Silver-nanoparticles as plasmon-resonant enhancers for eumelanin's photoacoustic signal in a self-structured hybrid nanoprobe

Exploring the antitumorigenic properties of agro-food byproducts: A comprehensive scientific review

Natural byproducts have garnered significant attention for their potential antitumorigenic properties. The current scenario sketched by the goals of circular economy approaches the research towards the utilization of agro-waste biomasses as valuable source of biological active metabolites. This comprehensive scientific review explores the various mechanisms through which these natural compounds exert anticancer effects, including apoptosis induction, cell cycle arrest, inhibition of angiogenesis, and suppression of metastasis. The review highlights key bioactive molecules such as polyphenols, flavonoids, alkaloids, and terpenoids, examining their molecular interactions with cancer cells. Furthermore, the potential of these natural byproducts as adjuvant therapies in combination with conventional treatments is discussed. By summarizing recent advancements and identifying future research directions, this review underscores the promise of natural byproducts from as a source of novel anticancer agents. A specific section is dedicated to outline the role of innovative materials, such as nanoparticles, hydrogels, and biopolymers, that are being developed to enhance the delivery and efficacy of active components. These carriers offer improved stability, targeted delivery, and controlled release of natural compounds, maximizing their therapeutic potential while minimizing side effects.

Potential applications for photoacoustic imaging using functional nanoparticles: A comprehensive overview

This paper presents a comprehensive overview of the potential applications for Photo-Acoustic (PA) imaging employing functional nanoparticles. The exploration begins with an introduction to nanotechnology and nanomaterials, highlighting the advancements in these fields and their crucial role in shaping the future. A detailed discussion of the various types of nanomaterials and their functional properties sets the stage for a thorough examination of the fundamentals of the PA effect. This includes a thorough chronological review of advancements, experimental methodologies, and the intricacies of the source and detection of PA signals. The utilization of amplitude and frequency modulation, design of PA cells, pressure sensor-based signal detection, and quantification methods are explored in-depth, along with additional mechanisms induced by PA signals. The paper then delves into the versatile applications of photoacoustic imaging facilitated by functional nanomaterials. It investigates the influence of nanomaterial shape, size variation, and the role of composition, alloys, and hybrid materials in harnessing the potential of PA imaging. The paper culminates with an insightful discussion on the future scope of this field, focusing specifically on the potential applications of photoacoustic (PA) effect in the domain of biomedical imaging and nanomedicine. Finally, by providing the comprehensive overview, the current work provides a valuable resource underscoring the transformative potential of PA imaging technique in biomedical research and clinical practice.

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.

Hybrid Nanoparticle-Assisted Chemo-Photothermal Therapy and Photoacoustic Imaging in a Three-Dimensional Breast Cancer Cell Model

Bioinspired nanoparticles have recently been gaining attention as promising multifunctional nanoplatforms for therapeutic applications in cancer, including breast cancer. Here, the efficiency of the chemo-photothermal and photoacoustic properties of hybrid albumin-modified nanoparticles (HSA-NPs) loaded with doxorubicin was evaluated in a three-dimensional breast cancer cell model. The HSA-NPs showed a higher uptake and deeper penetration into breast cancer spheroids than healthy breast cell 3D cultures. Confocal microscopy revealed that, in tumour spheroids incubated with doxorubicin-loaded NPs for 16 h, doxorubicin was mainly localised in the cytoplasm, while a strong signal was detectable at the nuclear level after 24 h, suggesting a time-dependent uptake. To evaluate the cytotoxicity of doxorubicin-loaded NPs, tumour spheroids were treated for up to 96 h with increasing concentrations of NPs, showing marked toxicity only at the highest concentration of doxorubicin. When doxorubicin administration was combined with laser photothermal irradiation, enhanced cytotoxicity was observed at lower concentrations and incubation times. Finally, the photoacoustic properties of doxorubicin-loaded NPs were evaluated in tumour spheroids, showing a detectable signal increasing with NP concentration. Overall, our data show that the combined effect of chemo-photothermal therapy results in a shorter exposure time to doxorubicin and a lower drug dose. Furthermore, owing to the photoacoustic properties of the NPs, this nanoplatform may represent a good candidate for theranostic applications.

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.

Plasmonic nanosensors for pharmaceutical and biomedical analysis

The detection and identification of clinical biomarkers with related sensitivity have become a source of considerable concern for biomedical analysis. There have been increasing efforts toward the development of single-molecule analytical platforms to overcome this concern. The latest developments in plasmonic nanomaterials include fascinating advances in energy, catalyst chemistry, optics, biotechnology, and medicine. Nanomaterials can be successfully applied to biomolecule and drug detection in plasmonic nanosensors for pharmaceutical and biomedical analysis. Plasmonic-based sensing technology exhibits high sensitivity and selectivity depending on surface plasmon resonance (SPR) or localized surface plasmon resonance (LSPR) phenomena. In this critical paper, we offer an overview of the methodology of the SPR, LSPR, surface-enhanced Raman scattering (SERS), surface-enhanced infrared absorption (SEIRA), surface-enhanced fluorescence (SEF), and plasmonic nanoplatforms advanced for pharmaceutical and biomedical applications. First of all, we present here a brief discussion of the above trends. We have devoted the last section to the explanation of SPR, LSPR, SERS, SEIRA, and SEF platforms, which have found a wide range of applications, and reviewed recent advances for biomedical and pharmaceutical analysis.

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.

Nanoparticles Design for Theranostic Approach in Cancer Disease

Presently, there are no conclusive treatments for many types of cancer, mainly due to the advanced phase of the disease at the time of diagnosis and to the side effects of existing therapies. Present diagnostic and therapeutic procedures need to be improved to supply early detection abilities and perform a more specific therapy with reduced systemic toxicity. In this review, improvements in nanotechnology allowing the design of multifunctional nanoparticles for cancer detection, therapy, and monitoring are reported. Nanoparticles, thanks to the nanomaterials they are made of, can be used as contrast agents for various diagnostic techniques such as MRI, optical imaging, and photoacoustic imaging. Furthermore, when used as drug carriers, they can accumulate in tumor tissues through the passive or/and active targeting, protect encapsulated drugs from degradation, raise tumor exposure to chemotherapeutic agents improving treatment effects. In addition, nanocarriers can simultaneously deliver more than one therapeutic agent enhancing the effectiveness of therapy and can co-deliver imaging and therapy agents to provide integration of diagnostics, therapy, and follow-up. Furthermore, the use of nanocarriers allows to use different therapeutic approaches, such as chemotherapy and hyperthermia to exploit synergistic effects. Theranostic approach to diagnose and treat cancer show a great potential to improve human health, however, despite technological advances in this field, the transfer into clinical practice is still a long way off.

Silica Meets Tannic Acid: Designing Green Nanoplatforms for Environment Preservation

Hybrid tannic acid-silica-based porous nanoparticles, TA-SiO2 NPs, have been synthesized under mild conditions in the presence of green and renewable tannic acid biopolymer, a glycoside polymer of gallic acid present in a large part of plants. Tannic acid (TA) was exploited as both a structuring directing agent and green chelating site for heavy metal ions recovery from aqueous solutions. Particles morphologies and porosity were easily tuned by varying the TA initial amount. The sample produced with the largest TA amount showed a specific surface area an order of magnitude larger than silica nanoparticles. The adsorption performance was investigated by using TA-SiO2 NPs as adsorbents for copper (II) ions from an aqueous solution. The effects of the initial Cu2+ ions concentration and the pH values on the adsorption capability were also investigated. The resulting TA-SiO2 NPs exhibited a different adsorption behaviour towards Cu2+, which was demonstrated through different tests. The largest adsorption (i.e., ~50 wt% of the initial Cu2+ amount) was obtained with the more porous nanoplatforms bearing a higher final TA content. The TA-nanoplatforms, stable in pH value around neutral conditions, can be easily produced and their use would well comply with a green strategy to reduce wastewater pollution.

Controlled Release of Doxorubicin for Targeted Chemo-Photothermal Therapy in Breast Cancer HS578T Cells Using Albumin Modified Hybrid Nanocarriers

Hybrid nanomaterials have attracted research interest owing to their intriguing properties, which may offer new diagnostic options with triggering features, able to realize a new kind of tunable nanotherapeutics. Hybrid silica/melanin nanoparticles (NPs) containing silver seeds (Me-laSil_Ag-HSA NPs) disclosed relevant photoacoustic contrast for molecular imaging. In this study we explored therapeutic function in the same nanoplatform. For this purpose, MelaSil_Ag-HSA were loaded with doxorubicin (DOX) (MelaSil_Ag-HSA@DOX) and tested to assess the efficiency of drug delivery combined with concurrent photothermal treatment. The excellent photothermal properties allowed enhanced cytotoxic activity at significantly lower doses than neat chemotherapeutic treatment. The results revealed that MelaSil_Ag-HSA@DOX is a promising platform for an integrated photothermal (PT) chemotherapy approach, reducing the efficacy concentration of the DOX and, thus, potentially limiting the several adverse side effects of the drug in in vivo treatments.

Photoacoustics for listening to metal nanoparticle super-aggregates

Photoacoustic signal detection has been used to build a new strategy to determine the mesoscale self-assembly of metal nanoparticles in terms of size distribution and aggregate packing density (metal nanoparticle filling factor). A synergistic approach integrating photoacoustic signal and theoretical studies, validated by conventional light scattering and electron microscopy techniques, allows us to obtain a well-defined morphological interpretation of nanoparticle-based super-aggregates. By pumping light in a complex system, the acousto-thermal effect was listened to, providing information on the aggregation phenomena. Super-aggregates of covalently interconnected silver nanoparticles (AgNPs) functionalized with an organometallic dithiol are identified in solution, as a proof of concept for the versatility of the photoacoustic approach. According to our results, tiny AgNPs (size less than 10 nm) assembled into a 3D-network of super-aggregates (SA-AgNPs) with sizes in the range 100-200 nm and a filling factor in the range of 30-50%. Low-cost, rapid, and easy photoacoustic measurement in the low frequency range (less than 100 Hz) was revealed to be an innovative method to characterize the fundamental structure/property correlation of metal nanoparticle super-aggregates. This morpho-optical approach, which uses the absorption and scattering properties of nanoparticles in the liquid phase, opens new perspectives for advanced biomedical and structural applications.

Hybrid humic acid/titanium dioxide nanomaterials as highly effective antimicrobial agents against gram(-) pathogens and antibiotic contaminants in wastewater

Humic acids (HAs) provide an important bio-source for redox-active materials. Their functional chemical groups are responsible for several properties, such as metal ion chelating activity, adsorption ability towards small molecules and antibacterial activity, through reactive oxygen species (ROS) generation. However, the poor selectivity and instability of HAs in solution hinder their application. A promising strategy for overcoming these disadvantages is conjugation with an inorganic phase, which leads to more stable hybrid nanomaterials with tuneable functionalities. In this study, we demonstrate that hybrid humic acid/titanium dioxide nanostructured materials that are prepared via a versatile in situ hydrothermal strategy display promising antibacterial activity against various pathogens and behave as selective sequestering agents of amoxicillin and tetracycline antibiotics from wastewater. A physicochemical investigation in which a combination of techniques were utilized, which included TEM, BET, ¹³C-CPMAS-NMR, EPR, DLS and SANS, shed light on the structure-property-function relationships of the nanohybrids. The proposed approach traces a technological path for the exploitation of organic biowaste in the design at the molecular scale of multifunctional nanomaterials, which is useful for addressing environmental and health problems that are related to water contamination by antibiotics and pathogens.

Nanoparticle Surface Functionalization: How to Improve Biocompatibility and Cellular Internalization

The use of nanoparticles (NP) in diagnosis and treatment of many human diseases, including cancer, is of increasing interest. However, cytotoxic effects of NPs on cells and the uptake efficiency significantly limit their use in clinical practice. The physico-chemical properties of NPs including surface composition, superficial charge, size and shape are considered the key factors that affect the biocompatibility and uptake efficiency of these nanoplatforms. Thanks to the possibility of modifying physico-chemical properties of NPs, it is possible to improve their biocompatibility and uptake efficiency through the functionalization of the NP surface. In this review, we summarize some of the most recent studies in which NP surface modification enhances biocompatibility and uptake. Furthermore, the most used techniques used to assess biocompatibility and uptake are also reported.

Engineering Plasmonic Nanoparticles for Enhanced Photoacoustic Imaging

Photoacoustic (PA) imaging is an emerging imaging modality whereby pulsed laser illumination generates pressure transients that are detectable using conventional ultrasound. Plasmonic nanoparticles such as gold nanorods and nanostars are often used as PA contrast agents. The thermoelastic expansion model best describes the PA response from plasmonic nanoparticles: Light absorption causes a small increase in temperature leading to thermoelastic expansion. The conversion of optical energy into pressure waves (po) is dependent on several features: (i) the absorption coefficient (μa), (ii) the thermal expansion coefficient (β), (iii) specific heat capacity (Cp) of the absorbing material, (iv) speed of sound in the medium (c), and (v) the illumination fluence (F). Controlling the geometry, composition, coatings, and solvents around plasmonic nanostructures can help tune these variables to generate the optimum PA signal. The thermoelastic expansion model is not limited to plasmonic structures and holds true for all absorbing molecules. Here, we focus on ways to engineer these variables to enhance the PA response from plasmonic nanoparticles.

Melanin and Melanin-Like Hybrid Materials in Regenerative Medicine

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

A Comparative Study on Physicochemical, Photocatalytic, and Biological Properties of Silver Nanoparticles Formed Using Extracts of Different Parts of Cudrania tricuspidata

Green-synthesized silver nanoparticles (SNPs) have great potential for biomedical applications, due to their distinctive optical, chemical, and catalytic properties. In this study, we aimed to develop green-synthesized SNPs from extracts of Cudrania tricuspidata (CT) roots (CTR), stems (CTS), leaves (CTL), and fruit (CTF) and to evaluate their physicochemical, photocatalytic, and biological properties. CTR, CTS, CTL, and CTF extracts were evaluated and compared for their total phenol and flavonoid content, reducing capacity, and antioxidant activity. The results revealed that CTR, CTS, CTL, and CTF extracts have high phenol and flavonoid content, as well as a powerful antioxidant and reducing capacity. CTR and CTS extracts showed the strongest effects. The results from UV-Vis spectra analysis, dynamic light scattering, high-resolution transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy showed the successful formation of CT-SNPs with surface morphology, crystallinity, reduction capacity, capsulation, and stabilization. Synthesized CT-SNPs successfully photocatalyzed methylene blue, methyl orange, rhodamine B, and Reactive Black 5 within 20 min. The CTR- and CTS-SNPs showed better antibacterial properties against different pathogenic microbes (Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Salmonella enteritidis) than the CTL- and CTF-SNPs. CTS- and CTR-SNPs showed the most effective cytotoxicity and antiapoptosis properties in human hepatocellular carcinoma cells (HepG2 and SK-Hep-1). CT-SNPs also seemed to be more biologically active than the CT extracts. The results of this study provide evidence of the establishment of CT extract SNPs and their physicochemical, photocatalytic, and biological properties.

Albumin-Modified Melanin-Silica Hybrid Nanoparticles Target Breast Cancer Cells via a SPARC-Dependent Mechanism

Bioconjugation of a recently developed photoacoustic nanoprobe, based on silica-templated eumelanin-silver hybrid nanoparticles (MelaSil_Ag-NPs), with human serum albumin (HSA) is disclosed herein as an efficient and practical strategy to improve photostability and to perform SPARC mediated internalization in breast cancer cells. Modification of NPs with HSA induced a slight viability decrease in breast cancer cells (HS578T) and normal breast cells (MCF10a) when incubated with HSA-NPs up to 100 μg/mL concentration for 72 h and a complete suppression of hemotoxicity for long incubation times. Uptake experiments with MelaSil_Ag-HSA NPs indicated very high and selective internalization via SPARC in HS578T (SPARC positive cells) but not in MCF10a (SPARC negative cells), as evaluated by using endocytosis inhibitors. The binding of SPARC to HSA was confirmed by Co-IP and Dot-blot assays. Additional studies were performed to analyze the interaction of MelaSil_Ag-HSA NPs with protein corona. Data showed a dramatic diminution of interacting proteins in HSA conjugated NPs compared to bare NPs. HSA-coated MelaSil_Ag-NPs are thus disclosed as a novel functional nanohybrid for potential photoacoustic imaging applications.

Ellagic acid-Fe nanoscale coordination polymer with higher longitudinal relaxivity for dual-modality T1-weighted magnetic resonance and photoacoustic tumor imaging

Dual-modality contrast agents for T₁-weighted magnetic resonance imaging (MRI) and photoacoustic imaging have attracted substantial attention as they combine the advantages of unlimited penetration depth and high sensitivity. However, most of the reported agents are Gd-based materials that exhibit nephrotoxicity, and few studies have focused on Fe-based materials owing to their lower relaxivity. This work describes the development of an ellagic acid (EA)-Fe nanoscale coordination polymer with high longitudinal relaxivity and strong near-infrared absorption for dual-modality T₁-weighted MRI and photoacoustic imaging. The longitudinal relaxivity (r₁) of the prepared EA-Fe@BSA nanoparticles was 2.54 mM^-1 s^-1, an increase of 185% compared with previously reported gallic acid-Fe nanoparticles. Furthermore, in vitro and in vivo experiments demonstrate that the EA-Fe@BSA NPs are an excellent T₁-weighted MRI and photoacoustic dual-modality contrast agent with the advantages of convenient synthesis and low toxicity, exhibiting great potential for clinical use in tumor imaging.

Improving Interaction at Polymer-Filler Interface: The Efficacy of Wrinkle Texture

One of the main issues in preparing polymer-based nanocomposites with effective properties is to achieve a good dispersion of the nanoparticles into the matrix. Chemical interfacial modifications by specific coupling agents represents a good way to reach this objective. Actually, time consuming compatibilization procedures strongly compromise the sustainability of these strategies. In this study, the role of particles' architectures in their dispersion into a poly-lactic acid matrix and their subsequent influences on physical-chemical properties of the obtained nanocomposites were investigated. Two kinds of silica nanoparticles, "smooth" and "wrinkled," with different surface areas (≈30 and ≈600 m2/g respectively) were synthesized through a modified Stöber method and used, without any chemical surface pre-treatments, as fillers to produce poly-lactic acid based nanocomposites. The key role played by wrinkled texture in modifying the physical interaction at the polymer-filler interface and in driving composite properties, was investigated and reflected in the final bulk properties. Detailed investigations revealed the presence of wrinkled nanoparticles, leading to (i) an enormous increase of the chain relaxation time, by almost 30 times compared to the neat PLA matrix; (ii) intensification of the shear-thinning behavior at low shear-rates; and (iii) slightly slower thermal degradation of polylactic acid.

PEGylated Tantalum Nanoparticles: A Metallic Photoacoustic Contrast Agent for Multiwavelength Imaging of Tumors

Elemental tantalum is a well-known biomedical metal in clinics due to its extremely high biocompatibility, which is superior to that of other biomedical metallic materials. Hence, it is of significance to expand the scope of biomedical applications of tantalum. Herein, it is reported that tantalum nanoparticles (Ta NPs), upon surface modification with polyethylene glycol (PEG) molecules via a silane-coupling approach, are employed as a metallic photoacoustic (PA) contrast agent for multiwavelength imaging of tumors. By virtue of the broad optical absorbance from the visible to near-infrared region and high photothermal conversion efficiency (27.9%), PEGylated Ta NPs depict high multiwavelength contrast capability for enhancing PA imaging to satisfy the various demands (penetration depth, background noise, etc.) of clinical diagnosis as needed. Particularly, the PA intensity of the tumor region postinjection is greatly increased by 4.87, 7.47, and 6.87-fold than that of preinjection under 680, 808, and 970 nm laser irradiation, respectively. In addition, Ta NPs with negligible cytotoxicity are capable of eliminating undesirable reactive oxygen species, ensuring the safety for biomedical applications. This work introduces a silane-coupling strategy for the surface engineering of Ta NPs, and highlights the potential of Ta NPs as a biocompatible metallic contrast agent for multiwavelength photoacoustic image.