Abstract
Among the several types of inorganic nanoparticles available, silica nanoparticles (SNP) have earned their relevance in biological applications namely, as bioimaging agents. In fact, fluorescent SNP (FSNP) have been explored in this field as protective nanocarriers, overcoming some limitations presented by conventional organic dyes such as high photobleaching rates. A crucial aspect on the use of fluorescent SNP relates to their surface properties, since it determines the extent of interaction between nanoparticles and biological systems, namely in terms of colloidal stability in water, cellular recognition and internalization, tracking, biodistribution and specificity, among others. Therefore, it is imperative to understand the mechanisms underlying the interaction between biosystems and the SNP surfaces, making surface functionalization a relevant step in order to take full advantage of particle properties. The versatility of the surface chemistry on silica platforms, together with the intrinsic hydrophilicity and biocompatibility, make these systems suitable for bioimaging applications, such as those mentioned in this review.
Highlights
Silica nanoparticles (SNPs) have a wide range of biomedical applications being already used as drug delivery systems and as bioimaging agents (°uorescent, magnetic resonance imaging (MRI), Raman imaging).[1,2,3,4,5,6,7,8,9]
While mesoporous SNP are normally used as drug delivery systems through physical or chemical adsorption, colloidal SNP have been often employed to encapsulate or to graft at the surface active agents.[12,13]
It is imperative to understand how biomolecules interact with SNP surfaces and how to manipulate such interaction in order to take full advantage of SNP properties. Having these challenges in mind, this review will focus on recent e®orts for the development of SNP as bioimaging platforms and on the role of surface functionalization on the interactions with biological systems
Summary
Silica nanoparticles (SNPs) have a wide range of biomedical applications being already used as drug delivery systems (such as in chemotherapy, photodynamic therapy, gene therapy, protein adsorption, immunoassays) and as bioimaging agents (°uorescent, magnetic resonance imaging (MRI), Raman imaging).[1,2,3,4,5,6,7,8,9] Currently, mesoporous and amorphous SNP have been extensively used in the biomedicaleld.[9,10] While mesoporous SNP are normally used as drug delivery systems through physical or chemical adsorption, colloidal SNP have been often employed to encapsulate or to graft at the surface active agents.[12,13]. The development of biomarkers addresses important aspects concerning biocompatibility, toxicity or aggregation problems that might limit their application in living systems or tissues In this context, SNP have gained increasing importance as new platforms, i.e., as protecting shells of diverse organic/inorganic compounds and as coatings of other types of nanoparticles.[14,15,16,17,18] Important consequences of such type of coating are the improvement of water compatibilty, for molecules poorly soluble, and limitation of eventual detrimental e®ects occurring in the encapsulated compounds[19] Besides, SNP are chemically stable at physiological pH and resist to microbial attacks, making these nanoparticles advantageous over biodegradable ones.[20,21] Currently, there is a wide range of organic or metal-organic compounds and nanoparticles that have been successfully entrapped in SNP for bioimaging purposes.[22,23,24,25,26,27] the easy surface functionalization can decrease biological side e®ects and increase bioavailability and selectivity. Having these challenges in mind, this review will focus on recent e®orts for the development of SNP as bioimaging platforms and on the role of surface functionalization on the interactions with biological systems
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