Luminescent Silicon Diatom Replicas: Self‐Reporting and Degradable Drug Carriers with Biologically Derived Shape for Sustained Delivery of Therapeutics

Abstract

Current development of drug microcarriers is mainly based on spherical shapes, which are not biologically favorable geometries for complex interactions with biological systems. Scalable synthesis of drug carriers with nonspherical and anisotropic shapes featuring sustained drug‐releasing performances, biocompatibility, degradability, and sensing capabilities is challenging. These challenges are addressed in this work by employing Nature's optimized designs obtained from low‐cost diatomaceous earth mineral derived from single‐cell algae diatoms. Silica diatoms with unique shapes and 3D microcapsule morphology are converted into silicon diatom replicas with identical structure by a magnesiothermic reduction process. The results reveal that prepared silicon diatoms have a set of unique properties including favorable microcapsule structure with high surface area and micro/mesoporosity providing high drug loading, fast biodegradability, and intrinsic luminescence, which make them highly suitable for low‐cost production of advanced drug microcarriers. Their sustained drug release >30 days combined with self‐reporting function based on silicon luminescence properties using nonluminescent and luminescent drugs for intravitreal drug therapy is successfully demonstrated. These silicon diatoms offer promising potential toward scalable production of low‐cost and advanced microcarriers for broad medical therapies, including theranostics and microrobotic guided drug delivery devices.

From The Mine to Cancer Therapy: Natural and Biodegradable Theranostic Silicon Nanocarriers from Diatoms for Sustained Delivery of Chemotherapeutics

“…Diatoms single cells, encapsulated in biomineralized silica walls (frustules) are one of the most outstanding example of biologically derived porous silica, with complex porous 3D architectures, and enormous diversity of species characteristic morphologies and well‐ordered patterns at micro and nanoscale . Diatom silica microshells (size 2–15 μm) having their unique hollow and pill‐box micro structures with micro and nanoscale porosity, high surface area and excellent biocompatibility is shown to be a promising and low‐cost biomaterial for drug delivery applications . The diatom silica material from fossilized diatoms is available in large quantities from the mining industry as low‐cost material (ca $200 per tonne) and has a long history of the use in food industry.…”

“…However, one drawback of using diatom silica for drug delivery is their limited biodegradability and slow clearance from the body. This problem is addressed in our previous study, showing the successful conversion of silica diatom microcapsules into fully biodegradable porous silicon replicas by magnesiothermic reduction process that makes it possible to preserve the original morphology and porosity of diatom structures . The resulting silicon diatom microcarriers were demonstrated to have an excellent drug‐delivery performance and unique self‐reporting luminescent properties, making them an outstanding alternative to synthetic porous Si nanocarriers .…”

Tracking the Fate of Porous Silicon Nanoparticles Delivering a Peptide Payload by Intrinsic Photoluminescence Lifetime

“…The release kinetics of the peptide payload, determined by measuring fluorescence intensity from the 6‐FAM label in the supernatant (after separation from the PSiNPs by centrifugation), matched the aqueous degradation profile of the PSiNPs: the loss in PL intensity from the PSiNPs correlated linearly with the appearance of fluorescence from the FAM label (Figure S5c, Supporting Information). This correlation between drug release and decrease in steady‐state PL intensity has been reported previously for the release of siRNA, protein, and small molecule payloads from porous Si particles . However, the time‐resolved PL spectrum has not previously been used to monitor payload release from a porous Si delivery vehicle.…”

“…It is already well established that as a silicon nanostructure dissolves in an aqueous medium, it displays a spectral blueshift and a decrease in lifetime of the excited state . Also, prior work has reported correlations between these spectral properties and payload release from PSiNPs in vitro, which has been described as a “self‐reporting” characteristic . In this work we show how analysis of a combination of the intensity and the lifetime of PL allows both tracking and assessment of the state of degradation of PSiNPs, and we provide the first demonstration of the application of this concept in an animal model.…”

Synthetic vs Natural: Diatoms Bioderived Porous Materials for the Next Generation of Healthcare Nanodevices

“…Figure reports a schematic of silica to silicon diatoms conversion by magnesiothermic reduction process, drug loading, drug release and degradation of microvectors. Silica diatoms shown unique properties compared to silica ones, such as fast biodegradability and intrinsic luminescence . Intravenous injection of diatom microparticles into mice was also demonstrated; the targeted delivery of anticancer drugs by genetically engineered particles and the biodistribution and tissue damage of biosilica were investigated.…”