Local release of tacrolimus from hydrogel-based drug delivery system is controlled by inflammatory enzymes in vivo and can be monitored non-invasively using in vivo imaging.

Dzhuliya Dzhonova,Ashish Dhayani,Radu Olariu,Adriano Taddeo,Jonathan Leckenby,Robert Rieben,Praveen Kumar Vemula,Yara Banz,Jean-Christophe Prost,Anandhi Upendran

doi:10.1371/journal.pone.0203409

Abstract

BackgroundLocal drug delivery systems that adjust the release of immunosuppressive drug in response to the nature and intensity of inflammation represent a promising approach to reduce systemic immunosuppression and its side effects in allotransplantation. Here we aimed to demonstrate that release of tacrolimus from triglycerol monostearate hydrogel is inflammation-dependent in vivo. We further report that by loading the hydrogel with a near-infrared dye, it is possible to monitor drug release non-invasively in an in vivo model of vascularized composite allotransplantation.Materials and methodsInflammation was induced by local challenge with lipopolysaccharides in naïve rats 7 days after injection of tacrolimus-loaded hydrogel in the hind limb. Tacrolimus levels in blood and tissues were measured at selected time points. A near-infrared dye was encapsulated in the hydrogel together with tacrolimus in order to monitor hydrogel deposits and drug release in vitro and in vivo in a model of vascularized composite allotransplantation.ResultsInjection of lipopolysaccharides led to increased blood and skin tacrolimus levels (p = 0.0076, day 7 vs. day 12 in blood, and p = 0.0007 in treated limbs, 48 h after injection compared to controls). Moreover, lipopolysaccharides-injected animals had higher tacrolimus levels in treated limbs compared to contralateral limbs (p = 0.0003 for skin and p = 0.0053 for muscle). Imaging of hydrogel deposits and tacrolimus release was achieved by encapsulating near-infrared dye in the hydrogel for 160 days. The correlation of tacrolimus and near-infrared dye release from hydrogel was R2 = 0.6297 and R2 = 0.5619 in blood and grafts of transplanted animals respectively and R2 = 0.6066 in vitro.ConclusionsHere we demonstrate the inflammation-responsiveness of a tacrolimus-loaded hydrogel in vivo. Moreover, we show that encapsulating a near-infrared dye in the hydrogel provides a reliable correlation of tacrolimus and dye release from the hydrogel, and an accessible non-invasive method for monitoring drug release from hydrogel deposits.

Highlights

Vascularized composite allotransplantation (VCA)–the transplantation of tissues, such as hands, face and abdominal wall–has experienced an exhilarating development in the past two decades
Injection of lipopolysaccharides led to increased blood and skin tacrolimus levels (p = 0.0076, day 7 vs. day 12 in blood, and p = 0.0007 in treated limbs, 48 h after injection compared to controls)
Lipopolysaccharides-injected animals had higher tacrolimus levels in treated limbs compared to contralateral limbs

Summary

Introduction

Vascularized composite allotransplantation (VCA)–the transplantation of tissues, such as hands, face and abdominal wall–has experienced an exhilarating development in the past two decades. Several groups have developed drug delivery approaches for targeted immunosuppression, with the aim to decrease systemic toxicity and improve graft outcome. These approaches have been recently reviewed [2] and include the use of topical tacrolimus (TAC) [3,4] and clobetasol [4], intra-graft injections of TAC [5] and biodegradable disks containing TAC-loaded microspheres [6]. We reported that repeated intra-graft TGMS-TAC injections in a Brown Norwayto-Lewis rat hind-limb transplantation model prolonged graft survival for >280 days, with sub-therapeutic drug levels in blood for extended periods of time [8], making this approach a promising alternative to systemic immunosuppression in VCA patients. We further report that by loading the hydrogel with a near-infrared dye, it is possible to monitor drug release non-invasively in an in vivo model of vascularized composite allotransplantation

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