Diatom Biosilica in Targeted Drug Delivery and Biosensing Applications: Recent Studies

Abstract

Diatoms are single-cell algae encased in a cell wall (named frustule) composed of transparent, biogenic (or opaline) silica with intricate and strikingly regular patterns. Over the past 30 years, these microorganisms have proven to be a valuable replacement for synthetic silica that satisfies numerous pharmaceutical requirements for the realization of drug delivery vectors, biosensing supports and photonic crystals. It is not only the structural features of the diatoms, but also the possibility of chemically modifying the frustule that permits the relatively straightforward transformation of the biosilica into potential devices for biomedical applications. In this short review, we explore the applications of diatoms-derived biosilica in the drug delivery and biosensing fields. Specifically, we consider the use of diatoms for the targeted delivery of anticancer and antibiotic drugs and how the same microalgae are employed in the fabrications of biosensors whose analyte signal response is evaluated via fluorescence and surface-enhanced Raman scattering techniques. We limit our discussion to studies published in the last seven years, with the intention of minimizing possible redundancy with respect to previously published contributions.

Recent Advances of Material‐Decorated Photosynthetic Microorganisms and Their Aspects in Biomedical Applications

“…The breathable scaffold formulated by immobilizing the photosynthetic microorganisms in biocompatible materials could resolve the limited oxygen diffusion independent of blood supply, promoting both in vitro and in vivo tissue generation. Based on Porous structure and large surface area, Functional surface with reactive silanol group (Si-OH) Microcarrier for targeting cargo delivery [20,24] Spirulina Platensis High cargo-loading efficiency, Biodegradable Microcarrier for targeting cargo delivery [18,19] Helical structure for actuated motion, Microrobots for targeting cargo delivery [31,32] In vivo photosynthetic oxygenation Rich autofluorescent pigment Oxygen-dependent synergistic theranostic platform [72,87] Chlamydomonas reinhardtii Self-propelling motion, Phototaxis Microrobots for targeting cargo delivery, [27,34] In vivo photosynthetic oxygenation Photosynthetic scaffold for wound healing and tissue engineering [98,105]…”

Novel Drug and Gene Delivery System and Imaging Agent Based on Marine Diatom Biosilica Nanoparticles

“…The enhanced cellular uptake and nuclear aggregation of DOX-loaded-MSNs in MCF-7/ADR cancer cells may have resulted from the overriding of the drug flow mechanism and/or down-regulation of P-gp by the MSNs, resulting in the cytotoxicity eight times higher than the DOX alone. Functionalized MSNs not only increase cell proliferation suppression in the ADR cells with DOX treatment, but are also capable of delivering multiple agents, such as anti-tumor and MDR reversal molecules [ 178 ]. Due to the nanoscale and unique properties of the MSNs, aided with a rational design process, MDR can be overcome through an enhanced cellular uptake, increased intracellular aggregation, and an elevated drug efficacy [ 179 ].…”

Photochemical Reduction of Silver Nanoparticles on Diatoms

“…Additionally, a fluorophore on the surface of a frustule experiences an increase in the density of optical states, which results in enhanced emission due to the Purcell effect [ 15 , 16 ]. This dual-modal optical enhancement results in boosted fluorescence signals for the easier detection of analytes [ 17 ]. Due to their unique structural properties, diatoms are capable of enhancing the localized surface plasmon resonance (LSPR), leading to near-field optical amplification of the signal [ 17 ] due to the photonic, hierarchical, micro-scale periodicity of the diatom frustule pores that allow for the signal enhancement of the electromagnetic field induced by LSPR ‘hot spots’ with large SERS enhancement factors [ 14 ].…”

“…This dual-modal optical enhancement results in boosted fluorescence signals for the easier detection of analytes [ 17 ]. Due to their unique structural properties, diatoms are capable of enhancing the localized surface plasmon resonance (LSPR), leading to near-field optical amplification of the signal [ 17 ] due to the photonic, hierarchical, micro-scale periodicity of the diatom frustule pores that allow for the signal enhancement of the electromagnetic field induced by LSPR ‘hot spots’ with large SERS enhancement factors [ 14 ]. As a consequence, diatom biosilica has found wide applications in the fields of biosensing [ 18 ], diagnostics [ 19 ], and therapeutics.…”