Labile Catalytic Packaging of DNA/siRNA: Control of Gold Nanoparticles "out" of DNA/siRNA Complexes
Alex M. Chen, Zhang, M., Oleh Taratula, Dongguang Wei, Thresia Thomas, T. J. Thomas, Tamara Minko, and Huixin He., ACS Nano, 2010, 4, 3679-3788.
In this work, we report an interesting finding that Au nanoparticles (NPs) physically anchored with several low generation polypropylenimine (PPI) dendrimers can effectively assemble DNA/siRNA into discrete nanopartcles, where the Au NPs can be controlled "out" of the final DNA/siRNA nanoparticles. Therefore it becomes possible to eliminate the potential toxic problems associated with Au NPs by selectively removing the Au NPs from the resulting nucleic acid complexes before their delivery to targeted cells. This is a new concept of using engineered inorganic nanoparticles for DNA/siRNA condensation and delivery. In contrast to the siRNA nanostructures (mainly random aggregated nanofibers) formed from low generation dendrimer alone (PPI Generation 3), the siRNA complex nanoparticles packaged by this novel approach (Au nanoparticles modified with G3 PPI dendrimers) can be internalized by cancer cells and the delivered siRNAs can effectively silence their targeted mRNA. The efficiency of mRNA silencing by the proposed nanoparticles is even superior to higher generation dendrimers (PPI Generation 5).
Simple Production of Graphene Sheets by Direct Dispersion with Aromatic Doping and Healing Agents
Ming Zhang, Rishi R. Parajuli, Daniel Mastrogiovanni, Boya Dai, Phil Lo, William Cheung, Roman Brukh, Pui Lam Chiu, Tao Zhou, Zhongfan Liu, Eric Garfunkel, and Huixin He. Small, 2010, 6, 1100-1107.
In this work, we report a simple and scalable exfoliation approach to produce high quality single layer graphene sheets. In a typical experimental procedure, graphite powders were exfoliated by sonicating in an aqueous solution of pyrene molecules that had been functionalized with different water soluble groups. Highly conductive graphene sheets stabilized in aqueous suspensions were directly produced without requiring toxic reducing agents and expensive solvents. Most importantly, different from other surfactants and polymers, that has been used to prevent graphene sheets from aggregation in solution, the pyrene molecules also act as nanographene molecules to heal the possible defects in the graphene sheets during annealing. Remarkably, they also appear to act as electrical "glue" soldering adjacent graphene sheets such that electric contacts between graphene sheets can be dramatically improved across the film. Graphene films with conductivity of 181,200 S/m (778 ?/square) with light transmittance greater than 90% in the 400–800 nm wavelength range are reproducibly obtained, which is the highest conductivity values ever achieved for graphene films fabricated by graphite exfoliation approaches (note that graphene films fabricated by chemical vapour deposition (CVD) method can reach 200 ?/square at 80% optical transparency). Nevertheless, this simple and scalable approach is extremely promising to produce high quality graphene films for a wide range of optoelectronic applications, including photovoltaics.
Co-delivery of Doxorubicin and siRNAs into Multidrug Resistant Cancer Cells by Mesoporous Silica Nanoparticles for Enhanced Chemotherapy Efficacy
Alex M. Chen, Min Zhang, Dongguang Wei, Dirk Stueber, Oleh Taratula, Tamara Minko, and Huixin He. Small, 2009, 5, 2673-2677.
In this work, we explored to utilize mesoporous silica nanoparticles (MSNs) to co-deliver doxorubicin (Dox) (as a model apoptosis-inducing anticancer drug), and a siRNA (as a suppressor of cellular antiapoptotic defense) simultaneously into multidrug resistant cancer cells for efficient cancer therapy. As illustrated in Scheme, the MSNs were modified to encapsulate Dox inside the pores to achieve minimal premature drug release. Then the Dox-loaded MSNs were modified with generation 2 (G2) amine-terminated polyamidoamine (PAMAM) dendrimers. The dendrimer-modified MSN can efficiently complex with siRNAs targeted against mRNA encoding Bcl-2 protein, which is the main player for nonpump resistance. We found thus-formed complex can be delivered into multidrug resistant A2780/AD human ovarian cancer cells to induce cell death. The anticancer efficacy of Dox increased 132 times compared to free Dox, mainly because the simultaneously delivered siRNA significantly suppressed the Bcl-2 mRNA, and efficiently overcome the nonpump resistance. Moreover, our data suggested that the delivered Dox by the MSNs are primarily localized in perinuclear region upon internalization, providing additional advantage in possibly bypassing pump resistance, therefore further enhancing the drug efficacy. This result is much different from some liposome co-delivery systems, in which antisense oligonucleotides targeted to pump and nonpump resistances must be simultaneously delivered in order to significantly increase drug efficacy. We attributed this difference to the different internalization pathway and drug release mechanism. We envisioned that this co-delivery system can be generalized to other anticancer drugs and other cancer cell lines.
Anti-HER2 IgY Antibody-Functionalized Single-Walled Carbon Nanotubes for Detection and Selective Destruction of Breast Cancer Cells
Xiao, Y., Gao, X., Taratula, O., Treado, S., Mitra, S., Salva, R., Wagner, P. D., Srivastava, S., He, H. X. BMC Cancer, 2009, 9, 351 (1-11).
In this work, anti-HER2 IgY-SWNT complexes were constructed by covalently conjugating carboxylated SWNTs with anti-HER2 chicken IgY antibodies, which are more specific and sensitive than mammalian IgGs. We demonstrated the dual functionality of the complex for both detection and selective destruction of cancer cells in an in vitro model. Raman signal collected at single-cell level from the complex-treated receptor-positive breast cancer cells was significantly greater than that from various control cells. Near Inferred (NIR) irradiation selectively destroyed the complex targeted breast cancer cells without harming receptor-free cells. The cell death was effectuated without the need of internalization of SWNTs by the cancer cells, a finding that has not been reported previously.
Surface-Engineered Targeted PPI Dendrimers for Efficient Intracellular and Intratumoral siRNA delivery
Taratula, O., Garbuzenko, O. B., Kirkpatrick, P., Pandya, I., Savla, S., Pozharov, V. P., He, H. X., Minko, T. Journal of Controlled Release, 2009, 140, 284-293.
Low penetration ability of Small Interfering RNA (siRNA) through the cellular plasma membrane combined with its limited stability in blood plasma, limits the effectiveness of the systemic delivery of siRNA. In order to overcome such difficulties, we constructed a nanocarrier-based delivery system by taking advantage of the lessons learned from the problems in the delivery of DNA. In the present study, siRNA nanoparticles were first formulated with poly(propyleneimmine) (PPI) dendrimers. To provide lateral and steric stability to withstand the aggressive extracellular environment, the formed siRNA nanoparticles were caged with a dithiol containing crosslinker molecules followed by coating them with PEG polymer. A synthetic analog of Luteinizing Hormone-Releasing Hormone (LHRH) peptide was conjugated to the distal end of PEG polymer to direct the siRNA nanoparticles specifically to the cancer cells. Our results demonstrated that this layer-by-layer modification and targeting approach confers the siRNA nanoparticles extracellular stability and intracellular bioavailability, provides for their specific uptake by tumor cells, accumulation of delivered siRNA in the cytoplasm of cancer cells, and the efficient gene silencing. In addition, in vivo body distribution data confirmed high specificity of the proposed targeting delivery approach which created the basis for the prevention of adverse side effects of the treatment.
Improved Conductivity of
Carbon Nanotube Networks by In-situ Polymerization of a
Thin Skin of Conducting Polymer
Ma, Y. F., Cheung, W., Wei, D. G.,
Bogozi, A., Chiu, P. L., Wang, L., Pontoriero, F.,
Mendelshon, R. and He, H. X. ACS Nano, 2008, 2,
There is increasing enthusiasm for the use of carbon
nanotube network films as conductive flexible electrodes
for a wide variety of applications. However, all the
reported conductivities of the single walled carbon
nanotubes (SWNTs) network films were significantly lower
than the conductivity of a carbon nanotube rope (axial
conductivity). This has been attributed to the high
contact resistance between the tubes in the networks.
Tremendous efforts have been made over the past decade to
prepare polymer and carbon nanotube composites with an aim
to synergistically combine the merits of each individual
component. However, all the reported composites show
enhanced conductivity over the polymeric side, much lower
electronic performance when compared to the carbon
nanotube network film side. In this work, we have
demonstrated experimentally, for the first time, that
in-situ polymerization of a thin “skin” of highly
conductive polymer around and along the SWNTs can greatly
decrease the contact resistance. The polymer skin also
acts as “conductive glue” effectively assembling the SWNTs
into a conductive network, which decreased the amount of
SWNTs needed to reach the high conductive regime of the
network. The highly conductive composite network and the
method to fabricate the highly conductive composite can be
widely used for large area flexible electronics, including
flexible solar cells, and organic light emitting devices.
The Electronic Role of DNA Functionalized Carbon Nanotubes: Efficacy for In-situ Fabrication of Conducting Polymer Nanocomposites
Ma, Y. F., Chiu, P. L., Serrano, A.,
Ali, S. K., Chen, A. M, and He, H. X.
J. Am. Chem. Soc. 2008, 130, 7921-7928.
To truly synergistically combine the merits of each
individual component in the conducting polymer
nanocomposites, it is essential to understand the
monomer-nanotube interfacial chemical and electronic
interactions during polymerization and polymer-nanotube
interfacial interactions after the polymerization, which
has not been fully addressed.
Taking advantages of the well-documented surface chemistry
and electronic structure of single stranded DNA dispersed
and functionalized single walled carbon nanotubes (ss-DNA-SWNTs),
we systematically studied the impacts of the electronic
structure of a carbon nanotube and the monomer-nanotube
interfacial interaction on the kinetics of the
nanocomposite fabrication and the quality of the obtained
composites. For the first time, we found that the
polymerization process can be 4,500 times faster and much
less oxidant needed to initiate the reaction when a
conducting polymer was polymerized in the presence of
intact ss-DNA-SWNTs, which are electron rich. More
importantly, the quality of the composite was
synergistically improved, as demonstrated by the
significantly enhanced electrical performance of the
obtained nanocomposite. However, the synergistic
conductance enhancement cannot be obtained by simply
mixing a preformed conducting polymer with the ss-DNA/SWNTs.
Surprisingly, the enhancement was not achievable by
in-situ polymerization with pre-oxidized SWNTs, which are
electron deficient. In addition, the polymerization
process is also much slower in the presence of
pre-oxidized ss-DNA-SWNTs. Understanding these reaction
characteristics is important to effectively optimize the
fabrication parameters and ensure the formation of
composites in a controllable fashion for a variety of
potential applications. Based on these remarkable
observations, currently they are developing a “greener”
approach for the fabrication of nanocomposites.
Fabrication of A Water-Soluble, Self-Doped Polyaniline
Nanocomposite: the Unique Role of DNA Functionalized
Single-Walled Carbon Nanotubes
Yufeng Ma, Shah K
Ali, Ling Wang, Pui Lam Chiu, Richard Mendelsohn and
J. Am. Chem. Soc. 2006, 128,
Dispersion of carbon
nanotubes into solvents affects their surface chemistries,
electronic structures, and subsequent functionalization. In
this communication, a water-soluble self-doped
polyaniline nanocomposite was
fabricated by in-situ polymerization of the
monomers in the presence of single-stranded DNA dispersed- and
functionalized- single-walled carbon nanotubes.
For the first time, we found that the carbon nanotubes became
novel active stabilizers due to the DNA
functionalization. The nanotubes reduced the polyaniline
backbone from the unstable, degradable, fully oxidized
pernigraniline state to the stable, conducting emeraldine
state due to their reductive ability,
which could improve the chemical stability of the self-doped
polyaniline. Electrical measurements demonstrate that the
conductivity of the nanocomposite was much higher than that of
the pure self-doped polyaniline in both acidic and neutral
Enhanced Sensitivity for Biosensors: Multiple Functions of
DNA Wrapped Single Walled Carbon Nanotubes in Self-Doped Polyaniline Nanocomposites
Yufeng Ma, Shah R Ali, Afua S. Dodoo, and Huixin He,
J. Phys. Chem. B, 2006, 110, 16359-16365.
A nanocomposite of poly(anilineboronic acid), a self-doped
polyaniline, with ss-DNA wrapped single walled carbon
nanotube (ss-DNA/SWNTs) was fabricated on a gold electrode
by in-situ electrochemical polymerization of
3-aminophenylboronic acid monomers in the presence of ssDNA/SWNTs.
We used this nanocomposite to detect nanomolar
concentrations of dopamine and found that the sensitivity
increased four orders of magnitude compared to the detection
only neat poly(anilineboronic acid) was used to modify the
electrode. For the first time, this work reports the
multiple functions of the ss-DNA/SWNTs in the fabrication
and biosensor application of a self-doped polyaniline/ssDNA/SWNT
nanocomposite. First, the ssDNA/SWNTs acted as effective
molecular templates during polymerization of self-doped
polyanline so that not only was the polymerization speed
increased, but also the
quality of the polymer was greatly improved. Second, they
functioned as novel active stabilizers after the
polymerization, which significantly enhanced the stability
of the film. Furthermore, the ss-DNA/SWNTs also acted as
conductive polyanionic doping agents in
the resulting polyaniline film, which showed enhanced
conductivity and redox activity. Finally, the large surface
area of carbon nanotubes greatly increased the density of
the functional groups available for sensitive detection of
the target analyte. We envision that polyaniline with other
functional groups, as well as other conducting polymers, may
be produced for different targeted
applications by this approach.
Oligodeoxynucleotide nanostructure formation in the
presence of polypropyleneimine dendrimers and their uptake
in breast cancer cells
Alex M. Chen, Latha M. Santhakumaran, Sandhya K. Nair,
Peter S. Amenta, Thresia Thomas, Huixin He, and T. J.
Thomas, Published in Nanotechnology, 2006, 17, 5449-5460.
This is a collaboration study with
Drs. Thomas at University of Medicine and Dentistry at New
Jersey. We studied the efficacy of 5 generations of
polypropyleneimine (PPI) dendrimers to provoke
nanoparticle formation from a 21-nt antisense
oligodeoxynucleotide (ODN). Nanoparticle formation was
observed with all generations of dendrimers by light
scattering and microscopic techniques. The efficacy of the
dendrimers increased with generation number. Atomic force
microscopy (AFM) was used to study the morphology of the
structures at different condensation stages.
Based on the observed nanofibers in the beginning
we propose a zipping condensation mechanism, which is very
different from the condensation pathways of high molecular
weight DNA polymers. Electron microscopy showed the
presence of toroidal nanoparticles. Confocal microscopic
analysis showed that the nanoparticles formed with G-4 and
G-5 dendrimers could undergo facile cellular uptake in a
breast cancer cell line, MDA-MB-231, whereas particles
formed with G-1 to G-3 dendrimers lacked this ability.
Nanoparticles formed with G-1 to G-3 dendrimers showed
significantly lower zeta potential (5.2-6.5 mV) than those
(12-18 mV) of particles formed with G-4 and G-5
These results show that the structure
and charge density of the dendrimers are important in ODN
nanoparticle formation and cellular transport and that G-4
and G-5 dendrimers are useful in cellular delivery of
Figure 1. AFM images of condensates formed by the
21-nt ODN in the presence of PPI dendrimers after
10-minute condensation. ODN had a concentration of 0.4
µM and dendrimer was 2.5 µM in a solution containing the
approximate physiological concentration of salts. Panels
are (A) G-1, (B) G-2, (C) G-3, (inset) Phase image with
the same scale of the main image indicated by a red
arrow. (D) G-4, (E) G-5, and (F) G-5. Bar represents
250 nm in all panels.
AFM images of condensates formed by the 21-nt ODN in
the presence of PPI dendrimers after 1 hour of
condensation (panels A, B, C, D, E and F). ODN had a
concentration of 0.4 µM and dendrimer was 2.5 µM in a
solution containing the approximate physiological
concentration of salts. (A) G-1, (B) G-1 (zoom image
of one part of panel (A)), (C) G-2, (D) G-3, (E) G-4,
(F) G-5. Bar represents 4 µm in panel (A), 1 µm in
panels (B, C, D, F) and 300 nm in panel (E).
Representative images of cellular uptake of
fluorescein-labeled 21-nt ODN by MDA-MB-231 cell by
confocal microscopy. ODN uptake in the absence (A, B,
C, D) or the presence (E, F, G, H) of G-4 dendrimer is
shown. Differential interference contrast (DIC) images
of cells are shown in panels A and E. Nuclei stained
with DAPI (B and F), detection of fluorescein-labeled
oligonucleotide (C and G) and overlay of images (D and
H) are shown. Final concentration of ODN and G-4
dendrimer in the cell culture medium were 0.2 µM each.
Figure 4. Schematic representation of the
proposed zipping mechanism for the condensation of the
21-nt ODN by PPI dendrimers. PPI dendrimers first
"zip" the ODN molecules by electrostatic interactions
to form extended chains. The extended chains could
wrap around to form aggregated complex structures,
which then further condense into spheroidal
structures. The extended chains could also interact
with each other in parallel to form ribbon- and
rod-like structures and then wrap around to form
Assembly of Highly Aligned DNA Strands onto Si Chips
Zhang, J. M., Ma, Y. F., Stachura, S. He, H. X.,
Langmuir, 2005, 21, 4180-4184.
This work reports a robust and efficient approach to assemble highly aligned DNA strands onto Si chips. The method combines advantages from molecular combing and microcontact printing to realize controlling both the density and direction of DNA strands on the Si chip. In
addition, it also can be utilized to prepare stretched DNA
structures on solid surfaces. Compared to approaches that
use molecular combing directly on silanated surfaces, the
stretched single-chain DNA structures are straighter. Furthermore, by exploiting the hydrophobic property of the intrinsic poly(dimethylsiloxane) (PDMS) stamp, this study also describes a simple way to simply produce straight bundled DNA arrays on Si and other substrates.
Polyaniline Nanowires on Si Surfaces Fabricated with DNA
Yufeng Ma, Jianming Zhang, Guojin Zhang and Huixin He*,
J. Am. Chem. Soc. 2004, 126, 7097–7101.
It is essential to put individual, freestanding nanowires
onto insulating substrates and integrate them to useful
devices. Here we report a strategy for fabrication of
conducting polymer nanowires on thermally oxidized Si
surfaces using DNA as templates. The direct use of stretched
and immobilized DNA strands as templates avoided the
agglomeration of DNA caused by shielding of charges on DNA
when polyaniline/DNA complexes formed in solution. Most
importantly, the oriented DNA strands immobilized on Si
surface predetermined the position and the orientation of
the nanowires. The approach described here is the first step
toward uniting the programmable-assembly ability of DNA with
the unique electronic properties of conducting polymers for
high-density functional nanodevices. The conductivity of the
nanowires is very sensitive to the proton doping-undoping
process suggesting that the nanowires hold a great promise
for sensitive chemical sensor applications.