In traditional nanolitre injection, the dead volume of the syringe and needle is backfilled with oil as a displacement transfer. This makes the process messy and risks contamination of the injected sample. NanoFil’s low volume, flexible tubing eliminates the need for oil. Injection is now simpler, and less messy, and there is no possibility of oil contamination in critical applications such as ophthalmology research Retinal Pigment Epithelial (RPE) and Intra Ocular (IO) injection.

When the inner diameter of the tip on a conventional syringe is reduced to less than 100 micron, it is very difficult to back fill the solution at a reasonable speed. NanoFil solves this problem by using a tip coupling mechanism that makes it possible to change the syringe tip during the experiment.

APPLICATIONS

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 submicrolitre 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 bevelled 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 microlitres. All of the components in the kit are constructed of inert, solvent resistant, and autoclavable materials for easy cleaning after viral injection.

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 II 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 nanolitre level of accuracy and reproducibility. It is best suited for applications such as the RPE and IO injection.

Installed on WPI’s UMP-II microsyringe pump: This will allow the user to achieve nanolitre resolution and reproducibility. For neural system injection, mount the UMPII on a stereotaxic frame.

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 microlitre resolution.

TIPS

The replaceable needles used with the NanoFil are available with either blunt or bevelled tips. The blunt tip is used for injection into soft tissue and when a uniform solution distribution is needed. The bevelled 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 micron, the error caused by tip diffusion is in the nanolitre range level ( (100 micron)^3 = 1 nanolitre ). With a 36 gauge needle installed on the NanoFil, the error caused by diffusion will be reduced to the sub nanolitre level, making accurate injection of a nanolitre possible.

All of WPI’s bevelled tips have a unique 25 degree tri-surface bevel that is optimized for microinjection. A 10 degree single-surface bevelled 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 bevelled tip solves this problem with two extra bevelled surfaces. The tip of a single surface bevelled tip is actually a blade instead of a point. It dulls very quickly. In contrast, the tri-surfaced 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 bevelled tip penetrates easier and lasts longer than other manufacturer’s 33 gauge, 10 degree single bevelled tips. With a 35 gauge tri-surface bevelled 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.

CHOOSING A TIP

Simply load the sample using a larger tip, such as the 26 gauge needle provided with the syringe, and then replace it with a micro tip for sample injection. On a conventional 10 microlitre syringe, a solid ring or bushing is permanently bonded to the tubing. Replacing the tip in middle of the experiment is not practical. With the NanoFil, different gauge tips can be exchanged on the syringe by a simple twist of the brass lock, gently pulling out the tip, and replacing with the desired new tip. To secure the tip, NanoFil uses an olive shaped silicon gasket that is similar to, but much sturdier than, some of the microelectrode holders used for electrophysiology recording. The 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 Chromatography (GC) and Capillary Electrophoresis (CE) can also be easily coupled to the syringe. Specially designed tips as small as 36 gauge (110 micron OD) are offered in both blunt and bevelled 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.

 AVAILABLE TIPS

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 microlitres of dead volume in its luer hub, the dead volume of this tip is less than 0.6 microlitres. It is useful for loading electrodes with solutions that have a limited volume or are too expensive to waste.

33 gauge: This tip is similar to Hamilton’s 7762 and 7803 series removable needles in both tip length and outer diameter. However, our bevelled 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 bevelled tip, our 35 gauge 25 degree bevelled tip can reduce the depth of penetration by almost 80%. The distance between the tip and the upper rim of the opening is 1024 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. Depending on the viscosity of the sample, the user might also need to pre-load the syringe with a regular tip before switching to this tip for injection. We recommend using the 35 gauge tip instead of the 36 gauge unless it is absolutely necessary.

 

Tip Order Number	Tip O.D. A	Tip I.D. B	Tip Length C	Total Length D	Shank O.D.	Tip Material
NF33BV-2 / NF33BL-2	210 µM	115 µM	10.0 mm	40.0 mm	460 µM	Stainless Steel
NF34BV-2 / NF34BL-2	185 µM	85 µM	5.0 mm	35.0 mm	460 µM	Stainless Steel
NF35BV-2 / NF35BL-2	135 µM	55 µM	5.0 mm	35.0 mm	460 µM	Stainless Steel
NF36BV-2 / NF36BL-2	110 µM	35 µM	3.0 mm	33.0 mm	460 µM	Stainless Steel
NF33FBV-2 / NF33FBL-2	200 µM	100 µM	5.0 mm	35.0 mm	460 µM	Titanium Alloy
NFQ34-5	160 µM	100 µM	55.0 mm	75.0 mm	460 µM	Quartz