Platinum group element-based nanozymes for biomedical applications: An overview

Nanozyme can substitute a natural Ogataea polymorpha catalase enzyme in vivo

Nanomaterials possessing artificial, enzyme-like catalytic activity (nanozymes, NZs) have a great potential for application in research, immunological assays, biosensors, in vivo imaging, and as therapeutic agents. Despite the obvious advances in construction and understanding of functional properties of NZs, there is still no clear evidence of whether they can complement the loss of corresponding enzymatic activity in vivo. Herein, we report the first, to the best to our knowledge, example of successful substitution of natural enzyme activity by catalase-like platinum (nPt) and platinum-gold (nPtAu) nanoparticles transferred to the cells of methylotrophic yeast Ogataea polymorpha. The nPt NZs were synthesized by the chemical reduction method and used as a seed to produce the nPt(core)Au(shell) particles. The produced nPt NZs were 68.1 and 91.3 nm in size, while the hydrids were of 531.2 and 615.1 nm. Both nPt and nPtAu demonstrated catalase activity in vitro. The catalase-deficient strain Ogataea polymorpha C-105 was shown to be able to grow on methanol and a mixture of glucose and methanol in the presence although not in the absence of NZs, this correlating with the decrease in intracellular hydrogen peroxide production. The results provide the first example of complementation of the natural enzyme function by synthetic NZs, the phenomenon which can further be used in a screening for new catalase-like nanozymes and as a fruitful tool to modify living cells by nanoparticles possessing catalytic activity and to use such modified cells as sensitive elements in cell-based biosensors.

Latest advances in biomimetic nanomaterials for diagnosis and treatment of cardiovascular disease

Cardiovascular disease remains one of the leading causes of death in China, with increasingly serious negative effects on people and society. Despite significant advances in preventing and treating cardiovascular diseases, such as atrial fibrillation/flutter and heart failure over the last few years, much more remains to be done. Therefore, developing innovative methods for identifying and managing cardiovascular disorders is critical. Nanomaterials provide multiple benefits in biomedicine, primarily better catalytic activity, drug loading, targeting, and imaging. Biomimetic materials and nanoparticles are specially combined to synthesize biomimetic nanoparticles that successfully reduce the nanoparticles' toxicity and immunogenicity while enhancing histocompatibility. Additionally, the biological targeting capability of nanoparticles facilitates the diagnosis and therapy of cardiovascular disease. Nowadays, nanomedicine still faces numerous challenges, which necessitates creating nanoparticles that are highly selective, toxic-free, and better clinically applicable. This study reviews the scientific accomplishments in this field over the past few years covering the classification, applications, and prospects of noble metal biomimetic nanozymes and biomimetic nanocarriers.

Editorial: Special issue on advances in nanomedicine

Nanomaterials are being increasingly used to develop new methods of disease diagnosis and treatment, thereby providing novel paradigms to break through the current limitations of medicine. However, there is still a long way toward the complete revolution for nanomedicine in the diagnosis and treatment of diseases. As nanoparticles are highly complex products and difficult to characterize, there are still many challenges. This special issue on Advances in Nanomedicine includes a series of topical reviews and original research articles that highlight the recent advances in diagnosis and therapy of nanomaterials.

Electrochemical sensors based on metal nanoparticles with biocatalytic activity

Biosensors have attracted a great deal of attention, as they allow for the translation of the standard laboratory-based methods into small, portable devices. The field of biosensors has been growing, introducing innovations into their design to improve their sensing characteristics and reduce sample volume and user intervention. Enzymes are commonly used for determination purposes providing a high selectivity and sensitivity; however, their poor shelf-life is a limiting factor. Researchers have been studying the possibility of substituting enzymes with other materials with an enzyme-like activity and improved long-term stability and suitability for point-of-care biosensors. Extra attention is paid to metal and metal oxide nanoparticles, which are essential components of numerous enzyme-less catalytic sensors. The bottleneck of utilising metal-containing nanoparticles in sensing devices is achieving high selectivity and sensitivity. This review demonstrates similarities and differences between numerous metal nanoparticle-based sensors described in the literature to pinpoint the crucial factors determining their catalytic performance. Unlike other reviews, sensors are categorised by the type of metal to study their catalytic activity dependency on the environmental conditions. The results are based on studies on nanoparticle properties to narrow the gap between fundamental and applied research. The analysis shows that the catalytic activity of nanozymes is strongly dependent on their intrinsic properties (e.g. composition, size, shape) and external conditions (e.g. pH, type of electrolyte, and its chemical composition). Understanding the mechanisms behind the metal catalytic activity and how it can be improved helps designing a nanozyme-based sensor with the performance matching those of an enzyme-based device.

Ionic liquid-assisted chemiluminescent immunoassay of prostate specific antigen using nanoceria as an alkaline phosphatase-like nanozyme label

An alkaline phosphatase-like nanozyme was applied for an immunoassay for the first time. By using nanoceria as the alkaline phosphatase-like catalytic label and CDP-star as the substrate, the chemiluminescent detection of prostate specific antigen was demonstrated. More importantly, the addition of ionic liquid can significantly increase the sensitivity of the immunoassay. With the aid of ionic liquid, an order of magnitude improvement in the sensitivity was achieved with a detection limit of 53 fg mL^-1.