Biological assays are experimental methods for assessing the presence, localization, or biological activity of a substance in living cells and biological matrices. Such methods are essential to biological science and technology. Many applications require novel assays to answer new questions, and existing assays must be implemented in a way that is robust and reproducible. Assay development and validation are routinely performed at SRI.
Biological assay types
Cell-based assays
Measurements made on cultured cells provide information about the chemical and physical state of the cells. These assays probe the biological effects of changing physiological conditions or added agents such as drugs or toxins. SRI researchers use cell-based assays to identify new therapeutic targets, discover new drugs, test chemicals for toxicity, detect pathogen infection, engineer cell function, and study the normal mechanisms underlying cell behavior.
SRI has extensive experience developing cell-based assays that address a wide range of biological questions and challenges:
- Cell viability/compound cytotoxicity assays
- Apoptosis
- RNAi-based target validation
- Cell proliferation
- Autophagy
- Intracellular pathogen assays
- Novel fluorescence probes
Functional genomics and proteomics
Functional genomics is a field of biology that focuses on the expression and function of genes and their protein products. It comprises methods to study and characterize the molecular interactions that translate into structure, function, and behavior of cells and organisms. Tools to measure many products of gene expression in parallel are essential to this area of research. They include proteomics methods for characterizing complex collections of proteins.
SRI’s experience developing assays for functional genomics and proteomics includes:
- Shotgun and quantitative approaches
- Characterization of post-translational modifications
- Gene expression analysis using mRNA arrays and miRNA arrays
- Gene editing with CRISPR/Cas 9
- SiRNA
- Gene expression analysis using reporter genes
Imaging and analysis
Imaging technologies enable scientists to see biological phenomena that are invisible to the unaided human eye. Biologists at SRI apply imaging and image analysis methods to a wide range of investigations, including detecting and locating proteins within living cells and tissues, visualizing the internal structures and biochemistry of living organisms, and visualizing biological structures that are simply too small to see.
SRI’s expertise in biological imaging and image analysis includes:
- Specialized histology
- High content imaging
- Transmission and scanning electron microscopy
- Noninvasive fluorescence, bioluminescence, and X-ray imaging
- Immunocytochemistry
- Confocal and Fluorescence microscopy
- Quantitative image analysis
Clinical laboratory analyses
SRI’s Clinical Analysis Laboratory is fully compliant with FDA Good Laboratory Practice (GLP) regulations and uses state-of-the-art instrumentation and data management to offer full capabilities for standard and specialized services for both human and veterinary clinical research samples.
Our capabilities include:
- Broad range of routine and specialized hematology and clinical chemistry services
- Routine and specialized analyses for coagulation and urinalysis parameters
- Recently FDA- and EMEA-approved biomarkers of toxicity for kidney, liver, muscle, and other target organs
Discovery ADMET and in vitro metabolism
SRI is a leader in the development and application of in vitro models for ADMET evaluations (ADMET: Absorption, Distribution, Metabolism, Excretion, and Toxicity). Obtaining data on potential toxicity early in the development process can help you make informed decisions to move promising leads forward and exclude liabilities. Our staff has extensive experience in elucidating tissue-specific mechanisms of toxicity for various species and organs. We pioneered the application of human tissue preparations to predicting interspecies differences in drug metabolism, potential drug interactions, and human drug metabolizing enzymes.
Predictive ADMET
- Membrane permeability: PAMPA, Caco-2, MDCK cells
- Metabolic stability: liver or small intestine microsomes
- Plasma stability
- Cytochrome P450 (CYP) inhibition
- Plasma protein binding
- p-Glycoprotein substrate assays
- In vivo pharmacokinetic screens
- High-throughput LC-MS/MS quantitation
- First in vivo dose to mice
In vitro metabolism and toxicity
- Metabolite profiling and identification
- Reaction phenotyping: CYP, UGT, SULT
- Drug-drug interactions
- Peroxisome proliferation
- Co-incubation screens
- Therapeutic index estimations
- Cytotoxicity and hepatotoxicity screening
- Mini-Ames mutagenicity screen
- Mini I (hERG) cardiotox liability screen
Drug metabolism and pharmacokinetics
SRI offers comprehensive drug metabolism and pharmacokinetic (DMPK) services to meet your needs. We give you access to a complete range of capabilities, beginning with dose administration followed by full-service bioanalytical support and pharmacokinetic data analysis and interpretation. We offer PK studies that fully comply with U.S. FDA GLP regulations.
Bioanalytical quantitative methods
- Bioanalytical method development and validation
- Small molecules: LC/ MS/MS, GC-MS, HPLC with UV, fluorescence, radiochemical detection
- Proteins: ELISA, antibody titer
- Quantitative PCR
- DNA/RNA test article, e.g., plasmid, virus
- Biodistribution, persistence, integration
- mRNA expression levels
- Subcellular localization
- Chromosomal integration
Pharmacokinetic and pharmacodynamic analyses
- Single-dose pharmacokinetics
- Bioavailability
- Multiple-dose pharmacokinetics
- Drug accumulation
- Metabolite identification
- WinNonlinTM compartmental and noncompartmental analysis
- PK/PD interpretation
- Bioequivalence
- Allometric estimations
- Formulation screening
Comprehensive ADME
- Absorption and clearance
- Tissue distribution
- DNA/RNA biodistribution, persistence, integration
- Interspecies comparative metabolism
- Metabolite profile
- Excretion and mass balance
- Radiolabeled drug synthesis
Immunology services
SRI International Immunology Services Facility provides quality services in the area of immunology, virology, autoimmunity and inflammation that covers all stages of drug discovery and development. With state-of-the-art instruments, laboratory, and validated software systems, the Immunology team offers customized services to meet clients’ needs which includes but is not limited to assay development and validation for preclinical and clinical studies, as well as preclinical and clinical sample analysis.
- Assessment of immunogenicity (flow cytometry, ELISA, and ELISPOT)
- Cellular and humoral
- Antidrug antibody (ADA)
- Neutralizing antibody (NAb)
- Measurement of large molecules in biological fluids
- Measurement of antibodies, proteins, and peptides in biological fluids
- Measurement of vaccine efficacy, potency and stability
- Immunotoxicology evaluation
- Measurement of cytokines
- Biomarker analysis (flow cytometry and ELISA)
- Receptor binding and cell-based assays
Published work
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Association of the rs17782313, rs17773430 and rs34114122 Polymorphisms of/near MC4R Gene with Obesity-Related Biomarkers in a Spanish Pediatric Cohort
Our results highlight that metabolic risk factors, especially alterations in carbohydrate metabolism, were related to rs17782313.
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Evaluation of a device-agnostic approach to predict sleep from raw accelerometry data collected by Apple Watch Series 7, Garmin Vivoactive 4, and ActiGraph GT9X Link in children with sleep disruptions
This study demonstrates that raw acceleration data from consumer wearable devices has the potential to be harnessed to predict sleep in children.
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Survival and Hematologic Benefits of Romiplostim After Acute Radiation Exposure Supported FDA Approval Under the Animal Rule
The goal of our study was to evaluate the postirradiation survival and hematologic benefits of a single dose of RP with or without pegfilgrastim.
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Bedtime screen use behaviors and sleep outcomes: Findings from the Adolescent Brain Cognitive Development (ABCD) Study
We aim to determine associations between bedtime screen time behaviors and sleep outcomes in a national study of early adolescents.
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Circadian Disruption and Mental Health: The Chronotherapeutic Potential of Microbiome-Based and Dietary Strategies
Here, we provide an overview of the link between circadian disruption and mental illness.
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Effects of emerging alcohol use on developmental trajectories of functional sleep measures in adolescents
We tracked developmental changes in polysomnographic (PSG) and electroencephalographic (EEG) sleep measures and their relationship with emergent alcohol use in adolescents considering confounding effects (e.g., cannabis use).
