1. Optimizing Stability and Concentration of Dye-Doped Organosilicate Nanoparticles
Mentor: Dr. Venumadhav Korampally
Mentee: Nicole Hoffmann
Abstract
This project will be undertaken with Dr. Venumadhav Korampally from the Electrical
Engineering department. It will be centered on optimizing the creation of nanoparticles. The
fluorescent nanoparticles (NPs) have a hydrophobic core and a hydrophilic shell. This design
allows for even dispersion in aqueous solutions with minimal dye leakage [2]. Part of this
research process is optimizing the NP stability to prevent clumping of particles. When subjected
to light, the electrons jump to an excited state and emit different wavelengths of light based on
the dye when they return. This light can allow for detection of the NPs in biological applications;
having different colored dyes allows for more options [1]. These NPs will have altered
concentrations and aging times to discover the best and cheapest process. Ultimately, the goal of
NP research is to attach NPs to specific molecules/therapies that can help target cancer cells or
better boost the immune system in a noninvasive way [3].
Background and Context
Nanoparticles are one type of nanomaterial. Nanomaterial ranges from 1 to 100
nanometers. Because it is so small, nanotechnology is very effective for drug delivery and
targeting; the particles can diffuse through the cell very easily. It is possible to attach antibodies
or other drugs to these NPs, increasing the stability of the particles and preventing them from
clumping together [3]. A large component of this research project is optimizing this stability.
Currently, the particles tend to clump together, especially over time. It is vital to keep them

2. evenly dispersed throughout the solutions they are in; they will be the most useful in biological
applications when stable [3].
This grouping together is detrimental to the success of this project. To prevent this from
happening, there are several different components of the NP. The center of the particle is filled
with fluorescent dye. Because some of the dyes used are toxic, the core is encased in
organosilica, as explained in the Methods section. However, this core is hydrophobic, causing
the particles to clump together in aqueous solutions, much like propane and water. One idea was
to form a core made of silica, which is hydrophilic. This was meant to encase the toxic dye, but
the pores in the silica shell caused the dye to leak. As a solution to prevent these two problems,
the dye is encased in an organosilica core and surrounded by an outer silica shell. The
hydrophilic silica allows the NP to evenly distribute through the water and the hydrophobic
organosilica prevents the dye from leaking into the water [2].
The fluorescent dye is very useful from a biomedical engineering aspect. When light such
as UV (350nm) is shined, the electrons in the dye become excited. They jump to a higher energy
level. When they return from this level, they give off energy in the form of light. Because some
energy can be given off as heat during emission, the energy of excitation is greater than the
energy of emission. This light is given off in different colors based on the type of dye. It is
important to have these different colors; inside the body, it helps to have different colors for
different locations and tissues [1].
Statement of Project Objectives
 Research nanoparticles
 Learn how to synthesize nanoparticles

3.  Prevent nanoparticles from clumping together
 Optimize dye concentrations
 Monitor and study aging process
Methods
First, the dye rich organosilicate cores will be made. The following information discusses
how the polymer chains react based on their structures. SiO2 (silicon) has a siloxane backbone
and is a key chemical for core creation. PMSSQ (polymethyl silsesquioxane) is a polymer with
methyl (CH3), ethoxy (OC2H5), and hydroxyl (OH) groups.
Si – OC2H5 + H2O becomes Si – OH + C2H5OH.
Hydroxide condenses when next to each other: Si – O – Si – OH + HO – Si – O – Si.
The above becomes O – Si – O – Si + H2O.
PMSSQ, as discussed before, unravels when exposed to a good solvent. For our purposes,
we are using ethanol (EtOH). It condenses when exposed to a bad solvent, like PPG
(polypropylene glycol). For dye incorporation, the PMSSQ is mixed with ethanol, dye
(rhodamine chloride) is added, and then mixed with PPG to encapsulate the dye and create the
nanoparticles. The process is outlined below.
First, 5 g of PMSSQ is mixed with 5 g of 200 proof ethanol in a glass vial. Then, dye is
added. The concentration varies with testing to determine a good amount; so far, this has ranged
from 5 to 80 mg of dye. This solution is vortexed and sonicated for thorough mixing. Next, 5 g
of PPG is added to another vial. Then, this second PPG vial is added to the first vial, combining

4. the chemicals. This vial is covered in aluminum foil to protect the light-sensitive NPs. This core
solution is left to age.
This process will take several days, depending on dye concentration, because the NPs
have to assemble after the preparation process. They will age at room temperature and be
carefully monitored; if the particles age too long, they will solidify into an unusable substance
like gelatin. After completely aging, they will be stored in a freezer and are ready for shell
creation.
Next, the shells are created to surround the cores. The cores, filled with dye, have OH and
CH3 molecules on the outside. These are hydrophobic. In fact, the shells may be imperfect just
because of the CH3 groups. Tetra-ethoxy silane (TEOS), a molecule composed of Si bonded with
four OC2H5 groups and is important to the shell creation. The solution also uses ethanol and
ammonium hydroxide (NH4OH). The process is fairly straightforward and outlined below.
18 mL of ethanol is measured and transferred into a glass vial. Next, 25 μL of TEOS, 25
μL of NH4OH, and 100 μL DI (deionized water) are added. Finally, 2 mL of NP cores are added.
In a few experiments, dye was also added to this solution to prevent leakage. The solution is
vortexed and left to age. This aging can take from a week to a month. Then, the NPs are ready
for recovery as outlined below.
The NPs must be cleansed of excess dye. First, 5 μL of HCl, and 100 μL of NPs (with
shells and cores) are added to 1 mL of DI. This acidic solution causes the particles to clump
together, making them easier to retrieve. This solution is centrifuged for 60 seconds at 14.5
thousand RPM. After, the leftover solution is removed, leaving the NP pellet. If the pellet is a
rich red color, it has been fully aged. Next, 5 μL of HCl and 1 mL DI are added again. The

5. solution is vortexed and centrifuged. This washing process, with HCl and 1 mL DI, can be
repeated as many times as necessary. Then, a final wash will be done with only 1 mL of DI.
Next, the charge will be returned to stabilize the particles. 5 μL of NH4OH and 1 mL of
DI are added to the pellet and mixed. Before centrifuging, the vial is sonicated for 5 to 10
minutes to mix the solution on a molecular level. This process is repeated as many times as
necessary, although it is frequently equal to the number of HCl washes. When the NPs are stable,
the solution will become more clear than opaque and remain this way. The NPs will eventually
clump together with time, but one goal of this project is to extend their lifetime. This can be done
by keeping the NPs in the refrigerator.
The pH of the NPs will be tested and changed by manipulating the number of HCl
(acidic) and NH4OH (basic) additions. Solutions with different pH values will be created. NPs
will be distributed throughout these solutions. The purpose of these pH tests is to optimize the
stability of the particles and watch for a correlation between pH and stability.
In addition, different processes will be examined. Poly-lysine has the potential to help
stabilize the NPs. It will be tested as a surface modifier. NPs will also vary in dye concentration
and aging time.
Outcomes
It is already known that the NPs are absorbed into Panc-1 (pancreatic cancer) cells.
Optimizing the stability of these NPs will further improve this absorption. It is hypothesized that
pH plays a role in this even dispersion. This will be tested, and the ideal pH will be discovered
and used. If pH appears to not matter, which is highly unlikely, then other variables will be
tested.

6. In addition, dye concentration will be altered to find an amount that ages quickly but is
still detectable in cells. It is known that lower concentrations of dye cause the solution to age
very quickly. This can be troublesome; the cores may turn to gelatin if not closely watched.
Changing the amount of dye is a difficult process, but could reveal vital information. The final
product will be presented at NIU’s Undergraduate Research and Artistry Day (URAD).
Statement of Significance and Impact
Because of their size, nanoparticles can easily diffuse through cells. This makes them a
great asset when conducting biological research or working to cure diseases. Nanoparticles can
be used to deliver medicine to the body by infusing them with drugs [3]. This way, illnesses like
cancer can be treated and prevented. By targeting specific signaling pathways that promote
cancer progression, they can prevent cancer cell growth. Antibodies can also be attached to
prevent diseases and boost the immune system. Currently, NPs are not always uniform in coating
and clump together over time. By working to produce a reliable method of creation and testing
their absorption rate into cells, it is possible to improve this process. In order to use NPs to save
lives, it is necessary to have a consistent and dependable process.
By perfecting this process, it is possible to find a way to prevent cancer cells from
growing and work on infusing the nanoparticles with natural or chemical drugs. Having a
reliable, dependable process for NP production is very important to the biomedical engineering
field. This research is producing a vessel with the possibility to save lives. Improving and
perfecting this process will provide a multitude of new opportunities for the medical field. NPs
provide a noninvasive way to save lives.

7. Literature
[1] L. Wang and W. Tan, "Multicolor FRET Silica Nanoparticles by Single Wavelength
Excitation," Nano Letters, vol. 6, no. 1, pp. 84–88, Dec. 2005.
[2] V. Korampally et al., "Confeito-like assembly of Organosilicate-caged Fluorophores:
Ultrabright Suprananoparticles for fluorescence imaging," Nanotechnology, vol. 23, no. 17, pp.
1–11, 2012.
[3] V . Korampally et al., "Novel route towards large scale synthesis of bright, water dispersible
core-shell fluorescent dye doped organosilicate nanoparticles," IEEE International Conference
on Electro/Information Technology, pp. 562–566, Jun. 2014.