From Green Leaves To Silver Nanoparticles: Nature-Inspired Strategies Against Antimicrobial Resistance

Can the plants growing around us solve the antimicrobial resistance crisis? 

When we think about plants, we usually think about the natural beauty they bring to our surroundings. Rarely do we consider that the same green leaves we pass every day may hold clues to tackling one of the greatest challenges in modern microbiology: antimicrobial resistance (AMR). 

If you walk through any garden, park or woodland, you are surrounded by one of nature's most abundant molecules: chlorophyll. 

For many of us, chlorophyll may simply just be the pigment that makes plants green and facilitates photosynthesis, the process plants use to make foodi. Yet beyond its role in plant biology, chlorophyll may hold surprising potential in combating AMR.  

There have been more reports of antibiotic-resistant bacteria emerging recently, which shows us that bacteria continue to evolve resistance to conventional antibiotics and researchers are increasingly working on the development and implementation of alternative antimicrobial strategies. Among these, antimicrobial photodynamic therapy (aPDT) has emerged as a promising approach. Interestingly, chlorophyll and chlorophyll-derived compounds are attracting attention as naturally occurring photosensitisers that can be used within these systems 

Looking Beyond Traditional Antibiotics

Antimicrobial resistance is threatening decades of medical progress, making once-treatable infections harder to manage and increasing illness, healthcare costs and mortality worldwide. However, the impact of antimicrobial resistance extends far beyond healthcare. In industrial microbiology, resistant microorganisms can compromise food production, contaminate manufacturing environments, weaken sanitation measures and promote biofilm formation on surfaces and equipment. This poses serious challenges for industries such as food processing, pharmaceuticals, water treatment and biotechnology, all of which depend on effective microbial control to maintain safety, quality and complianceii.  

It has therefore been noted that there is a pressing need for antimicrobial approaches that can inactivate bacteria efficiently without the risk of inducing resistances. In this regard, an alternative approach is aPDT, a technology that combines a photosensitiser, light, and oxygen to generate reactive oxygen species (ROS). These highly reactive molecules attack bacterial cell membranes, proteins, nucleic acids and metabolic enzymes, which ultimately leads to microbial deathiii.  

Unlike conventional antibiotics, aPDT attacks multiple cellular targets simultaneously, making it considerably more difficult for bacteria to develop resistance, making this therapy more attractive to researchers.

Chlorophyll: More Than a Plant Pigment

When exposed to appropriate wavelengths of light, chlorophyll can act as a natural photosensitiser, producing reactive oxygen species capable of damaging microbial cells2. In essence, one of nature's most abundant molecules can be transformed into a light-activated antibacterial system. Studies have already shown that chlorophyll extracts and chlorophyll-derived compounds exhibit antimicrobial activity against both Gram-positive and Gram-negative bacteria. Their appeal lies not only in this broad-spectrum efficacy, but also in the fact that plants are abundant, renewable, and globally distributed, positioning chlorophyll as a promising sustainable source of antimicrobial agents. 

However, researchers are now exploring ways to make the aPDT process even more effectiveiv. While chlorophyll based aPDT has shown promising antibacterial activity, there is growing interest in enhancing its performance through incorporation of materials that can overcome the protective mechanisms presented by resistant bacteria.  

Silver has long been recognised for its antibacterial properties, and advances in nanotechnology have enabled the development of silver nanoparticles which exhibit potent antimicrobial activity through multiple mechanismsv. They can attach to and disrupt bacterial cell membranes, increasing permeability and causing leakage of essential cellular components. They also penetrate cells, where they interact with proteins and DNA, impairing critical cellular functions and promoting the production of reactive oxygen species (ROS) that damage intracellular structures. Additionally, the gradual release of silver ions (Ag⁺) further enhances antimicrobial efficacy by interfering with metabolic processes and genetic material. This multi-target mode of action makes silver nanoparticles effective against a broad range of microorganisms vi. 

In chlorophyll-based aPDT systems, silver nanoparticles may act synergistically by enhancing antimicrobial efficacy. Upon illumination, chlorophyll generates reactive oxygen species, while silver nanoparticles disrupt bacterial defences through complementary antimicrobial mechanisms. Together, they exert a multi-targeted effect that compromises bacterial survival

By combining plant-derived photosensitisers with nanotechnology, researchers may be able to develop antimicrobial systems that are both highly effective and less likely to contribute to resistance development. In this era of rising antimicrobial resistance, such combinations offer a powerful reminder that future antimicrobial innovations may emerge not only from the laboratory, but also from the natural world that surrounds us.