Microfluidic lab-on-a-chip and organ-chips

Who it is for

• Pharmaceutical and biotech companies testing drug toxicity on human kidney, liver, heart or gut tissue
• Organ-chip and microphysiological-system makers that want flight data
• Academic groups funded under programmes like NIH NCATS and ISS National Lab Tissue Chips in Space
• Space agencies studying astronaut health risks (heart, kidney, bone, immune) and countermeasures
• Contract research organisations that offer in-vitro toxicology services

What earlier flights found

How LELP-1 runs it

Sample. Four to six human organ-chips supplied by the customer. Reference case: a kidney proximal tubule chip made with primary human tubule cells, with treated and vehicle chips side by side. The same layout works for liver, gut or heart chips. Container. Optically clear organ-chips on a fluidic manifold inside the BSL-2 triple-contained large bay, with a micro-pump per chip, bubble traps, valved reservoirs (medium, drug, fixative, RNA-stabilising reagent) and a cooled effluent-collection carousel. Launch. Live, mature tissue under continuous perfusion at 37 C (finished organ-chips are not launched frozen; the ISS heart tissues were handed over live 2 days before launch). The bay is loaded late and stays powered through launch. Light and gas. No light needed except brief imaging LEDs. HEPES-buffered medium with no CO2 (the ISS heart study used 5% CO2, which LELP-1 cannot supply). Oxygen comes from gas-permeable chip walls and tubing exposed to the sealed bay air.

1. day -4

   Ground: customer seeds the chips and perfuses them until the tissue forms. Chips that fail barrier or imaging checks are rejected. Sterile assembly and leak checks, because nobody can remove a contaminated chip in orbit.

2. day -1

   Late load: chips, filled reservoirs and the empty effluent carousel go into the large bay. The bay is sealed, held at 37 C and kept on power. The ground-control set is loaded the same way.

3. day 0

   Launch. Pumps keep a low continuous flow and the bay holds 37 C through ascent. The robotic arm stays parked.

4. day 1

   First in-orbit health check: brightfield image of every chip, check of flow and pressure for bubbles or blockage, first effluent fraction collected at 4 C.

5. day 2

   Days 2-6: acclimation under perfusion (the ISS kidney study used 6 days). One brightfield and fluorescence image set per day. One effluent fraction per chip every 24 h into the 4 C carousel.

6. day 7

   Dosing: the valves switch half the chips to medium containing the drug and half to vehicle medium. Imaging every 6 h.

7. day 8

   Effluent fractions every 12 h for injury and inflammation markers. Image sets continue.

8. day 9

   End point after 2 days of dosing: half the chips are flushed with an RNAlater-type RNA-stabilising reagent and half are fixed with 4% paraformaldehyde. Lines are sealed and the bay drops to 4 C.

9. day 10

   Bay held at 4 C through deorbit, re-entry and splashdown. Cassette goes to the customer's courier about 20 min after splashdown.

The payload module, in CAD

Every item in the module sheet, drawn and packed into the large bay deck by deck. The back face mates with the bay: blind-mate connector, and a cold wall against the bay's thermoelectric block. The front face carries Dexter-L's grapple fixture, and the fluid lines run down a channel just behind it. What you load before launch is marked blue in the configurator's payload guide.

CAD generated by cad/build_modules.py (CadQuery, OpenCascade kernel) from the catalog's module items: concept geometry, not a released design. Standard parts keep their real formats; the rest are sized from their catalog mass. The front panel and grapple fixture are left off in the 3-D view and are in the STEP.

• The XY stage travels 96.5 x 57.9 mm, so every one of the 24 wells reaches the objective; with the stage the imaging stack is 232 x 151 mm, which sets the module's depth budget.
• Reagent volumes the catalog does not state are split evenly from 75 % of the reservoir item's mass.
• Fluid pack: 5 reagent bags in 2 layers (210 x 101 x 46 mm), every port on a front edge.
• The catalog gives 0.30 kg for structure and containment; as an aluminium box that is a 0.14 mm skin on 0.09 kg of posts and shelves. Thin: the bay rails have to carry the launch loads, or the module needs more structure mass.
• The grapple fixture stands 26 mm proud of the front panel, into the bay opening; everything else is inside the bay envelope.

Ground control

Chips from the same cell lot and seeding batch run in an identical flight-spare bay on the ground, with the same pumps, reservoirs, flow rates, imaging schedule, dosing time and fixation time. The ground run follows the flight about 2 h behind, driven by the flight telemetry, and replays the recorded flight temperatures and 4 C hold durations. Where possible it also gets a launch-vibration profile and the same pre-launch storage time, so microgravity is the main difference. Extra chips stay in a standard CO2 incubator as a baseline for the hardware itself.

Coming home

Our estimate, not a source value. All chips are fixed or RNA-stabilised in orbit and effluent is collected at 4 C, so nothing needs to stay alive through return. The chain is held at 4 C: about 1 day in orbit after fixation, re-entry, about 20 min to the recovery ship, then 1-2 days to the lab. The ISS heart study stored PFA-fixed samples at 4 C, which matches this plan. But both ISS studies kept RNAlater samples or vitamin D effluent at -80 C, which LELP-1 cannot do. Customers must test RNA quality and labile markers after a 4 C hold of the same length on the ground, and the ground control must use the same hold times.

Limits of this flight

• Short exposure: LELP-1 runs at most 14 days. The ISS heart study ran about 30 days. The ISS kidney study found no unique response after 6 days plus 2 days of treatment, and the authors call for study of longer exposure. Slow effects may not show up in a LELP-1 flight.
• No crew: nobody can clear a bubble, re-prime a line or swap a leaking or contaminated chip. A failed chip is lost, so each condition needs at least two chips.
• Live launch: mature organ-chips are launched live, so they must survive late loading, any launch slip and ascent at 37 C. BioSentinel lost its yeast to long pre-launch storage, and EcAMSat cells were stressed by multi-week storage, so launch-slip limits must be agreed with the customer.
• No -80 C freezing in orbit: samples are fixed or RNA-stabilised and returned at 4 C. Both ISS chip studies froze some samples at -80 C. Markers that need frozen samples may degrade.
• No CO2 or incubator gas control: the ISS heart tissues were kept at 5% CO2, but LELP-1 media must be HEPES-buffered and oxygen depends on gas-permeable chip materials. The customer must qualify the chip and medium in a sealed, CO2-free bay on the ground first. Some chip plastics (e.g. PDMS) may absorb small hydrophobic drugs, so the drug must also be qualified on the same chips.
• No in-flight 1 g control: LELP-1 has no centrifuge, so the 1 g comparison is only on the ground, and launch, re-entry and radiation effects are mixed in with the microgravity effect.
• Few chips per bay (about 4-6) and microlitre effluent volumes limit how many doses and assays one bay supports. Big dose-response studies need several bays.
• Microgravity at the bay is good (about 1e-6 g) but drops to about 1e-4 to 1e-3 g while the arm moves, so arm moves must be scheduled away from key steps.
• The protocol and module here are a reference design in a digital twin. LELP-1 has not flown yet, and none of the heritage results above were obtained on LELP-1.