HUMAN 3D CARDIAC SAFETY
& Cardiotoxicity testing
Detect cardiac liabilities. Understand their functional impact.
Assess how your compounds affect cardiac contractility, electrophysiology, repolarization and calcium handling with SmartHeart®, 4Dcell's human 3D cardiac testing platform.
4Dcell designs fit-for-purpose cardiac safety studies for pharmaceutical and biotechnology teams. Each study combines quantitative tissue-level measurements, quality-control information and scientific interpretation to support compound selection and the investigation of unexpected cardiac effects.
Beyond ion-channel screening: investigate cardiac function
Drug-induced cardiotoxicity can result from multiple mechanisms, including altered repolarization, disrupted calcium handling, abnormal beating activity and impaired cardiac contractility.
While conventional ion-channel assays provide essential mechanistic information, they do not directly characterize the integrated functional response of cardiac tissue.
SmartHeart® uses self-assembled, ring-shaped 3D microtissues combining human iPSC-derived cardiomyocytes and cardiac fibroblasts. The platform enables quantitative analysis of cardiac mechanical activity, with complementary electrophysiological and calcium-handling measurements.
These functional readouts help investigate how compound-induced molecular effects translate into measurable changes in cardiac tissue behavior.
Human 3D cardiac safety assays
Cardiac contractility & inotropic safety
Detect unwanted positive or negative inotropic effects during drug development.
Drug candidates can impair cardiac mechanical function independently of major electrophysiological abnormalities.
The SmartHeart® Contractility Assay quantifies the contraction of human cardiac microtissues using brightfield video analysis and automated tissue tracking.
Key readouts
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Contraction strain and derived contractile stress
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Maximum and mean contraction speed
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Maximum and mean relaxation speed
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Contraction and relaxation timing
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Beating frequency and regularity
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Concentration–response profiles and EC50/IC50 estimates when supported by the data
Itraconazole induced a significant negative inotropic response in SmartHeart® human 3D cardiac microtissues (IC50 = 914 nM; negative directional contrast, p = 0.0175; n = 42 microtissues across three independent experiments).
The response was characterized under acute sequential dosing conditions at Day 21 in 2 mM Ca²⁺ Tyrode's solution.
Applications
Detection and characterization of unwanted positive or negative inotropy, altered contraction or relaxation kinetics, and drug-induced functional cardiac liabilities during drug discovery and lead optimization.
The core SmartHeart® Contractility Assay has undergone fit-for-purpose qualification using seven reference compounds with established positive or negative inotropic effects.
Electrophysiology & proarrhythmic risk assessment
Investigate drug-induced alterations in cardiac electrical activity and repolarization.
SmartHeart® supports optical action potential measurements using voltage-sensitive fluorescence imaging to characterize electrophysiological responses in human 3D cardiac microtissues.
Key readouts
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Action potential duration (APD) and repolarization kinetics
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Action potential amplitude and upstroke characteristics
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Depolarization and repolarization changes
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Beating frequency and rhythm irregularity
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Concentration-dependent electrophysiological responses
Dofetilide-induced changes in action potential duration (APD10, APD50 and APD90) in SmartHeart® human 3D cardiac microtissues. The concentration-dependent increase in APD90 reflects delayed cardiac repolarization, a key electrophysiological marker associated with proarrhythmic risk.
Applications
Investigation of ion-channel-related cardiac liabilities, altered repolarization and electrophysiological mechanisms associated with proarrhythmic risk, including those relevant to QT prolongation and torsade de pointes (TdP).
Optical APD measurements provide mechanistic information on cardiac electrical behavior and are not equivalent to clinical ECG-derived QT/QTc intervals.
Calcium handling & excitation–contraction coupling
Explore calcium-dependent mechanisms underlying cardiac functional changes.
Intracellular calcium dynamics regulate cardiac excitation–contraction coupling and influence both electrical activity and mechanical contraction.
Complementary fluorescence-based calcium transient measurements can be incorporated to investigate drug-induced changes in calcium handling.
Key readouts
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Calcium transient amplitude
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Calcium rise and decay kinetics
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Calcium transient duration
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Beating frequency and regularity
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Concentration-dependent calcium responses
Applications
Mechanistic investigation of compound-induced changes in calcium cycling, excitation–contraction coupling and calcium-dependent cardiac dysfunction.
Calcium-handling studies are designed according to the experimental objective, with study conditions and assay performance assessed for the intended application.
Chronic & delayed cardiotoxicity
Investigate cardiac effects that may emerge beyond acute compound exposure.
4Dcell can develop tailored longer-duration or repeated-exposure studies to investigate delayed changes in cardiac tissue function.
Potential endpoints
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Time-dependent changes in contractility and beating activity
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Functional responses following repeated compound exposure
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Tissue morphology and structural integrity
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Recovery or reversibility following compound withdrawal
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Complementary viability, imaging or molecular measurements
Applications
Investigation of delayed or cumulative cardiotoxicity, persistent functional changes and exposure-dependent cardiac responses.
Longer-duration studies are developed on a fit-for-purpose basis. Experimental conditions, relevant endpoints and performance requirements are established for each project.
Experimental evidence supporting SmartHeart® cardiac safety testing
Electrophysiological assessment of CiPA reference compounds
SmartHeart® has been evaluated with seven reference compounds from the Comprehensive in vitro Proarrhythmia Assay panel, covering different torsade de pointes risk categories and pharmacological mechanisms.
The studies identified compound-specific changes in action-potential characteristics, repolarization, beating activity and cardiac mechanical function.
For example, dofetilide produced a concentration-dependent prolongation of late action-potential repolarization, accompanied by changes in beating frequency and contractile activity.
These results support the mechanistic investigation of drug-induced electrophysiological and functional changes.
Fit-for-purpose contractility qualification
The SmartHeart® Contractility Assay was evaluated with seven reference compounds with known positive or negative inotropic activity and different mechanisms of action.
Under the qualified study design:
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The assay identified the expected direction of the inotropic response for all seven tested compounds
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Three independent experiments were performed per compound
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At least 20 evaluable cardiac microtissues were analyzed per compound across the experiments
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The estimated minimum detectable effect ranged from 3.7% to 5.7% of baseline, depending on the readout
These results support the detection and characterization of drug-induced inotropic responses within the qualified operating conditions.
The qualification applies to the tested acute exposure workflow.
Positive and negative inotropic responses measured with the SmartHeart® Contractility Assay.
Bay K 8644 increased cardiac contraction strain (EC50 = 24.7 nM; n = 27 microtissues), while quinidine reduced contractile activity (IC50 = 1.31 µM; n = 28 microtissues).
Both responses were characterized across three independent experiments under qualified acute assay conditions, demonstrating SmartHeart®'s ability to detect and quantify opposing inotropic effects in human 3D cardiac microtissues.
Published Scientific Evidence for SmartHeart® Cardiac Testing
The scientific foundation of SmartHeart® was established in a peer-reviewed eLife publication demonstrating the generation of human 3D cardiac microtissues and their measurable responses to pharmacological compounds.
The study characterized contractile responses to isoproterenol and verapamil, as well as arrhythmogenic effects induced by dofetilide.
Additional results were presented in a published scientific abstract in the Journal of Pharmacological and Toxicological Methods (2025), including functional responses to isoproterenol, nifedipine and mexiletine.
These published findings complement 4Dcell's internal fit-for-purpose qualification studies and support the use of SmartHeart® for investigating drug-induced changes in human cardiac function. They do not constitute independent regulatory qualification of the platform.
Séguret et al., eLife (2024) — Development and pharmacological characterization of 3D ring-shaped human cardiac tissues. DOI: 10.7554/eLife.87739
Khedher et al., Journal of Pharmacological and Toxicological Methods, 2025. Published abstract. DOI: 10.1016/j.vascn.2025.107821
From cardiac safety question to quantitative results
1. Define your cardiac safety question
We work with your team to identify the potential cardiac liability, the compound's expected pharmacology and the functional endpoints needed to address your research question.
2. Design your experiment
The experimental strategy is tailored to the compound and study objectives, including concentration range, exposure duration, control conditions, selected readouts and qualification requirements.
3. Measure cardiac functional responses
Compound-induced changes are assessed using the selected combination of contractility, electrophysiological, calcium-handling or complementary measurements.
4. Analyze and interpret the results
4Dcell provides quantitative data, quality-control information, concentration–response analysis and scientific interpretation within the defined experimental scope and method limitations.
5. Deliver the Scientific Report
We provide the agreed quantitative results, study methods, quality-control information, scientific interpretation and relevant limitations to support evaluation of the compound's cardiac safety profile.
Integrated human 3D cardiac tissue
SmartHeart® combines human iPSC-derived cardiomyocytes and cardiac fibroblasts in self-assembled, ring-shaped 3D microtissues. This multicellular architecture enables coordinated tissue contraction and integrated functional assessment beyond isolated cellular responses.
Quantitative functional measurements
SmartX™ Analysis extracts cardiac contractility metrics from brightfield recordings, including tissue deformation, derived contractile stress, contraction and relaxation kinetics, and beating activity.
Scalable 96-well format
SmartHeart® combines tissue-level functional measurements with a standard 96-well plate format, supporting concentration–response studies, parallel compound testing and integration into preclinical drug discovery workflows.
Nine microtissues per well for robust functional data
Each SmartHeart® well contains nine individual cardiac microtissues, providing multiple tissue-level measurements under the same experimental conditions. This unique architecture enables assessment of within-well variability, supports tissue-level quality control and strengthens the interpretation of compound-induced functional responses.
Complementary cardiac readouts
Contractility measurements can be complemented by electrophysiological and calcium-handling assays when additional mechanistic information is required.
Flexible study design & scientific support
4Dcell scientists help define study conditions, experimental controls, readouts, quality-control requirements and data interpretation according to the compound and research objective.
Why choose SmartHeart® for cardiac safety testing?
Frequently Asked Questions
Discuss your cardiac safety testing project
Investigate potential cardiac liabilities with human 3D functional data.
Whether you need to characterize an unexpected inotropic effect, investigate a repolarization-related safety signal or develop a tailored cardiotoxicity study, our scientists can help define an experimental strategy matched to your compound and research objectives.