The efficacy of self-assembled cationic antimicrobial peptide nanoparticles against Cryptococcus neoformans for the treatment of meningitis Huaying Wang a , Kaijin Xu a , Lihong Liu b , Jeremy P.K. Tan b , Yunbo Chen a , Yongtao Li a , Weimin Fan a, c , Zeqing Wei a , Jifang Sheng a , Yi-Yan Yang b, ** , Lanjuan Li a, * a State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, First Affiliated Hospital, College of Medicine, Zhejiang University, 79 Qingchun Road, Hangzhou 310003, China b Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, Singapore 138669, Singapore c Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29425, USA article info Article history: Received 3 December 2009 Accepted 14 December 2009 Available online 31 December 2009 Keywords: Antimicrobial peptide Cationic nanoparticles Cryptococcus neoformans Meningitis Blood-brain barrier (BBB) abstract Cationic antimicrobial peptides have received considerable interest as new therapeutics with the potential for treatment of multiple-drug resistant infections. We recently reported that cholesterol- conjugated G 3 R 6 TAT (CG 3 R 6 TAT) formed cationic nanoparticles via self-assembly, which demonstrated strong antimicrobial activities against various types of microbes in vitro. In this study, the possibility of using these nanoparticles for treatment of Cryptococcus neoformans (yeast)-induced brain infections was studied. The antimicrobial activity of the nanoparticles was tested against 12 clinical isolates of C. neo- formans in comparison with conventional antifungal agents amphotericin B and fluconazole. Minimum inhibitory concentrations (MICs) of the nanoparticles were determined to be much lower than those of fluconazole in all the isolates, but slightly higher than those of amphotericin B in some isolates. At a concentration three times higher than the MIC, the nanoparticles completely sterilized C. neoformans after 3.5 h. Cell wall disruption and release of cytoplasmic content were observed under TEM. The biodistribution studies of FITC-loaded nanoparticles in rabbits revealed that the nanoparticles were able to cross the blood-brain barrier (BBB). The efficacy of nanoparticles was further evaluated in a C. neo- formans meningitis rabbit model. The nanoparticles crossed the BBB and suppressed the yeast growth in the brain tissues with similar efficiency as amphotericin B did. In addition, unlike amphotericin B, they neither caused significant damage to the liver and kidney functions nor interfered with the balance of electrolytes in the blood. CG 3 R 6 TAT nanoparticles can be a promising antimicrobial agent for treatment of brain infections caused by C. neoformans. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction The incidence of infections caused by the encapsulated yeast Cryptococcus neoformans has risen markedly over the past 20 years as a result of the HIV epidemic and increasing use of immuno- suppressive therapies [1]. Cryptococcal meningitis is a common opportunistic infection and AIDS-defining illness especially in patients with late-stage HIV infection. It also occurs in patients with other forms of immunosuppression or even in apparently immu- nocompetent individuals. The use of amphotericin B induction therapy followed by consolidation therapy with fluconazole has been considered as the standard treatment for Cryptococcal meningitis [2]. Despite excellent clinical trials and evidence-based treatment guidelines, clinical response rates in HIV-infected patients are not satisfactory, with a persistently high mortality rate of 10–30%. The treatment is complicated by the poor penetration of amphotericin B across the blood–brain barrier (BBB) [3]. Approaches such as an increment in dosage, injection through the myelin sheath and liposome modification with a brain targeting peptide have been proposed to achieve therapeutic concentration of amphotericin B in the brain [4]. However, dose-dependent nephrotoxicity, infusion-related adverse effects such as fever, chills, nausea, vomiting and headache have limited the use of ampho- tericin B [5]. The poor penetration of antimicrobial agent into cerebrospinal fluid (CSF) is not the only factor associated with the low treatment efficiency of Cryptococcal meningitis. In addition, the increasing number of C. neoformans isolates resistant to fluconazole and amphotericin B [6,7] represents another therapeutic challenge. Therefore, it is of increasing need to develop antimicrobial agents * Corresponding author. Tel.: þ86 571 87709001; fax: þ86 571 87081933. ** Corresponding author. Tel.: þ65 68247106; fax: þ65 64789084. E-mail addresses: yyyang@ibn.a-star.edu.sg (Y.-Y. Yang), ljli@zju.edu.cn (L. Li). Contents lists available at ScienceDirect Biomaterials journal homepage: www.elsevier.com/locate/biomaterials 0142-9612/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.biomaterials.2009.12.042 Biomaterials 31 (2010) 2874–2881