Recent advances in melanin-like nanomaterials in biomedical applications: a mini review

Melanin Nanoparticles as a Safe and Effective Iron Chelation Therapy: An ex vivo Assessment of Human Placental Transfer in Pregnant Beta-Thalassemia

Background

Iron toxicity is a major contributor to adverse pregnancy outcomes in women with transfusion-dependent thalassemia. Currently used iron chelators are not recommended during pregnancy, as they can cross the placenta causing potential risk to the fetus. However, ceasing medication may adversely affect the mother's health in both the short- and long-term.

Objective

We previously demonstrated that melanin nanoparticles can effectively chelate iron, and this has been confirmed by others in iron-overloaded mice. This study aims to assess whether these nanoparticles cross the placenta and evaluate their biocompatibility and haemocompatibility.

Study Design

A library of 50 nm, 200 nm, and 500 nm melanin nanoparticles were synthesized and coated with Polyethylene Glycol (PEG) to improve their stability. The particles were tested for chelating iron efficacy in and biocompatibility. An in vitro BeWo (choriocarcinoma) cell model and ex vivo human placental perfusion system were used to assess nanoparticle transplacental passage.

Results

Melanin nanoparticles of all sizes were able to chelate iron with a maximum adsorption of 14 mm iron/g of material; significantly higher than Desferrioxamine (DFO) of the same concentration. It was also determined that PEGylated melanin nanoparticles with appropriate size (cut off 200 nm) could be restricted from passing across the placental barrier in an in vitro model using a human choriocarcinoma cell line and in an ex vivo human placental perfusion model. The particles did not cause red cell haemolysis or blood clotting at concentrations up to 1 mM.

Conclusion

It was demonstrated herein that transport of MNPs across the placental barrier is highly dependent on particle size (cut off size of 200 nm PEGylated MNPs). Findings suggest the possibility of providing a safe method of iron chelation during pregnancy. Future work using in vivo models will be applied to study systemic particle interactions.

Dietary Natural Melanin Nanozymes Delay Aging and Ameliorate Neurodegeneration via Improving Gut Microbiota and Redox Homeostasis

Aging is an inevitable multifactor process that causes a decline in organ function and increases the risk of age-related diseases and death. Thus, the development of highly effective and safe therapeutic strategies to delay aging and age-related diseases is urgently required. In this study, we isolated natural melanin nanozymes (NMNs) from the ink sacs of live octopuses. The NMNs exhibited excellent superoxide-dismutase-mimicking and radical scavenging activities. In SAMP8 mice, treatment with NMNs improved their cognition and memory functions while restoring their aging-impaired liver function and lipid metabolism, thereby prolonging their lifespan. Moreover, the NMNs reversed metabolic changes in their aged brains and reconstructed their gut microbiota composition by enhancing microbial community diversity. Our findings indicate that NMNs treatment could be a promising approach for delaying aging and preventing age-associated physiological decline in humans.

Mussel-like polydopamine-assisted aggregation-induced emission nanodot for enhanced broad-spectrum antimicrobial activity: In vitro and in vivo validation

Emerging luminogens with aggregation-induced emission properties, namely AIEgens, demonstrated excellent anti-bacteria activity potential. However, their application still limited by the low antibacterial activity caused by the poor binding with bacteria. Polydopamine (PDA), an important biological macromolecule, possesses superior adhesion ability toward various material surface, including bacteria. In this study, the novel mussel-like PDA-assisted AIE Nanodot was proposed, achieving with robust bacterial binding ability and enhanced broad-spectrum antibacterial activity. Binding ability inherited from the PDA enables the constructed PDA-assisted AIE Nanodot to adhere efficiently to the bacterial membrane surface. Meanwhile, the AIE properties endowed them with monitoring capability, allowing for tracking their interaction with bacteria through facile fluorescence imaging in real time. More importantly, excellent killing of both Gram-positive and Gram-negative bacteria were successfully achieved in vitro antibacterial tests with excellent biocompatibility. Furthermore, in the treatment of Methicillin-resistant S. aureus (MRSA)-infected mouse-wound model, the mice exhibited accelerated wound healing with low bacterial load. This novel integrated strategy introduced a simple but effectively design to enhance the binding and antibacterial ability of AIEgens and would diversify the existing pool of antibacterial agents.

Physiological Roles of Eumelanin- and Melanogenesis-Associated Diseases: A Look at the Potentialities of Engineered and Microbial Eumelanin in Clinical Practice

This paper aims to highlight the physiological actions exerted by eumelanin present in several organs/tissues of the human body and to rationalise the often conflicting functional roles played by this biopolymer on the basis of its peculiar properties. Besides pigmentary disorders, a growing number of organ injuries and degenerative pathologies are presently ascribed to the modification of physiological eumelanin levels in terms of alterations in its chemical/structural features, and of a partial loss or uneven distribution of the pigment. The present review analyses the more recent research dedicated to the physiological and pathological actions of eumelanin and provides an insight into some melanogenesis-associated diseases of the skin, eye, ear, and brain, including the most significant neurodegenerative disorders. Also described are the potentialities of therapies based on the localised supply of exogeneous EU and the opportunities that EU produced via synthetic biology offers in order to redesign therapeutical and diagnostic applications.

Biosustainable Hybrid Nanoplatforms as Photoacoustic Agents

The development of biosafe theranostic nanoplatforms has attracted great attention due to their multifunctional behavior, reduced potential toxicity, and improved long-term safety. When considering photoacoustic contrast agents and photothermal conversion tools, melanin and constructs like melanin are highly appealing due to their ability to absorb optical energy and convert it into heat. Following a sustainable approach, in this study, silver-melanin like-silica nanoplatforms are synthesized exploiting different bio-available and inexpensive phenolic acids as potential melanogenic precursors and exploring their role in tuning the final systems architecture. The UV-Vis combined with X-Ray Diffraction investigation proves metallic silver formation, while Transmission Electron Microscopy analysis reveals that different morphologies can be obtained by properly selecting the phenolic precursors. By looking at the characterization results, a tentative formation mechanism is proposed to explain how phenolic precursors' redox behavior may affect the nanoplatforms' structure. The antibacterial activity experiments showed that all synthesized systems have a strong inhibitory effect on Escherichia coli, even at low concentrations. Furthermore, very sensitive Photoacoustic Imaging capabilities and significant photothermal behavior under laser irradiation are exhibited. Finally, a marked influence of phenol nature on the final system architecture is revealed resulting in a significant effect on both biological and photoacoustic features of the obtained systems. These melanin-based hybrid systems exhibit excellent potential as triggerable nanoplatforms for various biomedical applications.

Melanin Biopolymers in Pharmacology and Medicine-Skin Pigmentation Disorders, Implications for Drug Action, Adverse Effects and Therapy

Melanins are biopolymeric pigments formed by a multi-step oxidation process of tyrosine in highly specialized cells called melanocytes. Melanin pigments are mainly found in the skin, iris, hair follicles, and inner ear. The photoprotective properties of melanin biopolymers have been linked to their perinuclear localization to protect DNA, but their ability to scavenge metal ions and antioxidant properties has also been noted. Interactions between drugs and melanins are of clinical relevance. The formation of drug-melanin complexes can affect both the efficacy of pharmacotherapy and the occurrence of adverse effects such as phototoxic reactions and discoloration. Because the amount and type of melanin synthesized in the body is subject to multifactorial regulation-determined by both internal factors such as genetic predisposition, inflammation, and hormonal balance and external factors such as contact with allergens or exposure to UV radiation-different effects on the melanogenesis process can be observed. These factors can directly influence skin pigmentation disorders, resulting in hypopigmentation or hyperpigmentation of a genetic or acquired nature. In this review, we will present information on melanocyte biology, melanogenesis, and the multifactorial influence of melanin on pharmacological parameters during pharmacotherapy. In addition, the types of skin color disorders, with special emphasis on the process of their development, symptoms, and methods of treatment, are presented in this article.

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

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

Aptamer-Based Smart Targeting and Spatial Trigger-Response Drug-Delivery Systems for Anticancer Therapy

In recent years, the field of drug delivery has witnessed remarkable progress, driven by the quest for more effective and precise therapeutic interventions. Among the myriad strategies employed, the integration of aptamers as targeting moieties and stimuli-responsive systems has emerged as a promising avenue, particularly in the context of anticancer therapy. This review explores cutting-edge advancements in targeted drug-delivery systems, focusing on the integration of aptamers and stimuli-responsive platforms for enhanced spatial anticancer therapy. In the aptamer-based drug-delivery systems, we delve into the versatile applications of aptamers, examining their conjugation with gold, silica, and carbon materials. The synergistic interplay between aptamers and these materials is discussed, emphasizing their potential in achieving precise and targeted drug delivery. Additionally, we explore stimuli-responsive drug-delivery systems with an emphasis on spatial anticancer therapy. Tumor microenvironment-responsive nanoparticles are elucidated, and their capacity to exploit the dynamic conditions within cancerous tissues for controlled drug release is detailed. External stimuli-responsive strategies, including ultrasound-mediated, photo-responsive, and magnetic-guided drug-delivery systems, are examined for their role in achieving synergistic anticancer effects. This review integrates diverse approaches in the quest for precision medicine, showcasing the potential of aptamers and stimuli-responsive systems to revolutionize drug-delivery strategies for enhanced anticancer therapy.

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.

Cobalt-doped hollow polydopamine for oxygen generation and GSH consumption enhanced chemo-PTT combined cancer therapy

Nanotechnology has revolutionized the field of therapeutics by introducing a plethora of nanomaterials capable of enhancing traditional drug efficacy or paving the way for innovative treatment methods. Within this domain, we propose a novel Cobalt-doped hollow polydopamine nanosphere system. This system, incorporating Doxorubicin loading and hyaluronic acid (HA) surface coating (CoHPDA@DOX-HA), is designed for combined tumor therapy. The overarching aim is to diminish the administration dosage, mitigate the cytotoxic side effects of chemotherapy drugs, augment chemosensitivity within neoplastic tissues, and attain superior results in tumor treatment via combined therapeutic strategies. The targeted molecule, hyaluronic acid (HA), amplifies the biocompatibility of CoHPDA@DOX-HA throughout circulation and fosters endocytosis of the nanoparticle system within cancer cells. This nanosphere system possesses pH sensitivity properties, allowing for a meticulous drug release within the acidic microenvironment of tumor cells. Concurrently, Polydopamine (PDA) facilitates proficient photothermal therapy upon exposure to 808 nm laser irradiation. This process further amplifies the Glutathione (GSH) depletion, and when coupled with the oxygen production capabilities of the Cobalt-doped hollow PDA, significantly enhances the chemo-photothermal therapeutic efficiency. Findings from the treatment of tumor-bearing mice substantiate that even at dosages equivalent to a singular DOX administration, the CoHPDA@DOX-HA can provide efficacious synergistic therapy. Therefore, it is anticipated that multifunctional nanomaterials with Photoacoustic Tomography (PAT) imaging capabilities, targeted delivery, and a controlled collaborative therapeutic framework may serve as promising alternatives for accurate diagnostics and efficacious treatment strategies.

Enhanced Photoacoustic Response by Synergistic Ag-Melanin Interplay at the Core of Ternary Biocompatible Hybrid Silica-Based Nanoparticles

Photoacoustics (PA) is gaining increasing credit among biomolecular imaging methodologies by virtue of its poor invasiveness, deep penetration, high spatial resolution, and excellent endogenous contrast, without the use of any ionizing radiation. Recently, we disclosed the excellent PA response of a self-structured biocompatible nanoprobe, consisting of ternary hybrid nanoparticles with a silver core and a melanin component embedded into a silica matrix. Although preliminary evidence suggested a crucial role of the Ag sonophore and the melanin-containing nanoenvironment, whether and in what manner the PA response is controlled and affected by the self-structured hybrid nanosystems remained unclear. Because of their potential as multifunctional platforms for biomedical applications, a detailed investigation of the metal-polymer-matrix interplay underlying the PA response was undertaken to understand the physical and chemical factors determining the enhanced response and to optimize the architecture, composition, and performance of the nanoparticles for efficient imaging applications. Herein, we provide the evidence for a strong synergistic interaction between eumelanin and Ag which suggests an important role in the in situ-generated metal-organic interface. In particular, we show that a strict ratio between melanin and silver precursors and an accurate choice of metal nanoparticle dimension and the kind of metal are essential for achieving strong enhancements of the PA response. Systematic variation of the metal/melanin component is thus shown to offer the means of tuning the stability and intensity of the photoacoustic response for various biomedical and theranostic applications.

Applications of Polydopamine in Implant Surface Modification

There is great clinical demand for orthopedic and dental implant surface modification methods to prevent osseointegration failure and improve implant biological functions. Notably, dopamine (DA) can be polymerized to form polydopamine (PDA), which is similar to the adhesive proteins secreted by mussels, to form a stable bond between the bone surface and implants. Therefore, PDA has the potential to be used as an implant surface modification material with good hydrophilicity, roughness, morphology, mechanical strength, biocompatibility, antibacterial activity, cellular adhesion, and osteogenesis. In addition, PDA degradation releases DA into the surrounding microenvironment, which is found to play an important role in regulating DA receptors on both osteoblasts and osteoclasts during the bone remodeling process. Furthermore, the adhesion properties of PDA suggest its use as an intermediate layer in assisting other functional bone remodeling materials, such as nanoparticles, growth factors, peptides, and hydrogels, to form "dual modifications." The purpose of this review is to summarize the recent progress in research on PDA and its derivatives as orthopedic and dental implant surface modification materials and to analyze the multiple functions of PDA.

Site-specific fabrication of a melanin-like pigment through spatially confined progressive assembly on an initiator-loaded template

Melanin-like nanomaterials have emerged in surface biofunctionalization in a material-independent manner due to their versatile adhesion arising from their catechol-rich structures. However, the unique adhesive properties of these materials ironically raise difficulties in their site-specific fabrication. Here, we report a method for site-specific fabrication and patterning of melanin-like pigments, using progressive assembly on an initiator-loaded template (PAINT), different from conventional lithographical methods. In this method, the local progressive assembly could be naturally induced on the given surface pretreated with initiators mediating oxidation of the catecholic precursor, as the intermediates generated from the precursors during the progressive assembly possess sufficient intrinsic underwater adhesion for localization without diffusion into solution. The pigment fabricated by PAINT showed efficient NIR-to-heat conversion properties, which can be useful in biomedical applications such as the disinfection of medical devices and cancer therapies.

Oxygen-supplying syringe to create hyperoxia-inducible hydrogels for in situ tissue regeneration

Recent trends in the design of regenerative materials include the development of bioactive matrices to harness the innate healing ability of the body using various biophysicochemical stimuli (defined as in situ tissue regeneration). Among these, hyperoxia (>21% pO₂) is a well-known therapeutic factor for promoting tissue regeneration, such as immune cell recruitment, cell proliferation, angiogenesis, and fibroblast differentiation into myofibroblast. Although various strategies to induce hyperoxia are reported, developing advanced hyperoxia-inducing biomaterials for tissue regeneration is still challenging. In this study, a catalase-immobilized syringe (defined as an Oxyringe) via calcium peroxide-mediated surface modification is developed as a new type of oxygen-supplying system. Hyperoxia-inducible hydrogels are fabricated utilizing Oxyringe. This hydrogel plays a role as a physical barrier for hemostasis. In addition, hyperoxic matrices induce transient hyperoxia in vivo (up to 46.0% pO₂). Interestingly, the hydrogel-induced hyperoxia boost the initial macrophage recruitment and rapid inflammation resolution. Furthermore, hyperoxic oxygen release of hydrogels facilitates neovascularization and cell proliferation involved in the proliferation phase, expediting tissue maturation related to the remodeling phase in wound healing. In summary, Oxyringe has excellent potential as an advanced oxygen-supplying platform to create hyperoxia-inducing hydrogels for in situ tissue regeneration.

Mesoporous, anisotropic nanostructures from bioinspired polymeric catecholamine neurotransmitters and their potential application as photoacoustic imaging agents

Mesoporous polydopamine (PDA) nanobowls, which can be prepared using Pluronic® F-127, ammonia, and 1,3,5-trimethylbenzene (TMB), are one of the most studied anisotropic nanoparticle systems. However, only limited reports on polymerised analogues polynorepinephrine (PNE) and polyepinephrine (PEP) exist. Herein, we present modifications to a one-pot, soft template method, originally applied to make PDA nanobowls, to fabricate new shape-anisotropic nanoparticles (mesoporous nanospheres or "nano-golf balls" and nanobowls) using PNE and PEP for the first time. These modifications include the use of different oil phases (TMB, toluene and o-xylene) and ammonia concentrations to induce anisotropic growth of PDA, PNE, and PEP particles. Moreover, this work features the application of oddly shaped PDA, PNE, and PEP nanoparticles as intravascular photoacoustic imaging enhancers in Intralipid®-India ink-based tissue-mimicking phantoms. Photoacoustic imaging experiments showed that mesoporous nanobowls exhibit stronger enhancement, in comparison to their mesoporous nano-golf ball and nanoaggregate counterparts. The photoacoustic enhancement also followed the general trend PDA > PNE > PEP due to the differences in the rates of polymerisation of the monomers and the optical absorption of the resulting polymers. Lastly, about two- to four-fold enhancement in photoacoustic signals was observed for the mesoporous nanostructures, when compared to smooth nanospheres and their nano-aggregates. These results suggest that shape manipulation can aid in overcoming the inherently lower performance of PNE and PEP as photoacoustic imaging agents, compared to PDA. Since nanomaterials with mesoporous and anisotropic morphologies have significant, unexplored potential with emerging applications, these results set the groundwork for future studies on photoacoustically active oddly shaped PNE- and PEP-based nanosystems.

Optical Epidermal Mimicry from Ultraviolet to Infrared Wavelengths

Optical tissue phantoms present substantial value for medical imaging and therapeutic applications. We have developed an epidermal tissue phantom to mimic the optical properties of human skin from the ultraviolet to the infrared region, exceeding the breadth of existing studies. An epoxy matrix is combined with melanin-mimicking polydopamine via a cost-effective fabrication strategy. Reflectance and transmittance measurements enable calculation of the wavelength-dependent complex refractive index and absorption coefficient. Results are compared with literature data to establish agreement with a real human epidermis. By analyzing emissive power at a typical skin temperature, the epidermal tissue phantom is shown to accurately mimic the radiative properties of human skin. This simple, multifunctional material represents a promising substitute for human tissue for a variety of medical and bioengineering applications.

A comparative characterization study between fungal and bacterial eumelanin pigments

Melanins are the most common and the most enigmatic natural pigments in the nature that found in many different taxa group such as bacteria, yeasts, fungi, insects, plants, reptiles, birds and mammals. These biological macromolecules are highly complex cross-linked, heterogeneous biopolymers and composed of polymerized phenolic and/or indolic compounds. Recently, interest in these ubiquitous biopolymers has been increasing considerably in many different areas such as medicine, pharmacology, cosmetics, organic electronic and optoelectronics because of their versatile properties. In this study, four different extracellular eumelanin pigments (two bacterial eumelanins and two fungal eumelanins) were characterized by different spectrometric techniques such as FT-IR, XRD, NMR and UV-vis. In XRD analyzes, purified fungal and bacterial eumelanin pigments were characterized by giving a wide peak at about 22o with an angle of 2θ. Furthermore, in the 1 H NMR spectra of these biopolymers, it was observed that all pigments have signals in both aromatic and aliphatic regions. In addition to these analyzes, nanostructures of these biopolymers were characterized using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Finally, eumelanin pigment producer microorganisms were molecularly characterized. 16 S rDNA and 18 S rDNA sequence analysis results of these microorganisms (Streptomyces fulvissimus MPPS4, Streptomyces xiamenensis MPPS6, Aspergillus niger MPPF16 and Aspergillus terreus MPPF25) were deposited in NCBI GenBank® database with accession number MT825594, MT973972, MW652652 and MW652653 respectively.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-022-01012-1.

Next-Generation Colloidal Materials for Ultrasound Imaging Applications

Ultrasound has important applications, predominantly in the field of diagnostic imaging. Presently, colloidal systems such as microbubbles, phase-change emulsion droplets and particle systems with acoustic properties and multiresponsiveness are being developed to address typical issues faced when using commercial ultrasound contrast agents, and to extend the utility of such systems to targeted drug delivery and multimodal imaging. Current technologies and increasing research data on the chemistry, physics and materials science of new colloidal systems are also leading to the development of more complex, novel and application-specific colloidal assemblies with ultrasound contrast enhancement and other properties, which could be beneficial for multiple biomedical applications, especially imaging-guided treatments. In this article, we review recent developments in new colloids with applications that use ultrasound contrast enhancement. This work also highlights the emergence of colloidal materials fabricated from or modified with biologically derived and bio-inspired materials, particularly in the form of biopolymers and biomembranes. Challenges, limitations, potential developments and future directions of these next-generation colloidal systems are also presented and discussed.

State of the Art in Carbon Nanomaterials for Photoacoustic Imaging

Photoacoustic imaging using energy conversion from light to ultrasound waves has been developed as a powerful tool to investigate in vivo phenomena due to their complex characteristics. In photoacoustic imaging, endogenous chromophores such as oxygenated hemoglobin, deoxygenated hemoglobin, melanin, and lipid provide useful biomedical information at the molecular level. However, these intrinsic absorbers show strong absorbance only in visible or infrared optical windows and have limited light transmission, making them difficult to apply for clinical translation. Therefore, the development of novel exogenous contrast agents capable of increasing imaging depth while ensuring strong light absorption is required. We report here the application of carbon nanomaterials that exhibit unique physical, mechanical, and electrochemical properties as imaging probes in photoacoustic imaging. Classified into specific structures, carbon nanomaterials are synthesized with different substances according to the imaging purposes to modulate the absorption spectra and highly enhance photoacoustic signals. In addition, functional drugs can be loaded into the carbon nanomaterials composite, and effective in vivo monitoring and photothermal therapy can be performed with cell-specific targeting. Diverse applied cases suggest the high potential of carbon nanomaterial-based photoacoustic imaging in in vivo monitoring for clinical research.

NIR-Mediated drug release and tumor theranostics using melanin-loaded liposomes

BACKGROUND

Heat generation in a drug delivery carrier by exposure to near-infrared (NIR) light with excellent tissue transmittance is an effective strategy for drug release and tumor therapy. Because liposomes have amphiphilic properties, they are useful as drug carriers. Liposomes are also very suitable for drug delivery strategies using heat generation by NIR laser because lipid bilayers are easily broken by heat. Thermally generated bubbles from liposomes not only induce drug release, but also enable ultrasound imaging.

METHODS

Melanin, perfluorohexane (PFH), and 5-fluorouracil (5-FU)-loaded liposomes (melanin@PFH@5-FU-liposomes) that can generate heat and bubble by NIR laser irradiation were prepared by a thin film method. Conversion of light to heat and bubble generation of melanin@PFH@5-FU-liposomes were evaluated using an infrared (IR) thermal imaging camera and an ultrasound imaging system both in vitro and in vivo. To investigate tumor therapeutic effect, NIR laser of 808 nm was used to irradiate tumor site for 10 min after injecting melanin@PFH@5-FU-liposome into tail veins of CT26-bearing mice.

RESULTS

Melanin@PFH@5-FU-liposomes showed a spherical shape with a size of 209.6 ± 4.3 nm. Upon NIR laser irradiation, melanin@PFH@5-FU-liposomes exhibited effective temperature increase both in vitro and in vivo. In this regard, temperature increase caused a phase transition of PFH to induce bubble generation dramatically, resulting in effective drug release behavior and ultrasound imaging. The temperature of the tumor site was increased to 52 t and contrast was greatly enhanced during ultrasound imaging due to the generation of bubble. More importantly, tumor growth was effectively inhibited by injection of melanin@PFH@5-FU-liposomes with laser irradiation.

CONCLUSIONS

Based on intrinsic photothermal properties of melanin and phase transition properties of PFH, melanin@PFH@5-FU-liposomes exhibited effective heat and bubble generation upon NIR laser irradiation. The elevated temperature induced bubble generation, resulting in contrast enhancement of ultrasound imaging. Melanin@PFH@5-FU-liposomes under NIR laser irradiation induced the death of cancer cells, thereby effectively inhibiting tumor growth. These results suggest that melanin@PFH@5-FU-liposomes can be utilized as a promising agent for photothermal tumor therapy and ultrasound imaging.

Enhanced photoacoustic imaging in tissue-mimicking phantoms using polydopamine-shelled perfluorocarbon emulsion droplets

The current work features process parameters for the ultrasound (25 kHz)-assisted fabrication of polydopamine-shelled perfluorocarbon (PDA/PFC) emulsion droplets with bimodal (modes at 100-600 nm and 1-6 µm) and unimodal (200-600 nm) size distributions. Initial screening of these materials revealed that only PDA/PFC emulsion droplets with bimodal distributions showed photoacoustic signal enhancement due to large size of their optically absorbing PDA shells. Performance of this particular type of emulsion droplets as photoacoustic agents were evaluated in Intralipid®-India ink media, mimicking the optical scattering and absorbanceof various tissuetypes. From these measurements, it was observed that PDA/PFC droplets with bimodal size distributions can enhance the photoacoustic signal of blood-mimicking phantom by up to five folds in various tissue-mimicking phantoms with absorption coefficients from 0.1 to 1.0 cm^-1. Furthermore, using the information from enhanced photoacoustic images at 750 nm, the ultimate imaging depth was explored for polydopamine-shelled, perfluorohexane (PDA/PFH) emulsion droplets by photon trajectory simulations in 3D using a Monte Carlo approach. Based on these simulations, maximal tissue imaging depths for PDA/PFH emulsion droplets range from 10 to 40 mm, depending on the tissue type. These results demonstrate for the first time that ultrasonically fabricated PDA/PFC emulsion droplets have great potential as photoacoustic imaging agents that can be complemented with other reported characteristics of PDA/PFC emulsion droplets for extended applications in theranostics and other imaging modalities.

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.

Treatment of bladder cancer by geoinspired synthetic chrysotile nanocarrier-delivered circPRMT5 siRNA

Background

Circular RNAs (circRNAs) have important functions in many fields of cancer biology. In particular, we previously reported that the oncogenic circRNA, circPRMT5, has a major role in bladder cancer progression. Therapy based on circRNAs have good prospects as anticancer strategies. While anti-circRNAs are emerging as therapeutics, the specific in vivo delivery of anti-circRNAs into cancer cells has not been reported and remains challenging.

Methods

Synthesized chrysotile nanotubes (SCNTs) with a relatively uniform length (~ 200 nm) have been designed to deliver an siRNA against the oncogenic circPRMT5 (si-circPRMT5) inhibit circPRMT5. In addition, the antitumor effects and safety evaluation of SCNTs/si-circPRMT5 was assessed with a series of in vitro and in vivo assays.

Results

The results showed that SCNTs/si-circPRMT5 nanomaterials prolong si-circPRMT5’s half-life in circulation, enhance its specific uptake by tumor cells, and maximize the silencing efficiency of circPRMT5. In vitro, SCNTs encapsulating si-circPRMT5 could inhibit bladder cancer cell growth and progression. In vivo, SCNTs/si-circPRMT5 inhibited growth and metastasis in three bladder tumor models (a subcutaneous model, a tail vein injection lung metastatic model, and an in situ model) without obvious toxicities. Mechanistic study showed that SCNTs/si-circPRMT5 regulated the miR-30c/SNAIL1/E-cadherin axis, inhibiting bladder cancer growth and progression.

Conclusion

The results highlight the potential therapeutic utility of SCNTs/si-circPRMT5 to deliver si-circPRMT5 to treat bladder cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40824-022-00251-z.

RGD-functionalised melanin nanoparticles for intraoperative photoacoustic imaging-guided breast cancer surgery

PURPOSE

Obtaining tumour-free margins is critical for avoiding re-excision and reducing local recurrence following breast-conserving surgery; however, it remains challenging. Imaging-guided surgery provides precise detection of residual lesions and assists surgical resection. Herein, we described water-soluble melanin nanoparticles (MNPs) conjugated with cyclic Arg-Gly-Asp (cRGD) peptides for breast cancer photoacoustic imaging (PAI) and surgical navigation.

METHODS

The cRGD-MNPs were synthesised and characterized for morphology, photoacoustic characteristics and stability. Tumour targeting and toxicity of cRGD-MNPs were determined by using either breast cancer cells, MDA-MB-231 tumour-bearing mice or the FVB/N-Tg (MMTV-PyVT) 634Mul/J mice model. PAI was used to locate the tumour and guide surgical resection in MDA-MB-231 tumour-bearing mice.

RESULTS

The cRGD-MNPs exhibited excellent in vitro and in vivo tumour targeting with low toxicity. Intravenous administration of cRGD-MNPs to MDA-MB-231 tumour-bearing mice showed an approximately 2.1-fold enhancement in photoacoustic (PA) intensity at 2 h, and the ratio of the PA intensity at the tumour site to that in the surrounding normal tissue was 3.2 ± 0.1, which was higher than that using MNPs (1.7 ± 0.3). Similarly, the PA signal in the spontaneous breast cancer increased ~ 2.5-fold at 2 h post-injection of cRGD-MNPs in MMTV-PyVT transgenic mice. Preoperative PAI assessed tumour volume and offered three-dimensional (3D) reconstruction images for accurate surgical planning. Surgical resection following real-time PAI showed high consistency with histopathological analysis.

CONCLUSION

These results highlight that cRGD-MNP-mediated PAI provide a powerful tool for breast cancer imaging and precise tumour resection. cRGD-MNPs with fine PA properties have great potential for clinical translation.

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).

Influence of a Polyneurotransmitter on DNA-Mediated Förster-Based Resonance Energy Transfer: A Path Leading to White Light Generation

The physiologically important biomolecule, dopamine (DA), shows strong self-oxidation and aggregation behaviors, which have been controlled and modulated to result in fluorescent polydopamine (F-PDA) nanoparticles. On the other hand, the simultaneous binding of two diverse deoxyribonucleic acid (DNA) binding probes, 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) and ethidium bromide (EtBr), has been elaborately established to follow the Förster-based resonance energy transfer (FRET) pathway. The comparative understanding of this DNA-mediated FRET in three media, phosphate buffer saline (PBS) of pH 7.4, DA, and F-PDA, has concluded that the FRET efficiency in the three media follows the order: PBS > DA > F-PDA. This controlled FRET in the fluorescent F-PDA matrix serves a pivotal role for efficient white light (WL) generation with excellent Commission Internationale de l'Eclairage (CIE) parameters that match well with that of pure WL emission. The obtained WL emission has been shown to be very specific with respect to concentrations of different participating components and the excitation wavelength of the illuminating source. Furthermore, the optical properties of the WL emitting solution have been observed to be retained excellently inside the well-known agarose gel matrix. Finally, the mechanistic pathway behind such a FRET-based WL generation has been established in detail, and to the best of our knowledge, the current study offers the first and only report that discloses the influence of a fluorescent polyneurotransmitter matrix for successful generation of WL emission.

Conjugated Organic Photothermal Films for Spatiotemporal Thermal Engineering

With the growth of photoenergy harvesting and thermal engineering, photothermal materials (PTMs) have attracted substantial interest due to their unique functions such as localized heat generation, spatiotemporal thermal controllability, invisibility, and light harvesting capabilities. In particular, π-conjugated organic PTMs show advantages over inorganic or metallic PTMs in thin film applications due to their large light absorptivity, ease of synthesis and tunability of molecular structures for realizing high NIR absorption, flexibility, and solution processability. This review is intended to provide an overview of organic PTMs, including both molecular and polymeric PTMs. A description of the photothermal (PT) effect and conversion efficiency (ηPT ) for organic films is provided. After that, the chemical structure and optical properties of organic PTMs are discussed. Finally, emerging applications of organic PT films from the perspective of spatiotemporal thermal engineering principles are illustrated.

Recent developments in mussel-inspired materials for biomedical applications

Over the decades, researchers have strived to synthesize and modify nature-inspired biomaterials, with the primary aim to address the challenges of designing functional biomaterials for regenerative medicine and tissue engineering. Among these challenges, biocompatibility and cellular interactions have been extensively investigated. Some of the most desirable characteristics for biomaterials in these applications are the loading of bioactive molecules, strong adhesion to moist areas, improvement of cellular adhesion, and self-healing properties. Mussel-inspired biomaterials have received growing interest mainly due to the changes in mechanical and biological functions of the scaffold due to catechol modification. Here, we summarize the chemical and biological principles and the latest advancements in production, as well as the use of mussel-inspired biomaterials. Our main focus is the polydopamine coating, the conjugation of catechol with other polymers, and the biomedical applications that polydopamine moieties are used for, such as matrices for drug delivery, tissue regeneration, and hemostatic control. We also present a critical conclusion and an inspired view on the prospects for the development and application of mussel-inspired materials.

Preclinical studies conducted on nanozyme antioxidants: shortcomings and challenges based on US FDA regulations

The wide prevalence of oxidative stress-induced diseases has led to a growing demand for antioxidant therapeutics worldwide. Nanozyme antioxidants are drawing enormous attention as practical alternatives for conventional antioxidants. The considerable body of research over the last decade and the promising results achieved signify the potential of nanozyme antioxidants to secure a place in the expanding market of antioxidant therapeutics. Nonetheless, there is no report on clinical trials for their further evaluation. Through analyzing in-depth selected papers which have conducted in vivo studies on nanozyme antioxidants, this review aims to pinpoint and discuss possible reasons impeding development of research toward clinical studies and to offer some practical solutions for future studies to bridge the gap between preclinical and clinical stages.

Micropatterned Silk-Fibroin/Eumelanin Composite Films for Bioelectronic Applications

There has been growing interest in the use of natural bionanomaterials and nanostructured systems for diverse biomedical applications. Such materials can confer unique functional properties as well as address concerns pertaining to sustainability in production. In this work, we propose the biofabrication of micropatterned silk fibroin/eumelanin composite thin films to be used in electroactive and bioactive applications in bioelectronics and biomedical engineering. Eumelanin is the most common form of melanin, naturally derived from the ink of cuttlefish, having antioxidant and electroactive properties. Another natural biomaterial, the protein silk fibroin, is modified with photoreactive chemical groups, which allows the formation of electroactive eumelanin thin films with different microstructures. The silk fibroin/eumelanin composites are fabricated to obtain thin films as well as electroactive microstructures using UV curing. Here, we report for the first time the preparation, characterization, and physical, electrochemical, and biological properties of these natural silk fibroin/eumelanin composite films. Higher concentrations of eumelanin incorporated into the films exhibit a higher charge storage capacity and good electroactivity even after 100 redox cycles. In addition, the microscale structure and the cellular activity of the fibroin/eumelanin films are assessed for understanding of the biological properties of the composite. The developed micropatterned fibroin/eumelanin films can be applied as natural electroactive substrates for bioapplications (e.g., bioelectronics, sensing, and theranostics) because of their biocompatible properties.

Applications of Melanin and Melanin-Like Nanoparticles in Cancer Therapy: A Review of Recent Advances

Thanks to the growing knowledge about cancers and their interactions with the immune system, a huge number of therapeutic cancer vaccines have been developed in the past two decades. Despite encouraging results in pre-clinical models, cancer vaccines have not yet achieved significant clinical efficacy. Several factors may contribute to such poor results, including the difficulty of triggering a strong immune response and the immunosuppressive tumor microenvironment. Many strategies are currently being explored. Different types of adjuvants have been incorporated into vaccine formulations to improve their efficacy, as cancer antigens are usually poorly immunogenic. Nanoparticle systems are promising tools as they act as carriers for antigens and can be surface-modified so that they specifically target antigen-presenting cells in lymph nodes. Bioinspired nanomaterials are ideal candidates thanks to their biocompatibility. Recently, melanin-based nanoparticles were reported to efficiently localize into draining lymphoid tissues and trigger immune responses against loaded antigens. In addition, by virtue of their photochemical properties, melanin-based nanoparticles can also play an immunomodulatory role to promote anti-cancer responses in the context of photothermal therapy. In this review, we discuss the above-mentioned properties of melanin, and summarize the promising results of the melanin-based cancer vaccines recently reported in preclinical models.

Melanins as Sustainable Resources for Advanced Biotechnological Applications

Melanins are a class of biopolymers that are widespread in nature and have diverse origins, chemical compositions, and functions. Their chemical, electrical, optical, and paramagnetic properties offer opportunities for applications in materials science, particularly for medical and technical uses. This review focuses on the application of analytical techniques to study melanins in multidisciplinary contexts with a view to their use as sustainable resources for advanced biotechnological applications, and how these may facilitate the achievement of the United Nations Sustainable Development Goals.

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.

Highly Penetrable and On-Demand Oxygen Release with Tumor Activity Composite Nanosystem for Photothermal/Photodynamic Synergetic Therapy

A deep penetrating and pH-responsive composite nanosystem was strategically developed to improve the efficacy of synergetic photothermal/photodynamic therapy (PTT/PDT) against hypoxic tumor. The designed nanosystem ([PHC]PP@HA NPs) was constructed by coloading hemoglobin (Hb) and chlorin e6 on polydopamine to build small-sized PHC NPs, which were encapsulated inside the polymer micelles (poly(ethylene glycol)-poly(ethylenimine)) and then capped with functionalized hyaluronic acid. The pH-responsive feature made [PHC]PP@HA NPs retain an initial size of ∼140 nm in blood circulation but rapidly release small PHC NPs (∼10 nm) with a high tumor-penetrating ability in the tumor microenvironment. The in vitro penetration experiment showed that the penetration depth of PHC NPs in the multicellular tumor spheroids exceeded 110 μm. The [PHC]PP@HA NPs exhibited excellent biocompatibility, deep tumor permeability, high photothermal conversion efficiency (47.09%), and low combination index (0.59) under hypoxic conditions. Notably, the nanosystem can freely adjust the release of oxygen and damaging PHC NPs in an on-demand manner on the basis of the feedback of tumor activity. This feedback tumor therapy significantly improved the synergistic effect of PTT/PDT and reduced its toxic side effects. The in vivo antitumor results showed that the tumor inhibition rate of [PHC]PP@HA NPs with an on-demand oxygen supply of Hb was ∼100%, which was much better than those of PTT alone and Hb-free nanoparticles ([PC]PP@HA NPs). Consequently, the [PHC]PP@HA NP-mediated PTT/PDT guided by feedback tumor therapy achieved an efficient tumor ablation with an extremely low tumor recurrence rate (8.3%) 60 d later, indicating the versatile potential of PTT/PDT.

Bio-Applications of Multifunctional Melanin Nanoparticles: From Nanomedicine to Nanocosmetics

Bioinspired nanomaterials are ideal components for nanomedicine, by virtue of their expected biocompatibility or even complete lack of toxicity. Natural and artificial melanin-based nanoparticles (MNP), including polydopamine nanoparticles (PDA NP), excel for their extraordinary combination of additional optical, electronic, chemical, photophysical, and photochemical properties. Thanks to these features, melanin plays an important multifunctional role in the design of new platforms for nanomedicine where this material works not only as a mechanical support or scaffold, but as an active component for imaging, even multimodal, and simple or synergistic therapy. The number of examples of bio-applications of MNP increased dramatically in the last decade. Here, we review the most recent ones, focusing on the multiplicity of functions that melanin performs in theranostics platforms with increasing complexity. For the sake of clarity, we start analyzing briefly the main properties of melanin and its derivative as well as main natural sources and synthetic methods, moving to imaging application from mono-modal (fluorescence, photoacoustic, and magnetic resonance) to multi-modal, and then to mono-therapy (drug delivery, anti-oxidant, photothermal, and photodynamic), and finally to theranostics and synergistic therapies, including gene- and immuno- in combination to photothermal and photodynamic. Nanomedicine aims not only at the treatment of diseases, but also to their prevention, and melanin in nature performs a protective action, in the form of nanopigment, against UV-Vis radiations and oxidants. With these functions being at the border between nanomedicine and cosmetics nanotechnology, recently examples of applications of artificial MNP in cosmetics are increasing, paving the road to the birth of the new science of nanocosmetics. In the last part of this review, we summarize and discuss these important recent results that establish evidence of the interconnection between nanomedicine and cosmetics nanotechnology.

Electro-responsive controlled drug delivery from melanin nanoparticles

Electro-responsive controlled drug delivery has been receiving an increasing interest as one of the on-demand drug delivery systems, aiming the improvement of the therapeutics efficacy by controlling the amount of drug release at a specific time and target site. Herein, we report a simple method to develop an electro-responsive controlled drug delivery system using functionalized melanin nanoparticles (FMNPs) with polydopamine and polypyrrole to precisely control the release of dexamethasone (Dex). Optimized FMNPs showed 376.77 ± 62.05 nm of particle size, a polydispersity index of 0.26 ± 0.09 and a zeta-potential (ZP) of -32.59 ± 3.61 mV. FMNPs evidenced a spherical shape, which was confirmed by scanning electron microscopy. Fourier-transform infrared spectrometry analysis confirmed the deposition of the polymers on the FMNPs' surface. The incorporation efficiency of the optimized Dex-loaded FMNPs was 94.45 ± 0.63% and the increase of ZP to -40.34 ± 4.65 mV was attributed to the anionic nature of Dex. In vitro Dex release studies without stimuli revealed a maximum Dex release below 10%. Applying electrical stimulation, Dex release was augmented, with a maximum of ca. 32% after 24 h. The designed FMNPs provide a powerful biomaterial-based technological tool for electro-responsive controlled drug delivery, capable of surpassing the associated lack of efficiency and stability of current carriers.

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

Introduction

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

Materials and Methods

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

Results

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

Conclusion

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

Nature-Inspired Adhesive Catecholamines for Highly Concentrated Colorimetric Signal in Spatial Biomarker Labeling

Colorants have been utilized for precise biomarker detection in rapid and convenient colorimetric bioassays. However, the diffusion of colorants in solution often results in poor sensitivity, which is a major obstacle to the clinical translation of current colorants. To address this issue, in the current study, a unique colorant is developed that possesses adhesiveness for concentration near the target biomarker, avoiding diffusion. In nature, the synergistic interplay between catechol and amine functional groups is thought to be key for the unique mechanism of marine mussel adhesion. In addition, polymerized catecholamines are found in nature as biopigments, that is, in melanin. The dual role of catechol/catecholamine moieties in natural organics inspire to design novel colorimetric bioassays based on an adhesive colorant. Horseradish peroxidase (HRP) is used to initiate in situ polymerization of the catecholic precursors with amine-containing additive molecules and simultaneously attach them near the HRP-labeled biomarkers. This novel catecholamine-based adhesive colorant provides an excellent quantitative (naked-eye) visible signal and it also generates superb spatial information on the biomarkers on complex surfaces (e.g., cell membranes).

Melanin-Like Nanomaterials for Advanced Biomedical Applications: A Versatile Platform with Extraordinary Promise

Developing efficient, sustainable, and biocompatible high-tech nanoplatforms derived from naturally existing components in living organisms is highly beneficial for diverse advanced biomedical applications. Melanins are nontoxic natural biopolymers owning widespread distribution in various biosystems, possessing fascinating physicochemical properties and playing significant physiological roles. The multifunctionality together with intrinsic biocompatibility renders bioinspired melanin-like nanomaterials considerably promising as a versatile and powerful nanoplatform with broad bioapplication prospects. This panoramic Review starts with an overview of the fundamental physicochemical properties, preparation methods, and polymerization mechanisms of melanins. A systematical and well-bedded description of recent advancements of melanin-like nanomaterials regarding diverse biomedical applications is then given, mainly focusing on biological imaging, photothermal therapy, drug delivery for tumor treatment, and other emerging biomedicine-related implementations. Finally, current challenges toward clinical translation with an emphasis on innovative design strategies and future striving directions are rationally discussed. This comprehensive and detailed Review provides a deep understanding of the current research status of melanin-like nanomaterials and is expected to motivate further optimization of the design of novel tailorable and marketable multifunctional nanoplatforms in biomedicine.