Sunlight-activated nanospray enables painless, antibiotic-free therapy for infected diabetic wounds
A novel photodynamic platform combines antibacterial action, hemostasis and pain relief under natural sunlight
Chronic infected wounds, especially diabetic foot ulcers, remain a major clinical challenge due to persistent bacterial infections, impaired healing and severe pain. A research team has now reported a multifunctional photodynamic nanospray that harnesses natural sunlight to address all three problems simultaneously.
The newly developed platform, termed SPS, is a self-assembled nanoparticle composed of a near-infrared photosensitizer conjugated with chitosan oligosaccharides. This design allows the material to be activated by either natural sunlight or low-power near-infrared light, generating reactive oxygen species that efficiently kill bacteria, including methicillin-resistant Staphylococcus aureus (MRSA).
In laboratory tests, SPS showed stronger antibacterial activity than the antibiotic vancomycin when exposed to sunlight, while remaining inactive in the dark, ensuring high safety. Microscopy studies revealed severe bacterial membrane disruption after treatment, confirming a direct bactericidal mechanism.
Beyond infection control, the nanospray demonstrated rapid hemostatic capability. In animal bleeding models, sunlight-activated SPS significantly reduced blood loss and shortened bleeding time, an important advantage for open or chronic wounds.
Remarkably, the treatment also produced a pronounced analgesic effect. Behavioral and electrophysiological studies in mice showed that SPS combined with sunlight reduced pain sensitivity to near-normal levels. This effect was linked to the downregulation of pain-related ion channels and the normalization of neuronal excitability in the spinal cord.
In a diabetic wound infection model, wounds treated with SPS under sunlight healed substantially faster, with improved collagen deposition and reduced inflammation, compared with control groups. Importantly, comprehensive biosafety evaluations showed no detectable damage to major organs or abnormal blood parameters.
Because the therapy relies on natural sunlight rather than lasers or antibiotics, it could be particularly valuable in resource-limited settings or for home-based wound care. The authors suggest that this painless, hemostatic and anti-inflammatory sunlight-driven therapy represents a promising new direction for the management of infected chronic wounds.
Journal
National Science Review
DOI
Research reveals hidden diversity of E. coli driving diabetic foot infections
New research led by King’s College London, in collaboration with the University of Westminster, has shed light on the diversity and characteristics of E. coli strains that drive diabetic foot infections
New research led by King’s College London, in collaboration with the University of Westminster, has shed light on the diversity and characteristics of E. coli strains that drive diabetic foot infections.
Published in Microbiology Spectrum, the research provides the first comprehensive genomic characterisation of E. coli strains isolated directly from diabetic foot ulcers across multiple continents. The findings could help to explain why some infections become particularly difficult to treat and why they can lead to severe, sometimes life-threatening, outcomes.
Diabetic foot infections remain one of the most serious complications of diabetes and are a leading cause of lower-limb amputation worldwide. Although clinicians have recognised that these chronic wound infections are often complex, little is known about the specific pathogens involved, particularly E. coli, despite its frequent detection in clinical samples.
Researchers analysed whole-genome sequences from 42 E. coli strains isolated from infected diabetic foot ulcers in patients across Nigeria, the UK, Ghana, Sweden, Malaysia, China, South Korea, Brazil, India and the USA. By sequencing the complete DNA of each bacterial strain, the team was able to examine global patterns in the biology of E. coli associated with diabetic foot disease. This approach enabled the researchers to compare genetic differences between strains, identify genes linked to antibiotic resistance, and pinpoint factors that contribute to disease severity.
The genomic analysis showed that the E. coli strains were highly diverse. The bacteria belonged to many different genetic groups and carried a wide range of genes linked to antibiotic resistance and disease. This demonstrates that there is no single type of E. coli responsible for diabetic foot infections, and distinct lineages were independently capable of adapting to the diabetic foot environment.
By analysing how the strains are related and identifying the resistance mechanisms and virulence traits (the features or tools that make a microbe more harmful) they carry, the research helps explain why some diabetic foot infections are particularly difficult to treat or can progress rapidly to severe illness.
Notably, around 8 per cent of the strains were classified as multidrug-resistant or extensively drug-resistant, meaning they are resistant to multiple or nearly all available antibiotics.
Dr Vincenzo Torraca, Lecturer in Infectious Disease at King’s College London and senior author of the paper, said: “Understanding these bacteria at a genomic level is a crucial step towards improving diagnosis and enabling more targeted treatments for people with diabetes. By identifying which E. coli strains are most common and which antibiotics they are likely to resist, clinicians can choose therapies that are more likely to work, helping to reduce prolonged infection, hospitalisation, and the risk of amputation.”
Victor Ajumobi, a second-year PhD student at King’s College London and the University of Westminster, and first author of the paper, added: “This information will be particularly valuable in low-resource settings, where E. coli infections of diabetic foot ulcers are more common and where rapid diagnostic tools for antimicrobial resistance are not always readily available.”
Future research will focus on understanding how specific virulence factors identified in the study contribute to disease progression. Many of the isolates carry genes that enable E. coli to attach to host tissues or evade the immune system. Investigating how these traits operate within the diabetic foot environment could reveal new therapeutic targets and support the development of improved treatment strategies.
Read the full paper: https://doi.org/10.1128/spectrum.02837-25
Journal
Microbiology Spectrum
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