The adherence of worms to standard plastic tips makes accurate dispensing difficult. While using glass tips can overcome this problem, their application is limited when sterility and frequent tip changing is needed, for example, when performing liquid culture RNAi screens using 96-well plates (Lehner et al., 2006). RNAi screen protocols often require ~10 L1 worms to be dispensed into each well of a 96 well plate, however using standard P200 tips with worms in M9 alone resulted in an average variance of ± 6 L1 worms per well. We found that worms suspended in M9 with Triton X-100 decreased this adherence, resulting in an average variance of ± 2 L1 worms in each 10µl volume.
Both Triton X-100 and Tween-20 can be used to decrease this adherence to standard P200 tips. Since autoclaving either of these reagents is not recommended, sterilization can be carried out via filtration using a 2µm filter. The lower viscosity of Triton X-100 over Tween-20 greatly aided filtration and sterility tests showed no associated contamination. We found that using concentrations of Triton X in M9 ranging from 0.1% to as low as 0.01% proved to be effective in decreasing worm adherence throughout our assay. No negative issues regarding the growth or progeny of worms were observed when compared to a control plate containing no Triton X. Therefore this method could serve useful when applied to protocols that require consistently small numbers of worms in large repetitions.
References
Lehner B, Tischler J, Fraser, AG. (2006). RNAi screens in Caenorhabditis elegans in a 96-well liquid format and their application to the systematic identification of genetic interactions. Nat. Protoc. 1, 1617-20. 
