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

Polydopamine-Coated Manganese Carbonate Nanoparticles for Amplified Magnetic Resonance Imaging-Guided Photothermal Therapy

This study reports a multifunctional nanoparticle (NP) that can be used for amplified magnetic resonance image (MRI)-guided photothermal therapy (PTT) due to its surface coating with a polydopamine (PDA) shell. Importantly, by means of introducing the surface coating of PDA, large quantities of water can be trapped around the NPs allowing more efficient water exchange, leading to greatly improved MR contrast signals compared with those from NPs without the PDA coating. Further, a distinct photothermal effect can be obtained arising from the strong absorption of PDA in the near-infrared (NIR) region. By synthesizing multifunctional MnCO₃@PDA NPs, for example, we found that the longitudinal relaxivity (r₁) of MnCO₃ NPs can improve from 5.7 to 8.3 mM^-1 s^-1. Subsequently, in vitro MRI and PTT results verified that MnCO₃@PDA could serve as an excellent MRI/PTT theranostic agent. Furthermore, the MnCO₃@PDA NPs were applied as an MRI/PTT theranostic agent for in vivo MRI-guided photothermal ablation of tumors by intratumoral injection in 4T1 tumor-bearing mice. The MR imaging result shows a significantly bright MR image in the tumor site. The MnCO₃@PDA-mediated PTT result shows high therapeutic efficiency as a result of high photothermal conversion efficiency. The present strategy of amplified MRI-guided PTT based on PDA coating of NPs will be widely applicable to other multifunctional NPs.

Mn2+-coordinated PDA@DOX/PLGA nanoparticles as a smart theranostic agent for synergistic chemo-photothermal tumor therapy

Nanoparticle drug delivery carriers, which can implement high performances of multi-functions, are of great interest, especially for improving cancer therapy. Herein, we reported a new approach to construct Mn2+-coordinated doxorubicin (DOX)-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles as a platform for synergistic chemo-photothermal tumor therapy. DOX-loaded PLGA (DOX/PLGA) nanoparticles were first synthesized through a double emulsion-solvent evaporation method, and then modified with polydopamine (PDA) through self-polymerization of dopamine, leading to the formation of PDA@DOX/PLGA nanoparticles. Mn2+ ions were then coordinated on the surfaces of PDA@DOX/PLGA to obtain Mn2+-PDA@DOX/PLGA nanoparticles. In our system, Mn2+-PDA@DOX/PLGA nanoparticles could destroy tumors in a mouse model directly, by thermal energy deposition, and could also simulate the chemotherapy by thermal-responsive delivery of DOX to enhance tumor therapy. Furthermore, the coordination of Mn2+ could afford the high magnetic resonance (MR) imaging capability with sensitivity to temperature and pH. The results demonstrated that Mn2+-PDA@ DOX/PLGA nanoparticles had a great potential as a smart theranostic agent due to their imaging and tumor-growth-inhibition properties.

Silica-Coated Metal Chelating-Melanin Nanoparticles as a Dual-Modal Contrast Enhancement Imaging and Therapeutic Agent

Bioinspired melanin nanoparticle (Mel NP) synthesized with dopamine has been of great interest in various biomedical applications. However, the utilization of fascinating characters of Mel NP such as innate MR contrast effects, high affinity to metal ions, strong light absorption requires special design with strategic synthetic method for its own purpose. Here, we have introduced paramagnetic Gd3+ metal ions and silica nanocoating on Mel NP for the dual-modal MRI/fluorescent contrast-enhanced imaging and therapeutics. The Gd3+ chelating kinetics of Mel NP by quinone and hydroquinone residues were optimized in various conditions of Gd3+ amounts and pH in solution for improving MRI contrast enhancing properties of the Mel NP. Then, bioinert silica was coated on the surfaces of Gd-chelated Mel NP (Gd-Mel@SiO2 NP) with a modified sol-gel process. The silica nanocoating allowed increased outer sphere water diffusion time, resulting a significantly brighter MR T1 contrast effect of Gd-Mel@SiO2 NP, comparing with a bare Gd-Mel NP or clinical grade T1 contrast agent. Further, when the Gd-Mel@SiO2 NP was labeled with fluorescent molecules, a significantly enhanced fluorescent intensity was achieved by the silica nanocoating that preventing the innate fluorescent deactivation property of melanin. Finally, in vitro/in vivo dual-modal contrast enhanced MRI/fluorescent imaging and feasibility of image-guided cancer therapeutic applications using Gd-Mel@SiO2 NPs were successfully evaluated in a clinically relevant human prostate cancer xenograft mouse model.

Improved Anticancer Photothermal Therapy Using the Bystander Effect Enhanced by Antiarrhythmic Peptide Conjugated Dopamine-Modified Reduced Graphene Oxide Nanocomposite

Despite tremendous efforts toward developing novel near-infrared (NIR)-absorbing nanomaterials, improvement in therapeutic efficiency remains a formidable challenge in photothermal cancer therapy. This study aims to synthesize a specific peptide conjugated polydopamine-modified reduced graphene oxide (pDA/rGO) nanocomposite that promotes the bystander effect to facilitate cancer treatment using NIR-activated photothermal therapy. To prepare a nanoplatform capable of promoting the bystander effect in cancer cells, we immobilized antiarrhythmic peptide 10 (AAP10) on the surface of dopamine-modified rGO (AAP10-pDA/rGO). Our AAP10-pDA/rGO could promote the bystander effect by increasing the expression of connexin 43 protein in MCF-7 breast-cancer cells. Because of its tremendous ability to absorb NIR absorption, AAP10-pDA/rGO offers a high photothermal effect under NIR irradiation. This leads to a massive death of MCF-7 cells via the bystander effect. Using tumor-bearing mice as the model, it is found that NIR radiation effectively ablates breast tumor in the presence of AAP10-pDA/rGO and inhibits tumor growth by ≈100%. Therefore, this research integrates the bystander and photothermal effects into a single nanoplatform in order to facilitate an efficient photothermal therapy. Furthermore, our AAP10-pDA/rGO, which exhibits both hyperthermia and the bystander effect, can prevent breast-cancer recurrence and, therefore, has great potential for future clinical and research applications.

Bio-inspired synthesis of PEGylated polypyrrole@polydopamine nanocomposites as theranostic agents for T1-weighted MR imaging guided photothermal therapy

Polypyrrole nanoparticle (PPy) based theranostic agents for magnetic resonance imaging (MRI) guided photothermal therapy (PTT) have received increasing attention in recent years.

Dopamine-Induced Formation of Ultrasmall Few-Layer MoS2 Homogeneously Embedded in N-Doped Carbon Framework for Enhanced Lithium-Ion Storage

Molybdenum disulfide with a layered structure and high theoretical capacity is attracting extensive attention for high-performance lithium-ion batteries. In this study, a simple and scalable method by freeze-drying of (NH₄)₂MoS₄ and dopamine mixed solutions along with subsequent calcination is developed to realize the self-assembly of hierarchical MoS₂/carbon composite nanosheets via the effect of dopamine-induced morphology transformation, in which ultrasmall few-layer MoS₂ nanosheets were homogeneously embedded into a N-doped carbon framework (denoted as MoS₂@N-CF). The embedded ultrasmall MoS₂ nanosheets (∼5 nm in length) in the composites consist of less than five layers with an expanded interlayer spacing of the (002) plane. When tested as anode materials for rechargeable Li-ion batteries, the obtained MoS₂@N-CF nanosheets exhibit outstanding electrochemical performance in terms of high specific capacity (839.2 mAh g^-1 at 1 A g^-1), high initial Coulombic efficiency (85.2%), and superior rate performance (702.1 mAh g^-1 at 4 A g^-1). Such intriguing electrochemical performance was attributed to the synergistic effect of uniform dispersion of few-layer MoS₂ into the carbon framework, expanded interlayer spacing, and enhanced electronic conductivity in the unique hierarchical architecture. This work provides a simple and effective strategy for the uniform integration of MoS₂ with carbonaceous materials to significantly boost their electrochemical performance.

Structure and Function of Iron-Loaded Synthetic Melanin

We describe a synthetic method for increasing and controlling the iron loading of synthetic melanin nanoparticles and use the resulting materials to perform a systematic quantitative investigation on their structure-property relationship. A comprehensive analysis by magnetometry, electron paramagnetic resonance, and nuclear magnetic relaxation dispersion reveals the complexities of their magnetic behavior and how these intraparticle magnetic interactions manifest in useful material properties such as their performance as MRI contrast agents. This analysis allows predictions of the optimal iron loading through a quantitative modeling of antiferromagnetic coupling that arises from proximal iron ions. This study provides a detailed understanding of this complex class of synthetic biomaterials and gives insight into interactions and structures prevalent in naturally occurring melanins.

Indocyanine green-loaded polydopamine-iron ions coordination nanoparticles for photoacoustic/magnetic resonance dual-modal imaging-guided cancer photothermal therapy

Multi-modal imaging-guided cancer photothermal therapy (PTT) with advanced theranostic nanoagents can efficiently improve therapeutic efficacy and reduce treatment side effects. Herein, we have developed a theranostic nanoagent based on indocyanine green (ICG)-loaded polydopamine (PDA)-iron ions coordination nanoparticles (PDA-Fe³⁺-ICG NPs), which are used for photoacoustic (PA) and magnetic resonance (MR) dual-modal imaging-guided cancer PTT treatments. In this nanoplatform, ICG molecules, the U.S. Food and Drug Administration approved near-infrared (NIR) dye, absorbing on PDA NPs (a melanin-like biopolymer) to significantly increase the NIR optical absorption of PDA NPs nearly 6 times and decreases their fluorescence emission, which can improve the PA contrast ability and promote the photothermal conversion efficiency of PDA NPs. Meanwhile, Fe³⁺ ions chelated on the PDA NPs act as a T₁-weighted MRI contrast agent (r₁ = 14 mM^-1 s^-1). In a mouse 4T1 breast tumor model, PA/MRI dual-modal imaging and highly efficient PTT treatments with low laser density were achieved with remarkable therapeutic efficiency and minimal side effects. This study illustrates that the highly integrated and biocompatible PDA-based NPs can serve as a versatile nanoplatform by loading different imaging molecules and drugs for multi-modal imaging and cancer combination therapy.

Near-Infrared Polymeric Nanoparticles with High Content of Cyanine for Bimodal Imaging and Photothermal Therapy

The discovery and synthesis of theranostic nanomedicines with high loading of imaging and therapeutic agents is challenging. In this work, a polymer assembling strategy was used to make nanoparticles with exceptionally high loading of theranostic agent. As an example, poly(heptamethine) was synthesized via multicomponent Passerini reaction, and then assembled into nanoparticles in the presence of poly(ethylene glycol)2k-block-poly(d,l-lactide)2k (PEG-PLA) with high heptamethine loading (>50%). The formed nanoparticles could be used for bimodal bioimaging and photothermal therapy. The bimodal bioimaging provided complementary message about biodistribution, and photothermal treatment inhibited the growth of cervical carcinoma upon laser irradiation. This assembly of polymers formed by imaging and therapeutic agents opens new possibilities for the construction of multifunctional nanomedicines.

pH/NIR Light-Controlled Multidrug Release via a Mussel-Inspired Nanocomposite Hydrogel for Chemo-Photothermal Cancer Therapy

This study reports on an intelligent composite hydrogel with both pH-dependent drug release in a cancer environment and heat generation based on NIR laser exposure, for the combined application of photothermal therapy (PTT) and multidrug chemotherapy. For the first time in the literature, Dopamine nanoparticle (DP) was incorporated as a highly effective photothermal agent as well as anticancer drug, bortezomib (BTZ) carrier inside a stimuli responsive pNIPAAm-co-pAAm hydrogel. When light is applied to the composite hydrogel, DP nanoparticle absorbs the light, which is dissipated locally as heat to impact cancer cells via hyperthermia. On the other hand, facile release of the anticancer drug BTZ from the surface of DP encapsulated hydrogel could be achieved due to the dissociation between catechol groups of DP and the boronic acid functionality of BTZ in typical acidic cancer environment. In order to increase the synergistic effect by dual drug delivery, Doxorubicin (DOXO) were also loaded to pNIPAAm-co-pAAm/DP-BTZ hydrogel and the effect of monotherapy as well as combined therapy were detailed by a complete characterization. Our results suggest that these mussel inspired nanocomposite with excellent heating property and controllable multidrug release can be considered as a potential material for cancer therapy.

Recent advances in different modal imaging-guided photothermal therapy

Photothermal therapy (PTT) has recently attracted considerable attention owing to its controllable treatment process, high tumour eradication efficiency and minimal side effects on non-cancer cells. PTT can melt cancerous cells by localising tissue hyperthermia induced by internalised therapeutic agents with a high photothermal conversion efficiency under external laser irradiation. Numerous in vitro and in vivo studies have shown the significant potential of PTT to treat tumours in future practical applications. Unfortunately, the lack of visualisation towards agent delivery and internalisation, as well as imaging-guided comprehensive evaluation of therapeutic outcome, limits its further application. Developments in combined photothermal therapeutic nanoplatforms guided by different imaging modalities have compensated for the major drawback of PTT alone, proving PTT to be a promising technique in biomedical applications. In this review, we introduce recent developments in different imaging modalities including single-modal, dual-modal, triple-modal and even multi-modal imaging-guided PTT, together with imaging-guided multi-functional theranostic nanoplatforms.

Hierarchical bioceramic scaffolds with 3D-plotted macropores and mussel-inspired surface nanolayers for stimulating osteogenesis

The hierarchical structure of biomaterials plays an important role in the process of tissue reconstruction and regeneration. 3D-plotted scaffolds have been widely used for bone tissue engineering due to their controlled macropore structure and mechanical properties. However, the lack of micro- or nano-structures on the strut surface of 3D-plotted scaffolds, especially for bioceramic scaffolds, limits their biological activity. Inspired by the adhesive versatility of mussels and the active ion-chelating capacity of polydopamine, we set out to prepare a hierarchical bioceramic scaffold with controlled macropores and mussel-inspired surface nanolayers by combining the 3D-plotting technique with the polydopamine/apatite hybrid strategy in order to synergistically accelerate the osteogenesis and angiogenesis. β-Tricalcium phosphate (TCP) scaffolds were firstly 3D-plotted and then treated in dopamine-Tris/HCl and dopamine-SBF solutions to obtain TCP-DOPA-Tris and TCP-DOPA-SBF scaffolds, respectively. It was found that polydopamine/apatite hybrid nanolayers were formed on the surface of both TCP-DOPA-Tris and TCP-DOPA-SBF scaffolds and TCP-DOPA-SBF scaffolds induced apatite mineralization for the second time during the cell culture. As compared to TCP scaffolds, both TCP-DOPA-Tris and TCP-DOPA-SBF scaffolds significantly promoted the osteogenesis of bone marrow stromal cells (BMSCs) as well as the angiogenesis of human umbilical vein endothelial cells (HUVECs), and the TCP-DOPA-SBF group presented the highest in vitro osteogenic/angiogenic activity among the three groups. Furthermore, both TCP-DOPA-Tris and TCP-DOPA-SBF scaffolds significantly improved the formation of new bone in vivo as compared to TCP scaffolds without a nanostructured surface. Our results suggest that the utilization of a mussel-inspired Ca, P-chelated polydopamine nanolayer on 3D-plotted bioceramic scaffolds is a viable and effective strategy to construct a hierarchical structure for synergistically accelerating osteogenesis.

Glucose-Derived Carbonaceous Nanospheres for Photoacoustic Imaging and Photothermal Therapy

Carbon nanomaterials with small size and unique optical properties have attracted intensive interest for their promising biomedical applications. In this work, glucose-derived carbonaceous nanospheres (CNSs) with high photothermal conversion efficiency up to 35.1% are explored for the first time as a novel carbon-based theranostic agent. Different from most other carbon nanomaterials, the obtained CNSs are highly biocompatible and nontoxic because of their intrinsic hydrophilic property and the use of glucose as raw materials. Under near-infrared laser irradiation (808 nm, 6 W cm(-2)) for 10 min, less than 15% of PC-3M-IE8 cells exposed to CNSs aqueous dispersions (0.16 mg/mL) remained alive. After intravenous administration of CNSs aqueous dispersions into nude mice, the photoacoustic intensity of the tumor region is about 2.5 times higher than that of preinjection. These results indicate that CNSs are suitable for simultaneous photoacoustic imaging and photothermal ablation of cancer cells and can serve as promising biocompatible carbon-based agents for further clinical trials.

Polydopamine Nanoparticles as a Versatile Molecular Loading Platform to Enable Imaging-guided Cancer Combination Therapy

Cancer combination therapy to treat tumors with different therapeutic approaches can efficiently improve treatment efficacy and reduce side effects. Herein, we develop a theranostic nano-platform based on polydopamine (PDA) nanoparticles, which then are exploited as a versatile carrier to allow simultaneous loading of indocyanine green (ICG), doxorubicin (DOX) and manganese ions (PDA-ICG-PEG/DOX(Mn)), to enable imaging-guided chemo & photothermal cancer therapy. In this system, ICG acts as a photothermal agent, which shows red-shifted near-infrared (NIR) absorbance and enhanced photostability compared with free ICG. DOX, a model chemotherapy drug, is then loaded onto the surface of PDA-ICG-PEG with high efficiency. With Mn²⁺ ions intrinsically chelated, PDA-ICG-PEG/DOX(Mn) is able to offer contrast under T1-weighted magnetic resonance (MR) imaging. In a mouse tumor model, the MR imaging-guided combined chemo- & photothermal therapy achieves a remarkable synergistic therapeutic effect compared with the respective single treatment modality. This work demonstrates that PDA nanoparticles could serve as a versatile molecular loading platform for MR imaging guided combined chemo- & photothermal therapy with minimal side effects, showing great potential for cancer theranostics.

A novel polydopamine-based chemiluminescence resonance energy transfer method for microRNA detection coupling duplex-specific nuclease-aided target recycling strategy

MicroRNAs (miRNAs), functioning as oncogenes or tumor suppressors, play significant regulatory roles in regulating gene expression and become as biomarkers for disease diagnostics and therapeutics. In this work, we have coupled a polydopamine (PDA) nanosphere-assisted chemiluminescence resonance energy transfer (CRET) platform and a duplex-specific nuclease (DSN)-assisted signal amplification strategy to develop a novel method for specific miRNA detection. With the assistance of hemin, luminol, and H2O2, the horseradish peroxidase (HRP)-mimicking G-rich sequence in the sensing probe produces chemiluminescence, which is quickly quenched by the CRET effect between PDA as energy acceptor and excited luminol as energy donor. The target miRNA triggers DSN to partially degrade the sensing probe in the DNA-miRNA heteroduplex to repeatedly release G-quadruplex formed by G-rich sequence from PDA for the production of chemiluminescence. The method allows quantitative detection of target miRNA in the range of 80 pM-50 nM with a detection limit of 49.6 pM. The method also shows excellent specificity to discriminate single-base differences, and can accurately quantify miRNA in biological samples, with good agreement with the result from a commercial miRNA detection kit. The procedure requires no organic dyes or labels, and is a simple and cost-effective method for miRNA detection for early clinical diagnosis.