title: Enzymatically activated near infrared nanoprobes based on amphiphilic block copolymers for optical detection of cancer.
abstract: OBJECTIVE
  Nanotechnology offers the possibility of creating multi-functional structures that can provide solutions for biomedical problems. The nanoprobes herein described are an example of such structures, where nano-scaled particles have been designed to provide high specificity and contrast potential for optical detection of cancer. Specifically, enzymatically activated fluorescent nanoprobes (EANPs) were synthesized as cancer-specific contrast agents for optical imaging.
  
  
  METHODS
  EANPs were prepared by nanoprecipitation of blends of poly(lactic acid)-b-poly(ethylene glycol) and poly(lactic-co-glycolic acid)-b-poly(l-lysine). The lysine moieties were then covalently decorated with the near infrared (NIR) fluorescent molecule AlexaFluor-750 (AF750). Close proximity of the fluorescent molecules to each other resulted in fluorescence quenching, which was reversed by enzymatically mediated cleavage of poly(l-lysine) chains. EANPs were characterized by dynamic light scattering and electron microscopy. Enzymatic development of fluorescence was studied in vitro by fluorescence spectroscopy. Biocompatibility and contrast potential of EANPs were studied in cancerous and noncancerous cells. The potential of the nanoprobes as contrast agents for NIR fluorescence imaging was studied in tissue phantoms.
  
  
  RESULTS
  Spherical EANPs of ∼100 nm were synthesized via nanoprecipitation of polymer blends. Fluorescence activation of EANPs by treatment with a model protease was demonstrated with up to 15-fold optical signal enhancement within 120 minutes. Studies with MDA-MB-231 breast cancer cells demonstrated the cytocompatibility of EANPs, as well as enhanced fluorescence associated with enzymatic activation. Imaging studies in tissue phantoms confirmed the ability of a simple imaging system based on a laser source and CCD camera to image dilute suspensions of the nanoprobe at depths of up to 4 mm, as well as up to a 13-fold signal-to-background ratio for enzymatically activated EANPs compared to un-activated EANPs at the same concentration.
  
  
  CONCLUSIONS
  Nanoprecipitation of copolymer blends containing poly(l-lysine) was utilized as a method for preparation of highly functional nanoprobes with high potential as contrast agents for fluorescence based imaging of cancer. Lasers Surg. Med. 47:579-594, 2015. © 2015 Wiley Periodicals, Inc.
authors.affiliation: Materials Science, Engineering, and Commercialization Program, Texas State University, San Marcos, Texas 78666.
authors.forename: Tuğba
authors.initials: T
authors.lastname: Özel
authors.affiliation: Department of Biomedical Engineering, Beckman Laser Institute, University of California, Irvine, California 92697.
authors.forename: Sean
authors.initials: S
authors.lastname: White
authors.affiliation: Department of Biomedical Engineering, Beckman Laser Institute, University of California, Irvine, California 92697.|School of Medicine, Virginia Commonwealth University, Richmond, Virginia.
authors.forename: Elaine
authors.initials: E
authors.lastname: Nguyen
authors.affiliation: Department of Biomedical Engineering, Beckman Laser Institute, University of California, Irvine, California 92697.|The University of Texas at Austin, Austin, Texas 78712.
authors.forename: Austin
authors.initials: A
authors.lastname: Moy
authors.affiliation: The University of Texas at Austin, Austin, Texas 78712.|InnoSense LLC, Torrance, California 90505.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Brenes
authors.affiliation: Department of Biomedical Engineering, Beckman Laser Institute, University of California, Irvine, California 92697.|Department of Surgery, University of California, Irvine, California 92697.
authors.forename: Bernard
authors.initials: B
authors.lastname: Choi
authors.affiliation: Materials Science, Engineering, and Commercialization Program, Texas State University, San Marcos, Texas 78666.|InnoSense LLC, Torrance, California 90505.|Department of Chemistry and Biochemistry, Texas State University San Marcos, Texas 78666.
authors.forename: Tania
authors.initials: T
authors.lastname: Betancourt
keywords: PLA-PEG; PLGA; biodegradable polymers; enzymatically-responsive polymers; nanomedicine; nanoparticles; near infrared fluorescent contrast agents; near infrared optical imaging; optical contrast agents; protease activated probes