta potential, and DLS during 3 days, and the results suggested that Gd-HA NPs were stable.

DOX-loaded hydroxyapatite nanoclusters for colorectal cancer (CRC) chemotherapy: Evaluation based on the cancer cells and organoids

It is meaningful to find suitable in vitro models for preclinical toxicology and efficacy evaluation of nanodrugs and nanocarriers or drug screening and promoting clinical transformation of nanocarriers. The emergence and development of organoids technology provide a great possibility to achieve this goal. Herein, we constructed an in vitro 3D organoid model to study the inhibitory effect of nanocarriers on colorectal cancer. And designed hydroxyapatite nanoclusters (c-HAP) mediated by polydopamine (PDA) formed under alkaline conditions (pH 9.0), then used c-HAP to load DOX (c-HAP/DOX) as nanocarrier for improved chemotherapy. In vitro, drug release experiments show that c-HAP/DOX has suitable responsive to pH, can be triggered to the facile release of DOX in a slightly acidic environment (pH 6.0), and maintain specific stability in a neutral pH value (7.4) environment. c-HAP/DOX showed an excellent antitumor effect in the two-dimensional (2D) cell model and three-dimensional (3D) patient-derived colon cancer organoids (PDCCOs) model. In addition, c-HAP/DOX can release a sufficient amount of DOX to produce cytotoxicity in a slightly acidic environment, entering efficiently into the colorectal cancer cells caused endocytosis and induced apoptosis. Therefore, organoids can serve as an effective in vitro model to present the structure and function of colorectal cancer tissues and be used to evaluate the efficacy of nanocarriers for tumors.

Smart DNA nanogel coated polydopamine nanoparticle with high drug loading for chemo-photothermal therapy of cancer

A smart deoxyribose nucleic acid nanogel coated polydopamine nanosphere hybrid was designed for chemo-photothermal therapy of cancer. The nanohybrid showed good colloid stability, narrow size distribution, high drug loading, good biocompatibility, and high photothermal conversion efficiency, and could release the drug on desired tumor sites.

Fucoidan-based dual-targeting mesoporous polydopamine for enhanced MRI-guided chemo-photothermal therapy of HCC via P-selectin-mediated drug delivery

The development of novel theranostic agents with outstanding diagnostic and therapeutic performances is still strongly desired in the treatment of hepatocellular carcinoma (HCC). Here, a fucoidan-modified mesoporous polydopamine nanoparticle dual-loaded with gadolinium iron and doxorubicin (FMPDA/Gd³⁺/DOX) was prepared as an effective theranostic agent for magnetic resonance imaging (MRI)-guided chemo-photothermal therapy of HCC. It was found that FMPDA/Gd³⁺/DOX had a high photothermal conversion efficiency of 33.4% and excellent T₁-MRI performance with a longitudinal relaxivity (r₁) value of 14.966 mM^-1·s ^- 1. Moreover, the results suggested that FMPDA/Gd³⁺/DOX could effectively accumulate into the tumor foci by dual-targeting the tumor-infiltrated platelets and HCC cells, which resulted from the specific interaction between fucoidan and overexpressed p-selectin receptors. The excellent tumor-homing ability and MRI-guided chemo-photothermal therapy therefore endowed FMPDA/Gd³⁺/DOX with a strongest ability to inhibit tumor growth than the respective single treatment modality. Overall, our study demonstrated that FMPDA/Gd³⁺/DOX could be applied as a potential nanoplatform for safe and effective cancer theranostics.

Polydopamine/SiO2 Hybrid Structured Superamphiphobic Fabrics with Good Photothermal Behavior

In recent years, photothermal materials that can convert light into heat energy have attracted extensive attention. In this work, we report a simple and effective approach to construct a self-cleaning photothermal superamphiphobic fabric. Dopamine (DA) can self-polymerize into polydopamine (PDA) and adhere to the surface of cotton fabric as a secondary reaction platform. Then, SiO₂ nanoparticles were in situ grown on the PDA@fabric surface by the sol-gel method. The PDA clusters can not only provide good photothermal conversion performance but also be integrated with SiO₂ to create micro-nano rough structures. Finally, the surface of SiO₂ was modified by the long chain of fluorosilane to decrease the fabric surface energy, resulting in superamphiphobicity. The contact angles of water, ethylene glycol, and pump oil on the modified fabric surface could reach 161.1, 158.1, and 142.2°, respectively, making the fabric resistant to contamination by water, common beverages, and oil. Due to the adhesion of the PDA layer, the strong binding force between the fabric and SiO₂ particles enabled the modified fabric to withstand various chemical and mechanical attacks, showing excellent mechanical robustness and harsh environmental stability. More importantly, the surface temperature of the modified fabric could be increased from 19.6 to 37.0 °C, which is close to the human body temperature, under the irradiation of simulated sunlight (I = 15 A, 300 s). The photothermal superamphiphobic fabrics with self-cleaning properties show great promise in the photothermal conversion field.

Polydopamine-modified ZIF-8 nanoparticles as a drug carrier for combined chemo-photothermal osteosarcoma therapy

Single chemotherapy often causes severe adverse effects and chemoresistance which limits therapeutic efficacy. Recently, combination of chemotherapy with photothermal therapy (PTT) have received broad attention for synergistic treatment of osteosarcoma, ultimately resulting in the enhancement of therapeutic efficacy of anticancer drugs. In this study, we have developed a novel drug delivery system based on polydopamine (pDA)-modified ZIF-8 nanoparticles loaded with methotrexate (MTX) (pDA/MTX@ZIF-8 NPs). Herein, pDA modification avoided the explosive release of the drug, and improved the biocompatibility and near-infrared (NIR) light absorbance performance of nanoparticles. The as-prepared pDA/MTX@ZIF-8 NPs could be used as drug targeting delivery system and simultaneously displayed excellent photothermal effects under NIR irradiation. Biology assays in vitro indicated that the pDA/MTX@ZIF-8 NPs were able to efficiently induce MG63 cell apoptosis through reducing mitochondrial membrane potentials (MMPs), and the introduction of photothermal agents enhanced the antitumor effect and decreased the dose of chemotherapeutic drugs. Moreover, the optimized pDA/MTX@ZIF-8 NPs (40 μg/mL) exhibited better photothermal conversion performance and facilitated tumor cells death. These results triumphantly exhibit that the pDA/MTX@ZIF-8 NPs have a synergistic effect of chemo-photothermal therapy (combination index CI = 0.346) and excellent biocompatibility, which has unexceptionable prospects for the therapy of osteosarcoma.

Redox-activity of polydopamine for ultrafast preparation of self-healing and adhesive hydrogels

The high adhesive property of polydopamine (PDA) has spurred various hydrogels for biological and medical applications. Herein, a dual-catalytic redox system was constructed by using the inner dynamic redox-activity of PDA and free radical initiator ammonium persulfate (APS) to initiate the polymerization of acrylic acid (AA) monomer to obtain Fe-PDA hydrogels within 2 h at room temperature. Fe-PDA NPs functions as both initiator to activate APS to generate free radicals and promotes the formation of the hydrogel and dynamic cross-linking mediator between the polymer chains. The tensile strength and ductility of the obtained hydrogels vary with the content of Fe-PDA NPs. Hydrogel with 0.15 wt% of Fe-PDA NPs has the highest tensile strength (~0.62 MPa) and hydrogel with 0.6 wt% of Fe-PDA NPs has the highest elongation, about ~650%. The introduction of PDA NPs imparts PAA hydrogel with reproducible adhesive properties and self-healing ability. The doped iron ion further endows hydrogel enhanced photothermal properties (up to 160 ℃ with 808 nm laser irradiation for 120 s) and conductivity.

Nanostructured particles assembled from natural building blocks for advanced therapies

Advanced treatments based on immune system manipulation, gene transcription and regulation, specific organ and cell targeting, and/or photon energy conversion have emerged as promising therapeutic strategies against a range of challenging diseases. Naturally derived macromolecules (e.g., proteins, lipids, polysaccharides, and polyphenols) have increasingly found use as fundamental building blocks for nanostructured particles as their advantageous properties, including biocompatibility, biodegradability, inherent bioactivity, and diverse chemical properties make them suitable for advanced therapeutic applications. This review provides a timely and comprehensive summary of the use of a broad range of natural building blocks in the rapidly developing field of advanced therapeutics with insights specific to nanostructured particles. We focus on an up-to-date overview of the assembly of nanostructured particles using natural building blocks and summarize their key scientific and preclinical milestones for advanced therapies, including adoptive cell therapy, immunotherapy, gene therapy, active targeted drug delivery, photoacoustic therapy and imaging, photothermal therapy, and combinational therapy. A cross-comparison of the advantages and disadvantages of different natural building blocks are highlighted to elucidate the key design principles for such bio-derived nanoparticles toward improving their performance and adoption. Current challenges and future research directions are also discussed, which will accelerate our understanding of designing, engineering, and applying nanostructured particles for advanced therapies.

Fe(III)-Chelated Polydopamine Nanoparticles for Synergistic Tumor Therapies of Enhanced Photothermal Ablation and Antitumor Immune Activation

Both the low energy density of near-infrared (NIR) photothermal conversion during treatment and the recurrence and metastasis after local treatment have been the main obstacles and conundrums in polydopamine-mediated tumor photothermal therapy (PTT). Herein, On the basis of the enhancement of NIR absorption by ligand to metal charge transfer (LMCT) in transition-metal complexes and the activation of antitumor immunity by an appropriate concentration of Fe(III) ions, Fe(III)-chelated PDA nanoparticles (Fe-PDA NPs) with high loading and responsive release of iron ions were synthesized through a prechelation-polymerization method. First, Fe(III) chelated with the catechol groups in DA to form a mono-dopa-Fe(III) chelate, and then the polymerization of dopamine was initiated under alkaline conditions. The results revealed that the mono-dopa-Fe(III) chelate was still the main form of the Fe ion existing in Fe-PDA and was able to greatly enhance the light absorption behaviors of PDA in NIR, resulting a superior photothermal conversion ability (η = 55.5%). Moreover, the existence of Fe(III) also gave Fe-PDA a T₁-weighted MRI contrast-enhancement performance (r₁ = 7.668 mM^-1 s^-1) and it would enable the accurate ablation of primary tumors in vivo with Fe-PDA under NIR irradiation by means of the guidance of MRI and thermal imaging. Furthermore, Fe-PDA exhibited better H₂O₂-responsive biodegradability in comparison to PDA and easily released Fe ions in tumors, which could effectively promote the tumor-associated macrophage (TAM) repolarization to the M1 mode. TAM repolarization combined with the immunogenic cell death (ICD) induced by PTT could effectively enhance the efficacy of immunotherapy, preventing tumor recurrence and metastasis. The design of Fe-PDA nanoparticles should provide more inspiration for structural and functional improvements of melanin-based materials in tumor suppression.

Fe-Doped polydopamine nanoparticles with peroxidase-mimicking activity for the detection of hypoxanthine related to meat freshness

Rapid and accurate monitoring of food freshness to provide consumers with high-quality meat continues to be of tremendous importance to the food industry. In this report, an efficient Fe-doped polydopamine (Fe-PDA) nanozyme with peroxidase-mimicking activity was synthesized by a high-temperature hydrothermal method, and was applied to a spectrophotometric sensing system, which successfully reports the concentration of hypoxanthine (Hx) related to meat freshness. The Fe-PDA nanozyme showed excellent peroxidase simulation activity, which was primarily verified by steady-state kinetics experiments. In the presence of xanthine oxidase (XOD), Hx can react quantitatively with dissolved O₂ to generate H₂O₂, which can be further catalyzed and produce hydroxyl radicals (•OH) under acidic conditions via the Fe-PDA nanozyme and oxidize colorless TMB to blue oxTMB with absorbance at 653 nm. The absorbance at 653 nm expressed a clear linear relationship with hypoxanthine concentration in the range of 5.13-200 μM, and the detection limit was 1.54 μM. This method was further assessed by measuring the recovery of Hx added to meat samples, which showed promising accuracy. Overall, the developed Fe-PDA nanozyme with excellent peroxidase-mimicking activity is cost-effective, high-performance and easy to produce, offering an efficient and low-cost sensing system based on spectrophotometry for meat freshness determination as an alternative to conventional methods.

Improving the solubility of melanin nanoparticles from apricot kernels is a potent drug delivery system

Background:

Melanin can be used in biomedical nanomaterials, but its solubility in water and bioavailability are low.

Aim:

Melanin nanoparticles were prepared and then PEG-natural melanin nanoparticles (NMNP-PEG) were obtained with good performance and optimize their (water solubility, dispersion stability, chelating metal ions, photothermal stability, drug delivery, and biocompatibility), therefore improve the water solubility of melanin and broaden its application scope in biology, medicine, food, and other fields.

Methods:

MFAK (melanin from apricot kernels) and NMNP-PEG were prepared and characterized using ultraviolet-visible spectrophotometry (UV-Vis), high-performance liquid chromatography (HPLC), Fourier-transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (NMR), and electron microscopy. The chelation rate of metal ions, photothermal effect, doxorubicin loading, and cytotoxicity (MCF-7 cells) were examined.

Results:

UV-Vis, HPLC, FTIR, and NMR indicated that NMNPs contained melanin. NMNPs could be successfully modified using PEG. Under physiological pH conditions (pH 7.4), the metal ion chelation rate of NMNP-PEG increased with time and peaked at 12 h. The photothermal assay showed a temperature enhancement of 26.3°C with 1 mg/mL NMNP-PEG, compared with 1.9℃ with water. The NMNP-PEGs had a typical peak for doxorubicin in the FTIR spectrum, and the peak intensity was proportional to the drug loading. The release of doxorubicin in an acidic buffer was 40.8% at 24 h, almost threefold that in a neutral buffer (11.9%). There was no obvious cytotoxicity from NMNP-PEG.

Conclusion:

NMNP-PEG displays good stability, high metal ion chelation ability, efficient photothermal conversion potential, drug-retaining capability, sustained controlled drug release, and biocompatibility. This study provides a theoretical basis for NMNP-PEG applications in medicine (targeting specific sites to diagnose and treat diseases), food (extending the shelf life of food), and biology (as metal ion chelating agents to remove heavy metals from wastewater).

Recent Advances of Manganese-Based Hybrid Nanomaterials for Cancer Precision Medicine

Cancer precision medicine (CPM) could tailor the best treatment for individual cancer patients, while imaging techniques play important roles in its application. With the characteristics of noninvasion, nonionized, radiation-free, multidimensional imaging function, and real-time monitoring, magnetic resonance imaging (MRI) is an effective way for early tumor detection, and it has become a tower of strength in CPM imaging techniques. Due to linkage with nephrogenic systemic fibrosis (NSF), gadolinium (Gd)-based contrast agent (CA), which was long used in MRI, has been restricted by the Food and Drug Administration (FDA). In this review, we would like to introduce the manganese (Mn)-based CAs that could significantly increase the safety of MRI CAs by realizing more superior performance and functions simultaneously in the diagnosis and treatment of tumors. Also, recent advances in Mn-based hybrid nanomaterials for CPM are summarized and discussed.

A rational study of the influence of Mn2+-insertion in Prussian blue nanoparticles on their photothermal properties

We investigated a series of Mn²⁺-Prussian blue (PB) nanoparticles Na_zMn_xFe_1-x[Fe(CN)₆]_1-y□y·nH₂O of similar size, surface state and cubic morphology with various amounts of Mn²⁺ synthesized through a one step self-assembly reaction. We demonstrated by a combined experimental-theoretical approach that during the synthesis, Mn²⁺ substituted Fe³⁺ up to a Mn/Na-Mn-Fe ratio of 32 at% in the PB structure, while for higher amounts, the Mn₂[Fe(CN)₆] analogue is obtained. For comparison, the post-synthetic insertion of Mn2+ in PB nanoparticles was also investigated and completed with Monte-Carlo simulations to probe the plausible adsorption sites. The photothermal conversion efficiency (η) of selected samples was determined and showed a clear dependence on the Mn²⁺amount with a maximum efficiency for a Mn/Na-Mn-Fe ratio of 10 at% associated with a dependence on the nanoparticle concentration. Evaluation of the in vitro photothermal properties of these nanoparticles performed on triple negative human breast adenocarcinoma (MDA-MB-231) cells by using continuous and pulsed laser irradiation confirm their excellent PTT efficiency permitting low dose use.

Synthesis of Biomimetic Melanin-Like Multifunctional Nanoparticles for pH Responsive Magnetic Resonance Imaging and Photothermal Therapy

The design and development of multifunctional nanoparticles have attracted great interest in biomedical research. This study aims to prepare pH-responsive melanin-like nanoparticles for T₁-weighted magnetic resonance imaging (MRI) and photothermal therapy. The new multifunctional nanoparticles (amino-Fe-PDANPs) are synthesized by copolymerization of dopamine and its derivative amino-N-[2-(diethylamino) ethyl]-3,4-dihydroxy-benzenepropanamide (N-Dopa) at room temperature. The size of nanoparticles can be controlled by NaOH concentration. The incorporation of N-Dopa is characterized by NMR and FT-IR. From transmission electron microscopy (TEM), the nanoparticles exhibit excellent dispersion stability in water and are spherical in shape. The MRI measurement has demonstrated that amino-Fe-PDANPs have a significant signal enhancement in responding to the acidic solution. Confirmed by the photothermal study, the nanoparticles exhibit a high photothermal conversion efficiency. The melanin-like multifunctional nanoparticles integrate both diagnosis and therapeutic functionalities, indicating the potential for theranostic application.

Mutual Benefit between Cu(II) and Polydopamine for Improving Photothermal-Chemodynamic Therapy

Combination therapy has attracted extensive interest in alleviating the shortcomings of monotherapy and enhancing the treatment efficacy. In this work, hollow mesoporous silica nanoparticles (HMSNs) play the role of nanocarriers in the delivery of Cu(II)-doped polydopamine (PDA), termed as HMSNs@PDA-Cu, for synergistic therapy. PDA acts as a traditional photothermal agent to realize photothermal treatment (PTT). Chemodynamic therapy (CDT) is realized by the reaction of Cu(II) with intracellular glutathione (GSH), and subsequently, the generated Cu(I) reacts with H₂O₂ to produce toxic hydroxyl radical (^•OH) through a Fenton-like reaction. The photothermal performance of PDA is improved after its coordination with Cu(II). On the other hand, PDA exhibits superoxide dismutase (SOD)-mimicking activity. PDA converts O₂^•- to H₂O₂ and improves the production of H₂O₂, which promotes the therapeutic effect of CDT. Moreover, the high temperature caused by PTT further enhances the yield of ^•OH for CDT. This nanotheranostic platform perfectly applied to the tumor depletion of mice, presenting great potential for cancer metastasis therapy in vitro and in vivo.

Precise engineering of acorn-like Janus nanoparticles for cancer theranostics

The anisotropic Janus nanoparticles (JNPs) provide synergistic effects by concentrating multiple properties on a single carrier. Herein, we reported a novel and simple approach to fabricate acorn-like poly(acrylic acid)-mesoporous calcium phosphate/polydopamine (PAA-mCaP/PDA) JNPs, which were selectively functionalized with methoxy-poly(ethylene glycol)thiol (PEG-SH) on PDA domains to obtain superior stability, while the other mCaP sides served as a storage space and passage for the anti-cancer drug of doxorubicin (DOX). The unique acorn-like PAA-mCaP/PDA-PEG JNPs were utilized as novel theranostic agents for photoacoustic (PA) imaging-guided synergistic cancer chemo-phototherapy. More importantly, this synthetic strategy can be applied to synthesize various mesoporous Janus nanocarriers, paving the way toward designed synthesis of acorn-like JNPs in nanomedicine, biosensing and catalysis. STATEMENT OF SIGNIFICANCE: The distinct acorn-like poly(acrylic acid)-mesoporous calcium phosphate/polydopamine Janus nanoparticles (PAA-mCaP/PDA JNPs) with a spherical-shaped PAA-mCaP core and PDA half-shell were fabricated for the first time. To achieve superior stability, the acorn-like PAA-mCaP/PDA JNPs were selectively functionalized with methoxy-poly(ethylene glycol)thiol (PEG-SH) on PDA domains to obtain acorn-like PAA-mCaP/PDA-PEG JNPs. The resultant acorn-like PAA-mCaP/PDA-PEG JNPs own an excellent biocompatibility, high drug-loading contents, good photothermal conversion efficiency, photoacoustic (PA) imaging capacity and pH/NIR dual-responsive properties, enabling the acorn-like JNPs to be applied for PA imaging-guided synergistic cancer chemo-phototherapy. More importantly, the synthetic approach could be extended to prepare acorn-like mesoporous inorganic substances/PDA JNPs for specific applications.

Imaging-Guided Chemo-Photothermal Polydopamine Carbon Dots for EpCAM-Targeted Delivery toward Liver Tumor

We demonstrate a versatile nanoparticle with imaging-guided chemo-photothermal synergistic therapy and EpCAM-targeted delivery of liver tumor cells. EpCAM antibody (anti-EpCAM) and Pt(IV) were grafted onto the polydopamine carbon dots (PDA-CDs) by the amidation reaction. The EpCAM antibody of particles enables the targeted interaction with liver progenitor cells due to their overexpressed EpCAM protein. The tetravalent platinum prodrug [Pt(IV)] induces apoptosis with minimum toxic side effects through the interaction between cisplatin and tumor cell DNA. The nanoparticles displayed stable photothermal property and considerable anti-tumor therapeutic effect in vivo. Coupling with cellular imaging due to their fluorescence property, anti-EpCAM@PDA-CDs@Pt(IV) offers a convenient and effective platform for imaging-guided chemo-photothermal synergistic therapy toward liver cancers in the near future.

Bioinspired Theranostic Coordination Polymer Nanoparticles for Intranasal Dopamine Replacement in Parkinson's Disease

Dopamine (DA) is one of the main neurotransmitters found in the central nervous system and has a vital role in the function of dopaminergic (DArgic) neurons. A progressive loss of this specific subset of cells is one of the hallmarks of age-related neurodegenerative disorders such as Parkinson's disease (PD). Symptomatic therapy for PD has been centered in the precursor l-DOPA administration, an amino acid precursor of DA that crosses the blood-brain barrier (BBB) while DA does not, although this approach presents medium- to long-term side effects. To overcome this limitation, DA-nanoencapsulation therapies are actively being searched as an alternative for DA replacement. However, overcoming the low yield of encapsulation and/or poor biodistribution/bioavailability of DA is still a current challenge. Herein, we report the synthesis of a family of neuromelanin bioinspired polymeric nanoparticles. Our system is based on the encapsulation of DA within nanoparticles through its reversible coordination complexation to iron metal nodes polymerized with a bis-imidazol ligand. Our methodology, in addition to being simple and inexpensive, results in DA loading efficiencies of up to 60%. In vitro, DA nanoscale coordination polymers (DA-NCPs) exhibited lower toxicity, degradation kinetics, and enhanced uptake by BE(2)-M17 DArgic cells compared to free DA. Direct infusion of the particles in the ventricle of rats in vivo showed a rapid distribution within the brain of healthy rats, leading to an increase in striatal DA levels. More importantly, after 4 days of nasal administrations with DA-NCPs equivalent to 200 μg of the free drug per day, the number and duration of apomorphine-induced rotations was significantly lower from that in either vehicle or DA-treated rats performed for comparison purposes. Overall, this study demonstrates the advantages of using nanostructured DA for DA-replacement therapy.

Dual Modal Imaging-Guided Drug Delivery System for Combined Chemo-Photothermal Melanoma Therapy

PURPOSE

Malignant melanoma is one of the most devastating types of cancer with rapid relapse and low survival rate. Novel strategies for melanoma treatment are currently needed to enhance therapeutic efficiency for this disease. In this study, we fabricated a multifunctional drug delivery system that incorporates dacarbazine (DTIC) and indocyanine green (ICG) into manganese-doped mesoporous silica nanoparticles (MSN(Mn)) coupled with magnetic resonance imaging (MRI) and photothermal imaging (PI), for achieving the superior antitumor effect of combined chemo-photothermal therapy.

MATERIALS AND METHODS

MSN(Mn) were characterized in terms of size and structural properties, and drug loading and release efficiency MSN(Mn)-ICG/DTIC were analyzed by UV spectra. Photothermal imaging effect and MR imaging effect of MSN(Mn)-ICG/DTIC were detected by thermal imaging system and 3.0 T MRI scanner, respectively. Then, the combined chemo-phototherapy was verified in vitro and in vivo by morphological evaluation, ultrasonic and pathological evaluation.

RESULTS

The as-synthesized MSN(Mn) were characterized as mesoporous spherical nanoparticles with 125.57±5.96 nm. MSN(Mn)-ICG/DTIC have the function of drug loading-release which loading ratio of ICG and DTIC could reach to 34.25±2.20% and 50.00±3.24%, and 32.68±2.10% of DTIC was released, respectively. Manganese doping content could reach up to 65.09±2.55 wt%, providing excellent imaging capability in vivo which the corresponding relaxation efficiency was 14.33 mM-1s-1. And outstanding photothermal heating ability and stability highlighted the potential biomedical applicability of MSN(Mn)-ICG/DTIC to kill cancer cells. Experiments by A375 melanoma cells and tumor-bearing mice demonstrated that the compound MSN(Mn)-ICG/DTIC have excellent biocompatibility and our combined therapy platform delivered a superior antitumor effect compared to standalone treatment in vivo and in vitro.

CONCLUSION

Our findings demonstrate that composite MSN(Mn)-ICG/DTIC could serve as a multifunctional platform to achieve a highly effective chemo-photothermal combined therapy for melanoma treatment.

A mesoporous polydopamine nanoparticle enables highly efficient manganese encapsulation for enhanced MRI-guided photothermal therapy

Theranostic agents based on magnetic resonance imaging (MRI) and photothermal therapy (PTT) play an important role in tumor therapy. However, the available theranostic agents are facing great challenges such as biocompatibility, MRI contrast effect and photothermal conversion efficiency (η). In this work, mesoporous polydopamine nanoparticles (MPDAPs/Mn) were prepared on MRI and PTT combined theranostic nanoplatforms, of which the high loading manganese ions and specific surface areas enable good MRI contrast and excellent photothermal conversion efficiency, respectively. The MPDAPs/Mn have uniform morphology, good stability and biocompatibility. Meanwhile, in vitro and in vivo studies have confirmed their superior T₁-weighted MRI effect and photothermal conversion efficiency. Furthermore, MPDAPs/Mn have excellent antitumor efficacy in HeLa tumor-bearing mice. Therefore, this developed MPDAPs/Mn theranostic nanoplatform could be a promising candidate for MRI-guided photothermal cancer therapy.

A Gd-doped polydopamine (PDA)-based theranostic nanoplatform as a strong MR/PA dual-modal imaging agent for PTT/PDT synergistic therapy

Based on widely used photoacoustic imaging (PAI) and photothermal properties of polydopamine (PDA), a multifunctional Gd-PDA-Ce6@Gd-MOF (GPCG) nanosystem with a core-shell structure and strong imaging ability was constructed. Benefitting from the metal-organic framework (MOF) structure, GPCG nanoparticles (NPs) showed enhanced magnetic resonance imaging (MRI) ability with high relaxation rates (r1 = 13.72 mM-1 s-1 and r2 = 216.14 mM-1 s-1). The MRI effect of Gd ions combined with the PAI effect of PDA, giving GPCG NPs a dual-modal imaging ability. The core, mainly composed of PDA and photodynamic photosensitizer chlorin e6 (Ce6), achieved photothermal/photodynamic therapy (PTT/PDT) synergistic performance. Besides, to overcome the unexpected release of Ce6, the MOF shell realized pH-sensitive release and a high local concentration. Through in vivo studies, we concluded that GPCG NPs show a good inhibitory effect on tumor growth. In conclusion, we successfully obtained a GPCG theranostic nanoplatform and paved the way for subsequent design of imaging guided therapeutic nanostructures based on metal-doped PDA.

Polydopamine nanospheres with multiple quenching effect on TiO2/CdS:Mn for highly sensitive photoelectrochemical assay of tumor markers

A photoelectrochemical (PEC) immunosensing strategy based on the multiple quenching of polydopamine nanoparticles (PDA NPs) to Mn²⁺-doped CdS-modified TiO₂ nanoparticles (TiO₂/CdS:Mn) was designed for the highly sensitive detection of carcinoembryonic antigen (CEA). The uniform PDA NPs possessed good dispersibility, good biocompatibility, and abundant functional groups for biomolecule assembly. They also had unique photophysical properties, with light absorption spanning the visible to infrared light range. When the immune-recognition brought the PDA NPs close to the TiO₂/CdS:Mn interface, the PDA NPs competed with TiO₂/CdS:Mn to absorb light, consumed photoelectrons generated in the TiO₂/CdS:Mn, and hindered the access of electron donors to photoactive materials. The contribution from these aspects thus led to a significant decrease in photocurrent. Benefiting from the multiple quenching mechanism, the PEC immunosensor showed high sensitivity for CEA detection. Under optimal conditions, a low detection limit of 0.02 pg/mL and a wide linear relationship from 0.1 pg/mL to 100 ng/mL were obtained. The immunoassay showed good reproducibility and stability, and good selectivity and high accuracy in serum sample analysis. In this regard, PEC immunosensors may have great application potential for screening tumor markers and the prevention and monitoring of serious diseases.

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.

Melanin-Like Nanomedicine in Photothermal Therapy Applications

Photothermal therapy (PTT) mediated by nanomaterial has become an attractive tumor treatment method due to its obvious advantages. Among various nanomaterials, melanin-like nanoparticles with nature biocompatibility and photothermal conversion properties have attracted more and more attention. Melanin is a natural biological macromolecule widely distributed in the body and displays many fascinating physicochemical properties such as excellent biocompatibility and prominent photothermal conversion ability. Due to the similar properties, Melanin-like nanoparticles have been extensively studied and become promising candidates for clinical application. In this review, we give a comprehensive introduction to the recent advancements of melanin-like nanoparticles in the field of photothermal therapy in the past decade. In this review, the synthesis pathway, internal mechanism and basic physical and chemical properties of melanin-like nanomaterials are systematically classified and evaluated. It also summarizes the application of melanin-like nanoparticles in bioimaging and tumor photothermal therapy (PTT)in detail and discussed the challenges they faced in clinical translation rationally. Overall, melanin-like nanoparticles still have significant room for development in the field of biomedicine and are expected to applied in clinical PTT in the future.

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.

Sialic acid-engineered mesoporous polydopamine nanoparticles loaded with SPIO and Fe3+ as a novel theranostic agent for T1/T2 dual-mode MRI-guided combined chemo-photothermal treatment of hepatic cancer

Hepatic cancer is a serious disease with high morbidity and mortality. Theranostic agents with effective diagnostic and therapeutic capability are highly needed for the treatment of hepatic cancer. Herein, we aimed to develop a novel mesoporous polydopamine (MPDA)-based theranostic agent for T1/T2 dual magnetic resonance imaging (MRI)-guided cancer chemo-photothermal therapy. Superparamagnetic iron oxide (SPIO)-loaded MPDA NPs (MPDA@SPIO) was firstly prepared, followed by modifying with a targeted molecule of sialic acid (SA) and chelating with Fe³⁺ (SA-MPDA@SPIO/Fe³⁺ NPs). After that, doxorubicin (DOX)-loaded SA-MPDA@SPIO/Fe³⁺ NPs (SA-MPDA@SPIO/DOX/Fe³⁺) was prepared for tumor theranostics. The prepared SAPEG-MPDA@SPIO/Fe³⁺ NPs were water-dispersible and biocompatible as evidenced by MTT assay. In vitro photothermal and relaxivity property suggested that the novel theranostic agent possessed excellent photothermal conversion capability and photostability, with relaxivity of being r₁ = 4.29 mM⁻¹s⁻¹ and r₂ = 105.53 mM⁻¹s⁻¹, respectively. SAPEG-MPDA@SPIO/Fe³⁺ NPs could effectively encapsulate the DOX, showing dual pH- and thermal-triggered drug release behavior. In vitro and in vivo studies revealed that SA-MPDA@SPIO/DOX/Fe³⁺ NPs could effectively target to the hepatic tumor tissue, which was possibly due to the specific interaction between SA and the overexpressed E-selectin. This behavior also endowed SA-MPDA@SPIO/DOX/Fe³⁺ NPs with a more precise T1-T2 dual mode contrast imaging effect than the one without SA modification. In addition, SAPEG-MPDA@SPIO/DOX/Fe³⁺ NPs displayed a superior therapeutic effect, which was due to its active targeting ability and combined effects of chemotherapy and photothermal therapy. These results demonstrated that SAPEG-MPDA@SPIO/DOX/Fe³⁺ NPs is an effective targeted nanoplatform for tumor theranostics, having potential value in the effective treatment of hepatic cancer.

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Sialic acid (SA)-modified SPIO-loaded mesoporous polydopamine (MPDA) was prepared.

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SAPEG-MPDA@SPIO NPs was effective at dual loading Fe³⁺ ion and DOX.

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SAPEG-MPDA@SPIO/DOX/Fe³⁺ NPs showed pH- and NIR-responsible drug release behaviors.

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SAPEG-MPDA@SPIO/DOX/Fe³⁺ NPs could actively target to the hepatic tumor sites.

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The novel theranostic achieved dual-mode MRI guided chemo-photothermal therapy.

Single-step formulation of levodopa-based nanotheranostics - strategy for ultra-sensitive high longitudinal relaxivity MRI guided switchable therapeutics

Nanotheranostics (combined diagnosis and therapy) is emerging as an integral part of future therapeutic strategies. However, the development and fabrication of a nanotheranostic module involves multistep processes and always faces formulation challenges. The complexity involved in its multi-step formulations hinders its reproducible industrial production and clinical translation. Therefore, a facile synthesis of multifunctional nanotheranostics is critical to its translational success. In this report, we have developed a one-pot facile strategy to prepare a MRI-visible photothermal theranostic switchable module (T-SWITCH). These nanoparticles are synthesized through polymerization of levodopa together with the reduction of KMnO4 in the presence of silk sericin for the formation of manganese dioxide particles within the T-SWITCH. The synthesized T-SWITCH showed a uniform size distribution of around 95.77 nm and high longitudinal relaxivity coefficient (r1) of up to 61.94 mM-1 s-1. The reported r1 of the T-SWITCH is exceedingly higher than that of any other previously reported manganese-based contrast agents with first-rate in vitro and in vivo contrast enhancement capability. The T-SWITCH can be activated to switch its therapeutic mode using near-infrared (NIR) light. It exhibited strong excitable absorption in the safer and biological NIR window between 650 and 900 nm. We have validated the significant anti-cancer therapeutic efficacy of T-SWITCH both in vitro and in vivo through switchable photothermal therapy.

T1-Positive Mn2+-Doped Multi-Stimuli Responsive poly(L-DOPA) Nanoparticles for Photothermal and Photodynamic Combination Cancer Therapy

In this study, we designed near-infrared (NIR)-responsive Mn2+-doped melanin-like poly(L-DOPA) nanoparticles (MNPs), which act as multifunctional nano-platforms for cancer therapy. MNPs, exhibited favorable π-π stacking, drug loading, dual stimuli (NIR and glutathione) responsive drug release, photothermal and photodynamic therapeutic activities, and T1-positive contrast for magnetic resonance imaging (MRI). First, MNPs were fabricated via KMnO4 oxidation, where the embedded Mn2+ acted as a T1-weighted contrast agent. MNPs were then modified using a photosensitizer, Pheophorbide A, via a reducible disulfide linker for glutathione-responsive intracellular release, and then loaded with doxorubicin through π-π stacking and hydrogen bonding. The therapeutic potential of MNPs was further explored via targeted design. MNPs were conjugated with folic acid (FA) and loaded with SN38, thereby demonstrating their ability to bind to different anti-cancer drugs and their potential as a versatile platform, integrating targeted cancer therapy and MRI-guided photothermal and chemotherapeutic therapy. The multimodal therapeutic functions of MNPs were investigated in terms of T1-MR contrast phantom study, photothermal and photodynamic activity, stimuli-responsive drug release, enhanced cellular uptake, and in vivo tumor ablation studies.

Preparation of Multifunctional Dopamine-Coated Zerovalent Iron/Reduced Graphene Oxide for Targeted Phototheragnosis in Breast Cancer

The present study aimed to develop a multifunctional nanoparticle platform with properties that are beneficial in imaging, targeting, and synergistic cancer phototherapy. To this end, we synthesized novel nanoparticles composed of polydopamine, nano zero-valent iron (nZVI), and reduced graphene oxide (rGO). We immobilized nZVI on the surface of GO (nZVI/GO), then further modified nZVI/GO with dopamine to form polydopamine-conjugated nZVI/rGO (nZVI/rGO@pDA). Because nZVI/rGO@pDA absorbs near infrared radiation (NIR) and binds biomolecules of cancer cells, this platform is highly efficacious in photothermal and photodynamic cancer therapy and enables specific targeting of breast cancer cells. Use of nZVI/rGO@pDA at a low concentration (10 μg/mL) resulted in irreversible damage to MCF-7 cells under NIR irradiation (808 nm) without inducing cytotoxic effects in normal cells. Furthermore, nZVI/rGO@pDA showed high sensitivity in magnetic resonance imaging (MRI), comparable to nZVI@pDA, even at low concentration. Monitoring the treatment response through evaluation of MRI signal intensity of nZVI/rGO@pDA in phototherapeutic therapy revealed that the novel material combines the advantages of nZVI, rGO, and pDA to provide specific targeting capabilities, excellent biocompatibility, and cancer phototherapeutic and tumor imaging abilities. Thus, this platform offers great potential in terms of imaging and therapeutic effects in phototherapy treatment for breast cancer.

Size-Dependent Modulation of Polydopamine Nanospheres on Smart Nanoprobes for Detection of Pathogenic Bacteria at Single-Cell Level and Imaging-Guided Photothermal Bactericidal Activity

Pathogenic bacterial fouling in agriculture and food-associated products poses mounting food safety concerns today. Efficient integration of precise tracking and on-demand bacterial killing to achieve the source control of pathogenic bacteria at the single-cell level is one of the most valuable antifouling methods for safeguarding food safety but remains unexplored. Here, we report an all-in-one design strategy as a proof of concept to establish a stimuli-responsive nanoprobe PDANSs-FAM-Apt for the detection of Staphylococcus aureus (S. aureus) at the single-cell level, which could be capable of guiding the on-demand photothermal killing of bacteria upon near-infrared (NIR) light irradiation. By examining the size-dependent modulation of the fluorescence resonance energy transfer efficiency to polydopamine nanospheres (PDANSs), PDANSs-FAM-Apt was finally assembled by 6-carboxyfluorescein-terminated S. aureus, binding the aptamer (FAM-Apt) and PDANSs at ∼258 nm through π-π stacking interactions. As a result, PDANSs-FAM-Apt exhibits a remarkable fluorescence enhancement (∼261-fold) to S. aureus with a satisfactory detection limit of 1.0 cfu/mL, allowing for assay at the single-cell level and thus ultralow background fluorescence imaging of S. aureus as well as its biofilms. Moreover, PDANSs-FAM-Apt shows a high photothermal bactericidal property upon NIR light irradiation, endowing it with the strong capacity to efficiently produce heat for destroying S. aureus and its biofilms with the guidance of imaging results. This work emphasizes the versatility of using the combination of stimuli-responsive fluorescence imaging dependent on the PDANS size modulation and NIR light-activated photothermal antibacterial activity to design stimuli-responsive nanoprobes with an improved precision for pathogenic bacteria monitoring and source controlling, which opens a promising antifouling avenue to eliminate bacteria and disrupt bacterial biofilms in agriculture and food-related industries.

Facile synthesis of hollow mesoporous nickel sulfide nanoparticles for highly efficient combinatorial photothermal-chemotherapy of cancer

Traditional techniques for the synthesis of nickel sulfide (NiS) nanoparticles (NPs) always present drawbacks of morphological irregularity, non-porous structure and poor long-term stability, which are extremely unfavorable for establishing effective therapeutic agents. Here, a category of hollow mesoporous NiS (hm-NiS) NPs with uniform spherical structure and good aqueous dispersity were innovatively developed based on a modified solvothermal reaction technique. Upon the successful synthesis of hm-NiS NPs, dopamine was seeded and in situ polymerized into polydopamine (PDA) on the NP surface, followed by functionalization with thiol-polyethylene glycol (SH-PEG) and encapsulation of the chemotherapeutic drug, doxorubicin (DOX), to form hm-NiS@PDA/PEG/DOX (NiPPD) NPs. The resultant NiPPD NPs exhibited a decent photothermal response and stability, attributed to the optical absorption of the hm-NiS nanocore and PDA layer in the near-infrared (NIR) region. Furthermore, stimulus-responsive drug release was achieved under both acidic pH conditions and NIR laser irradiation, owing to the protonation of -NH₂ groups in the DOX molecules and local thermal shock, respectively. Lastly, a strong combinatorial photothermal-chemotherapeutic effect was demonstrated for tumor suppression with minimal systemic toxicity in vivo. Collectively, this state-of-the-art paradigm may provide useful insights to deepen the application of hm-NiS NPs for disease management and precision medicine.

Melanin and Melanin-Like Hybrid Materials in Regenerative Medicine

Melanins are a group of dark insoluble pigments found widespread in nature. In mammals, the brown-black eumelanins and the reddish-yellow pheomelanins are the main determinants of skin, hair, and eye pigmentation and play a significant role in photoprotection as well as in many biological functions ensuring homeostasis. Due to their broad-spectrum light absorption, radical scavenging, electric conductivity, and paramagnetic behavior, eumelanins are widely studied in the biomedical field. The continuing advancements in the development of biomimetic design strategies offer novel opportunities toward specifically engineered multifunctional biomaterials for regenerative medicine. Melanin and melanin-like coatings have been shown to increase cell attachment and proliferation on different substrates and to promote and ameliorate skin, bone, and nerve defect healing in several in vivo models. Herein, the state of the art and future perspectives of melanins as promising bioinspired platforms for natural regeneration processes are highlighted and discussed.

Ultralow-intensity near infrared light synchronously activated collaborative chemo/photothermal/photodynamic therapy

Although combined chemotherapy (Chemo), photothermal (PTT) and photodynamic (PDT) in cancer therapy has drawn significant attention due to its superior anticancer ability, the required high intensity of irradiation results in serious photo-toxicity to healthy neighboring cells, and thus limits its biomedical applications. Herein, we developed an ultralow-intensity near infrared (NIR) light synchronously activated collaborative Chemo/PTT/PDT nanoplatform. The nanoplatform is composed of a highly emissive upconversion (UC) core, chlorin e6 (Ce6) photosensitizer and the anticancer drug doxorubicin hydrochloride (DOX) co-loaded in a mesoporous silica (MS) shell, and polyethylene glycol-modified graphene (PGO) acts as both the photothermal reagent and smart switch for promoted drug release. Upon 808 nm NIR light exposure with ultralow intensity (0.25 W cm-2), which is below the maximum permissible exposure (MPE, 0.33 W cm-2) for skin, the mild hyperpyrexia of PGO induced both cancer cell irreversible death for PTT and greatly promoted drug release for enhanced Chemo. On the other hand, the upconverted 660 nm light from UC activated Ce6 to generate reactive oxygen species for PDT, while the upconverted 540 nm light from UC could be employed for visualizing the treatment process. The in vitro and in vivo anticancer experiments demonstrate that the ultralow-intensity NIR light synchronously activated Chemo/PTT/PDT nanoplatform exhibits remarkable therapeutic efficacy with minimal photodamage.

Surface Engineering of Metal-Organic Framework as pH-/NIR-Responsive Nanocarrier for Imaging-Guided Chemo-Photothermal Therapy

BACKGROUND

Metal-organic frameworks (MOFs) have attracted intensive research interest in the biomedical field because of their unique properties. However, in order to realize the high loading capacity and therapeutic efficacy, it is still urgent to develop a multifunctional MOFs-based nanoplatform.

MATERIALS AND METHODS

Herein, a pH/near-infrared (NIR) dual-responsive drug delivery system based on zeolitic imidazolate framework-8 (ZIF-8) is constructed for synergistic chemo-photothermal therapy and dual-modal magnetic resonance (MR)/photoacoustic (PA) imaging. The doxorubicin hydrochloride (DOX) is embedded into ZIF-8 through one-pot method, and the resultant ZIF-8/DOX is then successively modified with polydopamine, Mn ions and poly(ethylene glycol). The obtained ZIF-8/DMPP is systematically characterized, and both its in vitro and in vivo biological effects are evaluated in detail.

RESULTS

The ZIF-8/DMPP possesses a high drug-loading content of 18.9% and displays appropriate size and morphology. The pH-dependent degradation and drug release behavior of prepared ZIF-8/DMPP are confirmed. Importantly, the results demonstrate that the photothermal effect of ZIF-8/DMPP under NIR laser irradiation can significantly accelerate its drug releasing rate, further improving the intracellular drug concentrations. Thereafter, the augmented chemotherapeutic efficiency by photothermal effect against cancer cells is verified both in vitro and in vivo. Besides, the favorable MR and PA imaging capacity of ZIF-8/DMPP is also evidenced on the tumor model.

CONCLUSION

Taken together, the surface engineering of ZIF-8-based nanocarrier in this work offers a promising strategy for the multifunctional MOFs-based drug delivery system.

Dopamine-Modified Zero-Valent Iron Nanoparticles for Dual-Modality Photothermal and Photodynamic Breast Cancer Therapy

Phototherapy has the advantages of minimal invasion, few side effects, and improved accuracy for cancer therapy. The application of a polydopamine (PDA)-modified nano zero-valent iron (nZVI@PDA) as a new synergistic agent in combination with photodynamic/photothermal (PD/PT) therapy to kill cancer cells is discussed here. The nZVI@PDA offered high light-to-heat conversion and ROS generation efficiency under near-infrared (NIR) irradiation (808 nm), thus leading to irreversible damage to nZVI@PDA-treated MCF-7 cells at low concentration, without inducing apoptosis in normal cells. Irradiation of nZVI@PDA using an NIR laser converted the energy of the photons to heat and ROS. Our results showed that modification of the PDA on the surface of nZVI can improve the biocompatibility of the nZVI@PDA. This work integrated the PD and PT effects into a single nanodevice to afford a highly efficient cancer treatment. Meanwhile, nZVI@PDA, which combines the advantages of PDA and nZVI, displayed excellent biocompatibility and tumoricidal ability, thus suggesting its huge potential for future clinical research in cancer therapy.

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

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