Storage temperatures for cold-chain delivery in cell therapy: a study of alginate-encapsulated liver cell spheroids stored at -80°c or -170°c for up to 1 year

Selecting serum-free hepatocyte cryopreservation stage and storage temperature for the application of an "off-the-shelf" bioartificial liver system

The bioartificial liver (BAL) system can potentially rescue acute liver failure (ALF) patients by providing partial liver function until a suitable donor liver can be found or the native liver has self-regenerated. In this study, we established a suitable cryopreservation process for the development of an off-the-shelf BAL system. The viability of hepatocyte spheroids cryopreserved in liquid nitrogen was comparable to that of fresh primary hepatocyte spheroids. When hepatocyte spheroids were subjected to cryopreservation in a deep freezer, no statistically significant differences were observed in ammonia removal rate or urea secretion rate based on the cryopreservation period. However, the functional activity of the liver post-cryopreservation in a deep freezer was significantly lower than that observed following liquid nitrogen cryopreservation. Moreover, cryopreserving spheroid hydrogel beads in a deep freezer resulted in a significant decrease (approximately 30%) in both ammonia removal and urea secretion rates compared to the group cryopreserved in liquid nitrogen. The viabilities of spheroid hydrogel beads filled into the bioreactor of a BAL system were similar across all four groups. However, upon operating the BAL system for 24 h, the liver function activity was significantly higher in the group comprising hydrogel beads generated after thawing hepatocyte spheroids cryopreserved in liquid nitrogen. Consequently, the manufacturing of beads after the cryopreservation of hepatocyte spheroids is deemed the most suitable method, considering efficiency, economic feasibility, and liver function activity, for producing a BAL system.

Engineered Test Tissues: A Model for Quantifying the Effects of Cryopreservation Parameters

Engineered tissues are showing promise as implants to repair or replace damaged tissues in vivo or as in vitro tools to discover new therapies. A major challenge of the tissue engineering field is the sample preservation and storage until their transport and desired use. To successfully cryopreserve tissue, its viability, structure, and function must be retained post-thaw. The outcome of cryopreservation is impacted by several parameters, including the cryopreserving agent (CPA) utilized, the cooling rate, and the storage temperature. Although a number of CPAs are commercially available for cell cryopreservation, there are few CPAs designed specifically for tissue cryostorage and recovery. In this study, we present a flexible, relatively high-throughput method that utilizes engineered tissue rings as test tissues for screening the commercially available CPAs and cryopreservation parameters. Engineered test tissues can be fabricated with low batch-to-batch variability and characteristic morphology due to their endogenous extracellular matrix, and they have mechanical properties and a ring format suitable for testing with standard methods. The tissues were grown for 7 days in standard 48-well plates and cryopreserved in standard cryovials. The method allowed for the quantification of metabolic recovery, tissue apoptosis/necrosis, morphology, and mechanical properties. In addition to establishing the method, we tested different CPA formulations, freezing rates, and freezing points. Our proposed method enables timely preliminary screening of CPA formulations and cryopreservation parameters that may improve the storage of engineered tissues.

Oxygen-Generating Scaffolds: One Step Closer to the Clinical Translation of Tissue Engineered Products

The lack of oxygen supply in engineered constructs has been an ongoing challenge for tissue engineering and regenerative medicine. Upon implantation of an engineered tissue, spontaneous blood vessel formation does not happen rapidly, therefore, there is typically a limited availability of oxygen in engineered biomaterials. Providing oxygen in large tissue-engineered constructs is a major challenge that hinders the development of clinically relevant engineered tissues. Similarly, maintaining adequate oxygen levels in cell-laden tissue engineered products during transportation and storage is another hurdle. There is an unmet demand for functional scaffolds that could actively produce and deliver oxygen, attainable by incorporating oxygen-generating materials. Recent approaches include encapsulation of oxygen-generating agents such as solid peroxides, liquid peroxides, and fluorinated substances in the scaffolds. Recent approaches to mitigate the adverse effects, as well as achieving a sustained and controlled release of oxygen, are discussed. Importance of oxygen-generating materials in various tissue engineering approaches such as ex vivo tissue engineering, in situ tissue engineering, and bioprinting are highlighted in detail. In addition, the existing challenges, possible solutions, and future strategies that aim to design clinically relevant multifunctional oxygen-generating biomaterials are provided in this review paper.

Membrane Applications in Autologous Cell Therapy

Stem cell and cell therapies, particularly autologous cell therapies, are becoming a common practice. However, in order for these technologies to achieve wide-scale clinical application, the prohibitively high cost associated with these therapies must be addressed through creative engineering. Membranes can be a disruptive technology to reshape the bioprocessing and manufacture of cellular products and significantly reduce the cost of autologous cell therapies. Examples of successful membrane applications include expansions of CAR-T cells, various human stem cells, and production of extracellular vesicles (EVs) using hollow fibre membrane bioreactors. Novel membranes with tailored functions and surface properties and novel membrane modules that can accommodate the changing needs for surface area and transport properties are to be developed to fulfil this key role.

Freezing Technology: Control of Freezing, Thawing, and Ice Nucleation

From early dry-ice-based freezers and passive coolers, cryopreservation devices have come a long way. With increasing interest in the field of cryobiology from new scientific applications, the importance of reliable, traceable, and reproducible cold chain devices is sure to increase, ensuring more precise cryopreservation and enabling better post-thaw outcomes, both for the user and for biological samples. As with any cryopreservation process, it is important to optimize each part of the cold chain for each lab's biological samples, cryocontainers used, and logistical restraints. In this chapter we describe how freezing technology can be used for cryopreservation of cells.

Logistics of an advanced therapy medicinal product during COVID-19 pandemic in Italy: successful delivery of mesenchymal stromal cells in dry ice

Background

During the coronavirus disease-2019 (COVID-19) pandemic, Italian hospitals faced the most daunting challenges of their recent history, and only essential therapeutic interventions were feasible. From March to April 2020, the Laboratory of Advanced Cellular Therapies (Vicenza, Italy) received requests to treat a patient with severe COVID-19 and a patient with acute graft-versus-host disease with umbilical cord-derived mesenchymal stromal cells (UC-MSCs). Access to clinics was restricted due to the risk of contagion. Transport of UC-MSCs in liquid nitrogen was unmanageable, leaving shipment in dry ice as the only option.

Methods

We assessed effects of the transition from liquid nitrogen to dry ice on cell viability; apoptosis; phenotype; proliferation; immunomodulation; and clonogenesis; and validated dry ice-based transport of UC-MSCs to clinics.

Results

Our results showed no differences in cell functionality related to the two storage conditions, and demonstrated the preservation of immunomodulatory and clonogenic potentials in dry ice. UC-MSCs were successfully delivered to points-of-care, enabling favourable clinical outcomes.

Conclusions

This experience underscores the flexibility of a public cell factory in its adaptation of the logistics of an advanced therapy medicinal product during a public health crisis. Alternative supply chains should be evaluated for other cell products to guarantee delivery during catastrophes.

Cryopreservation as a Key Element in the Successful Delivery of Cell-Based Therapies-A Review

Cryopreservation is a key enabling technology in regenerative medicine that provides stable and secure extended cell storage for primary tissue isolates and constructs and prepared cell preparations. The essential detail of the process as it can be applied to cell-based therapies is set out in this review, covering tissue and cell isolation, cryoprotection, cooling and freezing, frozen storage and transport, thawing, and recovery. The aim is to provide clinical scientists with an overview of the benefits and difficulties associated with cryopreservation to assist them with problem resolution in their routine work, or to enable them to consider future involvement in cryopreservative procedures. It is also intended to facilitate networking between clinicians and cryo-researchers to review difficulties and problems to advance protocol optimization and innovative design.

Cryopreservation of Human Midbrain Dopaminergic Neural Progenitor Cells Poised for Neuronal Differentiation

Human pluripotent stem cells can be differentiated into midbrain dopaminergic (mDA) neurons by directing cells through a floor plate progenitor stage. The developmental identity of mDA neurons produced using floor plate protocols is similar to substantia nigra neurons, and this has improved the ability to model Parkinson's disease (PD) in a dish. Combined with the unlimited growth potential of pluripotent stem cells, mDA neural progenitor cell production can provide a scalable source of human dopaminergic (DA) neurons for diverse applications. However, due to the complexity and length of the protocols and inherent differences between cell lines, considerable variability of the final population of neurons is often observed. One solution to this problem is to cryopreserve committed mDA neural progenitor cells in a ready-to-use format. Creating a bank of cryopreserved mDA neural progenitor cells poised for neuronal differentiation could significantly improve reproducibility and facilitate collaborations. Here we have compared six (6) different commercial cryopreservation media and different freezing conditions for mDA neural progenitor cells differentiated from human embryonic stem cell (hESC) lines. Significant differences in cell recovery were observed at 24 h post-thawing, but no differences were observed immediately upon thawing. The presence of ROCK inhibitors improved cell recovery at 24 h for all cryopreservation media tested. A faster cooling rate of 1-2°C/min was significantly better than 0.5°C/min for all conditions tested, while rapid thawing at 37°C was not always superior to slow thawing at 4°C. Importantly, cryopreservation of mDA neural progenitor cells did not alter their potential to resume differentiation into mDA neurons. Banks of cryopreserved committed mDA neural progenitor cells provide a method to generate human DA neurons with reduced batch-to-batch variability, and establish a mechanism to share lineage-primed cells for collaborative research.

Technical Considerations in the Freezing, Low-Temperature Storage and Thawing of Stem Cells for Cellular Therapies

The commercial and clinical development of cellular therapy products will invariably require cryopreservation and frozen storage of cellular starting materials, intermediates and/or final product. Optimising cryopreservation is as important as optimisation of the cell culture process in obtaining maximum yield and a consistent end-product. Suboptimal cryopreservation can lead not only to batch-to-batch variation, lowered cellular functionality and reduced cell yield, but also to the potential selection of subpopulations with genetic or epigenetic characteristics divergent from the original cell line. Regulatory requirements also impact on cryopreservation as these will require a robust and reproducible approach to the freezing, storage and thawing of the product. This requires attention to all aspects of the application of low temperatures: from the choice of freezing container and cryoprotectant, the cooling rate employed and its mode of de-livery, the correct handling of the frozen material during storage and transportation, to the eventual thawing of the product by the end-user. Each of these influences all of the others to a greater or lesser extent and none should be ignored. This paper seeks to provide practical insights and alternative solutions to the technical challenges faced during cryopreservation of cells for use in cellular therapies.

Advances in the slow freezing cryopreservation of microencapsulated cells

Over the past few decades, the use of cell microencapsulation technology has been promoted for a wide range of applications as sustained drug delivery systems or as cells containing biosystems for regenerative medicine. However, difficulty in their preservation and storage has limited their availability to healthcare centers. Because the preservation in cryogenic temperatures poses many biological and biophysical challenges and that the technology has not been well understood, the slow cooling cryopreservation, which is the most used technique worldwide, has not given full measure of its full potential application yet. This review will discuss the different steps that should be understood and taken into account to preserve microencapsulated cells by slow freezing in a successful and simple manner. Moreover, it will review the slow freezing preservation of alginate-based microencapsulated cells and discuss some recommendations that the research community may pursue to optimize the preservation of microencapsulated cells, enabling the therapy translate from bench to the clinic.

A study of cryogenic tissue-engineered liver slices in calcium alginate gel for drug testing

To address issues such as transportation and the time-consuming nature of tissue-engineered liver for use as an effective drug metabolism and toxicity testing model, "ready-to-use" cryogenic tissue-engineered liver needs to be studied. The research developed a cryogenic tissue-engineered liver slice (TELS), which comprised of HepG2 cells and calcium alginate gel. Cell viability and liver-specific functions were examined after different cryopreservation and recovery culture times. Then, cryogenic TELSs were used as a drug-testing model and treated with Gefitinib. Cryogenic TELSs were stored at -80 °C to ensure high cell viability. During recovery in culture, the cells in the cryogenic TELS were evenly distributed, massively proliferated, and then formed spheroid-like aggregates from day 1 to day 13. The liver-specific functions in the cryogenic TELS were closely related to cryopreservation time and cell proliferation. As a reproducible drug-testing model, the cryogenic TELS showed an obvious drug reaction after treatment with the Gefitinib. The present study shows that the cryopreservation techniques can be used in drug-testing models.

A clinical-scale BioArtificial Liver, developed for GMP, improved clinical parameters of liver function in porcine liver failure

Liver failure, whether arising directly from acute liver failure or from decompensated chronic liver disease is an increasing problem worldwide and results in many deaths. In the UK only 10% of individuals requiring a liver transplant receive one. Thus the need for alternative treatments is paramount. A BioArtificial Liver machine could temporarily replace the functions of the liver, buying time for the patient's liver to repair and regenerate. We have designed, implemented and tested a clinical-scale BioArtificial Liver machine containing a biomass derived from a hepatoblastoma cell-line cultured as three dimensional organoids, using a fluidised bed bioreactor, together with single-use bioprocessing equipment, with complete control of nutrient provision with feedback BioXpert recipe processes, and yielding good phenotypic liver functions. The methodology has been designed to meet specifications for GMP production, required for manufacture of advanced therapy medicinal products (ATMPs). In a porcine model of severe liver failure, damage was assured in all animals by surgical ischaemia in pigs with human sized livers (1.2-1.6 kg liver weights). The BioArtificial liver (UCLBAL) improved important prognostic clinical liver-related parameters, eg, a significant improvement in coagulation, reduction in vasopressor requirements, improvement in blood pH and in parameters of intracranial pressure (ICP) and oxygenation.

Cryopreservation and re-culture of a 2.3 litre biomass for use in a bioartificial liver device

For large and complex tissue engineered constructs to be available on demand, long term storage using methods, such as cryopreservation, are essential. This study optimised parameters such as excess media concentration and warming rates and used the findings to enable the successful cryopreservation of 2.3 litres of alginate encapsulated liver cell spheroids. This volume of biomass is typical of those required for successful treatment of Acute Liver Failure using our Bioartificial Liver Device. Adding a buffer of medium above the biomass, as well as slow (0.6°C/min) warming rates was found to give the best results, so long as the warming through the equilibrium melting temperature was rapid. After 72 h post thaw-culture, viable cell number, glucose consumption, lactate production, and alpha-fetoprotein production had recovered to pre-freeze values in the 2.3 litre biomass (1.00 ± 0.05, 1.19 ± 0.10, 1.23 ± 0.18, 2.03 ± 0.04 per ml biomass of the pre-cryopreservation values respectively). It was also shown that further improvements in warming rates of the biomass could reduce recovery time to < 48 h. This is the first example of a biomass of this volume being successfully cryopreserved in a single cassette and re-cultured. It demonstrates that a bioartificial liver device can be cryopreserved, and has wider applications to scale-up large volume cryopreservation.

Viscosities encountered during the cryopreservation of dimethyl sulphoxide systems

This study determined the viscous conditions experienced by cells in the unfrozen freeze concentrated channels between ice crystals in slow cooling protocols. This was examined for both the binary Me₂SO-water and the ternary Me₂SO-NaCl-water systems. Viscosity increases from 6.9 ± 0.1 mPa s at -14.4 ± 0.3 °C to 958 ± 27 mPa s at -64.3 ± 0.4 °C in the binary system, and up to 55387 ± 1068 mPa s at -75 ± 0.5 °C in the ternary (10% Me₂SO, 0.9% NaCl by weight) solution were seen. This increase in viscosity limits molecular diffusion, reducing adsorption onto the crystal plane. These viscosities are significantly lower than observed in glycerol based systems and so cells in freeze concentrated channels cooled to between -60 °C and -75 °C will reside in a thick fluid not a near-solid state as is often assumed. In addition, the viscosities experienced during cooling of various Me₂SO based vitrification solutions is determined to below -70 °C, as is the impact which additional solutes exert on viscosity. These data show that additional solutes in a cryopreservation system cause disproportionate increases in viscosity. This in turn impacts diffusion rates and mixing abilities of high concentrations of cryoprotectants, and have applications to understanding the fundamental cooling responses of cells to Me₂SO based cryopreservation solutions.

Efficient long-term cryopreservation of pluripotent stem cells at -80 °C

Current long term cryopreservation of cell stocks routinely requires the use of liquid nitrogen (LN₂), because commonly used cryopreservation media containing cell membrane permeating cryoprotectants are thermally unstable when frozen at higher storage temperatures, e.g. -80 °C. This instability leads to ice recrystallization, causing progressive loss of cell viability over time under the storage conditions provided by most laboratory deep freezers. The dependency on LN₂ for cell storage significantly increases operational expense and raises issues related to impaired working efficiency and safety. Here we demonstrate that addition of Ficoll 70 to cryoprotectant solutions significantly improves system thermal stability at the working temperature (~-80 °C) of laboratory deep freezers. Moreover, a medium comprised of Ficoll 70 and dimethyl sulfoxide (DMSO) in presence or absence of fetal bovine serum (FBS) can provide reliable cryopreservation of various kinds of human and porcine pluripotent stem cells at -80 °C for periods that extend up to at least one year, with the post-thaw viability, plating efficiency, and full retention of pluripotent phenotype comparable to that achieved with LN₂ storage. These results illustrate the practicability of a promising long-term cryopreservation method that completely eliminates the need for LN₂.

Impact of Storage at -80°C on Encapsulated Liver Spheroids After Liquid Nitrogen Storage

For many bioengineered tissues to have practical clinical application, cryopreservation for use on demand is essential. This study examined different thermal histories on warming and short holding periods at different subzero temperatures on subsequent functional recoveries of alginate encapsulated liver spheroids (ELS) for use in a bioartificial liver device. This mimicked transport at liquid nitrogen (−196°C) or dry ice (∼−80°C) temperatures. Holding at −80°C on warming after −196°C storage resulted in ELS expressing significant (p < 0.001) damage compared with direct thaw from liquid nitrogen, with viable cell number falling from 74.0 ± 8.4 million viable cells/mL without −80°C storage to 1.9 ± 0.6 million viable cells/mL 72 h post-thaw after 8 days storage at −80°C. Even 1 day at −80°C after −196°C storage resulted in lower viability (down 21% 24 h post-thaw), viable cell count (down 29% 24 h post-thaw), glucose, and alpha-1-fetoprotein production (reduced by 59% and 95% 24 h from 1 day post-thaw, respectively). Storage at −80°C was determined to be harmful only during the warming cycle. Chemical measurements of the alginate component of ELS were unchanged by cryogenic exposure in either condition.

A scale down process for the development of large volume cryopreservation

The process of ice formation and propagation during cryopreservation impacts on the post-thaw outcome for a sample. Two processes, either network solidification or progressive solidification, can dominate the water–ice phase transition with network solidification typically present in small sample cryo-straws or cryo-vials. Progressive solidification is more often observed in larger volumes or environmental freezing. These different ice phase progressions could have a significant impact on cryopreservation in scale-up and larger volume cryo-banking protocols necessitating their study when considering cell therapy applications.

This study determines the impact of these different processes on alginate encapsulated liver spheroids (ELS) as a model system during cryopreservation, and develops a method to replicate these differences in an economical manner.

It was found in the current studies that progressive solidification resulted in fewer, but proportionally more viable cells 24 h post-thaw compared with network solidification. The differences between the groups diminished at later time points post-thaw as cells recovered the ability to undertake cell division, with no statistically significant differences seen by either 48 h or 72 h in recovery cultures.

Thus progressive solidification itself should not prove a significant hurdle in the search for successful cryopreservation in large volumes. However, some small but significant differences were noted in total viable cell recoveries and functional assessments between samples cooled with either progressive or network solidification, and these require further investigation.

Cryopreserved mouse fetal liver stromal cells treated with mitomycin C are able to support the growth of human embryonic stem cells

An immortalized mouse fetal liver stromal cell line, named KM3, has demonstrated the potential to support the growth and maintenance of human embryonic stem cells (hESCs). In this study, the characteristics of KM3 cells were examined following cryopreservation at -70°C and in liquid nitrogen for 15, 30 and 60 days following treatment with 10 μg/ml mitomycin C. In addition, whether the KM3 cells were suitable for use as feeder cells to support the growth of hESCs was evaluated. The inhibition of mitosis without cell death was observed when the KM3 cells were treated with 10 μg/ml mitomycin C for 2 h. The morphology of the KM3 cells cryopreserved in liquid nitrogen for 60 days was not markedly changed, and the cell survival rate was 84.60±1.14%. By contrast, the survival rate of the KM3 cells was 66.40±2.88% following cryopreservation at -70°C for 60 days; the cells readily detached, were maintained for a shorter time, and had a reduced expression level of basic fibroblast growth factor. hESCs cultured on KM3 cells cryopreserved in liquid nitrogen for 60 days showed the typical bird's nest structure, with clear boundaries and a differentiation rate of 16.33±2.08%. The differentiation rate of hESCs cultured on KM3 cells cryopreserved at -70°C for 60 days was 37.67±3.51%. These results indicate that the cryopreserved KM3 cells treated with mitomycin C may be directly used in the subculture of hESCs, and the effect is relatively good with -70°C short-term or liquid nitrogen cryopreservation.

Storage of human biospecimens: selection of the optimal storage temperature

Millions of biological samples are currently kept at low tempertures in cryobanks/biorepositories for long-term storage. The quality of the biospecimen when thawed, however, is not only determined by processing of the biospecimen but the storage conditions as well. The overall objective of this article is to describe the scientific basis for selecting a storage temperature for a biospecimen based on current scientific understanding. To that end, this article reviews some physical basics of the temperature, nucleation, and ice crystal growth present in biological samples stored at low temperatures (-20°C to -196°C), and our current understanding of the role of temperature on the activity of degradative molecules present in biospecimens. The scientific literature relevant to the stability of specific biomarkers in human fluid, cell, and tissue biospecimens is also summarized for the range of temperatures between -20°C to -196°C. These studies demonstrate the importance of storage temperature on the stability of critical biomarkers for fluid, cell, and tissue biospecimens.

Evaluation of encapsulated liver cell spheroids in a fluidised-bed bioartificial liver for treatment of ischaemic acute liver failure in pigs in a translational setting

Liver failure is an increasing problem. Donor-organ shortage results in patients dying before receiving a transplant. Since the liver can regenerate, alternative therapies providing temporary liver-support are sought. A bioartificial-liver would temporarily substitute function in liver failure buying time for liver regeneration/organ-procurement. Our aim: to develop a prototype bioartificial-liver-machine (BAL) comprising a human liver-derived cell-line, cultured to phenotypic competence and deliverable in a clinical setting to sites distant from its preparation. The objective of this study was to determine whether its use would improve functional parameters of liver failure in pigs with acute liver failure, to provide proof-of-principle. HepG2 cells encapsulated in alginate-beads, proliferated in a fluidised-bed-bioreactor providing a biomass of 4-6 × 10(10)cells, were transported from preparation-laboratory to point-of-use operating theatre (6000 miles) under perfluorodecalin at ambient temperature. Irreversible ischaemic liver failure was induced in anaesthetised pigs, after portal-systemic-shunt, by hepatic-artery-ligation. Biochemical parameters, intracranial pressure, and functional-clotting were measured in animals connected in an extracorporeal bioartificial-liver circuit. Efficacy was demonstrated comparing outcomes between animals connected to a circuit containing alginate-encapsulated cells (Cell-bead BAL), and those connected to circuit containing alginate capsules without cells (Empty-bead BAL). Cells of the biomass met regulatory standards for sterility and provenance. All animals developed progressive liver-failure after ischaemia induction. Efficacy of BAL was demonstrated since animals connected to a functional biomass (+ cells) had significantly smaller rises in intracranial pressure, lower ammonia levels, more bilirubin conjugation, improved acidosis and clotting restoration compared to animals connected to the circuit without cells. In the +cell group, human proteins accumulated in pigs' plasma. Delivery of biomass using a short-term cold-chain enabled transport and use without loss of function over 3 days. Thus, a fluidised-bed bioreactor containing alginate-encapsulated HepG2 cell-spheroids improved important parameters of acute liver failure in pigs. The system can readily be up-scaled and transported to point-of-use justifying development at clinical scale.

A novel multiplex-protein array for serum diagnostics of colorectal cancer: impact of pre-analytical storage conditions

INTRODUCTION

Biomarker discovery studies seldom report on pre-analytical effects. We used a novel multiplex protein biochip for colorectal cancer screening to investigate effects of different storage temperatures and repeated freeze-thaw cycles.

METHODS

This biochip, composed of CEA, IL-8, VEGF, M-CSF, S100A11, C3adesArg, CD26, and CRP, was applied to twenty highly standardized preserved serum samples.

RESULTS

Aliquot comparison of long-term storage at -80°C (n=20) versus -170°C (n=20) did not show significant differences for any of the eight markers. In contrast, three freeze-thaw cycles (3 × 20 aliquots) detected changes in the serum level for all markers (p<0.05) but S100A11 and CD26: levels of CEA, IL-8, C3adesArg, and CRP increased, while VEGF and M-CSF levels decreased. However, applying diagnostic thresholds for CEA, IL-8, and CRP revealed that freeze-thaw cycles did not affect diagnostic performance. In contrast, analysis of samples stored at -80°C compared to -170°C failed to detect one out of three detectable malignancies.

CONCLUSION

We conclude that three freeze-thaw cycles modulated serum marker levels significantly, but do not compromise biochip diagnostic performance. For our marker panel, serum preservation at -80°C seems comparable to -170°C; however, storage at -80°C could lead to misdiagnosis. Our findings emphasize the need for standardized sample collection, processing, storage, and reporting.