Sumona Sarkar

National Institute of Standards and Technology | NIST · Biosystems and Biomaterials Division

Repeatability of measurements from image analytics is difficult, due to the heterogeneity and complexity of cell samples, exact microscope stage positioning, and slide thickness. We present a method to define and use a reference focal plane that provides repeatable measurements with very high accuracy, by relying on control beads as reference mater...

Aim: Cell viability assays are critical for cell-based products. Here, we demonstrate a combined experimental and computational approach to identify fit-for-purpose cell assays that can predict changes in cell proliferation, a critical biological response in cell expansion. Materials & methods: Jurkat cells were systematically injured using heat (4...

The use of engineered cells, tissues, and organs has the opportunity to change the way injuries and diseases are treated. Commercialization of these groundbreaking technologies has been limited in part by the complex and costly nature of their manufacture. Process-related variability and even small changes in the manufacturing process of a living p...

Cell viability, an essential measurement for cell therapy products, lacks traceability. One of the most common cell viability tests is trypan blue dye exclusion where blue-stained cells are counted via brightfield imaging. Typically, live and dead cells are classified based on their pixel intensities which may vary arbitrarily making it difficult t...

Our work at NIST is focused on improving confidence in measurement. In this chapter we present examples of how NIST interacts with industry and other stakeholders involved with cell therapies to achieve this goal. NIST plays a special role in the development of reference materials and documentary standards and works closely with our stakeholders to...

Analytical methods are critical in the characterization and testing of cell and gene therapy products. Analytical method development occurs in parallel to product development and is refined as knowledge is accumulated during the development program. Validated analytical methods are generally required for product licensure, and steps should be taken...

Nanofiber scaffolds can induce osteogenic differentiation and cell morphology alterations of human bone marrow stromal cells (hBMSCs) without introduction of chemical cues. In this study, we investigate the predictive power of day 1 cell morphology, quantified by a machine learning based method, as an indicator of osteogenic differentiation modulat...

Trypan blue dye exclusion-based cell viability measurements are highly dependent upon image quality and consistency. In order to make measurements repeatable, one must be able to reliably capture images at a consistent focal plane, and with signal-to-noise ratio within appropriate limits to support proper execution of image analysis routines. Imagi...

Recent advances in the fields of cell and gene therapy and regenerative medicine have increased the need for a standardized approach to cell counting. International efforts in the development of documentary standards as well as workshops which include input from device manufacturers , regulators, researchers and manufacturing organizations have sou...

Statement of significance: Aggrecan is a natural biomolecule that is essential for connective tissue hydration and mechanics. Aggrecan is composed of negatively charged chondroitin sulfate bristles attached to a protein core in a bottlebrush configuration. With age and degeneration, enzymatic degradation of aggrecan outpaces cellular synthesis res...

The development of standards for the field of regenerative medicine has been noted as a high priority by several road-mapping activities. Additionally, the U.S. Congress recognizes the importance of standards in the 21st Century Cure Act. Standards will help to accelerate and streamline cell and gene therapy product development, ensure the quality...

The emergence of cell-based therapeutics has increased the need for high-quality, robust and validated measurements for cell characterization. Cell count, being one of the most fundamental measures for cell-based therapeutics, now requires increased levels of measurement confidence. The National Institute of Standards and Technology (NIST) and the...

Background aims: Cell counting measurements are critical in the research, development and manufacturing of cell-based products, yet determining cell quantity with accuracy and precision remains a challenge. Validating and evaluating a cell counting measurement process can be difficult because of the lack of appropriate reference material. Here we...

Many biomaterial scaffolds have been advanced to provide synthetic cell niches for tissue engineering and drug screening applications, however current methods for comparing scaffold niches focus on cell functional outcomes or attempt to normalize materials properties between different scaffold formats. We demonstrate a three-dimensional (3D) cellul...

The human vertebral column serves to transfer loads from the head, trunk, and upper body to the pelvis to provide flexibility in motion while also helping to protect the spinal cord. The main load-bearing entity of the spine is the intervertebral disc, which is subject to degeneration due to normal aging or injury due to loading. Many treatments ha...

Small leucine-rich proteoglycans (SLRPs) are a class of molecules prevalent in almost all tissues types and are thought to be responsible for collagen organization and macro-scale biological properties. However, when they are dysfunctional or degraded, severe pathological phenotypes are observed. Here we investigate macromolecular mimics to SLRPs u...

Nanofiber technology has emerged as a promising tool to recapitulate native extracellular matrix structure; however the properties of nanofibers governing cell-material interactions are still largely undetermined. We have investigated the role of both nanofiber structure and chemistry in directing the response of human bone marrow stromal cells (hB...

Cell therapy products (CTPs) represent a broad class of therapeutics poised to move toward commercialization due to recent discoveries, technological advances and increased investment. The industry is racing to develop, manufacture and translate promising therapeutics for treating a range of diseases and injuries but must address significant manufa...

Cell morphology has been identified as a potential indicator of stem cell response to biomaterials. However, determination of cell shape phenotype in biomaterials is complicated by heterogeneous cell populations, microenvironment heterogeneity, and multi-parametric definitions of cell morphology. To associate cell morphology with cell-material inte...

Unlabelled: The cell therapy industry has identified the inability to reliably characterize cells as possibly its greatest challenge and has called for standards and reference materials to provide assurance for measurements of cell properties. The challenges in characterization of cell therapy products can be largely addressed with systematic appr...

There is currently no method for assessing the nature of the cell niche provided by 3D biomaterial scaffolds. Analyzing human bone marrow stromal cell (hBMSC) 3D cell shape in response to different biomaterial scaffolds allowed the 3D cell niche promoted by biomaterial scaffolds to be evaluated. Primary hBMSCs (p5) were seeded (5,000 cells/cm2) in...

Uniaxial tension was applied to selectively digested single lamellar human cadaveric annulus fibrosus specimens to investigate the role of different biomolecules in annular biomechanics. Single layered and inter-lamellar annulus fibrosus samples were obtained from ten isolated cadaveric lumbar intervertebral discs in one of four orientations: longi...

The present invention encompasses methods and compositions for generating a biomimetic proteoglycan. The invention includes methods of treating a disease, disorder, or condition of soft tissue using a biomimetic proteoglycan.

The human vertebral column serves to transfer loads from the head, trunk, and upper body to the pelvis to provide flexibility in motion while also helping to protect the spinal cord. The main load-bearing entity of the spine is the intervertebral disc, which is subject to degeneration due to normal aging or injury due to loading. Many treatments ha...

Lower back pain resulting from intervertebral disc degeneration is one of the leading musculoskeletal disorders confronting our health system. In order to mechanically stabilize the disc early in the degenerative cascade and prevent the need for spinal fusion surgeries, we have proposed the development of a hybrid-bio/synthetic biomimetic proteogly...

Intervertebral disc (IVD) degeneration is accompanied by a loss of proteoglycans (PGs) in the nucleus pulposus (NP), resulting in a loss of charged chondroitin sulfate (CS) chains, decreasing mechanical function of the disc. PG mimics may be employed to restore NP functionality. Synthesis of CS bottle brush structures requires immobilization of CS...

A family of injectable poly(N-isopropyl acrylamide) (PNIPAAm) copolymer hydrogels has been fabricated in order to tune mechanical properties to support load-bearing function and dimensional recovery for possible use as load-bearing medical devices, such as a nucleus pulposus replacement for the intervertebral disc. PNIPAAm-polyethylene glycol (PEG)...

Successful artificial tissue scaffolds support regeneration by promoting cellular organization as well as appropriate mechanical and biological functionality. We have previously shown in vitro that 2-D substrates with micrometer-scale grooves (5 microm deep, 18 microm wide, with 12 microm spacing) can induce cell orientation and ECM alignment. Here...

The fabrication of functional small diameter blood vessel analogs has implications in vascular disease treatment. Current 3D models of the medial vessel layer lack micron-scale topographical cues that have shown promise in vitro by recapitulating native vascular smooth muscle cell (VSMC) behavior. A major obstacle to fabricating 3D scaffolds is mai...

The in vitro construction of tissue-engineered small diameter (<6mm) blood vessels with sufficient strength and mechanical compliance has evaded researchers. We hypothesize that the high spatial organization of the medial layer of vascular smooth muscle cells (VSMCs) and their surrounding matrix provides high burst strength, compliance, and stabili...