Ultrathin Nanosheet-Supported Ag@Ag2O Core-Shell Nanoparticles with Vastly Enhanced Photothermal Conversion Efficiency for NIR-II-Triggered Photothermal Therapy

Self-assembled IR dye/mitoxantrone loaded Porphysomes nanosystem for enhanced combinatorial chemo-photothermal cancer therapy

Chemo-photothermal therapy (PTT) is an emerging non-invasive cancer treatment modality. Light-responsive porphysomes (DPP IR Mtx @Lipo NPs) nanosystems ablate breast cancer cells upon oxidative stress and hyperthermia. The unique self-assembled porphysomes were formed spherical shape in the size range of 150 ± 30 nm formed by the co-assembly of porphyrins along with IR 775 and chemotherapeutic drug, Mitoxantrone (Mtx), forming a camouflaged nanosystem (DPP IR Mtx @Lipo NPs, porphysomes). The advent of the prepared porphysomes aids in proper tuning of NIR absorbance improving singlet oxygen species generation among other anticancer drugs. The eminent release of DPP and adjuvant chemo-drug, Mitoxantrone from the self-assembled porphysomes is triggered by IR 775, a NIR photosensitizer upon laser irradiation. These multifunctional DPP IR Mtx @Lipo NPs have an efficient photothermal conversion efficiency of 65.8% as well as bioimaging properties. In-vitro studies in 2D and 3D models showed a significant cell death of 4T1 cells via the apoptotic pathway when irradiated with NIR laser, causing minimal damage to nearby healthy cells. DPP IR Mtx @Lipo NPs exhibited commingled PDT/PTT interdependent via NIR laser exposure, leading to mitochondrial disruption. Interestingly, the transient transfection using p53-GFP in cancer cells followed by DPP IR Mtx @Lipo NPs treatment causes rapid cell death. The activation of p53-dependent apoptosis pathways was vividly expressed, evidenced by the upregulation of Bax and increased pattern of Caspase-3 cleavage. This effect was pronounced upon transfection and induction with DPP IR Mtx @Lipo NPs, particularly in comparison to non-transfected malignant breast cancer 4T1 cells.

A colorimetric biosensor with infrared sterilization based on CuSe nanoparticles for the detection of E. coli O157:H7 in food samples

It is critical to develop quick, accurate, and efficient sterilization for detecting Escherichia coli O157:H7 in order to prevent infections and outbreaks of foodborne illnesses. Herein, we established a colorimetric biosensor with sterilizing properties using copper selenide nanoparticles to detect E. coli O157:H7. The sample was mixed with magnetic nanoprobes and nanozyme probes to form a sandwich structure, and then the unbound nanozyme probes were collected by magnetic separation. Finally, the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate)-hydrogen peroxide (H2O2) reporting system was added for signal amplification. The change from colorless to green can be seen with the naked eye. Under the optimal conditions, the detection range of E. coli O157:H7 was 102-106 CFU/mL, and the detection limit was 0.35 × 102 CFU/mL. The total detection time was 80 minutes, which can be successfully applied to milk and mineral water. In addition, the colorimetric sensor can kill the target bacteria by irradiating it under a 980-nm laser for 5 minutes. In conclusion, this sensor is a promising tool for rapidly detecting foodborne pathogens and promptly eliminating bacteria.

IMPORTANCE

Escherichia coli O157:H7 is a major threat to public health. At present, the detection methods for E. coli O157:H7 mainly include traditional bacterial culture, immunology (enzyme-linked immune-sorbent assay) and molecular biology techniques (polymerase chain reaction). These methods have the limitations of professional operation, waste of time and energy, and high cost. Therefore, we have developed a simple, fast, bactericidal colorimetric biosensor to detect E. coli. O157:H7. The entire process was completed in 80 minutes. The method has been successfully applied to milk and mineral water samples with satisfactory results, proving that the method is an effective method for real-time detection and inactivation of bacteria.

Synthesis of Structure-Adjustable R-Au/Pt-CdS Nanohybrids with Strong Plasmon Coupling and Improved Photothermal Conversion Performance

Noble metal nanomaterials with a localized surface plasmon resonance effect exhibit outstanding advantages in areas such as photothermal therapy and photocatalysis. As a unique plasmonic metal nanostructure, gold nanobipyramids have been attracting much interest due to their strong specific local electric field intensity, large optical cross sections, and high refractive index sensitivity. In this study, we propose a novel three-component hetero-nanostructure composed of rough gold nanobipyramids (R-Au NBPs), Pt, and CdS. Initially, purified gold nanobipyramids are regrown to form R-Au NBPs that have a certain degree of roughness. These R-Au NBP substrates with a rough surface provide more hotspots and strengthen the intensity of localized electric fields. Subsequently, Pt and CdS nanoparticles are selectively deposited onto the surface of R-Au NBPs. Pt nanoparticles can provide more active sites. Each component of this hetero-nanostructure directly contacts others, creating multiple electron transfer channels. This novel design allows for tunable localized plasmon resonance wavelengths ranging from the visible to near-infrared regions. These factors contribute to the final superior photothermal conversion performance of the R-Au/Pt-CdS nanohybrids. Under the irradiation of near-infrared light (1064 nm), the photothermal conversion efficiency of R-Au/Pt-CdS reached 38.88%, which is 4.49, 1.5, and 1.22 times higher than that of Au NBPs, R-Au NBPs, and R-Au NBPs/Pt, respectively.

Layered Double Hydroxides: Recent Progress and Promising Perspectives Toward Biomedical Applications

Layered double hydroxides (LDHs) have been widely studied for biomedical applications due to their excellent properties, such as good biocompatibility, degradability, interlayer ion exchangeability, high loading capacity, pH-responsive release, and large specific surface area. Furthermore, the flexibility in the structural composition and ease of surface modification of LDHs makes it possible to develop specifically functionalized LDHs to meet the needs of different applications. In this review, the recent advances of LDHs for biomedical applications, which include LDH-based drug delivery systems, LDHs for cancer diagnosis and therapy, tissue engineering, coatings, functional membranes, and biosensors, are comprehensively discussed. From these various biomedical research fields, it can be seen that there is great potential and possibility for the use of LDHs in biomedical applications. However, at the same time, it must be recognized that the actual clinical translation of LDHs is still very limited. Therefore, the current limitations of related research on LDHs are discussed by combining limited examples of actual clinical translation with requirements for clinical translation of biomaterials. Finally, an outlook on future research related to LDHs is provided.

Atomically dispersed silver atoms incorporated in spinel cobalt oxide (Co3O4) for boosting oxygen evolution reaction

Incorporating noble metal single atoms into lattice of spinel cobalt oxide (Co3O4) is an attractive way to fabricate oxygen evolution reaction (OER) electrocatalysts because of the high activity and economic benefit. The commonly used high valence noble metal dopants such as ruthenium, iridium and rhodium tend to supersede Co3+ at octahedral site of Co3O4 and result in great activity, the origins of admirable activity were also wildly investigated. However, bare explorations on doping noble metal single atom into tetrahedral site of Co3O4 to construct OER catalyst have been reported, corresponding catalytic activity and mechanism remain mystery. Here, a promising structure that tetrahedrally substituent Ag single atom embedded in Co3O4 nanoparticles on the surface of carbon nanotube (Ag-Co3O4/CNT) was presented, and its performance in OER was probed. The high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption spectroscopy (XAS) demonstrate the successful embeddedness of atomical Ag atom in Co3O4 lattice, the resultant electronic interaction is conducive to promote charge transfer for OER. Theoretical calculations further disclose that atomical Ag dopant prefers to replace tetrahedral Co2+ rather than octahedral Co3+. The substitution Ag acts as the active site through Ag-Co bridge and facilitates the desorption process, which improves the turnover frequency (TOF) and boosts the intrinsic activity of Ag-Co3O4/CNT. Benefiting from the essentials above, Ag-Co3O4/CNT displays remarkable activity (236 mV@10 mA cm-2) and robust stability for alkaline OER. This finding offers a potential direction for the design of noble metal single atom involved Co3O4 based OER electrocatalysts.

Developing Single-Atomic Manganese Nanozymes for Synergistic Mild Photothermal/Multienzymatic Therapy

Synergistic mild photothermal/nanozyme therapy with outstanding hyperthermia performance and excellent multienzyme properties is highly needed for osteosarcoma treatment. Herein, we have developed efficient single-atom nanozymes (SANs) consisting of Mn sites atomically dispersed on nitrogen-doped carbon nanosheets (denoted as Mn-SANs) for synergistic mild photothermal/multienzymatic therapy against osteosarcoma. Benefiting from their black N-doped carbon nanosheet matrices, Mn-SANs showed an excellent NIR-II-triggered photothermal effect. On the other hand, Mn-SANs with atomically dispersed Mn sites have outstanding multienzyme activities. Mn-SANs can catalyze endogenous H2O2 in osteosarcoma into O2 by catalase (CAT)-like activity, which can effectively ease osteosarcoma hypoxia and trigger the oxidase (OXD)-like catalysis that converts O2 to the cytotoxic superoxide anion radical (•O2-). At the same time, Mn-SANs can also mimic glutathione oxidase (GSHOx) to effectively consume the antioxidant glutathione (GSH) in osteosarcoma and inhibit intracellular glutathione peroxidase 4 (GPX4) expression. Such intratumoral •O2- production, GSH depletion, and GPX4 inactivation mediated by Mn-SANs can create a large accumulation of lipid peroxides (LPO) and •O2-, leading to oxidative stress and disrupting the redox homeostasis in osteosarcoma cells, which can ultimately induce osteosarcoma cell death. More importantly, heat shock proteins (HSPs) can be significantly destroyed via Mn-SAN-mediated plentiful LPO and •O2- generation, thus effectively impairing osteosarcoma cells resistant to mild photothermal therapy. Overall, through the cooperative effect of chemical processes (boosting •O2-, consuming GSH, and enhancing LPO) and biological processes (inactivating GPX4 and hindering HSPs), collaborative mild photothermal/multienzymatic therapy mediated by Mn-SANs is a promising strategy for efficient osteosarcoma treatment.

Nanoarchitecture-based photothermal ablation of cancer: A systematic review

Photothermal therapy (PTT) is an emerging non-invasive method used in cancer treatment. In PTT, near-infrared laser light is absorbed by a chromophore and converted into heat within the tumor tissue. PTT for cancer usually combines a variety of interactive plasmonic nanomaterials with laser irradiation. PTT enjoys PT agents with high conversion efficiency to convert light into heat to destroy malignant tissue. In this review, published studies concerned with the use of nanoparticles (NPs) in PTT were collected by a systematic and comprehensive search of PubMed, Cochrane, Embase, and Scopus databases. Gold, silver and iron NPs were the most frequent choice in PTT. The use of surface modified NPs allowed selective delivery and led to a precise controlled increase in the local temperature. The presence of NPs during PTT can increase the reactive generation of oxygen species, damage the DNA and mitochondria, leading to cancer cell death mainly via apoptosis. Many studies recently used core-shell metal NPs, and the effects of the polymer coating or ligands targeted to specific cellular receptors in order to increase PTT efficiency were often reported. The effective parameters (NP type, size, concentration, coated polymers or attached ligands, exposure conditions, cell line or type, and cell death mechanisms) were investigated individually. With the advances in chemical synthesis technology, NPs with different shapes, sizes, and coatings can be prepared with desirable properties, to achieve multimodal cancer treatment with precision and specificity.

Numerical study on optimization of quantitative treatment conditions for skin cancer photothermal therapy considering multiple blood vessels

BACKGROUND

In recent years, lasers have gained considerable attention as a potential treatment option in the medical field. Photothermal therapy, in particular, has been investigated as a technique to remove tumor tissue by leveraging photothermal effects. The method involves raising the temperature of the tumor tissue to destroy it and has primarily been studied for skin cancer treatment.

OBJECTIVE

This study aimed to simulate a skin layer with squamous cell carcinoma by using numerical modeling and investigate the effect of different numbers of blood vessels on the temperature distribution in the medium under conditions such as varied laser intensity and gold nanoparticle volume fraction.

METHODS

Optical properties of the light absorption enhancer were calculated using the discrete dipole approximation method, and the temperature and velocity distribution were computed using continuity, momentum, and energy equations.

RESULTS

Quantitative determination of the apoptotic variable was performed to evaluate the treatment effect for each case, and the treatment condition with the maximum treatment effect was identified. Laser intensity with optimal therapeutic effect was confirmed to be 0.13 W, 0.15 W, 0.18 W, and 0.24 W, depending on the number of vessels, respectively, and the volume fraction of injected GNRs was confirmed to be 10-6 for all vessel numbers.

CONCLUSION

The results of this study can serve as a guide for selecting appropriate treatment conditions when conducting photothermal therapy in the future.

Multifunctional Antibacterial Nanoplatform Bi2WO6:Nd3+/Yb3+/Er3+@MoS2 with Self-Monitoring Photothermal and Photodynamic Treatment

Synergistic therapy combining photothermal therapy and photodynamic therapy is considered to be a promising approach to treat cancer, but the precise temperature control of deep tissue remains a great challenge in achieving effective treatment. Herein, a two-dimensional Bi2WO6:Nd3+/Yb3+/Er3+@MoS2 nanoplatform with photothermal and photodynamic functions was constructed, where semiconductor MoS2 serves as both a photothermal agent and a photosensitizer. The photothermal conversion performance and the reactive oxygen species generation capacity of the nanoplatform were validated under the irradiation of 808 nm laser; meanwhile, the two sets of luminescence intensity ratios (IYb3+/INd3+ and IEr3+/INd3+) in the biological window region were selected as near-infrared temperature probes to monitor the heat generated during the photosynergistic process in real time. The feasibility of nanoplatform as an intratissue temperature probe and antibacterial agent was further assessed by vitro experiments, which provides an idea for designing multifunctional photosynergistic therapy nanoplatform.

Defect Engineering in Biomedical Sciences

With the promotion of nanochemistry research, large numbers of nanomaterials have been applied in vivo to produce desirable cytotoxic substances in response to endogenous or exogenous stimuli for achieving disease-specific therapy. However, the performance of nanomaterials is a critical issue that is difficult to improve and optimize under biological conditions. Defect-engineered nanoparticles have become the most researched hot materials in biomedical applications recently due to their excellent physicochemical properties, such as optical properties and redox reaction capabilities. Importantly, the properties of nanomaterials can be easily adjusted by regulating the type and concentration of defects in the nanoparticles without requiring other complex designs. Therefore, this tutorial review focuses on biomedical defect engineering and briefly discusses defect classification, introduction strategies, and characterization techniques. Several representative defective nanomaterials are especially discussed in order to reveal the relationship between defects and properties. A series of disease treatment strategies based on defective engineered nanomaterials are summarized. By summarizing the design and application of defective engineered nanomaterials, a simple but effective methodology is provided for researchers to design and improve the therapeutic effects of nanomaterial-based therapeutic platforms from a materials science perspective.

Bimetallic core-shell nanocrystals: opportunities and challenges

With mastery over the colloidal synthesis of monometallic nanocrystals, a combination of two distinct metals with intricate architectures has emerged as a new direction of innovation. Among the diverse architectures, the one with a core-shell structure has attracted the most scientific endeavors owing to its merits of high controllability and variability. Along with the new hopes arising from the addition of a shell composed of a different metal, there comes unexpected complications for the surface composition, hindering both structural understanding and application performance. In this Focus article, we present a brief overview of the opportunities provided by the bimetallic core-shell nanocrystals, followed by a discussion of the technical challenge to elucidate the true composition of the outermost surface. Some of the promising solutions are then highlighted as well, aiming to inspire future efforts toward this frontier of research.

Radiation synthesis of MXene/Ag nanoparticle hybrids for efficient photothermal conversion of polyurethane films

Flexible conductive films based on light-to-heat conversion are promising for the next-generation electronic devices. A flexible waterborne polyurethane composite film (PU/MA) with excellent photothermal conversion performance was obtained by combination of PU and silver nanoparticle decorated MXene (MX/Ag). The silver nanoparticles (AgNPs) uniformly decorated on the MXene surface by γ-ray irradiation induced reduction. Because of the synergistic effect of MXene with outstanding light-to-heat conversion efficiency and the AgNPs with plasmonic effect, the surface temperature of the PU/MA-II (0.4%) composite with lower MXene content increased from room temperature to 60.7 °C at 5 min under 85 mW cm^-2 light irradiation. Besides, the tensile strength of PU/MA-II (0.4%) increased from 20.9 MPa (pure PU) to 27.5 MPa. The flexible PU/MA composite film shows great potential in the field of thermal management of flexible wearable electronic devices.

Ag/Ag2O with NIR-Triggered Antibacterial Activities: Photocatalytic Sterilization Enhanced by Low-Temperature Photothermal Effect

Purpose

A synergistic antibacterial system employing photocatalytic performance and low-temperature photothermal effect (LT-PTT) with the potential for infectious skin wound healing promotion was developed.

Methods

Ag/Ag₂O was synthesized with a two-step method, and its physicochemical properties were characterized. After its photocatalytic performance and photothermal effect were evaluated under 0.5 W/cm² 808 nm NIR laser irradiation, its antibacterial activities in both planktonic and biofilm forms were then studied in vitro targeting Staphylococcus Aureus (S. aureus), and the biocompatibility was tested with L-929 cell lines afterward. Finally, the animal model of dorsal skin wound infection was established on Sprague-Dawley rats and was used to assess infectious wound healing promotion of Ag/Ag₂O in vivo.

Results

Ag/Ag₂O showed boosted photocatalytic performance and local temperature accumulation compared with Ag₂O when exposed to 0.5 W/cm² 808 nm NIR irradiation, which therefore endowed Ag/Ag₂O with the ability to kill pathogens rapidly and cleavage bacterial biofilm in vitro. Furthermore, after treatment with Ag/Ag₂O and 0.5 W/cm² 808 nm NIR irradiation, infectious wounds of rats realized skin tissue regeneration from a histochemical level.

Conclusion

By exhibiting excellent NIR-triggered photocatalytic sterilization ability enhanced by low-temperature photothermal effect, Ag/Ag₂O was promising to be a novel, photo-responsive antibacterial agent.

Advances in Single-component inorganic nanostructures for photoacoustic imaging guided photothermal therapy

Phototheranostic based on photothermal therapy (PTT) and photoacoustic imaging (PAI), as one of avant-garde medical techniques, have sparked growing attention because it allows noninvasive, deeply penetrative, and highly selective and effective therapy. Among a variety of phototheranostic nanoagents, single-component inorganic nanostructures are found to be novel and attractive PAI and PTT combined nanotheranostic agents and received tremendous attention, which not only exhibit structural controllability, high tunability in physiochemical properties, size-dependent optical properties, high reproducibility, simple composition, easy functionalization, and simple synthesis process, but also can be endowed with multiple therapeutic and imaging functions, realizing the superior therapy result along with bringing less foreign materials into body, reducing systemic side effects and improving the bioavailability. In this review, according to their synthetic components, conventional single-component inorganic nanostructures are divided into metallic nanostructures, metal dichalcogenides, metal oxides, carbon based nanostructures, upconversion nanoparticles (UCNPs), metal organic frameworks (MOFs), MXenes, graphdiyne and other nanostructures. On the basis of this category, their detailed applications in PAI guide PTT of tumor treatment are systematically reviewed, including synthesis strategies, corresponding performances, and cancer diagnosis and therapeutic efficacy. Before these, the factors to influence on photothermal effect and the principle of in vivo PAI are briefly presented. Finally, we also comprehensively and thoroughly discussed the limitation, potential barriers, future perspectives for research and clinical translation of this single-component inorganic nanoagent in biomedical therapeutics.

Nanoparticles and Nanomaterials-Based Recent Approaches in Upgraded Targeting and Management of Cancer: A Review

Along with the extensive improvement in tumor biology research and different therapeutic developments, cancer remains a dominant and deadly disease. Tumor heterogeneity, systemic toxicities, and drug resistance are major hurdles in cancer therapy. Chemotherapy, radiotherapy, phototherapy, and surgical therapy are some prominent areas of cancer treatment. During chemotherapy for cancer, chemotherapeutic agents are distributed all over the body and also damage normal cells. With advancements in nanotechnology, nanoparticles utilized in all major areas of cancer therapy offer the probability to advance drug solubility, and stability, extend drug half-lives in plasma, reduce off-target effects, and quintessence drugs at a target site. The present review compiles the use of different types of nanoparticles in frequently and recently applied therapeutics of cancer therapy. A recent area of cancer treatment includes cancer stem cell therapy, DNA/RNA-based immunomodulation therapy, alteration of the microenvironment, and cell membrane-mediated biomimetic approach. Biocompatibility and bioaccumulation of nanoparticles is the major impediment in nano-based therapy. More research is required to develop the next generation of nanotherapeutics with the incorporation of new molecular entities, such as kinase inhibitors, siRNA, mRNA, and gene editing. We assume that nanotherapeutics will dramatically improve patient survival, move the model of cancer treatment, and develop certainty in the foreseeable future.

Vacancy defect-promoted nanomaterials for efficient phototherapy and phototherapy-based multimodal Synergistic Therapy

Phototherapy and multimodal synergistic phototherapy (including synergistic photothermal and photodynamic therapy as well as combined phototherapy and other therapies) are promising to achieve accurate diagnosis and efficient treatment for tumor, providing a novel opportunity to overcome cancer. Notably, various nanomaterials have made significant contributions to phototherapy through both improving therapeutic efficiency and reducing side effects. The most key factor affecting the performance of phototherapeutic nanomaterials is their microstructure which in principle determines their physicochemical properties and the resulting phototherapeutic efficiency. Vacancy defects ubiquitously existing in phototherapeutic nanomaterials have a great influence on their microstructure, and constructing and regulating vacancy defect in phototherapeutic nanomaterials is an essential and effective strategy for modulating their microstructure and improving their phototherapeutic efficacy. Thus, this inspires growing research interest in vacancy engineering strategies and vacancy-engineered nanomaterials for phototherapy. In this review, we summarize the understanding, construction, and application of vacancy defects in phototherapeutic nanomaterials. Starting from the perspective of defect chemistry and engineering, we also review the types, structural features, and properties of vacancy defects in phototherapeutic nanomaterials. Finally, we focus on the representative vacancy defective nanomaterials recently developed through vacancy engineering for phototherapy, and discuss the significant influence and role of vacancy defects on phototherapy and multimodal synergistic phototherapy. Therefore, we sincerely hope that this review can provide a profound understanding and inspiration for the design of advanced phototherapeutic nanomaterials, and significantly promote the development of the efficient therapies against tumor.

Molybdenum blue mediated photothermal immunoassay for CEA detection based on Ag4P2O7@Ag nanocomposites

A photothermal immunoassay was built for tumor marker detection based on Ag₄P₂O₇@Ag nanocomposites. Ag₄P₂O₇@Ag nanomaterials were synthesized by precipitation-photoreduction reaction, and characterized by transmission electron microscope (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectra (XPS) and X-ray powder diffraction (XRD). Come about PO₄^3- derived from Ag₄P₂O₇@Ag under acidic conditions react with ammonium molybdate in the action of reductant generating molybdenum blue. The photothermal change is due to molybdenum blue solution depending on the concentration of carcinoembryonic antigen (CEA) in immunoassay. Under optimal conditions, there is a linear relation between ΔT and CEA concentration in the range of 1 pg mL^-1-40 ng mL^-1 with the detection limit of 0.33 pg mL^-1. Meanwhile, the developed photothermal immunoassay displays preferable selectivity, repeatability, and stability.

Optimization of Photothermal Therapy Treatment Effect under Various Laser Irradiation Conditions

The photothermal effect refers to a phenomenon in which light energy is converted into heat energy, and in the medical field, therapeutics based on this phenomenon are used for anticancer treatment. A new treatment technique called photothermal therapy kills tumor tissue through a temperature increase and has the advantages of no bleeding and fast recovery. In this study, the results of photothermal therapy for squamous cell carcinoma in the skin layer were analyzed numerically for different laser profiles, intensities, and radii and various concentrations of gold nanoparticles (AuNPs). According to the heat-transfer theory, the temperature distribution in the tissue was calculated for the conditions under which photothermal therapy was performed, and the therapeutic effect was quantitatively confirmed through three apoptotic variables. In addition, the laser intensity and the volume fraction of AuNPs were optimized, and the results provide useful criteria for optimizing the treatment effects in photothermal therapy.

Synthetic Approaches to Colloidal Nanocrystal Heterostructures Based on Metal and Metal-Oxide Materials

Composite inorganic nanoarchitectures, based on combinations of distinct materials, represent advanced solid-state constructs, where coexistence and synergistic interactions among nonhomologous optical, magnetic, chemical, and catalytic properties lay a basis for the engineering of enhanced or even unconventional functionalities. Such systems thus hold relevance for both theoretical and applied nanotechnology-based research in diverse areas, spanning optics, electronics, energy management, (photo)catalysis, biomedicine, and environmental remediation. Wet-chemical colloidal synthetic techniques have now been refined to the point of allowing the fabrication of solution free-standing and easily processable multicomponent nanocrystals with sophisticated modular heterostructure, built upon a programmed spatial distribution of the crystal phase, composition, and anchored surface moieties. Such last-generation breeds of nanocrystals are thus composed of nanoscale domains of different materials, assembled controllably into core/shell or heteromer-type configurations through bonding epitaxial heterojunctions. This review offers a critical overview of achievements made in the design and synthetic elaboration of colloidal nanocrystal heterostructures based on diverse associations of transition metals (with emphasis on plasmonic metals) and transition-metal oxides. Synthetic strategies, all leveraging on the basic seed-mediated approach, are described and discussed with reference to the most credited mechanisms underpinning regioselective heteroepitaxial deposition. The unique properties and advanced applications allowed by such brand-new nanomaterials are also mentioned.