In vivo microplastic detection with photoacoustic imaging

Microplastics are posing an escalating threat to both ecological systems and human health. Yet, current methods for investigating their bioaccumulation are highly invasive, requiring destructive analysis of ex vivo tissues via mass spectrometry, dye labelling, or Raman microspectroscopy. This limits the study of biodistribution dynamics in preclinical models and human populations, leaving an urgent need for non-invasive alternatives. Meeting this challenge, for the first time in living tissue, the native optical absorption properties of microplastics are exploited to generate photoacoustic signal – imageable ultrasound emission following thermalisation of pulsed laser light. Distinct optical absorption profiles enable microplastic differentiation from endogenous biological signal sources, long-term tracking over 2 months in a mouse model, and microscale resolution of particle features verified histologically. This novel approach overcomes previous limitations of optical and nuclear imaging methods relying on fluorescent dyes or radio-isotopes, going beyond small transparent organisms such as zebrafish or nematodes, and half-life-dependent timescales, respectively. By enabling serial monitoring of microplastic biodistribution dynamics, this technique will help interrogate interacting factors such as ingestion route, microplastic shape, size and polymer type – and their effects on accumulation, degradation, clearance, and disease in animal models, and, ultimately, human subjects.