A multifunctional nanoparticle targets infection, releases nitric oxide, and uses light-triggered heating to eliminate bacteria and support healing in diabetic wounds with drug-resistant biofilms.
(Nanowerk Spotlight) Diabetic wounds infected by drug resistant bacteria are among the most stubborn and dangerous complications in medicine. These wounds persist not only because of bacterial infection, but because the surrounding tissue is trapped in a cycle of inflammation, poor circulation, and impaired repair. Elevated glucose levels in diabetic tissue fuel bacterial growth while weakening immune defenses. As infection progresses, the body’s ability to clear bacteria and rebuild tissue steadily declines.
Antibiotics often fail to penetrate bacterial biofilms, which are dense protective layers that shield microbes from treatment. Even advanced wound therapies, including growth factors and skin grafts, struggle to restore function in this hostile environment. The result is a condition that resists healing on multiple fronts, with high risk of chronic infection, tissue loss, and amputation.
One emerging approach to this problem involves enzyme inspired nanomaterials that mimic the immune system’s natural strategies for neutralizing pathogens. These synthetic materials, known as nanozymes, can catalyze the formation of reactive oxygen species, which are molecules that break down bacterial membranes. At the same time, photothermal therapies have gained attention for their ability to convert light into localized heat, disrupting infection sites with minimal impact on surrounding tissue.
Nitric oxide, a short lived gas naturally produced in the body, has shown promise as both an antibacterial agent and a promoter of blood vessel growth. Each of these technologies offers partial solutions. However, used in isolation, they present limitations such as poor selectivity, thermal damage, short drug half lives, or insufficient antibacterial strength.
A study published in Advanced Science (“Bacteria-Targeted Single-Atom Nanozyme With Photothermal-Augmented Multi-Enzymatic Cascade and NO Delivery for Enhanced Infected Wound Healing”) introduces a platform that combines all three approaches. The researchers developed a nanomaterial called CBPV that can be activated with near infrared light to selectively eliminate bacterial infections and support tissue regeneration in diabetic wounds. By integrating photothermal effects with catalytic chemistry and controlled gas delivery, this system addresses both the microbial and vascular challenges of chronic wound healing.
A schematic diagram illustrating the treatment of diabetic epidermal wounds and subcutaneous cysts using CBPV. a) The synthesis process of CBPV. b) Combined PTT, CDT, and NO therapy using CBPV and NIR-II laser for epidermal and subcutaneous infections. (Image: Reprinted from DOI:10.1002/advs.202509621, CC BY) (click on image to enlarge)
The core of the CBPV system is a copper based single atom nanozyme referred to as mCu SAE. These nanoparticles are designed with copper atoms embedded individually into a porous carbon matrix. Each copper atom is coordinated by three nitrogen atoms, a structure known as Cu N3. This configuration differs from the more common Cu N4 arrangement and enables more efficient interaction with hydrogen peroxide, a molecule abundant in infected tissue. The Cu N3 center catalyzes the breakdown of hydrogen peroxide into hydroxyl radicals, a powerful reactive oxygen species with antibacterial effects. Compared to earlier nanozyme designs, this system shows improved catalytic activity because more copper atoms are exposed and active.
To add light sensitivity, the carbon framework surrounding the copper centers was engineered to absorb near infrared light in the NIR II window, which spans 1000 to 1700 nanometers. This deeper penetrating wavelength range allows for more precise tissue targeting without overheating the skin surface. When irradiated with a 1064 nanometer laser, the nanoparticles convert light into heat, reaching temperatures above 65 degrees Celsius in solution. This thermal effect amplifies the catalytic activity of the copper centers and triggers the release of nitric oxide.
For nitric oxide delivery, the researchers loaded the particles with a small molecule donor called BNN6, which decomposes under heat to release the gas. The nitric oxide molecules serve two functions. They enhance antibacterial effects by forming peroxynitrite when combined with reactive oxygen species, and they stimulate fibroblast migration and blood vessel growth to support healing. The timing of nitric oxide release is also significant. During the early stages of infection, high levels contribute to bacterial clearance. Later, slower release of lower concentrations supports tissue repair.
To ensure the particles reach their target, the researchers modified the surface with vancomycin, an antibiotic that binds to bacterial cell wall structures. This modification helps the nanoparticles accumulate at infection sites while minimizing exposure to healthy tissue. The full formulation, referred to as CBPV, combines a copper based nanozyme core, a nitric oxide releasing component, and a targeting shell.
Each component of the system was verified through structural and chemical analysis. Transmission electron microscopy confirmed that the copper atoms were dispersed individually rather than forming clusters. Spectroscopy studies showed the presence of the Cu N3 structure and the successful loading of both BNN6 and vancomycin. Photothermal testing demonstrated that CBPV maintained stable heating performance under repeated laser exposure and showed a high photothermal conversion efficiency of 43.9 percent.
When tested in vitro, CBPV showed strong enzyme like activity. It catalyzed the production of both hydroxyl radicals and superoxide anions from hydrogen peroxide, even at low concentrations. The reaction kinetics followed expected Michaelis Menten behavior, with relatively low Km values indicating high substrate affinity. At elevated temperatures, the production of reactive oxygen species increased significantly, confirming the thermal enhancement of enzymatic activity.
Controlled nitric oxide release was confirmed using fluorescence based assays and chemical detection kits. Upon laser exposure, the CBPV particles released nitric oxide in a concentration and power dependent manner. Without light, the release was minimal. The presence of peroxynitrite was confirmed through fluorescence probes and electron spin resonance spectroscopy. These results showed that the combination of nitric oxide and reactive oxygen species under heat led to the formation of highly reactive compounds with strong antibacterial properties.
The system’s ability to kill bacteria was tested on both Escherichia coli and methicillin resistant Staphylococcus aureus. Under laser irradiation, CBPV achieved over 99 percent bacterial inactivation. It also disrupted bacterial biofilms by degrading their extracellular matrix and lysing the enclosed bacteria. Microscopy showed that bacterial surfaces became wrinkled and perforated after treatment, with leakage of intracellular material.
In animal models of diabetic wound infection, CBPV accelerated healing significantly compared to control treatments. Wounds treated with CBPV and NIR II irradiation showed smaller wound areas, increased collagen deposition, and enhanced blood vessel formation. Temperature monitoring during treatment confirmed that the heating effect was localized and within safe limits. In addition to reducing bacterial load, the therapy supported fibroblast migration and new vessel growth, both of which are essential for wound closure.
Biocompatibility tests showed minimal toxicity to normal cells and red blood cells. The PEG and vancomycin coating appeared to reduce cytotoxicity while enhancing bacterial targeting. The particles were stable in biological fluids and showed minimal leaching of copper ions, lowering the risk of unintended chemical exposure.
This study demonstrates how multiple therapeutic functions can be integrated into a single nanomaterial and activated precisely using external light. By combining catalytic reactive oxygen species generation, photothermal conversion, and nitric oxide delivery within a targeted architecture, the CBPV system addresses several major barriers in treating infected diabetic wounds. It eliminates bacteria, disrupts biofilms, and supports tissue regeneration in a spatially and temporally controlled way.
The work provides an example of how modular nanotechnologies can be used to tackle complex medical conditions that do not respond to conventional treatments. While the system remains at the preclinical stage, its results in both cell and animal models suggest a strong basis for further development.
Future research will need to assess scale up, long term safety, and methods suitable for clinical use. The integration of enzyme mimicking chemistry, localized heating, and gas signaling into a single material marks a potential step forward in infection targeted therapies that also support tissue repair.
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