Light-driven carbon nitride microswimmers with propulsion in biological and ionic media and responsive on-demand drug delivery

Abstract

We propose two-dimensional poly(heptazine imide) (PHI) carbon nitride microparticles as light-driven microswimmers in various ionic and biological media. Their high-speed (15 to 23 micrometer per second; 9.5 ± 5.4 body lengths per second) swimming in multicomponent ionic solutions with concentrations up to 5 M and without dedicated fuels is demonstrated, 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 these microswimmers is validated by cell viability tests with three different cell lines and primary cells. The nanopores of the swimmers are loaded with a model cancer drug, doxorubicin (DOX), resulting in a high (185%) loading efficiency without passive release. Controlled drug release is reported under different pH conditions and can be triggered on-demand by illumination. Light-triggered, boosted release of DOX and its active degradation products are demonstrated under 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 address 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 toward their biomedical, environmental, and other potential applications.

Photomemristive sensing via charge storage in 2D carbon nitrides

“…However, the application of wireless K-PHI particles for sensing holds more promise for applications where environmental or biological conditions are studied in situ . 48 …”

Magnetically steerable bacterial microrobots moving in 3D biological matrices for stimuli-responsive cargo delivery

“…Dexterous manipulation of tiny objects at the micro-and nanoscale to establish further understanding of active cargo delivery has been the cornerstone of microrobotic applications for minimally invasive therapies (1,2). Various microrobotic platforms have been developed, including fully synthetic micromotors actuated by external stimuli, such as magnetism (3)(4)(5), light (6), and acoustics (7,8). In contrast, biohybrid microrobots, which combine a motile microorganism (e.g., bacteria or algae) with an artificial component (e.g., micro/nanocarriers), are self-powered micromachines with intrinsic propulsion, sensing, and targeting mechanisms (9)(10)(11)(12).…”

Photocharging of Semiconductor Materials: Database, Quantitative Data Analysis, and Application in Organic Synthesis

“…constructed light‐driven microswimmers—devices capable for externally controlled autonomous propulsion and delivery of drugs in ionic and biological media. [ 57,58 ] As accumulation of electrons in SCP is typically accompanied by transfer of ubiquitous protons, photocatalytic reactions under continuous illumination and reactions employing SCP(e − /H + ) in dark proceed via proton‐coupled electron transfer (PCET) as summarized by Chen et al. [ 59 ] Indeed, due to high reactivity of SCP(e − /H + ) they are appealing reagents for reduction of various organic substrates in dark—such reactions were summarized by Kohtani et al.…”

“…[56] Using photochargeable PHIs, Sridhar et al constructed light-driven microswimmers-devices capable for externally controlled autonomous propulsion and delivery of drugs in ionic and biological media. [57,58] As accumulation of electrons in SCP is typically accompanied by transfer of ubiquitous protons, photocatalytic reactions under continuous illumination and reactions employing SCP(e − /H + ) in dark proceed via proton-coupled electron transfer (PCET) as summarized by Chen et al [59] Indeed, due to high reactivity of SCP(e − /H + ) they are appealing reagents for reduction of various organic substrates in dark-such reactions were summarized by Kohtani et al [60] Depending on the type of chemical reaction, several terms evolved around such use of photocharged SCPs: "dark" photocatalysis, [34] memory catalysis, [61,62] around-the-clock photocatalysis, [63] and illumination-driven electron accumulation in semiconductors. [35] To design rationally devices and processes employing photochargeable SCPs it is essential to know: 1) how many electrons can a certain SC store, 2) how fast a SC accumulates electrons, and 3) how fast a SC loses electrons upon addition of an oxidant in dark.…”