TABLE II.

Summary of the current literature on liver-on-a-chip (LOC): (1) type of device: solid organ chip—does not contain a membrane structure to mimic endothelial interactions, or scaffold-free, or barrier tissue—contains a membrane structure; (2) chip material; (3) substrate surface coating, (4) co-culturing (YES/NO); (5) cell lines used in the study; (6) length of the study; (7) operation flow rate and/or shear stress—also contains the values of the dimensionless parameters where mentioned; (8) application.

Reference	Type of LOC	Chip material	Substrate surface coating	Co-culturing (YES/NO)	Cell lines	Length of the study	Operation flow rate or/and shear stress	Application
Bhise et al.73	Solid organ chip	Multilayers of PDMS and PMMA glass——bottom	3-(trimethoxysilyl)propyl methacrylate	NO	HepG2 and C3A spheroids	Up to 30 days	200 μl/h	15 mM acute acetaminophen (APAP) exposure
Bonanini et al.93	Solid organ chip——OrganoPlate® Graft	Top plate: virgin polystyrene. Bottom plate: optical quality 150 μm glass (1H coverslip thickness). Microfluidics: glass, proprietary polymers	Collagen I Matrigel GFR	YES	Cryopreserved Upcyte® human hepatocytes human primary RFP-labeled HUVECs (Alphabioregen, #RFP4)	7 days	On a rocker at + 14° and −14° inclination every 8 min	Vascularisation and experimentation of tissues in vitro
Boos et al.94	Scaffold free—hanging drop	PDMS	0.1% gelatin solution Biolipidure	YES	Primary human liver microtissues mouse embryonic-stem-cell line ES-D3	Up to 10 days	Spheroids generation on a rocker at ± 2°  standing stop on a rocker at ±4°	Embryotoxic prodrug cyclophosphamide study
Bulutoglu et al.95	Solid organ chip	PDMS glass slide	50 μg/ml fibronectin	NO	Primary rat hepatocytes	Not mentioned	Not mentioned	Hypothesis testing about NAFLD progression
Chen et al.92	Solid organ chip	PDMS with glass slide	Not mentioned	YES	Hepa1–6 tumor spheroids JS-1 stellate cells	3 days	1 μl/min	Cancer cell stellate interactions under drug stimulation in a microchannel plate
Chen et al.75	Solid organ chip	PDMS	Collagen	YES	Human prostatic cancer cell (PC3) Mouse NIH/3T3 fibroblasts Human lung cancer cells (A549) Human breast cancer cells (MCF-7) Human liver cancer cells (HepG2) Primary rat hepatocytes	Not mentioned	30 μl/h flow rate 4.7 × 10−4 dyne/cm2 shear stress	Testing for statin using prodrug simvastatin and active drug atorvastatin testing
Chhabra et al.57	Solid organ chip	Not mentioned	ECM	YES	Human primary hepatocytes	Not mentioned	On a rocker at ±25° at a frequency of 1 Hz 6.21 dyn/cm2 shear stress	Not mentioned
Choi et al.7	Solid organ chip	PDMS	Pluronic F127	No	Primary rat hepatocytes	Up to 4 weeks	Static	Hepatic functions improvement
Corrado et al.96	Solid organ chip	Glass and polydimethylsiloxane	Not mentioned	NO	HepG2 μTPs HepG2 spheroids	14 days	Not mentioned	μTPs may be used to study the cytotoxic effects of xenobiotics
Delalat et al.97	Solid organ chip	Silicon and silicon dioxide	Potassium hydroxide	NO	Rat primary hepatocytes	4 weeks	90 μl/h	Microtrenches allow for maintenance of hepatocytes
Frey et al.98	Scaffold-free—hanging drop	PDMS	trichloro(1H,1H,2H,2H-per-fluorooctyl)silane	YES	Human colorectal carcinoma cells (HCT-116) Primary cell isolates from rat liver	Not mentioned	Maximal shear stress of 1.2 mPa Flow rate 10 μl/min Drop height 0.5 mm	Not mentioned
Gori et al.99	Solid organ chip	PDMS	Not mentioned	NO	HepG2	8 days	18 μl/day Negligible shear stress	Development of on-chip non-alcoholic fatty liver disease (NAFLD) models
Jang et al.100	Solid organ chip	OrganoPlate from MIMETAS and Leiden University	Matrigel	NO	HepG2	3 weeks	0.3 dyn/cm2 shear stress	Cultivation of HepG2 cells
Jang et al.101	Solid organ chip	Not mentioned	ECM	NO	Primary rat, human, or dog hepatocytes Sinusoidal rat, human, or dog liver endothelial cells with or without Kupffer and/or stellate cells	14 days	10 μl/h	Not mentioned
Kang et al.72	Solid organ chip	PDMS	Collagen I 30% (v/v) Matrigel for RAMECs	YES	Rat primary hepatocytes and Endothelial cells (primary rat adrenal medullary and bovine aortic)	Up to 30 days	30–40 μl/h	Urea synthesis using diacetylmonoxime Viral replication for hepatotropic hepatitis B virus (HBV) and analysis
Khetani et al.102	Scaffold free—micropatterned	Tissue culture-treated polystyrene omnitrays (Nunc)	Collagen I	YES	3T3-J2 fibroblasts : Primary rat hepatocytes = 4:1	Up to 6 weeks	Static	Hepatic functions improvement
Kim et al.103	Scaffold-free—culture plate	PMMA	Pluronic127	YES	HepG2 HS68 fibroblasts Primary HUVEC	Up to 7 days	Mimetas Rocker kept at 7° angle and six rotation cycles per hour	Pro-inflammatory protein, IL-1β, used to induce inflammation
Lee et al.104	Solid organ chip	PMMA	Gelatin and liver dECM	YES	Human HepaRG cells Human umbilical vein endothelial cells (HUVEC)	Not mentioned	25 μl/min final flow rate	APAP used to check hepatotoxicity
Lee et al.52	Solid organ chip	Acrylic—- top PDMS—- middle Glass—bottom	Collagen I (10 μg/well) for mutiwell No coating for the LOC	NO	Rat and human primary hepatocytes	Up to 7 days	10–20 nl/min Re < 0.01 Pe = 56 in flow channel Pe = 0.8 in the barrier channel	Hepatotoxicity of the anti-inflammatory drug diclofenac
Lee et al.70	Solid organ chip	PDMS—- top PEGDA-microsomes—- middle Glass—bottom	Not mentioned	NO	Rat primary hepatocytes	Not mentioned	Tilt angle not mentioned 5 μl/min flow rate of substrate solution Pe > 1000	P450 reaction with microsome in solution phase tested with different substrate concentrations ranging from 2  to 80 μM
Lee et al.71	Solid organ chip	PDMS	3% (w/v) BSA Collagen I	YES	Rat primary hepatocytes and HSCs	Up to 13 days	5.53 mm/h flow speed	Live/Dead assay Albumin and urea secretion analyzed by measuring concentration in medium
Li et al.105	Barrier tissue	Polyethylene terephthalate—- middle glass-bottom	Fibronectin (100 μg/ml) Collagen (100 μg/ml)	NO	Human primary hepatocytes Human dermal microvascular endothelial cells Human stellate cells	Not mentioned	80 μl/h in heptic channel 100 μl/h in vascular channel	Induction of inflammation in liver diseases
Mazari-Arrighi et al.106	Scaffold-free-cell fibres	Glass bovine collagen I 10% Matrigel 1.0% Na-alginate 100 mM CaCl2 3% w/w sucrose solution	Not mentioned	NO	Primary rat hepatocytes	Up to 30 days	20 μl/min in the core 80 μl/min in the shell 3.6 ml/min in the sheath	Hepatotoxicity of the drugs acetaminophen and diclofenac
Moya et al.107	Barrier tissue	Glass-bottom	Collagen	NO	Rat and human hepatocytes	Not mentioned	Not mentioned	OOC devices including printed sensors allowing for real-time physiological measurements
Nakao et al.69	Solid organ chip	PDMS—- top Glass-bottom	Collagen Matrigel (150 μg/ml)	NO	Rat primary hepatocytes	Up to 4 days	1.36 mm/s at center of medium flow channel No flow in cell culture area 1.3 Pa (shear stress) in medium flow channel No shear stress in cell culture area	CDF excreted into bile canaliculi by MRP2 protein
Rennert et al.91	Solid organ chip	Multi-Organ-Tissue-Flow (MOTiF) biochip Cyclic olefin copolymers (COC)—TOPAS	COC-TOPAS® Plasma treatment	YES	HepaRG cells HUVECs Peripheral Blood Mononuclear Cells (PBMCs)	Up to 4 weeks	50 mPa⋅(0.5 dyn/cm2) shear stress 50 μl/min perfusion rate	Not mentioned
Roth et al.108	Scaffold free—micropatterned	Polystyrene micropillar and microwell chip by MBD Korea	0.01% (w/v) PMA-OD attached PuraMatrix spots onto a micropillar chip	No	Human hepatoma (Hep3B)	Up to 3 days	Static	Adenoviral transduction and drug toxicity
Weng et al.74	Scaffold-free—micropatterned	PDMS	Collagen	NO	Primary liver cells (PLCs) and Primary HSCs	Up to 14 days	30 μl/min	APAP-induced hepatotoxicity
Yu et al.109	Barrier tissue	PDMS—- top Glass coverslip and parylene membrane—- middle Silicon—bottom	3,4-dihydroxy-l-phenylalanine (DOPA)	YES	Top—vascular cells Bottom—rat primary hepatocyte spheroids	Not mentioned	0.1 ml/h	Alternating flow microfluidic assisted co-culture model
Yu et al.110	Solid organ chip	Glass/silicon chip PDMS/glass cover	Collagen 1 (40 μl)	YES	Rat hepatocyte spheroids	24 days	Working range: between 0.06 and 0.2 ml/h Optimum flow rate: 0.1 ml/h	Not mentioned
Zhou et al.8	Solid organ chip	PDMS—top and middle Glass—bottom	Collagen 1	YES	Stellate cells Rat primary hepatocytes	Up to 3 weeks	Not mentioned	Aptamer-based biosensors for detecting secreted proteins in parallel

APAP, acetaminophen; BSA, bovine serum albumin; CDF, 5-(and-6)-carboxy-2′,7′-dichloro-fluorescein; COC, cyclic olefin copolymers; dECM, Decellularized extracellular matrix; ECM, extracellular matrix; GFR, growth factor reduced; HBV, hepatitis B virus; HSCs, hepatic stellate cells; LOC, liver-on-a-chip; NAFLD, non-alcoholic fatty liver disease; PDMS, poly(dimethylsiloxane); PEGDA, poly(ethylene glycol) diacrylate; PMA-OD, poly(maleic anhydride-alt-1-octadecene); PMMA, poly(methyl methacrylate); RAMECs, primary rat adrenal medullary endothelial cells; μTPs, microtissue precursors.