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NanoFil Sub-Microliter Injection System For Small Animal Research |
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Written by Administrator
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“Necessity is the mother of invention”
This quotation from the dialogue Republic by ancient Greek philosopher
Plato, could be considered one of the mantras of scientific research
and product development. Many specialized products used in research
were developed out of a specific need that was not already addressed in
the marketplace. We often use these products without even thinking
about their history, their development, or the imagination of the
person who invented them.
WPI's NanoFil is a perfect example of this scientific mantra. Dr.
Tawfik El-Samman of Lexicon Genetics Incorporated needed to inject sub
microliter samples into the retinal pigment epithelium of mice. He
wanted to hold the syringe himself and activate the injection using a
pump with a footpedal. Currently, there are no systems of the kind on
the market. WPI's Vice-President of Research and Development, Suyi Liu,
PhD, considered this problem and went to work inventing a solution.
Thus, NanoFil was born.
NanoFil is a unique low-volume syringe with a patented gasket that
allows tip exchanges during an experiment. Backfill the 10 microliter
syringe with sample using the large 26 gauge needle provided, then
exchange the needle for the tip of your choice and begin injections.
Unique Low-Volume Syringe
The patented silicone gasket makes it possible to hold not only metal
tips but also glass and quartz tubing. Many types of tubing can be
easily connected to the syringe as long as the outer diameter (OD) is
close to, but not more than, the inner diameter (ID) of the inside
barrel. The application potential of this design is tremendous.
Flexible quartz capillaries used in Gas Chromotography (GC) and
Capillary Electrophoresis (CE) can also be easily coupled to the
syringe. The replaceable needles used with the NanoFil are available
with either blunt or beveled tips. The blunt tip is used for injection
into soft tissue and when a uniform solution distribution is needed.
The beveled style is used for applications that involve the penetration
of a tough tissue. One of the main factors that limit the resolution
and accuracy of conventional micro syringes to the upper tens of
nanoliters range is diffusion in the large tip ID. When the tip ID is
equal or larger than 100 microns, the error caused by tip diffusion is
in the nanoliter range level ( (100 micron)^3 = 1 nanoliter ).
With a 36 gauge needle installed on the NanoFil, the error caused by
diffusion will be reduced to the sub nanoliter level, making accurate
injection of a nanoliter possible. All of WPI's beveled tips have a
unique 25 degree tri-surface bevel that is optimized for
microinjection. A 10 degree single-surface beveled tip penetrates
better than one with a 25 degree angle, however the distance between
the upper opening to the tip is longer.
As a result, it requires a deeper penetration of the tip to achieve the
same level of liquid delivery. Deeper penetration means more tissue
damage. WPI's unique 25 degree beveled tip solves this problem with two
extra beveled surfaces. The tip of a single surface beveled tip is
actually a blade instead of a point. It dulls very quickly. In
contrast, the trisurfaced tip has a real point. It not only penetrates
much better but is also much more durable.
Our tests show that our 33 gauge, 25 degree beveled tip penetrates
easier and lasts longer than other manufacturer's 33 gauge, 10 degree
single beveled tips. With a 35 gauge tri-surface beveled tip, the
resistance to the penetration becomes even less. Each of our tips
undergo a penetration test before leaving the factory to guarantee the
best results for our customers.
Selecting the correct tip for your application
Specially designed tips as small as 36 gauge (110 micron OD) are
offered in both blunt and beveled styles. Our studies have shown that
these tips will cause less trauma to the tissue than any other form of
micro syringe currently in use. NanoFil has a unique coupling mechanism
that allows many different forms of small tubing and tips to be coupled
with the syringe barrel. Based on application requirements, NanoFil can
be used in several different configurations
Direct injection by hand: This is the simplest and most economical way
to inject. Any of our tips can be inserted directly into the NanoFil
syringe. Even the SilFlex tubing can be inserted to switch from hand
injection to the other methods listed below. The limitation of this
method is the difficulty achieving sub microliter resolution. One user
has this comment:
"I think this is a fantastic product. I am using the hand-held syringes
for in utero, intraventricular cortical injections in embryonic mice to
perturb and elucidate developmental mechanisms during neurogenesis. The
tribeveled Flexifil syringes deliver precise volumes, minimize surgery
trauma, and increase post-procedure survival in younger embryos."
- Yun C. Yung, Graduate Student, The Scripps Research Institute
Installed on WPI's UMP-II microsyringe pump: This will allow the user
to achieve nanoliter resolution and reproducibility. For neural system
injection, mount the UMPII on a stereotaxic frame. Jeff Skaggs of
Oklahoma University uses the NanoFil with the UMPII pump and had this
comment: "Overall the system is very nice. It has drastically increased
my throughput."
WPI’s UMP-III microsyringe pump
SilFlex tubing and holder: The needle is mounted on a small plastic
holder that is connected to the NanoFil by a 35 cm length of flexible
tubing. The NanoFil is mounted on the UMP III pump. This configuration
allows the user to hold the animal in one hand and insert the needle
with the other.
When the needle reaches the desired location, activate the pump using
the footswitch and the pre-programmed injection volume will be
delivered. This configuration gives a nanoliter level of accuracy and
reproducibility. It is best suited for applications such as the RPE
(Retinal Pigment Epithelial) and IO (Intra Ocular) injection.
SilFlex tubing and holder
Available Tips
33 gauge: This tip is similar to Hamilton's 7762 and 7803 series
removable needles in both tip length and outer diameter. However, our
beveled tip version is shorter, more durable, and penetrates better due
to the special tri-surface grinding technique. In the past, 33 gauge
tips were the smallest size sold by other manufacturers and were
frequently cited in literature. However, our new 35 gauge tip is much
better for injections involving small animals, especially mice.
Compared with Hamilton' 33 gauge, 10 degree beveled tip, our 35 gauge
25 degree beveled tip can reduce the depth of penetration by almost
80%. The distance between the tip and the upper rim of the opening is 348 microns for the 33 gauge tip. The distance for our 35 gauge tip is
only 230 microns. In addition, the smaller tip size significantly
reduces the required penetration force. In nearly all applications, a
33 gauge tip can be replaced with our 35 gauge tip and produce better
results.
34 gauge: This is a transitional size between the 33 gauge and 35
gauge. If the 35 gauge is too weak and the 33 gauge is too large, this
makes a good alternative.
35 gauge: This was the most popular and preferred tip of most
scientists during our field trial. The combination of its strength,
length, durability, and clogging resistance creates a balance with very
little compromising of the individual properties. It is much smaller
than the 33 gauge tip offered by other manufacturers. It is only
slightly larger than the 36 gauge tip but is much stronger and less
likely to be clogged. Samples can be directly loaded with this tip. Its
5 mm length is sufficient enough for almost all injection applications
in mice.
36 gauge: This is the smallest tip that is commercially available. The
tip is so small that it can be inserted into the opening of the 33
gauge needle tip. Because this is pushing the limits of what current
technology can produce, there are some limitations to consider before
using. Its thin diameter makes it necessary to limit its length to 2.5
to 3.0 mm and still maintain a usable strength. Since the tip ID is in
the 25 to 50 micron range, it is very easily clogged. Therefore, only
well filtered solutions can be used. We recommend using the 35 gauge
tip instead of the 36 gauge unless it is absolutely necessary.
Flexifil: The Flexifil tip is made of a titanium alloy. The advantage
of this tubing is its durability. This "semi-flexible" tip can be bent
up to 90 degrees without damage. It is also much more corrosion
resistant than the stainless steel tip. Saline solutions left in the
tip will be less likely to clog it. Although this tip is specified as a
33 gauge tip, its outer diameter is slightly smaller than our 33 gauge
stainless steel tip.
Flexible Quartz Tubing: The flexible quartz tubing tip is made of 160
micron OD polyimide coated quartz tubing with a special adapter sleeve
mounted at the end. It is designed for filling glass capillary
electrodes or pipettes, just like WPI's traditional MF34G Microfil.
However, unlike the traditional MicroFil, which has about 50
microliters of dead volume in its luer hub, the dead volume of this tip
is less than 0.6 microliters. It is useful for loading electrodes with
solutions that have a limited volume or are too expensive to waste.
Application Kits
These kits are specially designed for eye research for injecting
retinal pigment epithelium (RPE) and intraocular (IO) in addition to
brain injection in mice. They need to be used with a NanoFil syringe
and UMP2 to achieve accurate, repetitive, and oil free injection in the
submicroliter range.
Each kit includes two pieces of Silflex tubing (one for a spare), a
holder assembly, spare gaskets, and an assortment of four tips - blunt
for the RPE kit and beveled tips for the IO kit. Each kit comes with
one each of 33, 34, 35 and 36 gauge tips so that first time users can
find the best size for their application.
The Silflex tubing is the most critical component of the kit. This 35
cm long, flexible tubing has a very precise outer diameter for airtight
fitting with the syringe. It also has a small inner diameter for
minimum dead volume, and is very durable when handled correctly. The
SilFlex is coupled to the injection tip with a mechanism similar to
that of the NanoFil. The dead volume of the entire kit (including the
tubing) is less than 3 microliters. All of the components in the kit
are constructed of inert, solvent resistant, and autoclaveable
materials for easy cleaning after viral injection.
NanoFil has become a solution for many problems with sub microliter
injection. It is constantly evolving and improving as new users stretch
the boundaries of its initial intended use.
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Last Updated ( Tuesday, 03 January 2012 )
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