Corking Nitrogen‐Doped Carbon Nanotube Cups with Gold Nanoparticles for Biodegradable Drug Delivery Applications

Seth C. Burkert1, Alexander Star1

1 Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania
Publication Name:  Current Protocols in Chemical Biology
Unit Number:   
DOI:  10.1002/9780470559277.ch150093
Online Posting Date:  December, 2015
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Carbon nanomaterials have been proposed as effective drug delivery devices; however their perceived biopersistence and toxicological profile may hinder their applications in medical therapeutics. Nitrogen doping of carbon nanotubes results in a unique “stacked‐cup” structure, with cups held together through van der Waals forces. Disrupting these weak interactions yields individual and short‐stacked nanocups that can subsequently be corked with gold nanoparticles, resulting in sealed containers for delivery of cargo. Peroxidase‐catalyzed reactions can effectively uncork these containers, followed by complete degradation of the graphitic capsule, resulting in effective release of therapeutic cargo while minimizing harmful side effects. The protocols reported herein describe the synthesis of stacked nitrogen‐doped carbon nanotube cups followed by effective separation into individual cups and gold nanoparticle cork formation resulting in loaded and sealed containers. © 2015 by John Wiley & Sons, Inc.

Keywords: drug‐delivery; chemical vapor deposition; nitrogen‐doped carbon nanotubes; graphitic exfoliation; citrate reduction; enzymatic biodegradation

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Table of Contents

  • Introduction
  • Basic Protocol 1: Synthesis of Stacked NCNCs Through Chemical Vapor Deposition (CVD)
  • Basic Protocol 2: Separation of Stacked NCNCs by Probe‐Tip Sonication and Subsequent Cargo Loading and Gold Nanoparticle Corking
  • Commentary
  • Literature Cited
  • Figures
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Basic Protocol 1: Synthesis of Stacked NCNCs Through Chemical Vapor Deposition (CVD)

  • Acetone (Fisher Scientific)
  • Ferrocene (98% purity; Sigma Aldrich)
  • Acetonitrile (99.5% purity; EMD Millipore)
  • Xylenes (98.5% purity; Fisher Scientific)
  • Kimwipes (Kimtech Science)
  • 5 foot glass rod
  • Quartz tube (½‐inch diameter × 4 feet long; Technical Glass Products)
  • Quartz crossplate (½ inch × 1 foot; Technical Glass Products)
  • 3 thermal blocks: 3‐inch diameter with ½‐inch hole bored down the axis and 3 inches long)
  • Kera wool (or other insulating material)
  • Stainless steel end caps, one with solution injectorThe injector is a homemade apparatus consisting of 2 tubes of similar length: a 1/8‐inch tube, which acts as the solution injector, nested inside a 1/4‐inch tube, which is responsible for gas flow. The connections for the injector are composed of swagelok 1/4‐inch pieces (see Fig. B).
  • 2 o‐rings (½‐inch diameter)
  • 2 stainless steel washers (½‐inch diameter)
  • Lindberg Blue M 3 zone furnace (Thermo Scientific)
  • 2 bubblers
  • Pure Ar gas tank cylinder
  • Syringe pump (Harvard Apparatus)
  • 2 mass flow controllers
  • Pure H 2 gas cylinder
  • Microbalance (Mettler Toledo)
  • 25‐ml airtight syringe (SGE Analytical Science)
  • Respirator
  • Double‐sided razor blade

Basic Protocol 2: Separation of Stacked NCNCs by Probe‐Tip Sonication and Subsequent Cargo Loading and Gold Nanoparticle Corking

  • Nitrogen‐doped carbon nanotube cups synthesized in protocol 1; alternatively, nitrogen‐doped carbon nanotubes exhibiting the similar “stacked‐cup” morphology can be purchased (NanoTechLabs, cat. no. # NTL‐12116)
  • 95% to 98% (v/v) sulfuric acid (H 2SO 4; Fisher Scientific)
  • 70% nitric acid (HNO 3; Fisher Scientific)
  • Nanopure water (Barnstead Nanopure filtration unit)
  • 0.01 M sodium hydroxide (NaOH; Spectrum Chemicals) in nanopure water
  • 0.01 M hydrochloric acid (HCl; Fisher Scientific) in nanopure water
  • 1 mg/ml chloroauric acid (HAuCl 4; Sigma Aldrich) in nanopure water
  • 1% (w/v) sodium citrate (Na 3C 6H 5O 7; Sigma Aldrich) in nanopure water
  • Microbalance (Mettler Toledo)
  • 250‐ml round‐bottom flask
  • Kimwipes (Kimtech Science)
  • Bath sonicator (Branson 5510)
  • Three‐prong clamp
  • Filtration apparatus
  • 0.2‐μm polytetrafluoroethylene (PTFE) filter (EMD Millipore, cat. no. JGWP02500)
  • 100‐ml beaker
  • Probe‐tip sonicator (e.g., Qsonica Q500 equipped with ½‐inch titanium probe tip, 20 kHz max intensity)
  • Oil bath (Silicone oil for melting point and boiling point apparatuses; Sigma Aldrich, cat. no. 146153) on hot plate with magnetic stirrer
  • 4‐dram (21 × 70‐mm) vial and cap (Fisher Scientific)
  • 10 × 3‐mm magnetic stir bar 13 × 100‐mm borosilicate glass culture tubes (Fisher Scientific)
IMPORTANT NOTE: Wear appropriate personal protective equipment (e.g., respirator, lab coat, gloves, goggles, and closed‐toe shoes) when weighing NCNCs or working with strong acids.
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Literature Cited

Literature Cited
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