Furthermore, the SPECT/CT images indicated that the NFC hydrogels did not degrade or deform as no pertechnetate was observed outside the site of injection, which is supported by the previous studies on cellulose biodurability (Märtson et al., 1999), flexibility, and structural integrity (Pääkkö et al., 2008). As a non-biodegradable material in the mammalian body, NFC could find potential use as a surgical tissue adhesive, space-filling injectable biomaterial

for tissue repair, long-term or single-dose local drug delivery, and tissue engineering. However, non-biodegradability is generally not desired. The removal of NFC from easily accessible sites (such as from subcutaneous tissue) through surgical means is fairly simple. In addition, the area could be locally treated with cellulose degrading enzymes to disintegrate the NFC hydrogels yielding mostly glucose as Pifithrin-�� the metabolized product. It has been shown that enzymatic degradation of NFC with cellulase is possible without increasing in vitro cytotoxicity ( Lou et al., 2014). However, patient acceptance towards injections is generally poor. Therefore NFC hydrogels have potential

as long-term or single-dose local delivery systems, especially with compounds of poor bioavailability or Galunisertib clinical trial where non-invasive routes remain a challenge. The release and distribution of 123I-β-CIT (a cocaine analogue) from NFC hydrogel implants were evaluated. 123I-β-CIT showed rapid release from the hydrogels, mostly distributing into the striatum and slightly around the hydrogel at the injection site. 123I-β-CIT showed a slightly slower rate of release when Adenosine imbedded with the hydrogel as opposed to the injections of saline and drug compound solutions. However, due to the rapid release, we determined that 123I-β-CIT does not show an apparent binding affinity to nanofibrillar cellulose itself. In addition, no major differences were found in the distribution of 123I-β-CIT

between the NFC/study compound injections and the saline/study compound injections. Therefore it is possible that the release of similar small compounds might not be altered by the NFC matrix. However it seems that the NFC hydrogel retains most of the 123I-β-CIT around itself and does not distribute as easily into the surrounding subcutaneous tissue than with the saline injections. We found it interesting that without affecting much of the release rate of the study compound, 123I-β-CIT is still more localized when administered with NFC. The release rate of the 99mTc-HSA was shown much slower than the release rate of the smaller study compound 123I-β-CIT. In addition, a very poor absorption from the injection site into the circulation was observed; furthermore, 99mTc-HSA distributed heavily into the surrounding subcutaneous tissue.