LOCAD - Portable Test System

Portable Test System

The Lab-On-a-Chip Application Development – Portable Test System (LOCAD-PTS) is a handheld device for microbial monitoring aboard the ISS. It evolved from the Endosafe-Portable Test System (Endosafe-PTS), developed by Charles River Laboratories for use in the pharmaceutical and health care industries. In 2004–2005, Charles River Laboratories teamed up with Carnegie Institution for Science and NASA Marshall Space Flight Center, including BAE Systems and Jacobs Technology, to modify the Endosafe-PTS device (and a sample handling system) for spaceflight. The LOCAD-PTS project has been funded in large part by NASA's Exploration Systems Mission Directorate (ESMD), under the Exploration Technology Development Program (ETDP), and specifically under the umbrella of Advanced Environmental Monitoring and Control (AEMC).

The device itself (or reader) weighs 2.2 pounds and is a combined spectrophotometer, heater and pump, operated with multiple interchangeable cartridges for the detection of different microbial molecules. There are three different LOCAD-PTS cartridges aboard the ISS, for the detection of three different microbial molecules: endotoxin, glucan and lipoteichoic acid. These three molecules are found mainly within gram-negative bacteria, fungi and gram-positive bacteria, respectively. Endotoxin and glucan are detected with the Limulus amebocyte lysate (LAL) enzyme cascade, derived from the horseshoe crab Limulus polyphemus. Lipoteichoic acid is detected with the Pro-Phenol Oxidase (PPO) enzyme cascade derived from the Jonah crab, Cancer borealis. By the amplification of a small signal, these enzyme cascades allow detection of very low amounts of starting microbial material. An astronaut can take a swab sample from a cabin surface, dissolve it in endotoxin-free water, and analyze it quantitatively with LOCAD-PTS in microgravity, all in under 15 minutes. Traditional culture-based methods aboard the ISS take several days and often require return of samples to Earth for more in-depth analysis by scientists on the ground.

LOCAD-PTS was launched to the ISS on December 9, 2006, aboard Space Shuttle Discovery STS-116. Following a four-month period of storage aboard the ISS, the device was first used by Expedition 14/15 Flight Engineer Suni Williams on March 31, 2007, to analyze surfaces within Unity. Since that time, LOCAD-PTS has been used extensively by the crews of Expedition 16–Expedition 18 to monitor microbial material throughout the ISS. The LOCAD Team has supported each operation of LOCAD-PTS aboard the ISS from consoles at the NASA Payload Operations and Integration Center (POIC) at NASA Marshall Space Flight Center. LOCAD-PTS will continue to be used aboard ISS through October 2009 by Expedition 20 astronauts Mike Barratt and Tim Kopra.

The first phase of ISS operations took place between March 2007 to February 2008 (Expeditions 14–16), when LAL cartridges were used to detect endotoxin on surfaces within the ISS. Endotoxin was found to be distributed throughout the ISS, despite previous indications that most bacteria on ISS surfaces were gram-positive. Endotoxin was detected at 50% of all surface sites and commonly found on surfaces within exercise, hygiene, sleeping and dining areas. Endotoxin was found at every surface site where Colony Forming Units (CFUs) were observed with culture-based contact slide methods. LAL-Glucan cartridges, for the detection of Beta-1,3-glucan, were launched to the ISS aboard Space Shuttle STS-123 in March 2008. Preliminary results with these cartridges showed similar patterns to those observed for endotoxin, but glucan was found at higher levels and found to be far more widespread throughout the ISS. The Gram+ cartridges, for the detection of lipoteichoic acid) were launched to the ISS aboard STS-126 on November 14, 2008. Tests with these cartridges have been performed during Expeditions 18 – 20.