Activated Carbon for Drug Delivery from Composite Biomaterials: The Effect of Grinding on Sirolimus Binding and Release

Abstract

Activated carbon (AC) could be potentially useful as a drug carrier in fiber polymer scaffolds destined for prolonged drug delivery. To be introduced, AC must be ground into smaller-sized particles to be introduced in scaffolds, as most biocompatible scaffolds consist of fibers with a diameter of less than 1 µm. In this study, the adsorption of sirolimus (SRL) from phosphate-buffered saline (PBS) solution and blood plasma (BP) onto AC of AX-21 type, as well as the release of SRL from AC depending on its fragmentation, were studied. Two-stage grinding of the AC, first with a ball mill, and then with a bead mill, was performed. Grinding with a bead mill was performed either in water or in polyvinylpyrrolidone to prevent aggregation of AC particles. Dynamic light scattering and scanning electron microscopy (SEM) demonstrated that the size of the particles obtained after grinding with a ball mill was 100–10,000 nm, and after grinding with a bead mill, 100–300 nm. Adsorption in PBS was significantly higher than in BP for all fractions, and depended on SRL concentration. The fraction obtained after grinding with a ball mill showed maximal SRL adsorption, both in PBS and BP, and slow SRL release, in comparison with other fractions. The 100–300 nm AC fractions were able to adsorb and completely release SRL into BP, in contrast to other fractions, which strongly bound a significant amount of SRL. The data obtained are to be used for controlled SRL delivery, and thus in the modification of drug delivery in biological media.

Activated Carbon-Enriched Electrospun-Produced Scaffolds for Drug Delivery/Release in Biological Systems

“…Here, we can conclude that the covering of ACNs with a PCL layer has no direct effect on the SRL interaction with ACNs because the maximum binding of SRL in PBS is very similar in terms of the maximum adsorption (up to 77%). The slight decrease in the rate of the SRL adsorption is obviously explained by the SRL diffusion through the PCL in fibers, unlike the AC suspension previously described in [ 20 ]. The work [ 10 ] describes that the adsorption of phenanthrene on composite material consisted of superfine, powdered, activated carbon (SPAC) and fibrous polystyrene (PS).…”

“…For the purpose of the present work, activated carbon AX-21 with a surface area, determined by the Brunauer–Emmett–Teller method (BET), and pore volume of 2330 m 2 /g and 1.7 cm 3 /g, respectively [ 22 ], was ground as described in [ 19 ] to obtain 100 nm-sized AC particles. The physicochemical properties of ground ACNs are described in detail in [ 20 ]. Prior research has shown that the fiber diameter and orientation affect cell adhesion and proliferation [ 23 , 24 , 25 ].…”

“…It was found that scaffolds of 5% PCL, 5% PCL/0.05% AC and 5% PCL/2.5% AC have similar characteristics. The signal corresponding to nitrogen in the scaffold of 5PCL/2.5AC is due to nitrogen-containing groups in the ACNs [ 20 ]. As can be seen from the comparison of the spectra ( Figure 4 ), the samples of 5% PCL and 5% PCL/0.05% AC/0.1mMTEA practically do not differ.…”

“…In a previous study, we presented the data on SRL adsorption onto ground AC in similar conditions [ 20 ]. The maximum SRL adsorption onto ground AC was 70–80% in PBS and 30–40% in BP.…”

“…Yet, there are a lot of AC types with different surfaces and pores that are able to bind an infinite set of organic molecules or biomolecules. Previously, we found that grinding AC up to 100 nm particles did not drastically change its binding capacity and could be used for filling ES-produced fibers [ 20 ]. One of the applications of drug-eluting scaffolds is the coating of vascular stents.…”