Unsung Heroes

13 Aug 2010 by Evoluted New Media

We are giving a Laboratory News salute to all those things in the life of a scientist that are taken for granted - this month, the pipette. A lab just wouldn’t be a lab without one, yet at 200 years old the humble pipette is still evolving

An indispensable piece of equipment used every day by hundreds of thousands of laboratory scientists in the modern biology laboratory, the lowly pipette can be taken for granted, yet few know that the forerunner of what we recognise as the modern laboratory handheld pipette was first invented in France in the late 18th century.

The need to measure and handle liquids has always been necessary to man, and the pipette was first developed in 1795 by the father of volumetric analysis, French chemist, François-Antoine-Henri Descroizelles. Described as a graduated glass cylinder it was somewhat similar to the modern day burette. Better known for his laws on gases and work on the measurement of alcohol by volume, the French chemist and physicist, Joseph Louis Gay-Lussac, turned his attention to this invention and produced an improved version some 30 years later, for which he suggested the name pipette or burette. The design remained largely unchanged until the era of mechanisation in the 20th century. Inspiration for the idea of air displacement appears to have come from the spring and piston mechanism inside an oil dispenser invented in 1903 for servicing bicycles, also drawing upon features developed in devices for measuring milk samples and lung capacity. These early pipettes dispensed liquids accurately enough for the scientists of the time, but improvement of what we now recognise as the standard mechanical pipette seems to have progressed rapidly only over the last 40 years in response to the demand for measurement of tiny and variable volumes of liquid.

The first modern micropipette was launched in the early 1970s – accurate enough for the demands of molecular biology yet compact enough to fit in the hand. Early designs for fixed and variable volume pipettes were patented in the US and Germany, and in Finland by Professor Suovaniemi, who also introduced and patented the incredibly successful Finn Multichannel. Interestingly all three designs were quite different in approach.

These early pipettes were somewhat heavy to operate, with no tip ejector and little compatibility with different manufacturers' tips. From the 1970s onwards, technological advances moved at a fairly rapid pace introducing many elements, such as the tip ejector and finger rest to improve the safety and usefulness of the mechanical pipette. A search of the official records of the US patent office (www.uspto.gov/) reveals that over 60 patents were filed in the past 40 years. Designs have also changed in line with manufacturing advances in precision injection molding and the need to increase productivity and accuracy while reducing laboratory risk.

Initially, the precise aspiration and dispensing of liquids was conducted using single tip, fixed volume pipettes. However, rather than employing a large set of single capacity pipettes, a drive for greater efficiency generated a need for individual instruments capable of dispensing variable volumes. A rapidly evolving laboratory environment, stimulated in part by the advent of ELISA technology and the introduction of the standardized microplate format, further instigated the transformation of pipettes, as they adopted the ability to dispense liquid across multiple channels. These changes have proven particularly valuable in the clinic, where modern, multichannel, largely automated pipettes now facilitate the speedy, precise, high throughput processing of large sample sets. At the current time, manual pipettes dispensing adjustable volumes across 16 channels are commonly in use, making the processing of larger plates faster, simpler and more accurate.

In many laboratories pipettes are an integral part of day to day activities. The use of such instruments can be repetitive and fatiguing by their very nature, so there is an enduring need to refine pipette technology to improve the end user experience. Of particular concern when using such apparatus is the risk of ‘repetitive strain injuries’ (RSIs) such as carpal tunnel syndrome, which are debilitating to users and reduce efficiency and accuracy. In pipetting, thumb plunger pressure and tip ejection are strongly associated with RSI, and therefore reducing these forces is paramount. According to the UK Health and Safety Executive (www.hse.gov.uk/pharmaceuticals/goodpractice/pipette.htm), research shows that using a pipette for long periods is associated with an increased risk of hand and shoulder ailments. The UK HSE also offers guidance on the ergonomic aspects of pipette design and use, and highlights the following points to consider when selecting a new pipette:

• Light in weight • Comfortable to hold • Good grip • No sharp edges or ridges • Suitable for right or left handed use • Easy tip ejection and fitting • Convenient plunger or main button position, avoiding over-stretching the thumb • Minimal force to push plunger (including the second push on manual pipettes) • Easy to set and read dosage • Positive feedback from button operation

Improved pipette ergonomics can prevent excess strain especially on the upper limbs, and neck and shoulder areas. The ease and lightness of pipetting tasks plays an important role in reducing stress, and even minor improvements in pipette construction – coupled with adequate rest and proper working conditions – can greatly enhance user comfort. Numerous patented innovations help reduce physical stress and discomfort. Manufacturers, such as Thermo Fisher Scientific, have made great strides in this area over the last two decades, introducing soft-touch tip ejectors; contoured and interchangeable handles; supportive and adjustable finger rests; and lighter materials. Pipettes are also available with different piston lengths to match with requirements.

There have been several key advances over the years:

Volume precision Advanced Volume Gearing (AVG) is a specially developed self-supporting modular volume adjustment mechanism. Since the AVG mechanism is separated from the pipette body, its accuracy, precision and durability are greatly improved. In addition, in order to eliminate the possible effects of hand warmth on the accuracy of measurements, the AVG mechanism is thermally isolated from the body of the pipette.

A user-friendly ‘set and forget’ locking volume setting mechanism can ensure the volume remains as set. The volume is adjusted by lifting the pipetting button up and setting the volume. Then by simply pushing the button back down, the volume is safely locked in place. Once the pipetting button is pushed down it rotates freely for extra comfort, without altering the volume settings.

When pipetting smaller volumes, sample viscosity and the capillary effect can seriously affect amount of sample ejected. As a result, features such as super blow-out, ensure the delivery of micro-size drops (see figure 1).

A large easy-to-read display is essential in providing clear and easy volume setting. Additionally, a fine adjustment ruler ensures the last digit can be checked easily, and presented against a clear linear scale. Precision can be further ensured via click volume adjustment, which enables volume increments between 0.002?l and 0.01ml, depending on the model. Ergonomic advances Modern pipettes should have a very light pipetting action that requires just a small amount of effort, dramatically reducing the risk of RSI. With such a smooth and steady action, pipetting will also be more accurate and precise, with better results over longer periods.

Certain ranges now come with a novel adjustable finger rest that can be adjusted through 120° to the most ergonomic and comfortable position for pipetting and tip ejection. This finger rest is also wide and therefore more comfortable, so the pipette can be held at the ideal pipetting angle and the hand can relax between pipetting cycles. This makes repetitive pipetting less tiring and more comfortable, and reduces the risk of RSI.

An ideal pipette also minimises the forces needed for tip ejection with a soft touch tip ejection mechanism. This innovative gearing mechanism produces more down force with less effort, releasing the tips with just a gentle push from a comfortable rounded tip ejector button – ideal for use with gloves (see figure 2).

High quality results depend on absolute sterility. To provide this and to prevent cross contamination, a pipette should be easily autoclavable at 121°C. All pipettes should be constructed with materials that have a high resistance to reagents, UV light and moisture.

An innovative range of pipettes is now available that incorporate an antimicrobial treatment, whereby the handle and the dispensing button are made of an antimicrobial polymer containing silver ions as the active ingredient. When the silver ions come into contact with microorganisms, the ions are taken up by microbial cells and interrupt critical functions, such as DNA replication, resulting in the death of the microbes. Silver is well known to be safe for human contact and effective against a broad spectrum of microorganisms. This treatment has been shown to kill 99.9% of the bacteria on the surface.

With laboratory space at a premium, it is common for a large number of researchers to be working in close proximity. Consequently, hand held equipment such as pipettes, need to be clearly labelled so that they can be quickly identified. As a result, certain pipette models now feature a separate slot enabling ID tags to be placed beside the display.

The pipette has risen from inauspicious beginnings to being the most ubiquitous piece of laboratory equipment. Evolving from a crude basic design to the sophisticated models seen in laboratories today, the pipette is now the mainstay of molecular biology, drug discovery and many laboratory protocols. Advances in materials, manufacturing processes and technology have led to a continually evolving design offering users an unheard-of range of features and versatility. Not bad for a 200-year old idea.