Biocompatible carbon nitride-based light-driven microswimmer propulsion in biological and ionic media with responsive on-demand drug delivery

TL;DR

This paper introduces biocompatible, light-driven carbon nitride microswimmers capable of high-speed propulsion and controlled drug delivery in ionic and biological media, addressing key limitations of previous microswimmers for biomedical applications.

Contribution

It presents a novel PHI-based microswimmer with high ion tolerance, biocompatibility, and on-demand drug release triggered by light, advancing microswimmer technology for biomedical uses.

Findings

High-speed swimming (15-23 μm/s) in ionic solutions up to 1 M without fuels.

High drug loading efficiency (185%) with controlled release triggered by pH and light.

Demonstrated biocompatibility with multiple cell types and primary cells.

Abstract

We propose two-dimensional organic poly(heptazine imide) (PHI) carbon nitride microparticles as light-driven microswimmers in various ionic and biological media. Their demonstrated high-speed (15-23 $\mu$m/s) swimming in multi-component ionic solutions with concentrations up to 1 M and without dedicated fuels is unprecedented, overcoming one of the bottlenecks of previous light-driven microswimmers. Such high ion tolerance is attributed to a favorable interplay between the particle's textural and structural nanoporosity and optoionic properties, facilitating ionic interactions in solutions with high salinity. Biocompatibility of the microswimmers is validated by cell viability tests with three different cell types and primary cells. The nanopores of the swimmers are loaded with a model cancer drug, doxorubicin (DOX), in high (185%) loading efficiency without passive release. Controlled drug release is reported in different pH conditions and can be triggered on-demand also by illumination. Light-triggered, boosted release of DOX and its active degradation products is demonstrated in oxygen-poor conditions using the intrinsic, environmentally sensitive and light-induced charge storage properties of PHI, which could enable future theranostic applications in oxygen-deprived tumor regions. These organic PHI microswimmers simultaneously solve the current light-driven microswimmer challenges of high ion tolerance, fuel-free high-speed propulsion in biological media, biocompatibility and controlled on-demand cargo release towards their biomedical, environmental and other potential future applications.