WPI's Ussing System offers researchers a quick, effective means of making low-resistance electrical connections to the Ussing chamber without need of long agar bridges or Calomel half-cells. Ag/AgCl half-cells screw into short tubes which plug firmly into place in the chamber's luer ports. These direct-connect electrodes eliminate the inconvenience and expense of Calomel half-cells in open liquids. The System includes one Ussing Chamber (four sizes available), Support Stand, Electrode Kit, Glass Circulation Reservoir (two sizes available), and a Tubing start-up kit (25 feet of 0.375-in. tubing, 10 feet of 0.156-in. tubing, plus four male luer fittings, two compressor clamps, one Y-connector, and one clip). Fourteen possible system configurations are listed at right. Components are also available separately. (Preamplifier in photo not included).

Ussing Chambers

• Ussing Chambers Direct connect low-resistance electrodes
• Simplified operation, easy to control temperature and clean after use
• Luer type leak-free attachment of tubing and electrodes
• Recessed electrode ports to avoid air bubble formation
• Secure membrane holding by sharp stainless steel pins or O-ring
• Specialized chamber adapts cell culture insert (Costar Snapwell) for monolayer cell culture
• Chambers with rectangular openings for tubular tissues from small animals

WPI's classical Ussing Chambers are well established perfusion chambers that are easy to operate, easy to control temperature, and easy to clean after use. Hundreds of them are used daily by scientists in the field. Ussing Chambers are machined from solid acrylic with eight entry ports for fluid lines, electrodes, or agar bridges. For easy, leak-free attachment of tubing and electrodes, all eight ports are luer type. The four ports for voltage and current electrodes are recessed to prevent formation of air bubbles in the chamber. The fluid compartments in each side of the chamber are separated by the epithelial membrane being studied. Five sharp stainless steel pins on one side of the chamber hold the membrane in position and mate with holes in the opposite chamber interface. (On the CHM4, tissue is held by an O-ring instead of pins.)

The new CHM5 chamber adapts the Costar Snapwell, a cell culture insert for monolayer cell culture, into WPI's "classical" epithelial voltage clamp system. Until now, classical Ussing Chambers have not been widely used for monolayer cell culture inserts because most inserts have a very deep profile, limiting good fluid perfusion at the surface of the membranes and limiting voltage electrodes from measuring the potential close to the surface of the membrane. CHM5 solves these problems: Perfusion fluid is introduced into the chamber at an angle so that it will flow directly to the surface of the membrane. The voltage electrode is also inserted into the chamber at an angle so as to reduce the distance between the surface of the membrane and the electrode.
Two new chambers with rectangular openings are designed for tubular tissue from small animals such as the mouse intestinal tract membrane (CHM6) and rat intestinal tract membrane (CHM7). The rectangular opening more closely matches the shape of the tissue than would a circular opening, significantly increasing the membrane area available for testing. The larger membrane area increases the transport rate of low permeability chemicals; it also reduces the electrical resistance of the system for easier current clamping.

Ussing chamber for Millipore Millicell 12mm tissue insert

New to our family of Ussing chambers is one designed specifically for the Millipore Millicell 12 mm tissue insert. This is the first chamber on the market to compensate for the deep profile of the Millipore insert. This deep profile makes it difficult to bring either the voltage measuring electrodes or fluid flow to the surface of the tissue membrane. Our innovative design virtually eliminates the “unstirred layer” of fluid which would otherwise slow down the response of perfusion experiments. In addition, voltage measurements are brought right up to the surface of the tissue membrane, facilitating voltage clamping, current clamping and TEER measurements.

Optional Drains
Drains may be added to Ussing chambers to allow quick and complete evacuation of radioactive or toxic substances. To have drains added at the time of order, add a "D" to the part number (such as "USS1LD"); $100 will be added to the cost of the chamber or system you are ordering.

Cartridge Electrodes
The Electrode Kit contains four voltage/current electrodes, plus four luer-tipped cartridges. Electrodes are threaded and screw securely into the end of each cartridge. The luer tip then plugs securely into the luer openings of the chamber. The cable from each electrode terminates with a 2 mm pin which may be plugged into voltage/current clamps such as WPI's DVC-1000 or EVC-4000.

The miniature electrode-gel cartridge is a small plastic tube with a male luer tip identical to those at the tip of hypodermic syringes. The tube may be filled with different gel materials; agar is commonly used but other gel materials may also be satisfactory. To make an agar gel filling, the cartridge tube is filled with a hot salt solution in which 2 to 4 percent agar by weight is dissolved. The salt solution is comprised of KCl (or NaCl) salt dissolved in distilled water to a concentration of 3 Moles or more. This assures that the cartridge gel will have a very low electrical resistance. A small billet or slug made of a Silver/Silver-Chloride mixture is inserted into the rear of the tube and as the solution cools, the Agar gel hardens to encapsulate the slug. A lead wire, bonded to the slug and insulated from the electrolyte-gel extends several feet to allow easy connection to electrical measuring apparatus.

As the concentrated KCl (or NaCl) slowly diffuses out of the cartridge it will be washed out through the outflow tube. Silver/Silver-Chloride is well known as an electrode material that has at least three important advantages. It exhibits a stable voltage when in contact with an electrolyte containing chloride ions (i.e., most salt solutions). Also, it offers low electrical resistance to the passage of current and does not easily become polarized when current flows. A good working practice is to exchange the upper and lower current electrodes periodically to avoid prolonged current flow in only one direction through the electrode. If the gel darkens or dries out, it may be cleaned out of the plastic case by soaking in hot water and refilled with fresh gel prepared as described above.

DRIREF-L is a modified EKC electrode refilled with KCl solution. It saves you the messy and tedious work of filling the cartridge with agar gel. DRIREF-L has the same type of low leakage KONBO plug as WPI's other Dri-Ref reference electrodes. It minimizes the contamination of the perfusion solution by the reference's electrolyte. It produces a very stable potential even if the user drastically changes the chloride ion concentration in the perfusion solution.

Support Stand PVC base (18x4x1/2-in.) has two 16-in. removable posts which serve as ring stands to support glassware and other equipment. Base will accommodate any chamber which is 3 to 4 in. long and up to 6 in. diameter.

Circulation Reservoirs
Hand-blown borosilicate glass, with jacketed chambers for temperature control, available in two sizes -- #5210 holds 20 ml per side, and #5362 (at left) holds 10 ml per side (useful when expensive chemicals are involved). Reservoir condenser caps prevent air bubbles and turbulence in fluid reservoirs.

Water Bath The Haake DC1-B3 Constant Temperature Water Bath (see page 67) has been tested at WPI and found to be ideal for WPI's Ussing system. It can provide simultaneous warming for up to 16 systems. Menu-driven control module allows easy temperature setting, correction and display, with temperature accuracy of ± 0.02°C.