Production, surface modification and biomedical applications of nanodiamonds: A sparkling tool for theranostics

Chemical Functionalization of Nanodiamonds: Opportunities and Challenges Ahead

“…[5,21] Fordrug delivery applications,the drugs can be adsorbed on the ND surface and then released in the desired environment. [22,23] However, non-covalent functionalization suffers from alack of reproducibility.This drawback is caused by the poor control of the overall adsorption process.I nf act, the inhomogeneous ND surface together with the non-uniform agglomeration state may drastically affect the interaction between the NDs and the adsorbed molecules.…”

“…Regarding covalent approaches,the most commonly used groups are carboxylic and hydroxyl groups.Carboxylic groups are quite abundant on D-NDs and can react with amines after activation. [23] Efficient activation of the carboxylic groups is obtained by thionyl chloride,w hich is able to convert the carboxylic acid into an acyl chloride (Scheme 4). However, this reagent is not specific and can also convert hydroxyl groups to chlorides via nucleophilic substitution.…”

“…[24] Milder activation protocols have been reported using classical carbodiimide/succinimide activation (EDC/NHS) [1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide] that allows reactions in water or buffer at room temperature. [23] This methodology has opened the application of NDs to the biomedical fields.S everal studies showed efficient grafting of alarge variety of moieties including small molecules,d yes,m onomers,p olymers,a nd proteins (Scheme 4). [23] Another extensively used reaction targeting the carboxylic groups is esterification.…”

“…[23] This methodology has opened the application of NDs to the biomedical fields.S everal studies showed efficient grafting of alarge variety of moieties including small molecules,d yes,m onomers,p olymers,a nd proteins (Scheme 4). [23] Another extensively used reaction targeting the carboxylic groups is esterification. In this case,a fter activation using carbodiimides and appropriate bases,t he NDs can be functionalized with the desired alcohol [for example,p olyethylene glycol (PEG) or polyglycerol (PG)].…”

“…In this case,a fter activation using carbodiimides and appropriate bases,t he NDs can be functionalized with the desired alcohol [for example,p olyethylene glycol (PEG) or polyglycerol (PG)]. [12,23] Compared to amidation, ester functionalization leads to less stable products which are more prone to hydrolysis.E sterification of NDs was normally used to graft biopolymers in order to enhance the colloidal stability and blood circulation. [25,26] Another popular functionalization is the derivatization of the hydroxyl groups.T hese groups are naturally present in both HPHT-NDs and D-NDs and their quantity can be enhanced via an appropriate surface homogenization.…”