Getting Under My Skin: Nanozymes

Active creation of recently rising nanotechnology materials

A key component to functioning body systems are enzymes. Enzymes are a protein that have a wide array of functions including getting rid of toxic substances (for example, alcohol), digestion, reducing inflammation and pain, and many others.

Currently, nanotechnology is on the rise due to the many possibilities it offers. This technology focuses on dimensions between 1 and 100 nanometers (in context, 1 nanometer is 1 billionth of a meter, or for further simplification, 1 billionth of the length of a baseball bat). Devices produced at this level allows them to be easily sent into the body as treatments.

Introduction

Often made from metal (gold, silver), carbon, and hybrid materials, nanozymes are man-made nanomaterials that mimic enzymes. Currently, nanozymes are thought to be a new era of antibacterial agents, which Bai et. al set out to test.

In the medical world, infections are notorious, and even so when infections are in deep soft tissue since it is so difficult to treat. In order to successfully get rid of deep infections, treatment consists of incisions, drainage, and long-term doses of antibiotics (to which bacteria may develop resistance toward and become super strains).

In this experiment, researchers utilized SAzymes (single-atom enzymes, have metal atoms as catalytic site - the site where a chemical reaction is started) that were made of copper and carbon. The SAzymes are described to be "atomically dispersed copper sites anchored on ultrathin 2D porous N-doped carbon nanosheets.

The SAzymes performed multienzyme activities (enzymes usually have one job, engineered nanozymes can have more than one) under NIR light (infrared light). Infrared light helped draw a response from SAzymes sent into the body.

Multienzyme Mimicking

In order to treat infections (especially deep infections), peroxidase catalase (POD) and oxidase (OXD) activities are crucial. OXD uses oxygen to reduce it into water. OXD helps facilitate conversion of hydrogen peroxide and oxygen into reactive oxygen species (ROS). ROS is crucial for immune function and pathogen killing, which is important for healing infections and wounds. However, too much ROS produced can be harmful to healthy cells, which is where POD comes in. POD works to protect cells by removing hydrogen peroxide.

In this specific experiment, CuN4-CNS SAzymes are used (diving into what exactly this means will take too long, just think of it as a specific type of SAzyme). When the CuN4-CNS SAzymes were compared to other SAzymes, it proved much more effective.

TMB (tetramethylbenzidine), acts as a stand-in for how well CuN4-CNS catalyzes.

Antibacterial Performance

To test for antibacterial performance, CuN4-CNS was added to E. coli and MRSA (a bacteria that is responsible for many infections that difficult to treat). Both bacteria have different formations of cell wall, and this is because it is necessary to see if all bacteria respond to the SAzyme.

Compared to bacteria treated with CuN4-CNS alone, bacteria treated with CuN4-CNS and hydrogen peroxide were reduced to a greater degree (35.6% and 46.8%, E. coli and MRSA). This can be attributed to the higher production of ROS. When a laser was directed onto the plate, E. coli and MRSA were reduced to 37.6% and 43.8%. However, when infrared light was shone on the plate instead of the laser, almost no bacteria (of both kinds) survived. Therefore, the most effective combination was CuN4-CNS, H2O2 (hydrogen peroxide), and infrared light.

Surface Skin Wound Healing

In order to test the efficiency of CuN4-CNS in vivo (within the living), rats were infected with MRSA. In the control group, on Day 4 of the infection, a large amount of pus was observed. On Day 7, pus had decreased, but was still observable.

For the wounds treated with CuN4-CNS, hydrogen peroxide, and infrared light, the wound was comparably smaller and started to scab on Day 7 without any observable sign of inflammation, with it fully healing on Day 14.

Antibiofilm Performance

A typical trait of deep infections are the formation of biofilms, a thin slimy layer of bacteria that sticks to surfaces. As expected, when treated with CuN4-CNS, there was more bacterial death, most likely from the OXD properties (and thus more ROS). However, since oxygen is lacking at these locations, death was not as great when treated with CuN4-CNS and hydrogen peroxide (as seen in other experiments). Additionally, when an infrared light was shone on the infection area, there was almost total death of bacteria.

Deep Infection Healing

Again, in order to test CuN4-CNS in vivo, an experiment was set up to validate the hypothesized effects on bacteria. The methods and results of this experiment are fairly similar to results of the skin wound experiment. Bacterial colonies were significantly reduced (almost totally) in infections treated with CuN4-CNS, hydrogen peroxide, and infrared light. Additionally, it was observed that there was less inflammatory infiltration. We can conclude that CuN4-CNS alone or CuN4-CNS and hydrogen peroxide only can only reverse deterioration.

Conclusion

In conclusion, it was found that CuN4-CNS SAzymes were excellent at mimicking enzyme activities (especially promoting ROS). These designed SAzymes are good at absorbing oxygen and carrying out other roles, allowing it easily mimic natural enzymes. Additionally, external NIR (infrared light), increased efficacy of the treatment.

This research paper only shows a glimpse into the amazing capabilities of nanotechnology. It is believed that nanotechnology could be used someday to treat cancer without affecting healthy cells (by sending designed particles that carry treatment into the body) and in many other technologies. This field is constantly evolving and can begin to be used in real-life treatments. Maybe one day I'll get some nanotechnology under my own skin.