Can photocatalytic materials combat AMR?

Spectrum Blue explores historical resistance to innovation in medicine, juxtaposing the current challenge of antimicrobial resistance with the potential of new technologies, such as photocatalytic materials, to address it.

We see innovation as inevitable. In reality, we are often met with resistance, especially when we are asked to act on something we cannot see.

Discovery of germ theory

In the 1840s, Ignaz Semmelweis worked in the maternity ward of the Vienna General Hospital. There, two nearly identical clinics had very different results. In hospitals staffed by doctors and medical students, women frequently died of puerperal fever. The other hospital, run by midwives, had a much lower mortality rate. The discrepancies were persistent and unexplained.

The turning point came after the death of Semmelweis’s colleague Jakob Korechka. He developed a fatal infection due to injury from a scalpel during an autopsy. The symptoms were very similar to those of the woman who died at the clinic. Semmelweis drew a connection that others had not seen: that substances from corpses carried by doctors were somehow causing the disease. Without a framework such as germ theory, he described these as “corpse particles.”

In 1847, he introduced a policy requiring hand washing with chlorinated lime before contact with patients. The effect was immediate and dramatic. Mortality rates have fallen from a high of 10–18% to approximately 1–2% (Semmelweis, 1861; Best and Neuhauser, 2004). However, the reaction was negative. Many doctors rejected the findings, in part because they implied that doctors themselves were responsible for their patients’ deaths. Some people objected that there was no theoretical explanation. Although the data were empirical, the mechanisms remained invisible. Semmelweis faced increasing opposition and his research was mostly rejected during his lifetime.

discovery of penicillin

Decades later, something invisible returns to the London laboratory. In 1928, Alexander Fleming noticed that one of his bacterial culture plates had become contaminated with mold, creating a clear area where bacteria could not grow. He identified the mold as Penicillium and recognized that it releases a substance with antibacterial properties. However, Fleming was unable to stabilize or purify this substance for therapeutic use, and for many years this observation remained a scientific curiosity rather than a medical solution.

It wasn’t until the late 1930s that Howard Florey, Ernst Chain, and a team at Oxford University revisited the problem. They developed a method to extract and concentrate penicillin, but the yield was very low and the compound was unstable. Early experiments treated infected mice and demonstrated clear survival benefits (Chain et al., 1940). Human trials were then conducted under constrained conditions, including attempts to recover penicillin from patients’ urine and reuse it because of limited supplies.

Contrary to popular belief, penicillin’s success was not a moment of discovery, but a process of overcoming chemical, biological, and logistical barriers. Still, expanding the scale of production during World War II required a coordinated effort by industry. What began as an observation in a petri dish became the basis of modern medicine only through continued efforts despite technical uncertainty and initial skepticism (Ligon, 2004).

Future antibacterial discovery

Today, we are once again faced with the limits of what we can see and control. Antimicrobial resistance is increasing across bacterial pathogens, and global estimates suggest that millions of people die from resistant infections each year (Murray et al., 2022). At the same time, fungal pathogens such as Candida auris are emerging in health care settings due to a combination of environmental persistence and resistance to multiple antifungal drugs (CDC, 2023). Although these microorganisms are not new, their impact has increased under current clinical and ecological conditions.

The pressure to respond is increasing, but the direction of that response is unclear. Much of modern medicine works downstream of the problem, responding after the infection has occurred, and is based on the assumption that treatment can outpace microbial adaptations.

An alternative is to move the point of intervention earlier, to the interface between the microorganism and its environment.

Photocatalytic materials are one such approach. These systems are often based on semiconductors such as titanium dioxide, which generate reactive oxygen species when exposed to light. These species interact directly with microorganisms on surfaces, destroying membranes, proteins, and genetic material (Fujishima et al., 2008). This mechanism is nonspecific and acts through oxidative stress rather than through targeted biochemical pathways.

A previous limitation was the need for UV activation, which limited practical application. More recent developments, including research patented by Spectrum Blue, have focused on modifying photocatalytic materials to function under visible light through doping strategies and pigment-based systems (Chen et al., 2010). This allows antimicrobial activity under ambient conditions without the need for controlled irradiation.

This changes the role of photocatalytic materials in infection control. Surfaces can actively reduce their microbial load on a continuous basis without resorting to separate cleaning events or repeated chemical treatments.

At the same time, this approach does not easily fit into existing evaluation frameworks. Current systems are designed to measure emergency interventions, such as disinfectants and antibiotics, rather than ongoing low-level antimicrobial activity embedded in materials.

As with Semmelweis’s time and the early development of penicillin, the challenges are not just technical. It’s conceptual. We must accept that microbial control may depend as much on environmental redesign as on the development of new treatments.

References

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https://www.cdc.gov/candida-auris/hcp/clinical-overview/index.html Fujishima, Akira and Chan, Shinton and Trike, Donald. (2008). Surface phenomena associated with TiO2 photocatalysis. Surface science report. 63.515-582. 10.1016/j.surfrep.2008.10.001.

This article will also be published in the quarterly magazine issue 26.