Biologically Inspired Polydopamine Capped Gold Nanorods for Drug Delivery and Light-Mediated Cancer Therapy

Tumor microenvironment responsive hollow mesoporous Co9S8@MnO2-ICG/DOX intelligent nanoplatform for synergistically enhanced tumor multimodal therapy

The development of multifunctional nanoplatform with combination of tumor microenvironment (TME)-responsive dual T₁/T₂ magnetic resonance (MR) imaging and synergistically self-enhanced photothermal/photodynamic/chemo-therapy is of significant importance for tumor theranostic, which still remains a great challenge. Herein, a novel hollow mesoporous double-shell Co₉S₈@MnO₂ nanoplatform loaded with photodynamic agent of indocyanine green molecules (ICG) and chemotherapy drug of doxorubicin (DOX) was designed for TME responsive dual T₁/T₂ enhanced MR imaging and synergistically enhanced anti-tumor therapy. The designed nanoplatform with MnO₂ shell can act as a TME-responsive oxygen self-supplied producer to alleviate tumor hypoxia and simultaneously improve photodynamic therapy (PDT) efficiency. Moreover, the TME-induced MnO₂ dissolving and near-infrared (NIR) triggered photothermal nature from Co₉S₈ shell can further promote the tumor-targeted DOX release, leading to the synergistically improved anti-tumor efficacy. And the simultaneous enhancement in dual T₁/T₂ MR signal was achieved for highly specific tumor diagnosis. The in vivo and in vitro results confirmed that the designed TME-triggered nanoplatform with synergistic combination therapy presented good biocompatibility, and superior inhibition of tumor growth than monotherapy. This study provides the opportunities of designing intelligent TME-activated nanoplatform for highly specific tumor MR imaging and collaborative self-enhanced tumor therapy.

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

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

Chemo-Photothermal Combination Cancer Therapy with ROS Scavenging, Extracellular Matrix Depletion, and Tumor Immune Activation by Telmisartan and Diselenide-Paclitaxel Prodrug Loaded Nanoparticles

Extracellular matrix (ECM) accumulating in the tumor microenvironment (TME) is generated by tumor-associated fibroblasts. It can elevate interstitial fluid pressure and form dense barriers in tumor tissues. Consequently, nanocarriers are hindered from permeating into deeper tumor sites. Thus, the programmed drug-releasing nanoparticles, G(TM)PPSP, were developed for TME remodeling and breast cancer therapy. Gelatin nanoparticles were linked with platinum nanoparticles (PtNPs) to obtain G(TM)PPSP with a size of 214.0 ± 5.0 nm. Telmisartan (TM) was loaded in gelatin nanoparticles. Paclitaxel (PTX) was attached to PtNPs via a dual redox responsive diselenide bond. TM release was mediated by MMP-2 because of gelatin degradation in TME, and then intracellular PTX was released because of diselenide linkage fracture triggered by ROS or glutathione. ECM was depleted owing to TGF-β downregulation by TM and direct ablation by the photothermal effect of PtNPs. 4T1 tumor progression was inhibited by PTX chemotherapy, intracellular ROS scavenging of PtNPs, and photothermal therapy (PTT). The tumor spheroid penetration assay proved G(TM)PPSP could permeate into deep tumor regions when MMP-2 existed. In vivo antitumor experiments implied G(TM)PPSP with PTT could inhibit tumor growth effectively and remodel TME via ECM depletion and immunity activation, indicating the potential of G(TM)PPSP-based chemo-photothermal combination therapy for breast cancer treatment.

Chiral Nematic Liquid Crystal Behavior of Core-Shell Hybrid Rods Consisting of Chiral Cellulose Nanocrystals Dressed with Non-chiral Conformal Polymeric Skins

The current work investigates how the nanoscale conformal coating layers of non-chiral polymeric materials can influence the chiral nematic liquid crystal (CLC) behaviors of the rodlike cellulose nanocrystals (CNCs), the bio-derived nanomaterials that have attracted significant attention. For this, we developed strategies to coat the CNC rods on the single-particle level with a homogeneous bioinspired polydopamine (PDA) layer, leading to well-defined core-shell CNC@PDA rods with various PDA coating thicknesses and excellent colloidal stability. Comprehensive investigation revealed that the CNC@PDA hybrid nanorods in concentrated suspensions form well-defined nematic liquid crystal phases with clear phase separation behavior that depend on the rod concentrations and ionic strengths, typical of charged rods. Most intriguingly, the nematic LC phases formed by the CNC@PDA rods with the PDA coating thickness achieved herein are indeed the perfect CLC phases, which form following the classic pathway of nucleation and coalesce of chiral tactoids and have colorful chiral fingerprints standing out from the dark suspensions. The pitches of the CLC phase increase sharply with increasing PDA coating thicknesses and are significantly larger than those of the pristine CNCs. Such observations can be attributed to the blurring effects of the PDA coating on the intrinsic surface chiral features of CNC of whatever origins that drive the formation of the CLC phases, resulting in weakening chiral interactions between CNC@PDA rods. Besides benefiting the understanding of the long-sought origin of the CLC phases of the pristine CNC, the current work demonstrates the possibility of controlling the CLC phase behaviors of CNC by tuning the thickness of the coating materials and also serves as the first example of directly transferring the unique chirality of CNC to other non-chiral materials.

Doxorubicin-loaded pH-responsive nanoparticles coated with chlorin e6 for drug delivery and synergetic chemo-photodynamic therapy

The integration of chemotherapy drugs and photosensitizers to form versatile nanoplatforms for achieving chemo-photodynamic synergetic therapy has shown great superiority in tumor theranostic applications. We constructed pH-responsive nanoparticles (DOX/PB NPs) encapsulating the chemotherapeutic drug doxorubicin (DOX) into the cores of PLGA NPs coated with bovine serum albumin (BSA) via a water-in-oil (W/O/W) emulsion method. A simple and efficient chemo-photodynamic synergetic nanoplatform (DOX/PB@Ce6 NPs) was obtained by the adsorption of photosensitizer chlorin e6 (Ce6) onto the surface of the DOX/PB NPs. With optimal size, pH-responsive drug release behavior and excellent singlet oxygen production, the DOX/PB@Ce6 NPs have the potential to enhance anti-tumor efficiency. The cellular uptake, cytotoxicity, chemo-photodynamic synergetic effect and biocompatibility of the NPs were evaluated based on HeLa cells via in vitro experiments. The in vitro chemo-photodynamic synergetic experiments indicated that the DOX/PB@Ce6 NPs had remarkable cancer cell killing efficiency under laser irradiation. Notably, by hemolysis assay, all the NPs displayed excellent blood compatibility and were expected to be applicable for intravenous injection. In summary, the designed DOX/PB@Ce6 NPs multifunctional theranostic nanoplatform had excellent reactive oxygen species generation and would be a potential therapeutic platform for chemo-photodynamic synergetic therapy.

Reprogramming Tumor Microenvironment with Photothermal Therapy

The tumor microenvironment significantly influences cancer progression and therapeutic response. Reprogramming of tumor microenvironment has emerged as a strategy to assist conventional cancer treatment. In recent years, photothermal therapy has received considerable attention owing to its noninvasiveness, high temporal-spatial resolution, and minimal drug resistance. Apart from ablating cancer cells by generating heat upon light irradiation, photothermal therapy can also affect the tumor microenvironment, such as disrupting the tumor extracellular matrix and tumor vasculature. Moreover, cancer cell death by hyperthermia could potentially activate the immune system to fight against tumor. In this topical review, we focus on the recent progress of photothermal therapy based on tumor microenvironment remodeling, aiming to better guide the design of nanoparticles for cancer photoimmunotherapy.

Amplified Photoacoustic Signal and Enhanced Photothermal Conversion of Polydopamine-Coated Gold Nanobipyramids for Phototheranostics and Synergistic Chemotherapy

Light-responsive nanoprobes were suffering from the threat of high-dose laser irradiation, and it was important for constructing new nanoprobes for safe and efficient phototheranostics. Here, polydopamine (PDA)-coated gold nanobipyramids (AuNBPs@PDA) were synthesized for amplified photoacoustic (PA) signal and enhanced photothermal conversion with low-dose laser irradiation and then doxorubicin (DOX)-loaded AuNBPs@PDA-DOX nanoprobes were constructed for PA imaging-guided synergistic photothermal therapy (PTT) and chemotherapy. The AuNBPs@PDA nanoparticles possessed higher photothermal conversion efficiency (42.07%) and stronger PA signal than those of AuNBP nanoparticles, and the AuNBPs@PDA-DOX nanoprobes showed dual-responsive DOX release of pH and photothermal stimulation. With low-dose laser irradiation (1.0 W/cm²) and low-concentration AuNBPs@PDA-DOX (60 μg/mL), the 4T1 cell viability was reduced to about 5%, owing to the combination of PTT and chemotherapy, compared with 42.3% of single chemotherapy and 25.3% of single PTT. Moreover, by modeling 4T1 tumor-bearing nude mice, in vivo PA imaging was achieved and the tumors were completely inhibited, demonstrating the excellent synergistic effect of PTT/chemotherapy. Therefore, the developed AuNBPs@PDA-DOX nanoprobes can be used for phototheranostics and synergistic chemotherapy, achieving low-dose laser irradiation and high-efficient visualized theranostics.

Nanoparticle Delivery Systems for DNA/RNA and their Potential Applications in Nanomedicine

The rapid development of nanotechnology has a great influence on the fields of biology, physiology, and medicine. Over recent years, nanoparticles have been widely presented as nanocarriers to help the delivery of gene, drugs, and other therapeutic agents with cellular targeting ability. Advances in the understanding of gene delivery and RNA interference (RNAi)-based therapy have brought increasing attention to understanding and tackling complex genetically related diseases, such as cancer, cardiovascular and pulmonary diseases, autoimmune diseases and infections. The combination of nanocarriers and DNA/RNA delivery may potentially improve their safety and therapeutic efficacy. However, there still exist many challenges before this approach can be practiced in the clinic. In this review, we provide a comprehensive summary on the types of nanoparticle systems used as nanocarriers, highlight the current use of nanocarriers in recombinant DNA and RNAi molecules delivery, and the current landscape of gene-based nanomedicine-ranging from diagnosis to therapeutics. Finally, we briefly discuss the biosafety concerns and limitations in the preclinical and clinical development of nanoparticle gene systems.

Functioned hollow glass microsphere as a self-floating adsorbent: Rapid and high-efficient removal of anionic dye

Rapid, high-efficient adsorbents with efficient solid-liquid separation ability has broad application prospects in the treatment of dye wastewater. In this study, polydopamine and methacryloyloxyethyltrimethyl ammonium chloride were grafted onto hollow glass microspheres to prepare the enhanced polydopamine shell structure adsorbent with self-floating ability. Furthermore, the adsorbent achieves high-efficiency surface solid-liquid separation, which overcomes the disadvantages of the traditional separation methods. Characterizations of the as-synthesized microspheres were performed using various techniques such as SEM, EDS, BET, XPS, FT-IR, TGA and XRD. The adsorbent achieved rapid and high-efficient adsorption of alizarin cyanine green F via the interactions of electrostatic attracting and π-π stacking, and under the optimal experimental conditions, the removal efficiency of 0.10 m mol L^-1 dye solution reaches 94.51%, and the adsorption process reaches equilibrium within 60 min. Adsorption isotherms and kinetics data of the adsorbent were well fitted by Langmuir isotherm and pseudo-second-order kinetic models, respectively. The as-synthesized adsorbent has excellent recyclability, and its adsorption performance can be maintained after 5 cycles of reuse. The self-floating adsorbent has great potential for the removal of dissolved contaminants and cost-effective separation.

Novel Tumor-Microenvironment-Based Sequential Catalytic Therapy by Fe(II)-Engineered Polydopamine Nanoparticles

Traditional tumor treatments suffer from severe side effects on account of their invasive process and inefficient outcomes. Featuring a unique physical microenvironment, the tumor microenvironment (TME) provides a new research direction for designing more efficient and safer treatment paradigms. In this study, we fabricated a polydopamine (PDA)-based TME-responsive nanosystem, which successfully integrates glucose degradation, the Fenton reaction, and photothermal therapy for efficient cancer therapy. Through a convenient hydrothermal method, Fe²⁺-doped Fe(II)-PDA nanoparticles were successfully fabricated, which show an excellent photothermal effect and interesting reactivity for the Fenton reaction. Instead of introducing toxic anticancer agents, natural glucose oxidase (GOD) was grafted on Fe(II)-PDA, forming a cascade catalytic nanomedicine for a specific response to the glucose in TME. GOD grafted on Fe(II)-PDA-GOD is ought to catalyze abundant glucose in TME into gluconic acid and H₂O₂. The concomitant generation of H₂O₂ can enhance the efficiency of the sequential Fenton reaction, producing abundant hydroxyl radicals (^•OH) for cancer therapy. Besides, the overconsumption of intratumoral glucose also could inhibit tumor growth by reducing the energy supply. Taken together, the in vitro and in vivo antitumor studies of such TME-based Fe(II)-PDA-GOD nanosystems displayed a favorable synergistic potency of glucose degradation, the Fenton reaction, and photothermal therapy against tumor growth. Our design expands the biological application of multifunctional PDA while providing novel strategies toward effective antitumor treatment with minimal side effects.

Engineering of Porous Silica Coated Gold Nanorods by Surface-Protected Etching and Their Applications in Drug Loading and Combined Cancer Therapy

Core-shell nanostructures, specifically gold nanorods coated with porous silica (GNR@p-SiO₂), were successfully fabricated by surface-protected etching. The nanostructures, photothermal effects, drug loading and drug release behaviors, cellular uptake, and combined chemo-photothermal therapy were investigated. The results showed that the as-prepared GNR@p-SiO₂ had a uniform porous silica outer layer. Etching process could be modulated by adjusting the etching time, concentrations of etching agents, and concentrations of protective agents. With doxorubicin (DOX) as the model drug, the drug loading capacity reached 18.9%, which was dependent on the DOX concentrations. The drug release profiles were dual stimulus-responsive to pH and laser irradiation. In addition, the GNR@p-SiO₂ nanoparticles were biocompatible and effectively internalized by cancer cells. Compared with chemotherapy or photothermal therapy administered individually, combined chemo-photothermal therapy using GNR@p-SiO₂ exhibited higher efficiency in killing cancer cells both in vitro and in vivo. Therefore, surface-protected etching is a powerful method for preparing core-shell nanostructures capped with mesoporous silica for combined cancer chemo-photothermal therapy.

NIR-II-Excited Intravital Two-Photon Microscopy Distinguishes Deep Cerebral and Tumor Vasculatures with an Ultrabright NIR-I AIE Luminogen

Intravital fluorescence imaging of vasculature morphology and dynamics in the brain and in tumors with large penetration depth and high signal-to-background ratio (SBR) is highly desirable for the study and theranostics of vascular-related diseases and cancers. Herein, a highly bright fluorophore (BTPETQ) with long-wavelength absorption and aggregation-induced near-infrared (NIR) emission (maximum at ≈700 nm) is designed for intravital two-photon fluorescence (2PF) imaging of a mouse brain and tumor vasculatures under NIR-II light (1200 nm) excitation. BTPETQ dots fabricated via nanoprecipitation show uniform size of around 42 nm and a high quantum yield of 19 ± 1% in aqueous media. The 2PF imaging of the mouse brain vasculatures labeled by BTPETQ dots reveals a 3D blood vessel network with an ultradeep depth of 924 µm. In addition, BTPETQ dots show enhanced 2PF in tumor vasculatures due to their unique leaky structures, which facilitates the differentiation of normal blood vessels from tumor vessels with high SBR in deep tumor tissues. Moreover, the extravasation and accumulation of BTPETQ dots in deep tumor (more than 900 µm) is visualized under NIR-II excitation. This study highlights the importance of developing NIR-II light excitable efficient NIR fluorophores for in vivo deep tissue and high contrast tumor imaging.

Construction of Bio/Nanointerfaces: Stable Gold Nanoparticle Bioconjugates in Complex Systems

The real application of DNA-functionalized gold nanoparticles (DNA-Au NPs) was limited by decreased stability and irreversible aggregation in high-ionic strength solutions and complex systems. Therefore, exploring a kind of DNA-Au NPs with excellent stability in high-ionic strength solutions and complex systems is challenging and significant. Herein, a novel universal bioconjugate strategy for constructing ultrastable DNA-Au NPs was designed based on the combination of polydopamine (PDA) shell and DNA linker. The obtained DNA-linked Au@polydopamine nanoparticles (DNA-Au@PDA NPs) showed colloidal stability in high-ionic strength solution and complex systems (such as human serum and cell culture supernatant). Moreover, the nanoparticles still maintained good dispersion after multiple freeze-thaw cycles. The high stability of DNA-Au@PDA NPs may be attributed to increasing the electrostatic and steric repulsions among nanoparticles through the effect of both PDA shell and DNA linker on Au@PDA NPs. For investigating the application of such nanoparticles, a highly sensitive assay for miRNA 141 detection was developed using DNA-Au@PDA NPs coupled with dynamic light scattering (DLS). Comparing with the regular DNA-Au NPs, DNA-Au@PDA NPs could detect as low as 50 pM miRNA 141 even in human whole serum. Taken together, the features of Bio/Nanointerface make the nanoparticle suitable for various applications in harsh biological and environmental conditions due to the stability. This work may provide a universal modification method for obtaining stable nanoparticles.

A polydopamine-based platform for anti-cancer drug delivery

Cancer is the second leading cause of death in the world with around 9.6 million deaths in 2018, approximately 70% of which occurred in the middle- and low-income countries; moreover, the economic impact of cancer is significant and escalating day by day. The total annual economic cost of cancer treatment in 2010 was estimated at approximately US$ 1.16 trillion. Researchers have explored cancer mitigation therapies such as chemo-thermal therapy, chemo-photothermal therapy and photodynamic-photothermal therapy. These combinational therapies facilitate better control on the tunability of the carrier for effectively diminishing cancer cells than individual therapies such as chemotherapy, photothermal therapy and targeted therapy. All these therapies come under novel drug delivery systems in which anti-cancer drugs attack the cancerous cells due to various stimuli (e.g. pH, thermal, UV, IR, acoustic and magnetic)-responsive properties of the anti-cancer drug carriers. Compared to conventional drug delivery systems, the novel drug delivery systems have several advantages such as targeted drug release, sustained and consistent blood levels within the therapeutic window, and decreased dosing frequency. Among the numerous polymeric carriers developed for drug delivery, polydopamine has been found to be more suitable as a carrier for these drug delivery functions due to its easy and cost-effective fabrication, excellent biocompatibility, multi-drug carrier capacity and stimuli sensitivity. Therefore, in this review, we have explored polydopamine-based carriers for anti-cancer drug delivery systems to mitigate cancer and simultaneously discussed basic synthesis routes for polydopamine.

Synthesis of Small Gold Nanorods and Their Subsequent Functionalization with Hairpin Single Stranded DNA

Small gold nanorods have a significantly large absorption/scattering ratio and are especially beneficial in exploiting photothermal effects, for example in photothermal therapy and remote drug release. This work systematically investigates the influence of growth conditions on the size, growth yield, and stability of small gold nanorods. The silver-assisted seed-mediated growth method was optimized to synthesize stable small gold nanorods with a high growth yield (>85%). Further study on the influence of silver ions on the growth facilitates the growth of small gold nanorods with tunable longitudinal surface plasmon resonance from 613 to 912 nm, with average dimensions of 13-25 nm in length and 5-6 nm in diameter. Moreover, the small gold nanorods were successfully functionalized with thiol-modified hairpin oligonucleotides (hpDNA) labeled with Cy5. Fluorescence intensity measurements show an increase in the presence of target DNA and an enhanced signal/background ratio when the longitudinal surface plasmon resonance of small gold nanorods overlaps with the excitation and emission wavelength of Cy5. This coincides with a reduced fluorescence lifetime of Cy5 in the hairpin structure, indicating surface plasmon resonance-enhanced energy transfer to the small gold nanorods. This study may provide insight on the synthesis and functionalization of small gold nanorods in biomedical sensing and therapy.

Tumor-targeting photodynamic therapy based on folate-modified polydopamine nanoparticles

BACKGROUND

Photodynamic therapy (PDT), a clinical anticancer therapeutic modality, has a long history in clinical cancer treatments since the 1970s. However, PDT has not been widely used largely because of metabolic problems and off-target phototoxicities of the current clinical photosensitizers.

PURPOSE

The objective of the study is to develop a high-efficiency and high-specificity carrier to precisely deliver photosensitizers to tumor sites, aiming at addressing metabolic problems, as well as the systemic damages current clinical photosensitizers are known to cause.

METHODS

We synthesized a polydopamine (PDA)-based carrier with the modification of folic acid (FA), which is to target the overexpressed folate receptors on tumor surfaces. We used this carrier to load a cationic phthalocyanine-type photosensitizer (Pc) and generated a PDA-FA-Pc nanomedicine. We determined the antitumor effects and the specificity to tumor cell lines in vitro. In addition, we established human cancer-xenografted mice models to evaluate the tumor-targeting property and anticancer efficacies in vivo.

RESULTS

Our PDA-FA-Pc nanomedicine demonstrated a high stability in normal physiological conditions, however, could specifically release photosensitizers in acidic conditions, eg, tumor microenvironment and lysosomes in cancer cells. Additionally, PDA-FA-Pc nanomedicine demonstrated a much higher cellular uptake and phototoxicity in cancer cell lines than in healthy cell lines. Moreover, the in vivo imaging data indicated excellent tumor-targeting properties of PDA-FA-Pc nanomedicine in human cancer-xenografted mice. Lastly, PDA-FA-Pc nanomedicine was found to significantly suppress tumor growth within two human cancer-xenografted mice models.

CONCLUSION

Our current study not only demonstrates PDA-FA-Pc nanomedicine as a highly potent and specific anticancer agent, but also suggests a strategy to address the metabolic and specificity problems of clinical photosensitizers.

Excretable IR-820 for in vivo NIR-II fluorescence cerebrovascular imaging and photothermal therapy of subcutaneous tumor

Rationale: Cerebrovascular diseases, together with malignancies, still pose a huge threat to human health nowadays. With the advantages of its high spatial resolution and large penetration depth, fluorescence bioimaging in the second near-infrared spectral region (NIR-II, 900-1700 nm) and its related imaging-guided therapy based on biocompatible fluorescence dyes have become a promising theranostics method. Methods: The biocompatibility of IR-820 we used in NIR-II fluorescence bioimaging was verified by long-term observation. The model of the mouse with a cranial window, the mouse model of middle cerebral artery occlusion (MCAO) and a subcutaneous xenograft mouse model of bladder tumor were established. NIR-II fluorescence cerebrovascular functional imaging was carried out by IR-820 assisted NIR-II fluorescence microscopy. Bladder tumor was treated by NIR-II fluorescence imaging-guided photothermal therapy. Results: We have found that IR-820 has considerable NIR-II fluorescence intensity, and shows increased brightness in serum than in water. Herein, we achieved real time and in vivo cerebrovascular functional imaging of mice with high spatial resolution and large penetration depth, based on IR-820 assisted NIR-II fluorescence microscopy. In addition, IR-820 was successfully employed for NIR-II fluorescence imaging and photothermal therapy of tumor in vivo, and the subcutaneous tumors were inhibited obviously or eradicated completely. Conclusion: Due to the considerable fluorescence intensity in NIR-II spectral region and the good photothermal effect, biocompatible and excretable IR-820 holds great potentials for functional angiography and cancer theranostics in clinical practice.

Polydopamine-Based Nanocarriers for Photosensitizer Delivery

Photodynamic therapy (PDT) has emerged as a non-invasive modality for treating tumors while a photosensitizer (PS) plays an indispensable role in PDT. Nevertheless, free PSs are limited by their low light stability, rapid blood clearance, and poor water solubility. Constructing a nanocarrier delivering PSs is an appealing and potential way to solve these issues. As a melanin-like biopolymer, polydopamine (PDA) is widely utilized in biomedical applications (drug delivery, tissue engineering, and cancer therapy) for its prominent properties, including favorable biocompatibility, easy preparation, and versatile functionality. PDA-based nanocarriers are thus leveraged to overcome the inherent shortcomings of free PSs. In this Mini-Review, we will firstly present an overview on the recent developments of PDA nanocarriers delivering PSs. Then, we introduce three distinctive strategies developed to combine PSs with PDA nanocarriers. The advantages and disadvantages of each strategy will be discussed. Finally, the current challenges and future opportunities of PDA-based PS nanocarriers will also be addressed.

Cancer-Cell-Activated Photodynamic Therapy Assisted by Cu(II)-Based Metal-Organic Framework

Activation of photosensitizers (PSs) in targeted lesion and minimization of reactive oxygen species (ROS) depletion by endogenous antioxidants constitute promising approaches to perform highly effective image-guided photodynamic therapy (PDT) with minimal non-specific phototoxicity. Traditional strategies to fabricate controllable PS platforms rely on molecular design, which requires specific modification of each PS before PDT. Therefore, construction of a general tumor-responsive PDT platform with minimum ROS loss from endogenous antioxidant, typically glutathione (GSH), is highly desirable. Herein, MOF-199, a Cu(II) carboxylate-based metal-organic framework (MOF), is selected to serve as an inert carrier to load PSs with prohibited photosensitization during delivery. After cellular uptake, Cu (II) in the MOFs effectively scavenges endogenous GSH, concomitantly induces decomposition of MOF-199 to release the encapsulated PSs, and recovers their ROS generation. In vitro and in vivo experiments demonstrate highly effective cancer cell ablation and anticancer PDT with diminished normal cell phototoxicity. This strategy is generally applicable to PSs with both aggregation-induced emission and aggregation-caused quenching to implement activatable and enhanced image-guided PDT.

Polydopamine Coating as a Scaffold for Ring-Opening Chemistry To Functionalize Gold Nanoparticles

Gold nanoparticles (GNPs) are promising nanomaterials for various biomedical applications owing to their remarkable optical properties and biocompatibility. However, their interfacial properties require modification for practical use in such applications. Herein, a simple method for modifying the surface of GNPs with polydopamine (PDA) to serve as a scaffold for the subsequent polymerization of hyperbranched polyglycerol (HPG) is reported. GNPs were first coated with PDA (GNP-PDA), and then ring-opening chemistry was used at this interface to modify GNP-PDA with HPG (GNP-PDA-HPG). The produced GNP-PDA-HPG shows not only excellent dispersibility in a salt-containing solution but also strong resistance to aggregation in high- and low-pH solutions, even after 10 days. Moreover, we demonstrate a one-pot method for functionalizing GNP-PDA with HPG and either COOH or trimethylammonium. Finally, we conjugated the trimethylammonium-functionalized GNP-PDA-HPG with fluorescent nanodiamonds to investigate the photothermal ability of the functional GNPs.

Polydopamine-coated gold nanostar for combined antitumor and antiangiogenic therapy in multidrug-resistant breast cancer

Cancer combination therapy can improve treatment efficacy and is widely utilized in the biomedical field. In this paper, we propose a facile strategy to develop a polydopamine (PDA)-coated Au nanostar (NS@PPFA) as a multifunctional nanoplatform for cancer targeting and combination therapy. The Au nanostar demonstrated high photothermal conversion efficiency because of the tip-enhanced plasmonic effect. Modification of PDA and folic acid on the NS surface improved its drug-loading efficiency and targeting capability. In vitro, compared with nontargeted cells, targeted breast cancer MCF-7 cells demonstrated efficient uptake of chemodrug-loaded NS-D@PPFA through the receptor-mediated endocytosis pathway. In combination with the photothermal effect induced by near-infrared laser irradiation, controlled payload release could be activated in response to both internal (acid) and external (photothermal) stimuli, leading to an efficient chemo-photothermal action against MCF-7 cells and drug-resistant MCF-7/ADR cells. By contrast, cellular damage was less obvious in normal HaCaT (human skin keratinocytes) and NIH-3T3 cells (murine fibroblasts). In addition, payload-free NS@PPFA exhibited a high binding affinity (K_d = 2.68 × 10^-10 M) toward vascular endothelial growth factor (VEGF-A165), which was at least two orders of magnitude stronger than that of highly abundant plasma proteins, such as human serum albumin. Furthermore, in vitro study showed that NS@PPFA could effectively inhibit VEGF-A165-induced proliferation, migration, and tube formation of human umbilical vein endothelial cells, resulting in additional therapeutic benefits for eradicating tumors through a simultaneous antiangiogenic action in chemo-photothermal treatment. The combined treatment also exhibited the lowest microvessel density, leading to a potent antitumor effect in vivo. Overall, our “all-in-one” nanoplatform is highly promising for tumor therapy, enabling effective treatment against multidrug-resistant cancers.

Gold Nanorods-Based Smart Nanoplatforms for Synergic Thermotherapy and Chemotherapy of Tumor Metastasis

The combination therapy of photothermal therapy and chemotherapy as a promising strategy has drawn extensive attention by overcoming the limitations of conventional treatments in tumor therapy. Gold nanorods-based nanoplatforms were herein designed by integrating doxorubicin (DOX)- and polydopamine-coated gold nanorods (GNRs@PDA) for tumor metastasis inhibition and multifunctional drug delivery. The GNRs@PDA-poly(ethylene glycol) (PEG)-DOX nanocomplex showed robust stability and excellent near-infrared (NIR) photothermal conversion efficiency under laser irradiation. The release of loaded DOX from GNRs@PDA-PEG-DOX nanocomposites was improved in tumor microenvironments. Furthermore, the PDA-functionalized GNR nanocomposites were expected to be potential photoacoustic imaging agents for imaging-guided tumor therapy. Upon NIR laser irradiation, the efficiency of tumor inhibition of GNRs@PDA-PEG-DOX is greater than that of the other group in vitro and in vivo, which was confirmed by immunohistochemistry staining, demonstrating a promising strategy for suppression of tumor metastasis and low long-term systemic toxicity. These results illustrated a promising strategy of tailor-made GNRs@PDA-PEG-DOX nanoplatforms for ablation of tumor and suppression of tumor metastasis in clinical application.

Polydopamine-coated Au nanorods for targeted fluorescent cell imaging and photothermal therapy

Au nanorods (AuNRs) have attracted a great interest as a platform for constructing various composite core/shell nanoparticles for theranostics applications. However, the development of robust methods for coating AuNRs with a biocompatible shell of high loading capacity and with functional groups still remains challenging. Here, we coated AuNRs with a polydopamine (PDA) shell and functionalized AuNR-PDA particles with folic acid and rhodamine 123 (R123) to fabricate AuNR-PDA-R123-folate nanocomposites. To the best of our knowledge, such AuNR-PDA-based composites combining fluorescent imaging and plasmonic phothothermal abilities have not been reported previously. The multifunctional nanoparticles were stable in cell buffer, nontoxic and suitable for targeted fluorescent imaging and photothermal therapy of cancer cells. We demonstrate the enhanced accumulation of folate-functionalized nanoparticles in folate-positive HeLa cells in contrast to the folate-negative HEK 293 cells using fluorescent microscopy. The replacement of folic acid with polyethylene glycol (PEG) leads to a decrease in nanoparticle uptake by both folate-positive and folate-negative cells. We performed NIR light-mediated targeted phototherapy using AuNR-PDA-R123-folate and obtained a remarkable cancer cell killing efficiency in vitro in comparison with only weak-efficient nontargeted PEGylated nanoparticles. Our work illustrates that AuNR-PDA could be a promising nanoplatform for multifunctional tumor theranostics in the future.

Facile fabrication of polydopamine nanotubes for combined chemo-photothermal therapy

Polydopamine nanoparticles with higher drug loading capacity and enhanced photothermal behavior.

DOX-assisted functionalization of green tea polyphenol nanoparticles for effective chemo-photothermal cancer therapy

Green tea polyphenol nanoparticles with chemotherapeutic and photothermal performance exhibited effective anti-tumor effects in vivo with intravenous injection.

Prompting peroxidase-like activity of gold nanorod composites by localized surface plasmon resonance for fast colorimetric detection of prostate specific antigen

The interaction between incident light and surface electrons in conductive nanoparticles produces localized plasmon oscillations with a resonant frequency that strongly depends on the composition, size, geometry, and dielectric environment. Hybrid heterostructure materials combining two or more materials in one structure represent a powerful way to achieve unique properties and multifunctionality compared to those of the individual nanoparticle components. Hybrid gold nanorods and gold nanoclusters (GNR/AuNCs) heterostructures prepared by intimate integration of GNRs with AuNCs exhibit both localized surface plasmon resonance (LSPR) property and peroxidase-like activity. It is found that the catalytic activity of the AuNC/GNR heterostructure could be remarkably enhanced by LSPR induced by photon-plasmon coupling in the visible to near-infrared (NIR) region. Meanwhile, the catalytic activity of enzyme-like AuNC/GNRs may be regulated by immunoreactions to realize specific recognition of a target analyte. Accordingly, a fast colorimetric assay within 5 min for the detection of prostate specific antigen (PSA) was developed based on a AuNC/GNRs heterostructure mask regulated by the target molecule under photon-plasmon coupling. The color intensity is inversely proportional to the PSA concentration, and quantitative analysis may be achieved in a range of 10 and 200 pg mL-1. This sensor was practically applied to detect PSA levels in prostate cancer serum samples and the determined values agreed well with those measured by the hospital using standard methods. This indicates that the AuNC/GNRs heterostructure-based assay has high accuracy for the analysis of practical samples. Moreover, the new method has the advantages of very fast determination and low sample volume requirements.

Single-Molecular Near-Infrared-II Theranostic Systems: Ultrastable Aggregation-Induced Emission Nanoparticles for Long-Term Tracing and Efficient Photothermal Therapy

Second near-infrared (NIR-II, 1000-1700 nm) fluorescence bioimaging has attracted tremendous scientific interest and already been used in many biomedical studies. However, reports on organic NIR-II fluorescent probes for in vivo photoinduced imaging and simultaneous therapy, as well as the long-term tracing of specific biological objects, are still very rare. Herein we designed a single-molecular and NIR-II-emissive theranostic system by encapsulating a kind of aggregation-induced emission luminogen (AIEgen, named BPN-BBTD) with amphiphilic polymer. The ultra-stable BPN-BBTD nanoparticles were employed for the NIR-II fluorescence imaging and photothermal therapy of bladder tumors in vivo. The 785 nm excitation triggered photothermal therapy could completely eradicate the subcutaneous tumor and inhibit the growth of orthotopic tumors. Furthermore, BPN-BBTD nanoparticles were capable of monitoring subcutaneous and orthotopic tumors for a long time (32 days). Single-molecular and NIR-II-emitted aggregation-induced emission nanoparticles hold potential for the diagnosis, precise treatment, and metastasis monitoring of tumors in the future.

Gold-nanobranched-shell based drug vehicles with ultrahigh photothermal efficiency for chemo-photothermal therapy

Development of combined chemo-photothermal nanoplatform is of great interest for enhancing antitumor efficacy. Herein, a multifunctional drug delivery system was synthesized based on gold-nanobranched coated betulinic acid liposomes (GNBS-BA-Lips) for chemo-photothermal synergistic therapy. In this system, GNBS-BA-Lips exhibited broad near-infrared (NIR) absorption, preferable photothermal response and good photostability under NIR irradiation. Importantly, the gold-nanobranched nanostructure possessed high photothermal conversion efficiency (η = 55.7%), and the temperature change (ΔT) reached 43.2 °C after laser irradiation for 5 min. Upon NIR irradiation, the nanocarriers apparently endowed higher cell uptake, resulting in an enhanced intracellular drug accumulation. Furthermore, the tumor growth inhibition ratio achieved from chemo-photothermal therapy of GNBS-BA-Lips was 86.9 ± 1.1%, which was higher than that of the chemotherapy or photothermal therapy alone, showing an outstanding synergistic anticancer effect. Our data suggested that the nanoplatform should be considered as a critical platform in the development of cancer multi-mode therapies.

Untemplated Resveratrol-Mediated Polydopamine Nanocapsule Formation

Nanocapsules can be designed for applications including drug delivery, catalysis, and biological imaging. The mussel-inspired material polydopamine is a promising shell layer for nanocapsules because of its free radical scavenging capacity, ability to react with a broad range of functional molecules, lack of toxicity, and biodegradability. Previous reports of polydopamine nanocapsule formation have relied on a templating approach. Herein, we report a template-free approach to polydopamine nanocapsule formation in the presence of resveratrol, a naturally occurring anti-inflammatory and antioxidant compound found in red wine and grapes. Synthesis of nanocapsules occurs spontaneously in an ethanolic resveratrol/dopamine·HCl solution at pH 8.5. UV-vis absorbance spectroscopy and X-ray photoelectron spectroscopy indicate that resveratrol is incorporated into the nanocapsules. We also observed the formation of a soluble fluorescent dopamine-resveratrol adduct during synthesis, which was identified by high-performance liquid chromatography, UV-vis spectroscopy, and electrospray ionization mass spectrometry. Using transmission electron microscopy and dynamic light scattering, we studied the influence of solvent composition, dopamine concentration, and resveratrol/dopamine ratio on the nanocapsule diameter and shell thickness. The resulting nanocapsules have excellent free radical scavenging activity as measured by a 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay. Our work provides a convenient pathway by which resveratrol, and possibly other hydrophobic bioactive compounds, may be encapsulated within polydopamine nanocapsules.

Application of polydopamine in tumor targeted drug delivery system and its drug release behavior

Inspired by the bionics of marine mussels, polydopamine (PDA), a new polymer with unique physicochemical properties was discovered. Due to its simple preparation, good biocompatibility, unique drug-loading methods, PDA has attracted tremendous attentions in field of drug delivery and imaging, and the combination of chemotherapy and other therapies or diagnostic methods, such as photothermotherapy (PTT), photoacoustic imaging (PAI), magnetic resonance imaging (MRI), etc. As an excellent drug carrier in tumor targeted drug delivery system, the drug release behavior of drug-loaded PDA-based nanoparticles is also an important factor to be considered in the establishment of drug delivery systems. Therefore, the purpose of this review is to provide a comprehensive overview of the various applications of PDA in tumor targeted drug delivery systems and to gain insight into the release behavior of the drug-loaded PDA-based nanocarriers. A sufficient understanding and discussion of these aspects is expected to provide a better way to design more rational and effective PDA-based tumor nano-targeted delivery systems. Apart from this, the prospects for the future application of PDA in this field and some unique insights are listed at the end of the article.

Multistimuli-responsive drug vehicles based on gold nanoflowers for chemophotothermal synergistic cancer therapy

AIM

To design and synthesize a novel multistimuli-responsive drug vehicle based on gold nanoflowers (AuNFs) for chemophotothermal synergistic cancer therapy.

MATERIALS & METHODS

Multistimuli-responsive drug-delivery system based on doxorubicin (DOX)/polydopamine (PDA)-functionalized AuNFs (Lan-AuNFs@PDA/DOX) was prepared. The structural characteristics, photothermal properties and stimuli-responsive drug release properties of Lan-AuNFs@PDA/DOX were evaluated. Antitumor studies in vivo and in vitro were performed.

RESULTS

Lan-AuNFs@PDA/DOX exhibited uniform morphology, excellent biocompatibility and photothermal conversion efficiency, which could also respond to stimulus including near infrared light and pH to trigger on demand drug release. The excellent synergistic therapeutic efficacy was confirmed both in vitro and in vivo.

CONCLUSION

Lan-AuNFs@PDA/DOX would be a promising drug carrier, endowing a great potential for multistimuli-responsive chemophotothermal synergistic cancer therapy.

Impact of nanoparticles on neuron biology: current research trends

Nanoparticles have enormous applications in textiles, cosmetics, electronics, and pharmaceuticals. But due to their exceptional physical and chemical properties, particularly antimicrobial, anticancer, antibacterial, anti-inflammatory properties, nanoparticles have many potential applications in diagnosis as well as in the treatment of various diseases. Over the past few years, nanoparticles have been extensively used to investigate their response on the neuronal cells. These nanoparticles cause stem cells to differentiate into neuronal cells and promote neuronal cell survivability and neuronal cell growth and expansion. The nanoparticles have been tested both in in vitro and in vivo models. The nanoparticles with various shapes, sizes, and chemical compositions mostly produced stimulatory effects on neuronal cells, but there are few that can cause inhibitory effects on the neuronal cells. In this review, we discuss stimulatory and inhibitory effects of various nanoparticles on the neuronal cells. The aim of this review was to summarize different effects of nanoparticles on the neuronal cells and try to understand the differential response of various nanoparticles. This review provides a bird's eye view approach on the effects of various nanoparticles on neuronal differentiation, neuronal survivability, neuronal growth, neuronal cell adhesion, and functional and behavioral recovery. Finally, this review helps the researchers to understand the different roles of nanoparticles (stimulatory and inhibitory) in neuronal cells to develop effective therapeutic and diagnostic strategies for neurodegenerative diseases.

Magnetically-targeted and near infrared fluorescence/magnetic resonance/photoacoustic imaging-guided combinational anti-tumor phototherapy based on polydopamine-capped magnetic Prussian blue nanoparticles

In recent years, Prussian blue (PB)-based nanoagents have become a new platform in photothermal cancer treatment. However, there is little research for PB-based nanoagents to achieve synergistic phototherapy guided by multimodal imaging diagnosis and monitoring. Herein, a novel single wavelength near infrared (NIR) laser-induced magnetically targeted theranostic nanoplatform has been successfully designed and synthesized for the first time based on polydopamine (PDA)/aluminum phthalocyanine (AlPc)/bovine serum albumin (BSA) coated magnetic Prussian blue nanoparticles (Fe₃O₄@PB NPs) for multiple imaging-guided combinatorial cancer therapy. The resultant multifunctional Fe₃O₄@PB@PDA/AlPc/BSA nanocomposites show excellent stability and superparamagnetism, facilitating them to achieve superior photothermal therapy in physiological environments under magnetic guidance. In addition, the delivery vehicles can remarkably increase tumor accumulation of AlPc, thus leading to an enhanced photodynamic therapy efficacy. Furthermore, Fe₃O₄@PB@PDA/AlPc/BSA can be utilized as a multimodality nanoprobe for simultaneous diversified imaging, including near-infrared fluorescence imaging (NIRFI), magnetic resonance imaging (MRI), and photoacoustic imaging (PAI). Most importantly, without noticeable dark toxicity, the obtained Fe₃O₄@PB@PDA/AlPc/BSA nanocomposites are able to significantly suppress tumor growth via combined photothermal and photodynamic therapies upon a single 660 nm laser irradiation, achieving a superior synergetic manner compared to monotherapy both in vitro and in vivo. Therefore, our strategy provides Fe₃O₄@PB@PDA/AlPc/BSA nanocomposites for trimodality cancer imaging-guided synergistic therapy, with a great potential for new generation theranostics nanoagents.

Engineering Polyzwitterion and Polydopamine Decorated Doxorubicin-Loaded Mesoporous Silica Nanoparticles as a pH-Sensitive Drug Delivery

Multifunctional drug carriers have great applications in biomedical field. In this study, we introduced both polydopamine (PDA) and zwitterionic polymer of poly(3-(3-methacrylamidopropyl-(dimethyl)-ammonio)propane-1-sulfonate) (PSPP) onto the surface of mesoporous silica nanoparticles (MSNs) to develop a novel nanoparticle (MSNs@PDA-PSPP), which was employed as a new kind of drug carrier for the delivery of doxorubicin (DOX). The PDA coating, as a gatekeeper, could endow the drug carrier with pH-sensitive drug release performance. The outermost PSPP layer would make the drug carrier possess protein resistance performance. The chemical structure and properties were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS) and thermogravimetric analysis (TGA). MSNs@PDA-PSPP could keep good colloidal stability within 72 h in phosphate buffered saline (PBS) and protein solutions. Meanwhile, MSNs@PDA-PSPP exhibited a high drug loading for DOX. In vitro drug release experiments suggested MSNs-DOX@PDA-PSPP exhibited pH-dependent drug release behaviors. Besides, MSNs@PDA-PSPP had no cytotoxicity to human hepatocellular carcinoma cells (HepG2 cells) even at a concentration of 125 µg/mL. More importantly, cellular uptake and in vitro anticancer activity tests suggested that MSNs-DOX@PDA-PSPP could be taken up by HepG2 cells and DOX could be successfully released and delivered into the cell nuclei. Taken together, MSNs@PDA-PSPP have great potential in the biomedical field.