Colorimetric glucose sensing with multiple-color changes by using a MnO2 NSs-TMB nanosystem

Manganese-derived biomaterials for tumor diagnosis and therapy

Manganese (Mn) is widely recognized owing to its low cost, non-toxic nature, and versatile oxidation states, leading to the emergence of various Mn-based nanomaterials with applications across diverse fields, particularly in tumor diagnosis and therapy. Systematic reviews specifically addressing the tumor diagnosis and therapy aspects of Mn-derived biomaterials are lacking. This review comprehensively explores the physicochemical characteristics and synthesis methods of Mn-derived biomaterials, emphasizing their role in tumor diagnostics, including magnetic resonance imaging, photoacoustic and photothermal imaging, ultrasound imaging, multimodal imaging, and biodetection. Moreover, the advantages of Mn-based materials in tumor treatment applications are discussed, including drug delivery, tumor microenvironment regulation, synergistic photothermal, photodynamic, and chemodynamic therapies, tumor immunotherapy, and imaging-guided therapy. The review concludes by providing insights into the current landscape and future directions for Mn-driven advancements in the field, serving as a comprehensive resource for researchers and clinicians.

A dual-signal optical sensing platform of CDs-MnO2 NS composites for facile detection of ascorbic acid based on a combination of Tyndall effect scattering and fluorescence

A dual-signal optical sensing platform was successfully developed for the determination of ascorbic acid (AA) based on blue fluorescent carbon dots (CDs) and manganese dioxide nanosheets (MnO2 NSs) with strong Tyndall effect (TE) scattering and fluorescence quenching capabilities. In this nanosystem, CDs-MnO2 NS composites were employed as probes to evaluate the AA concentration. Owing to the strong reduction, the presence of the target AA could reduce the MnO2 NSs to Mn2+ and induce the degradation of the MnO2 NSs, resulting in a significant decrease in the TE scattering intensity of the MnO2 NSs and the fluorescence recovery of the CDs. Therefore, a novel optical sensor based on TE scattering and fluorescence dual detectors was developed for the sensitive determination of AA. Under optimized conditions, the limits of detection (LODs) of the two modes were 113 and 3 nM, respectively. Furthermore, the dual-signal optical sensing platform was successfully applied for the detection of AA in human serum.

Ultralow Ru Single Atoms Confined in Cerium Oxide Nanoglues for Highly-Sensitive and Robust H2 O2 -Related Biocatalytic Diagnosis

Exploring highly efficient, portable, and robust biocatalysts is a great challenge in colorimetric biosensors. To overcome the challenging states in creating single-atom biocatalysts, such as insufficient activity and stability, here, this work has engineered a unique CeO2 support as nanoglue to tightly anchor the Ru single-atom sites (CeO2 -Ru) with strong electronic coupling for achieving highly sensitive and robust H2 O2 -related biocatalytic diagnosis. The morphology and chemical/electronic structure analysis demonstrates that the Ru atoms are well-dispersed on CeO2 surface to form high-density active sites. Benefiting from the unique structure, the prepared CeO2 -Ru exhibits outstanding peroxidase (POD) like catalytic activity and selectivity to H2 O2 . Steady-state kinetic study results show that the CeO2 -Ru presents the highest Vmax and turnover number than the state-of-the-art POD-like biocatalysts. Consequently, the CeO2 -Ru discloses a high efficiency, good selectivity, and robust stability in the colorimetric detection of L-cysteine, glucose, and uric acid. Notably, the limit of detection (LOD) can reach 0.176 × 10-3 m for the L-cysteine, 0.095 × 10-3 m for the glucose, and 0.088 × 10-3 m for the uric acid via cascade reaction. This work suggests that the proposed unique CeO2 nanoglue will offer a new path to create single-atom noble metal biocatalysts and take a step closer to future biotherapeutic and biocatalytic applications.

Biomedical applications of MnO2 nanomaterials as nanozyme-based theranostics

Manganese dioxide (MnO₂) nanoenzymes/nanozymes (MnO₂-NEs) are 1-100 nm nanomaterials that mimic catalytic, oxidative, peroxidase, and superoxide dismutase activities. The oxidative-like activity of MnO₂-NEs makes them suitable for developing effective and low-cost colorimetric detection assays of biomolecules. Interestingly, MnO₂-NEs also demonstrate scavenging properties against reactive oxygen species (ROS) in various pathological conditions. In addition, due to the decomposition of MnO₂-NEs in the tumor microenvironment (TME) and the production of Mn²⁺, they can act as a contrast agent for improving clinical imaging diagnostics. MnO₂-NEs also can use as an in situ oxygen production system in TME, thereby overcoming hypoxic conditions and their consequences in the progression of cancer. Furthermore, MnO₂-NEs as a shell and coating make the nanosystems smart and, therefore, in combination with other nanomaterials, the MnO₂-NEs can be used as an intelligent nanocarrier for delivering drugs, photosensitizers, and sonosensitizers in vivo. Moreover, these capabilities make MnO₂-NEs a promising candidate for the detection and treatment of different human diseases such as cancer, metabolic, infectious, and inflammatory pathological conditions. MnO₂-NEs also have ROS-scavenging and anti-bacterial properties against Gram-positive and Gram-negative bacterial strains, which make them suitable for wound healing applications. Given the importance of nanomaterials and their potential applications in biomedicine, this review aimed to discuss the biochemical properties and the theranostic roles of MnO₂-NEs and recent advances in their use in colorimetric detection assays of biomolecules, diagnostic imaging, drug delivery, and combinatorial therapy applications. Finally, the challenges of MnO₂-NEs applications in biomedicine will be discussed.

Ir Cluster-Anchored MOFs as Peroxidase-Mimetic Nanoreactors for Diagnosing Hydrogen Peroxide-Related Biomarkers

Exploring multifaceted and highly sensitive biosensors is a major challenge in biotechnology and medical diagnosis. Here, we create a new iridium (Ir) cluster-anchored metal-organic framework (MOF, namely, Ir_NCs@Ti-MOF via a coordination-assisted strategy) as a peroxidase (POD)-mimetic nanoreactor for colorimetrically diagnosing hydrogen peroxide-related biomarkers. Owing to the Ir_NCs-N/O coordination of Ti-MOF and unique enzymatic properties of Ir clusters, the Ir_NCs@Ti-MOF exhibits exceptional and exclusive POD-mimetic activities (K_m = 3.94 mM, V_max = 1.70 μM s^-1, and turnover number = 39.64 × 10^-3 s^-1 for H₂O₂), thus demonstrating excellent POD-mimetic detecting activity and also super substrate selectivity, which is considerably more efficient than recently reported POD mimetics. Colorimetric studies disclose that this Ir_NCs@Ti-MOF-based nanoreactor shows multifaceted and efficient diagnosing activities and substrate selectivity, such as a limit of detection (LOD): 14.12 μM for H₂O₂ at a range of 0-900 μM, LOD: 3.41 μM for l-cysteine at a range of 0-50 μM, and LOD: 20.0 μM for glucose at a range of 0-600 μM, which enables an ultrasensitive and visual determination of abundant H₂O₂-related biomarkers. The proposed design will not only provide highly sensitive and cheap colorimetric biosensors in medical resource-limited areas but also offer a new path to engineering customizable enzyme-mimetic nanoreactors as a powerful tool for accurate and rapid diagnosis.

Manganese dioxide nanosheet-containing reactors as antioxidant support for neuroblastoma cells

Supporting mammalian cells against reactive oxygen species such as hydrogen peroxide (H₂O₂) is essential. Bottom-up synthetic biology aims to integrate designed artificial units with mammalian cells. Here, we used manganese dioxide nanosheets (MnO₂-NSs) as catalytically active entities that have superoxide dismutase-like and catalase-like activities. The integration of these MnO₂-NSs into 7 μm reactors was able to assist SH-SY5Y neuroblastoma cells when stressed with H₂O₂. Complementary, Janus-shaped 800 nm reactors with one hemisphere coated with MnO₂-NSs showed directed locomotion in cell media with top speeds up to 50 μm s^-1 when exposed to 300 mM H₂O₂ as a fuel, while reactors homogeneously coated with MnO₂-NSs were not able to outperform Brownian motion. These Janus-shaped reactors were able to remove H₂O₂ from the media, protecting cells cultured in the proximity. This effort advanced the use of bottom-up synthetic biology concepts in neuroscience.