Since their discovery in the 1940s, antibiotics have revolutionized medicine, significantly reducing mortality rates from common infectious diseases and improving the safety of medical procedures. Antibiotics have even been credited with extending the average human life expectancy by an estimated 20 years.
However, the selective pressures created by the misuse and overuse of antibiotics in humans and animals have led to a reduction in the susceptibility of bacteria to these powerful drugs. Increasing drug resistance has been observed not only in bacteria but also in other infectious agents, including the human immunodeficiency virus (HIV) and parasites that cause malaria. This decrease in the sensitivity of microbes to drugs is called 'antimicrobial resistance' (AMR).
In 2019, AMR was the third leading cause of death after ischemic heart disease and stroke (1). Bacterial AMR in particular was directly responsible for 1.27 million deaths worldwide, surpassing the mortality rates of malaria and HIV-AIDS. By 2050, up to 10 million lives could be at risk from drug-resistant infections worldwide, with associated economic costs estimated to be around 90 trillion euros or 100 trillion USD (2).
The problem of antimicrobial resistance was only exacerbated during the COVID-19 pandemic by the massive use of antibiotics, especially early on when alternative treatments were not available. Critically, among the antibiotics that were misused during the pandemic were the so-called antibiotics of last resort, which are classified as "critical" by the World Health Organization because of their resistance levels (3).
However, while long-established classes of conventional antibiotics are becoming increasingly ineffective against a growing number of drug-resistant pathogens, the development of new antimicrobial agents has nearly stagnated.
The depletion of the antibiotic research and development (R&D) pipeline reflects the almost complete abandonment of antibiotic research by private industry because of the lack of profitability of antibiotics. Importantly, only 1 in 4 antibiotics in clinical development belong to a new class of agents or have a new mechanism of action, making most antibiotics under development susceptible to the same resistance mechanisms that already exist.
The inadequacy of the current antibiotic R&D pipeline was recently echoed by the World Health Organization, which stated that none of the antibiotics currently in development "sufficiently address the problem of drug resistance in the world’s most dangerous bacteria"(4). Thus, there is an urgent global need to develop safe and truly “new” antimicrobials that limit the development of bacterial resistance while preserving the viability of existing antibiotics.
Over the past decade, antimicrobial nanomaterials, which are novel to bacteria and therefore not inherently part of their natural defensive arsenal, have gained increasing attention as a new approach to treating antibiotic-resistant infections. 'Smart' nanomaterials rely on an external stimulus for their activation to exert a biological effect, such as antimicrobial activity. This allows the precise delivery of drugs to the site where they are needed, minimizing the side effects associated with systemic antimicrobial use and potentially improving patient compliance. Local delivery of antimicrobials may, in turn, mitigate the selective pressures created by high doses of systemic antimicrobials that can contribute to the emergence and spread of antimicrobial resistance.
Synthetic molecular nanomachines (MNMs) are an example of such stimuli-responsive compounds. Upon activation by light, MNMs undergo a controlled conformational change, leading to a mechanical effect. The resulting 'drilling' motion can then propel the molecule through a biological system.
This project aims to prototype the use of visible-light-activated MNM as a novel class of antimicrobials using a multidisciplinary approach, which includes chemical synthesis, nanotechnology, microbiology, and cellular biology that leverages the expertise in material science and infection biology of an international team of researchers in the US and Spain.
References:
1. C. J. L. Murray, K. S. Ikuta, F. Sharara, L. Swetschinski, G. R. Aguilar, A. Gray, C. Han, C. Bisignano, P. Rao, E. Wool, Global burden of bacterial antimicrobial resistance in 2019: a systematic analysis. Lancet (2022).
2. WHO, “No Time to Wait: Securing the future from drug-resistant infections” (2019).
3. WHO, “Critically important antimicrobials for human medicine: ranking of antimicrobial agents for risk management of antimicrobial resistance due to non-human use” (2017).
4. WHO, “2020 antibacterial agents in clinical and preclinical development: an overview and analysis” (2021).
