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

Construction of lymph nodes-targeting tumor vaccines by using the principle of DNA base complementary pairing to enhance anti-tumor cellular immune response

Tumor vaccines, a crucial immunotherapy, have gained growing interest because of their unique capability to initiate precise anti-tumor immune responses and establish enduring immune memory. Injected tumor vaccines passively diffuse to the adjacent draining lymph nodes, where the residing antigen-presenting cells capture and present tumor antigens to T cells. This process represents the initial phase of the immune response to the tumor vaccines and constitutes a pivotal determinant of their effectiveness. Nevertheless, the granularity paradox, arising from the different requirements between the passive targeting delivery of tumor vaccines to lymph nodes and the uptake by antigen-presenting cells, diminishes the efficacy of lymph node-targeting tumor vaccines. This study addressed this challenge by employing a vaccine formulation with a tunable, controlled particle size. Manganese dioxide (MnO2) nanoparticles were synthesized, loaded with ovalbumin (OVA), and modified with A50 or T20 DNA single strands to obtain MnO2/OVA/A50 and MnO2/OVA/T20, respectively. Administering the vaccines sequentially, upon reaching the lymph nodes, the two vaccines converge and simultaneously aggregate into MnO2/OVA/A50-T20 particles through base pairing. This process enhances both vaccine uptake and antigen delivery. In vitro and in vivo studies demonstrated that, the combined vaccine, comprising MnO2/OVA/A50 and MnO2/OVA/T20, exhibited robust immunization effects and remarkable anti-tumor efficacy in the melanoma animal models. The strategy of controlling tumor vaccine size and consequently improving tumor antigen presentation efficiency and vaccine efficacy via the DNA base-pairing principle, provides novel concepts for the development of efficient tumor vaccines.

The Convenience of Polydopamine in Designing SERS Biosensors with a Sustainable Prospect for Medical Application

Polydopamine (PDA) is a multifunctional biomimetic material that is friendly to biological organisms and the environment, and surface-enhanced Raman scattering (SERS) sensors have the potential to be reused. Inspired by these two factors, this review summarizes examples of PDA-modified materials at the micron or nanoscale to provide suggestions for designing intelligent and sustainable SERS biosensors that can quickly and accurately monitor disease progression. Undoubtedly, PDA is a kind of double-sided adhesive, introducing various desired metals, Raman signal molecules, recognition components, and diverse sensing platforms to enhance the sensitivity, specificity, repeatability, and practicality of SERS sensors. Particularly, core-shell and chain-like structures could be constructed by PDA facilely, and then combined with microfluidic chips, microarrays, and lateral flow assays to provide excellent references. In addition, PDA membranes with special patterns, and hydrophobic and strong mechanical properties can be used as independent platforms to carry SERS substances. As an organic semiconductor material capable of facilitating charge transfer, PDA may possess the potential for chemical enhancement in SERS. In-depth research on the properties of PDA will be helpful for the development of multi-mode sensing and the integration of diagnosis and treatment.

pH-responsive Glucosamine Anchored Polydopamine Coated Mesoporous Silica Nanoparticles for delivery of Anderson-type Polyoxomolybdate in Breast Cancer

AIM

This study aimed to develop novel pH-sensitive Glucosamine (Glu) targeted Polydopamine (PDA) coated mesoporous silica (SBA-15) nanoparticles (NPs) for selective delivery of anticancer Anderson-type manganese polyoxomolybdate (POMo) to breast cancer.

METHODS

The POMo@SBA-PDA-Glu NPs were prepared via direct hydrothermal synthesis of SBA, POMo loading, in situ PDA post functionalization, and Glu anchoring; the chemical structures were fully studied by different characterization methods. The anticancer activity was studied by MTT method and Annexin V-FITC apoptosis detection kit.

RESULTS

The optimized NPs had a hydrodynamic size (HS) of 195 nm, a zeta potential (ZP) of -18.9 mV, a loading content percent (LC%) of 45%, and a pH-responsive release profile. The targeted NPs showed increased anticancer activity against breast cancer cell lines compared to the free POMo with the highest cellular uptake and apoptosis level in the MDA-MB-231 cells.

CONCLUSIONS

POMo@SBA-PDA-Glu NPs could be a promising anticancer candidate for further studies.

Hydrazide-assisted directional antibody conjugation of gold nanoparticles to enhance immunochromatographic assay

The analytical performance of immunochromatographic assay (ICA) is usually determined by the biological activity of antibody and gold nanoparticle conjugates (AuNP probes). However, conventional probes are constructed using the nondirectional coupling method that can cause the improper orientation of antibodies with the poor accessibility of antigen-binding sites. To address these issues, we report a site-specific directional coupling strategy to enhance the bioactivity of AuNP probes through the specific covalent binding of the aldehyde group in the Fc domain of antibodies with the hydrazide group modified on the surface of AuNPs. Through this design, the antibodies can be erected on the AuNP surface to fully expose the Fab domain and achieve the maximized functional availability. Leveraging these AuNP probes as ICA labels, we demonstrate an improved detection of the hepatitis B surface antigen with less used amount of labeled antibody (0.2 mg/pmol AuNPs), shorter reaction time (10 min), better antibody bioactivity, and higher detection sensitivity (2 ng/mL) compared with the carbodiimide method. Overall, this work provides great promise for the design and the construction of high-performance probes to enhance the detection performance of ICA sensors.

A sensitive electrochemical DNA sensor for detecting Helicobacter pylori based on accordion-like Ti3C2Tx: a simple strategy

A novel electrochemical DNA sensor was designed to detect Helicobacter pylori based on accordion-like Ti₃C₂T_x. Here the multilayer Ti₃C₂T_x obtained by DMSO delamination was used to modify the glass carbon electrode, with a large specific surface area and excellent conductivity. Au nanoparticles were supported on the modified electrode and worked as an effective carrier to fix the capture probe (cpDNA) with sulfhydryl group through the firm binding of Au-S bond. Such an accordion-like Ti₃C₂T_x structure provides an ultrahigh electroactive surface area and ample binding sites for accommodating Au nanoparticles, which is advantageous for the signal amplification during the detection. And further, the sandwich structure formed by hybridizing cpDNA with target DNA sequence (tDNA) and rpDNA (rpDNA is a strand of DNA that can be base-paired with the tested tDNA) increases greatly the current signal and enhances the sensitivity of the electrochemical DNA sensor. Under optimal conditions, the developed electrochemical DNA sensor showed a wide linear range from 10^-11 to 10^-14 M and a low detection limit of 1.6 × 10^-16 M and exhibited good sensitivity, reproducibility, and stability. A novel electrochemical DNA sensor with simple sandwich structure was designed to detect H. pylori based on accordion-like Ti₃C₂T_x.

Hierarchical Gold Mesoflowers in Enzyme Engineering: An Environmentally Friendly Strategy for the Enhanced Enzymatic Performance and Biodiesel Production

To expand the field of nanomaterial and engineering of enzyme in eco-friendly processes, gold mesoflower (Au-MF) nanostructure was applied for preparation of three series of immobilized lipase (Au-MF/SAM 1-3) through biofunctionalization of surface by Ugi multicomponent reaction. The synthesized Au-MF/SAM 1-3/lipase as unique biocatalysts was confirmed by different analytical tools and techniques. Compared to the free lipase, the Au-MF/SAM 1-3/lipase showed more stability at high temperature and pH. Also, these biocatalysts showed high storage stability and reusability after 2 months and eight cycles, respectively. Moreover, the kinetic behavior was investigated and the results showed a minimal impairment of catalytic activity of immobilized lipase. The kinetic constants of the immobilized lipase, Au-MF/SAM 2/lipase, are K_m = 0.37 mM, V_max = 0.22 mM min^-1, and k_cat = 154 min^-1. The immobilized lipase showed smaller activation energy (E_a) than that of free enzyme, indicating that the immobilized enzyme is less sensitive to temperature. In the following, the biodiesel production from palmitic acid was studied in the presence of Au-MF/SAM 2/lipase as an efficient biocatalyst. The influence of different reaction parameters such as temperature, molar ratio of alcohol to palmitic acid, water content, and lipase amount was deeply investigated.

The mechanisms of HSA@PDA/Fe nanocomposites with enhanced nanozyme activity and their application in intracellular H2O2 detection

Nanozymes have drawn increasing attention with their broad applications but most nanozymes lack enzyme-like molecular structures, resulting in weak selectivity and low activity. Bioinspired molecular assembly provides an extremely promising strategy to mimic natural enzyme processes and develop function enhanced architectures. Herein, a new bioinspired molecular assembly strategy based on human serum albumin@polydopamine/Fe nanocomposites (HSA@PDA/Fe NCs) was proposed, in which Fe(iii)/Fe(ii) were anchored on HSA supported on PDA. HSA@PDA/Fe NCs with iron as the active center and HSA@PDA as the skeleton showed excellent peroxidase-like activity, which was nearly 1000 times higher than that of free Fe(iii). This may be attributed to the phenomenon that the cycle of quinones and the hydroxyl group on the nanocomposite surface greatly accelerate the conversion of Fe(iii)/Fe(ii) in acidic microenvironments. Systematic experimental studies illustrated that its activity was mainly affected by the metal active center, followed by the polymeric ligand, while the protein framework has little effect on its activity. Meanwhile, even after freeze-thaw and thermal cycle tests, it also showed excellent catalytic stability. Besides, a colorimetric assay based on HSA@PDA/Fe NCs was developed for detection of H₂O₂in vitro and in situ detection of H₂O₂ generated from live cells. This work will facilitate the developments on theoretical analysis, rational design and practical applications of nanozymes based on bioinspired molecular assemblies.