Amino Acid Functionalized Inorganic Nanoparticles as Cutting-Edge Therapeutic and Diagnostic Agents

Abstract

The field of medical diagnostics and therapeutics is being revolutionized by nanotechnology, from targeted drug delivery to cancer immunotherapy. Inorganic nanoparticles are widely used, albeit problems with agglutination, cytotoxicity, free radical generation, and instability in some biological environments limits their utility. Conjugation of biomolecules such as peptides to the surface of nanoparticles can mitigate such problems, as well as confer specialized theranostic (therapeutic and/or diagnostic) properties, useful across biomedical applications such as vaccines, drug delivery, and in vivo imaging. Coating with amino acids, rather than peptides, offers further a highly cost-effective approach (due to their ease of purification and availability), but is currently an underutilized way to decrease toxicity and enhance stability. Amino acid molecules are small (<200 Da) and have both positive and negative charge groups (zwitterionic) facilitating charge-specific molecule binding. Additionally, amino acids exert by themselves some useful biological functions, with antibacterial and viability enhancing properties (for eukaryotic cells). Overall particle size, nanoparticle core, and the specific amino acid used to functionalize their surface influence their biodistribution, and their effects on host immunity. In this review, we provide for the first time an overview of this emerging field, and identify gaps in knowledge for future research.

Revisiting the conformational adsorption of L‐ and D‐cysteine on Au nanoparticles by Raman spectroscopy

“…Such size‐dependant properties make the Au n (SR) m systems subject of study in surface science, molecular biology, materials science, and inorganic chemistry, with potential applications in sensing, drug delivery, nanoelectronics, and catalysis . In particular, in the biomedical field, the particle size defines cellular uptake and affects biodistribution into major organs . Particles with less than 5 nm in diameter can be cleared by the kidney, where as larger particles (50−100 nm) end up in the liver .…”

“…Au NPs capped with biocompatible water‐dispersible agents, such as amino acids, have proved to be suitable for biological applications . Amino acid‐capped Au NPs can be synthesized by adding the amino acid a priori (during synthesis) or a posteriori.…”

New Strategies in the Design of Nanomedicines to Oppose Uptake by the Mononuclear Phagocyte System and Enhance Cancer Therapeutic Efficacy

“…It is worth mentioning that many researchers have demonstrated the extraordinary treatment effect of nanomedicines on cancer recurrence and metastasis, which are major causes of cancer mortality. In particular, nanotheranostics, which integrates diagnosis and treatment agents in one nanocarrier, has been considered as an ideal platform for precisely personal treatment …”

A Novel Approach for Non-Invasive Lung Imaging and Targeting Lung Immune Cells

“…For instance, the coating on the particles surface can enhance their circulation time in the body by preventing efficient uptake by antigen presenting cells [25], or precluding aggregation due to a biological fluid such as serum or mucus [26,27]. Overall, amino acid coatings can be used to improve the biocompatibility, size and biodistribution, as well as potential interaction with immune cells, making them ideal molecules for conjugating on nanoparticles for therapeutic and diagnostic applications [28][29][30]. Therefore, the coating on the particle, along with its core, will both be significant when designing particles for pulmonary delivery and imaging.…”

“…Different coatings that can help modify the biodistribution of the particles in vivo include polyethene glycol, dextran and amino acids [29], which contain methyl, amino and carboxy functional groups. The availability of two functional groups (amino and carboxy) is beneficial as one can be utilized for attachment of drugs and other molecules, while the other is accessible to the nanoparticle.…”