Dendritic quinary PtRhMoCoFe high-entropy alloy as a robust immunosensing nanoplatform for ultrasensitive detection of biomarker

Recently, high-entropy alloys have superior physicochemical properties as compared to conventional alloys for their glamorous "cocktail effect". Nevertheless, they are scarcely applied to electrochemical immunoassays until now. Herein, uniform PtRhMoCoFe high-entropy alloyed nanodendrites (HEANDs) were synthesized by a wet-chemical co-reduction method, where glucose and oleylamine behaved as the co-reducing agents. Then, a series of characterizations were conducted to illustrate the synergistic effect among multiple metals and fascinating structural characteristics of PtRhMoCoFe HEANDs. The obtained high-entropy alloy was adopted to build a electrochemical label-free biosensor for ultrasensitive bioassay of biomarker cTnI. In the optimized analytical system, the resultant sensor exhibited a dynamic linear range of 0.0001-200 ng mL-1 and a low detection limit of 0.0095 pg mL-1 (S/N = 3). Eventually, this sensing platform was further explored in serum samples with satisfied recovery (102.0 %). This research renders some constructive insights for synthesis of high-entropy alloys and their expanded applications in bioassays and bio-devices.

Heterostructured BiVO4/CoPi nanoarrays as high-efficiency photoanode and AuPt nanodendrites as nanozyme for sensitive sensing of miRNA 141

MicroRNA (miRNA) is a new class of tumor biomarkers in human body for early diagnosis and therapy of cancers, whose detection has scientific significance and potential applications. Herein, a sensitive heterostructured BiVO₄/CoPi photoelectrochemical (PEC) biosensor was established for sensing miRNA 141 with assistance of home-synthesized AuPt nanodendrites (NDs) as nanozyme. Specifically, the BiVO₄/CoPi heterostructures displayed rough worm-like internetworks, as characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In parallel, the PEC and UV-vis diffuse reflectance spectroscopy tests confirmed their excellent optical property, combined by discussing the interfacial electron transfer mechanism. Additionally, the AuPt NDs displayed superior peroxidase-like property in the presence of H₂O₂ as identified by benchmarked tetramethylbenzidine (TMB) oxidation, coupled by showing remarkable catalysis for 3-amino-9-ethylcarbazole (AEC) oxidation to form biocatalytic precipitation (BCP). Integrated by a cyclic enzyme strategy, the developed PEC biosensor exhibited a wider linear range of 5 fM ∼1 pM and a lower limit of detection (LOD) as low as 0.17 fM (S/N = 3). This work provides some valuable insights for sensitive analysis of tumor-associated miRNA in clinic.

Label-free electrochemical biosensor for determination of procalcitonin based on graphene-wrapped Co nanoparticles encapsulated in carbon nanobrushes coupled with AuPtCu nanodendrites

A new label-free electrochemical immunosensor was constructed for quantitative detection of procalcitonin (PCT), by employing AuPtCu nanodendrites (AuPtCu NDs, prepared by a one-pot solvothermal method) and graphene-wrapped Co nanoparticles encapsulated in 3D N-doped carbon nanobrushes (G-Co@ NCNBs), obtained by self-catalyzed chemical vapor deposition as immune-sensing platform. Impressively, the home-made nanocomposite enlarged the highly accessible active sites and promoted the mass/electron transport, in turn showing the efficient synergistic catalysis towards H₂O₂ reduction, combined by greatly increasing the loading capacity of the PCT antibody (Ab). The as-constructed sensor displayed a dynamic linear range of 0.0001 ~ 100 ng mL^-1 along with an ultra-low limit of detection (LOD = 0.011 pg mL^-1, S/N = 3) and was further explored for determination of PCT in a diluted serum sample with acceptable results. The sensor provides some valuable guidelines for bioassay and early diagnosis of sepsis.

Pt-based (Zn, Cu) nanodendrites with enhanced catalytic efficiency and durability toward methanol electro-oxidation via trace Ir-doping engineering

Pt-based alloy nanomaterials with nanodendrites (NDs) structures are efficient electrocatalysts for methanol oxidation reaction (MOR), however their durability is greatly limited by the issue of transition metals dissolution. In this work, a facile trace Ir-doping strategy was proposed to fabricate Ir-PtZn and Ir-PtCu alloy NDs catalysts in aqueous medium, which significantly improved the electrocatalytic activity and durability for MOR. The as-prepared Ir-PtZn/Cu NDs catalysts showed distinct dendrites structures with the averaged diameter of 4.1 nm, and trace Ir doping subsequently improved the utilization of Pt atoms and promoted the oxidation efficiency of methanol. The electrochemical characterizations further demonstrated that the obtained Ir-PtZn/Cu NDs possessed enhanced mass activities of nearly 1.23 and 1.28-fold higher than those of undoped PtZn and PtCu, and approximately 2.35 and 2.67-fold higher than that of Pt/C in acid medium. More excitingly, after long-term durability test, the proposed Ir-PtZn and Ir-PtCu NDs still retained about 88.9% and 91.6% of its initial mass activities, which further highlights the key role of Ir-doping in determining catalyst performance. This work suggests that trace Ir-doping engineering could be a promising way to develop advanced electrocatalysts toward MOR for direct methanol fuel cell (DMFC) applications.

RNA-mediated, green synthesis of palladium nanodendrites for catalytic reduction of nitroarenes

Palladium (Pd)-catalyzed reactions mostly show structure sensitivity: i.e., the selectivity and activity of the reactions are highly dependent on the arrangement of Pd atoms. In this regard, branched Pd nanoparticles show enhanced catalytic performance owing to the presence of low coordinated Pd atoms. In this paper, a novel solution-phase synthesis of flower-like Pd nanodendrites using ribonucleic acid (RNA) as a capping agent and ascorbic acid as a reducing agent was described. On the other hand, the co-use of polyvinylpyrrolidone (PVP) and potassium bromide (KBr) instead of RNA at the same synthesis conditions led to cuboid nanoparticles, while the sole use of ascorbic acid resulted in faceted nanoparticles. The formation of nanodendritic morphology was attributed to the RNA-assisted growth through particle attachment. This scenario was supported by TEM analysis that demonstrated the aggregation of small particles to form larger nanoparticles at the onset of the reaction. The shape and size of the nanoparticles could be readily tuned by the RNA content used. XPS confirmed the formation of metallic Pd nanoparticles. The presence of crystalline planes of {1 1 1}, {2 0 0}, {2 2 0}, {3 1 1} and {2 2 2} was demonstrated by XRD and SAED analyses. The Pd nanodendrites were used for the reduction of p-nitrophenol (PNP) and 2,4,6-trinitrotoluene (TNT), and reduction rate constants (k) were calculated as 1.078 min^-1 (normalized rate constant, k_nor = 59.66 mmol^-1 s^-1) for PNP and 0.3181 min^-1 (k_nor = 17.6 mmol^-1 s^-1) for TNT with the corresponding turnover frequencies (TOFs) as 16.06 and 40.80 h^-1, respectively.

Molecular analysis of biocompatibility of anodized titanium with deposited silver nanodendrites

Titanium (>99.6% purity) and its anodically oxidized modifications, with and without deposited silver nanodendrites regarding its biocompatibility were evaluated. In human gingival fibroblasts and osteoblast cell lines grown on tested samples, the level of expression of genes encoding αV (ITGAV) and β1 (ITGB1) integrin subunits also genes encoding focal adhesion (FAK) and extracellular-signal regulated (ERK) kinases was assessed. For this purpose, the qualitative and quantitative PCR technique was used. The expression of studied genes was dependent on the origin of cell lines and the type of evaluated material. The high expression of PBGD and ITGAV genes in fibroblasts grown on the surface of anodically modified titanium with deposited silver nanodendrites indicates potentially high biocompatibility of these samples for soft tissue cells. The high expression of the ITGB1 and ERK1 genes and the enhanced expression of the FAK gene in osteoblasts cells grown on the tested material was also observed. Summarizing, the nanocrystalline Ti modified with silver deposits showed higher biocompatibility in comparison with the conventional pure Ti samples.

Tuning photothermal properties of gold nanodendrites for in vivo cancer therapy within a wide near infrared range by simply controlling their degree of branching

Although dendritic nanoparticles have been prepared by many different methods, control over their degree of branching (DB) is still impossible, preventing us from understanding the effect of the DB on the properties of the nanodendrites as cancer therapeutics. Herein, we developed a novel seed-mediated method to prepare gold nanodendrites (AuNDs) in an organic solvent using long chain amines as a structural directing agent. We discovered that the DB could be tuned facilely by simply adjusting synthetic parameters, such as the solvent type, the type and concentration of the long chain amines. We found that DB tuning resulted in dramatic tunability in the optical properties in the near infrared (NIR) range, which led to significantly different performance in the photothermal cancer therapy. Our in vitro and in vivo studies revealed that AuNDs with a higher DB were more efficient in photothermal tumor destruction under a lower wavelength NIR irradiation. In contrast, those with a lower DB performed better in tumor destruction under a higher wavelength NIR irradiation, indicating that AuNDs of even lower DB should have even better photothermal cancer therapy efficiency within the second NIR window. Thus, the tunable optical properties of AuNDs in the NIR range allow us to selectively determine a suitable laser wavelength for the best cancer therapeutic performance.