Journal of Cell Science & Therapy
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A Mini-Review on CO₂ Role in Cell Culture and Medicinal Applications

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Introduction

Cell/cellular biology or cytology is the study of cellular physiology; structure, function, and behaviour of cells; and biochemistry. It can be defined as the sub-culture or transfer of cells onto a new growing medium from a prior culture. It is used in different perspectives such as vaccine development, drug/compound screening, and others. Cell culture requirements are divided into (a) physiological parameters, such as temperature and gas mixture, and (b) growth media requirements. Under the physiological needs, three main factors are (i) appropriate temperature of about 37°C, (ii) CO₂ concentration at 5%, and (iii) humidity.

Similarly, for the growth medium, the required five significant compounds are (a) glucose, (b) amino acids, (c) vitamins, (d) ionic solutions, and (e) bicarbonate. Controlling the physicochemical (i.e., temperature, pH, osmotic pressure, O₂, and CO₂ tension) and physiological environment (i.e., hormone and nutrient concentrations) are the critical advantages for cells propagation. The growth media controls the cultural environment, apart from the temperature. Glucose and glutamine act as a source of energy. Amino acids are building blocks of protein. Vitamins promote cell survival and growth a balance of ions in a solution to maintain osmotic pressure within the cell culture medium.

Carbon dioxide (chemical symbol: CO₂ and molar wt: 44.01 g/mol) is a colourless and odourless gas. It comprises a single carbon atom bound to two oxygen atoms covalently. CO₂ is currently present in our earth’s atmosphere at a quantity of roughly 0.04%. CO₂ plays an essential function in aerobic metabolism for oxidation phases in microbial and human cells. It is a crucial component of respiration and is found in aerobic bioprocesses. Microorganisms or mammalian cells are also used to store finished items such as fine compounds and therapeutic proteins. It depends on several factors, including (i) cellular activity, (ii) physical restrictions, (iii) hydrostatic pressure, (iv) aeration and (v) efficiency of the bioreactor. The basic physicochemical properties of CO₂ significantly impact cellular physiology, production processes, metabolic activity, and transcriptional regulation in microbial and human cultures. These qualities can predict the factors that acidify the internal pH and protein. The CO₂ molecule interacts with cellular metabolism, resulting in various transcriptional responses. CO₂ is the end product of respiration and is therefore unavoidable in aerobic microbial and mammalian bio-processes [1]. It presents the optimization of cell culture (Figure 1).

Figure 1: Cell culture optimization.

Importance of CO₂ in Cell Culture

In recent days, CO₂ has played a vital role in cell-culture incubators. The significant uses of CO₂ in cell or tissue culture have the following benefits; (a) it maintains an optimum temperature, (b) it ensures the moisture-sterile environment and (c) it sustains an optimum constant physiological pH in the system. CO₂ level mainly depends on the application, whereas maintained between 3%-10%. CO₂ in cell culture aims to maintain a steady-state physiological pH through a CO₂-bicarbonate based buffer system. CO₂ from the environment can dissolve in cell culture media. A tiny amount of CO₂ will react with water to produce carbonic acid. Usually, CO₂ levels of 4%-10% in the air are routinely employed in most cell growth research. Table 1 presents the fundamental components required for the cell culture medium.

Table 1: Essential components for cell culture.

CO₂ Levels in Cell Culture

The pH of the culture is regulated by the growth media, which shields the cells from pH variations. Typically, an organic or CO₂- bicarbonate-based buffer is used to accomplish this process. Because the pH of the medium is dependent on a delicate equilibrium of dissolved CO₂ and Bicarbonate (HCO₃–), changes in atmospheric CO₂ might impact it. Most researchers utilise a CO₂ concentration of 5%–7% in the air, and most cell culture investigations require a CO₂ concentration of 4%–10%. CO₂ is essential for cell culture metabolism and medium dissolution [2]. When a small amount of CO₂ reacts with water, carbonic acid is generated. The amount of Sodium Bicarbonate (NaHCO₃) in the medium impacts the CO₂ required to maintain the pH. For normal tissues, the physiological pH is thought to be 7.2 to 7.4 [3]. Provides the role of CO₂ in medical applications (Table 2) [4,5].

Table 2: Role of CO₂ in medical applications [4,5].

CO₂ is ubiquitous in our world, and measuring it has been a goal for many academics from various professions, each with its own set of constraints and objectives. CO₂ sensing is employed in multiple applications, including food storage and agri-food production, medical science, maritime and environmental studies, and analytical chemistry laboratories. CO₂ monitoring in human subjects is most critical in medical practice. Transcutaneous CO₂ sensing combined with dye-based fluorescence CO₂ sensing appears to give the most possibility for producing a future non-invasive clinical CO₂ monitor because of the latter clinical restrictions. The accurate monitoring of vital signs is critical in medical practice for providing appropriate and effective care to patients. Monitoring blood gases, specifically Dioxygen (O₂) and Carbon Dioxide (CO₂), provides respiratory and circulatory signals about a patient’s condition. CO₂ monitoring techniques give a precise picture of a person’s health and offer an accurate health condition state. CO₂ monitoring is vital in humans for the medical field. It is performed in three different ways: (i) (arterial) blood puncture, (ii) airway capnometry, and (iii) transcutaneous capnography [6]. In medical applications, CO₂ measurement is a well-established approach for noninvasively monitoring a patient’s respiratory function that is commonly utilized in an emergency, intensive care, and anaesthesia. The multi-sensors are used to evaluate multi-parametric monitoring factors are connected to examine the patient status during intensive care units [7].

Discussion

CO₂ plays a vital role in medical research because cell cultures must be controlled and monitored in the most sterile and precise manner possible. It is necessary to keep undesirable bacteria and unwanted germs out of the cultures, allowing them to flourish in optimal conditions. Henceforth, it is possible to achieve the most significant outcomes in stem cell treatment, regenerative medicine, and plastic surgery. CO₂ provides the optimum atmosphere for a variety of reasons: (i) incubating human skin cells for life-saving skin transplants; (ii) stem cell research to fight diseases; (iii) stem cell therapy as a realistic surgical alternative (iv) plastic surgery, antiageing therapies, tissue repair, and dermatological treatments; and (v) regenerative medicine, multiplying human skin cells for healing processes. One of the most promising areas in modern study is regenerative medicine. By replenishing defective cells, dead tissue and injured organs can be repaired. To accomplish this, the patient’s skin is taken, duplicated in a CO₂ incubator, and then implanted back into the patient. This novel treatment method is revolutionary for victims of severe burns, as it avoids the considerable scarring that can occur as a result of typical transplantation operations. Progress in stem cell research is critical in the fight against diseases, particularly cancer therapy. In vitro generated tissues can mend or even replace damaged cells and organs via stem cell treatment. As a result, stem cell research is at the heart of regenerative medicine research. When handling cell cultures, maintaining sterile conditions and ensuring optimal safety are critical. As a result, an automated sterilization feature should be included in CO₂ incubator. This ensures that the risk of external contamination is minimum. In stem cell therapy, regenerative medicine has revolutionized cardiac surgery research. The Open-heart surgery is increasingly being pushed aside in favour of stem cell therapy. The procedure is as follows: tissue and cell clusters are cultivated in a CO₂ incubator before being transplanted into the patient via cell transplantation. These stem cells can be made in one of two ways: (a) the first one is the patient’s cells are taken and multiplied in a CO₂ incubator, and (b) the second one is that the living tissue such as heart valves and blood arteries are created from scratch by using a potential CO₂ incubator. In addition to tailored autologous stem cell therapy, CO₂ incubators are crucial instruments. The own body’s cells are used in various applications such as plastic surgery, anti-ageing therapies, tissue repair, and dermatological and orthopaedic treatments, among other things. The stem cells are collected and separated from the tissue after being retrieved. This increases contamination potential, so thorough sterility tests are carried out in the CO₂ incubator, where the cell cultures will eventually multiply. At the final stages, the genetic tests are carried out with maximum safety in a CO₂ incubator to ensure that the cells are as safe as possible before being implanted back into the patient. CO₂ incubator-grown skin cell transplants are used for patients with severe heat-related ailments and illnesses. In modern medicine, regenerative medicine is the best recovery method by using cell multiplication in a CO₂ incubator to cure significant heat-related injuries.

Conclusion

Cell culture is critical in modern research because it may simplify and comprehend the mechanism of massive complexity within an organism. CO₂ is gaining much interest in mammalian cell culture because it influences primary cell attributes such as growth rate, product quality/production rate, and intracellular pH. It acts as a natural product, critical substrate, and regulatory trigger in microbial and mammalian production. As a result, assuring the suitable CO₂ and pH usage mechanism in the cell culture system will undoubtedly lead to exploring vast concepts in the current critical study. Overall, CO₂ levels are essential for cellular metabolism, product quality, productivity rate, process performance and intracellular pH stability.

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