The Laryngoscope V C 2011 The American Laryngological, Rhinological and Otological Society, Inc. The Use of Lipid Microtubes as a Novel Slow-Release Delivery System for Laryngeal Injection Vasantha L. Kolachala, PhD; Eric E. Berg, MD; Samantha Shams, BA; Vivek Mukhatyar; Viranuj Sueblinvong, MD; Ravi V. Bellamkonda, PhD; Michael M. Johns, MD Objectives/Hypothesis: The potential utility of direct injection of bioactive substances in the treatment of vocal fold tis- sue fibrosis is limited by rapid clearance from the injection site. The objective of this study is to evaluate the potential of a lipid-based microtube delivery system to preserve the biological activity of injected substances and prolong their duration of pharmacological effects in the larynx. Study Design: Prospective in vitro and case–control in vivo murine study Methods: Lipid-based microtubes were loaded with Texas red-dextran (MT-TR) and hepatocyte growth factor (MT-HGF). In vitro and in vivo (using a murine vocal fold injection model) release of MT-TR and MT-HGF were determined to assess du- ration of microtube-mediated delivery. The biologic effects of MT-HGF on fibroblasts were assessed after treatment in the presence of transforming growth factor (TGF)-b. Results: In vitro release kinetics demonstrated slow release of MT-TR and MT-HGF, correlating with in vivo results dem- onstrating persistence of MT-HGF at 4 weeks postinjection. Bioefficacy was maintained, as MT-HGF was shown to inhibit TGF- b-mediated induction of procollagen mRNA levels in vitro 24 hours after treatment in fibroblast cells. Sustained release of HGF from microtubes at 6 days exacerbated the effects of TGF-b and increased levels of procollagen mRNA. Conclusions: Microtubes have significant potential utility as an efficacious means of sustained-release delivery of bioac- tive agents to the larynx. Atthough the role of HGF as an antifibrotic agent is questioned, its sustained bioefficacy after micro- tube encapsulation distinguishes microtubes from other delivery vehicles. Key Words: Laryngeal fibrosis, vocal cord injection, microtubes, hepatocyte growth factor. Level of Evidence: N/A Laryngoscope, 121:1237–1243, 2011 INTRODUCTION Current treatment strategies for fibrotic processes of the vocal fold, including vocal fold aging as well as physical- and radiation-induced injury, have limited effi- cacy. Without effective intervention, these processes induce dramatic changes to vocal fold histology resulting in dysphonia. Aged vocal folds, for example, pathologi- cally demonstrate reduced thickness, increased stiffness, dense collagen deposition, and decreased hyaluronic acid content when compared to young vocal folds. Recent evi- dence suggests that injection of growth factors such as hepatocyte growth factor (HGF) and basic fibroblast growth factor (bFGF) may have significant antifibrotic effects, helping to ameliorate the effects of such proc- esses. 1–6 Injection of these bioactive agents into laryngeal tissue is an attractive therapeutic tool; however, multiple vocal fold injections may be required to produce an effica- cious result. Daily and even weekly laryngeal injections are impractical for most patients and clinicians. The primary factor requiring serial injection is the rapid clearance and metabolism of injected substances from target tissue such as vocal folds. A sustained deliv- ery system that can both optimally control the rate of release and location of encapsulated substances is sorely needed. Fabrication techniques maintaining biological activity of the delivered substance are also critical. A variety of such systems have been investigated, including polymer-based vehicles. However, fabrication processes typically involve the use of harsh organic sol- vents that themselves may denature and deactivate encapsulated substances, resulting in low efficacy upon release, which is not desirable for drug delivery. Micro- tubes are an attractive, lipid-based sustained delivery vehicle for many drugs and biologically active substan- ces. With an excellent intrinsic biocompatibility and a high safety profile, they have potential for widespread medical application. They have a high loading efficiency From the Emory Voice Center (V .L.K., E.E.B., S.S., M.M.J.), Department of Otolaryngology—Head and Neck Surgery, Emory University School of Medicine, Atlanta, Georgia, U.S.A.; and Wallace H. Coulter Department of Biomedical Engineering (V .M., R.V .B.), Georgia Institute of Technology and Emory University, Atlanta, Georgia, U.S.A., Department of Internal Medicine (V .S.), Division of Pulmonary and Critical Care Medicine, Emory University School of Medicine, Atlanta, Georgia, U.S.A. Editor’s Note: This Manuscript was accepted for publication February 15, 2011. This research was conducted at Emory University, Atlanta, Georgia. This work was funded by internal funding from the Department of Otolaryngology—Head & Neck Surgery, Emory University, Atlanta, Georgia. The authors have no conflicts of interest to disclose. Send correspondence to Dr. Michael M. Johns, The Emory Voice Center, Emory University, Hospital Midtown, Medical Office Tower, 9th Floor, 550 Peachtree Street, Atlanta, GA 30308. E-mail: michael.johns2@ emory.edu DOI: 10.1002/lary.21796 Laryngoscope 121: June 2011 Kolachala et al.: Slow-Release Delivery System for Laryngeal Injection 1237