Download 632. Polyethylenimine Mediated Synthesis of Gold Nanoparticles for

Polyethylenimine mediated synthesis of gold nanoparticles for biomedical applications
P C Pandeya and Roger J. Narayanb
aDepartment of Chemistry, Indian Institute of Technology (Banaras Hindu University), Varanasi-221005, India
bJoint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Raleigh, NC, USA
Statement of Purpose: Synthesis of functional gold
nanoparticles (AuNPs) justifying selectivity in
biochemical interaction along with biocompatibility suited
for in vivo biomedical applications has been a challenging
issue. We report herein the role of polyethylenimine (PEI)
in controlled synthesis of AuNPs under ambient conditions
which has potentiality for sensing glutathione and selective
interaction with DNA binding proteins facilitating
endosomal escape for the nucleotide delivery. The choice
of organic reducing agents like formaldehyde
/acetaldehyde/
acetyl
acetone/tetrahydrofuran
hydroperoxide and other similar compounds allow rapid
conversion of PEI capped gold cations into AuNPs at room
temperature thus controlling the functional ability of
nanoparticles as a function of organic reducing agents.
Both small and higher molecular weight PEI facilitates fast
synthesis of AuNPs controlling cyto-toxicity during in vivo
biomedical applications. In addition to that the new
process also allow the synthetic insertion of gold
nanoparticles in mesoporous silica nanoparticles providing
a robust framework in which two or more components can
be incorporated to give multifunctional capabilities with
specific loading of bioactive molecule leading selective
drug delivery. The AuNPs have been characterized by UVVis and transmission electron microscopy revealing
excellent polycrystallinity and controlled nanogeometry.
The cationic polymer coating enhances the electrocatalytic
performances of nanoparticles. The typical biomedical
application on glutathione (GSH) sensing based on
peroxidase mimetic ability of as made AuNPs and loading
of paclitaxel in mesoporous architecture are studied. The
as synthesized AuNPs are extreme salt and pH resistant and
have potentiality for both homogeneous and heterogeneous
biocatalysis justifying novelty in efficient drug delivery.
Methods: Polyethylenimine (50 wt. % in H2O, average
Mn 1200, 60000, 25000) was obtained from SigmaAldrich. Tetrachloroauric acid hydrate was purchased from
HiMedia; acetaldehyde, Acetaldehyde, Acetone, tert- butyl
methyl ketone are obtained from Merck, India. All other
chemicals employed were of analytical grade. Aqueous
solutions were prepared by using doubly distilleddeionized water. Unless mentioned otherwise, all the
experiments were performed at room temperature (25oC).
The absorption spectra of nanoparticles were recorded
using a Hitachi U-2900 Spectrophotometer. Transmission
electron microscopy (TEM) images were recorded using
Morgagni 268D (Fei Electron Optics) operating at 200 kV.
PEI allow the conversion of gold cations into AuNPs at
relatively higher temperature i.e. 60oC within less than 5
min even in absence of any organic reducing agent.
Accordingly we investigated the formation of AuNPs at
60oC in absence of organic reducing agent. The use of
organic
reducing
agents
like
tetrahydrofuran
hydroperoxide
(THF-HPO)/acetyl
acetone/formaldehyde/acetaldehyde and many more under
similar conditions enable the conversion of gold cations
into AuNPs at room temperature. Accordingly we
investigated the synthesis of AuNPs under four different
conditions: (A) in absence of any organic reducing agent,
and in the presence of : (B) THF-HPO, (C) acetyl acetone
and (D) formaldehyde. Typically 40 l of 10 mM
tetrachloroauric acid in water was mixed with 30 l of 5
mg/ml PEI and incubated at 60oC for 5 min. However the
synthesis of AuNPs in the presence of organic reducing
agents was carried out at room temperature. Typically 40
l of 10 mM tetrachloroauric acid in methanol was mixed
with 30 l of 5 mg/ml PEI followed by the addition of 30
l of (B) THF-PHO, (C) acetyl acetone and (D)
formaldehyde. The reaction mixture was allowed to stand
at room temperature. The formation of nanoparticles took
over within different time course as a function of organic
reducing agents. Typical procedure of Polyethylenimine
(PEI) mediated synthesis of gold nanoparticles (AuNPs)
was similar as described earlier.
Results:
(i)
Polyethylenimine
(PEI)
and
formaldehyde/acetaldehyde allow rapid synthesis of gold
nanoparticles i.e. within < 5 min, (ii) both higher and lower
mol.wt.PEI enable the synthesis of AuNPs thus controlling
the cytotocity for biomedical applications as lower mol.wt.
PEI are non-toxic, (iii) the enable PEI selective interaction
with DNA binding proteins facilitating endosomal escape
for the nucleotide delivery, (iv) The process enable
synthetic insertion of gold nanoparticles into mesoporous
matrix of silica nanoparticles.
Figure 1. Polyethylenime and formaldehyde/acetaldehyde
mediated synthesis of gold nanoparticles. Inset show the TEM
images of the AuNPs.
Conclusions: The present article demonstrates the
synthesis of PEI-stabilized AuNPs through active
participation of PEI and organic reducing agents like
formaldehyde/acetaldehyde/tetrahydrofuran
hydroperoxide/acetyl acetone. The process enable the rapid
synthesis of PEI functionalized AuNPs within < 5 min
through control over M.W. of PEI between 800 to 25 kD
thus controlling the cytotoxicity in therapeutic applications
together facilitating the PEI-based transfection. PEIAuNPs shows excellent catalytic activity as peroxidase
mimetic and enable glutathione sensing based on
competitive interaction.In addition to that the process
enable the the synthetic insertion of gold nanoparticles in
mesoporous silica nanoparticles providing a robust
framework in which two or more components can be
incorporated to give multifunctional capabilities with
specific loading of bioactive molecule leading selective
drug delivery