Monthly Spin-Off #2 [Biodegradable vs. Non-Degradable]
Biodegradable or Non-Degradable Polymer Scaffolds:
Which is Right for Your IVRT Application?
Polymers have been around for centuries, from naturally-occurring polymers such as cotton and silk to polymers made in a lab (synthetic) such as polyester, polyurethane and nylon. The materials made from these polymers transitioned from commercial use into biomedical applications over the last 70 years, substantially growing in use over the last two decades. Many of these earlier polymers were nondegradable, meaning that they do not significantly break apart when implanted in the body or are exposed to different aqueous environments. Examples of nondegradable polymers are polyethylene terephthalate (polyester), polyurethane and polycarbonate. “Newer” polymers have been synthetically produced over the last several decades that are biodegradable. These types of polymers break down under certain environmental conditions (i.e. implanted in the body, exposure to aqueous environments), with some polymers slowly (weeks to months) dissolving over time and some rapidly (hours to days) dissolving. Some of the biodegradable polymers include poly-lactic-co-glycolic acid (PLGA), poly(l-lactic acid) (PLLA) and poly(glycolic acid) (PGA), just to name a few.
All of the polymers listed as examples have been used in many applications, from medical devices to benchtop research. This article will focus on selecting a polymer for benchtop research related to tissue culture, which is part of BioSurfaces’s In Vitro Research Tool (IVRT) offerings (https://www.biosurfaces.us/ivrt) using our Bio-Spun™ scaffolds. One question that arises is related to which type of polymer to use for your IVRT application. The answer really depends on several factors that only you have the answers to such as:
How long you will keep the cell culture going
Will you want the cells to come in direct contact with or without a scaffold,
Are you looking to translate these results into possible preclinical assessment
How thick does the resulting tissue model need to be
Polymer selection can play an important role for your IVRT applications.
Advantages of Nondegradable Polymers
Nondegradable polymers are valuable in different product applications across several areas ranging from long-term implants and topical devices to filters and IVRT. For long-term devices that are being implanted in the body, nondegradable polymers are able to stay in the body for the life of the patient. Materials made from nondegradable polymers typically have outstanding strength, which allows for them to be implanted into many areas in the body without the worry of the material tearing or breaking apart. Materials currently used for IVRT applications, typically comprised of either polyester or polycarbonate polymers, are in a film/membrane format (think Poland Spring water bottle format) that may contain small holes (pores) that are mechanically “drilled” into the film. The size of these holes can be adjusted by the manufacturer. These membranes are placed at the bottom of the plate/insert and is used for studying different tissues or also used for growing cells. Benefits of these types of polymers is that they have an excellent shelf life, stable under various sterilization methods and can be stored at room temperature.
Advantages of Biodegradable Polymers
Biodegradable polymers, similar to the nondegradable ones, can be extremely useful for a variety of different applications ranging from medical devices to consumer skin care products. These polymers are used in medical devices that require the material to dissolve such as sutures and dermal patches. Additionally, biodegradable polymers could be used to support, enhance, or replace damaged tissue and can also support biological functions. Another use for these biodegradable polymers is for the consumer skin care industry where products are constantly being used for short term application. These polymers can be used to transfer certain actives to the skin while having the material dissolve. For IVRT applications, there has been limited use of this technology. Many of these biodegradable materials are formed into films, similar to their nondegradable counterparts and placed on the bottom of a plate or insert well to potentially grow tissue on to transfer prior to the membrane dissolving or to use as a barrier to grow two or more different cell types on different sides such that a short-term barrier is formed between the cells.
Bio-Spun™ Scaffolds Changing the Status Quo for Current IVRT Membranes
As mentioned, a majority of the membranes used for IVRT are in a film-like form that may or may not contain pores. The surface of these membranes is not what cells are normally used to attaching and growing onto. This is the rationale for developing our Bio-Spun™ scaffolds. The structure of the Bio-Spun™ scaffolds looks similar the lattice that the body’s cells normally grown into called extracellular matrix. Our proprietary electrospinning process can turn these polymers use to make flat films into structures that cells prefer to grow on. Additionally, BioSurfaces’s process offers the ability to produce bilayered biodegradable Bio-Spun™ scaffolds, resulting in a scaffold that will have two different rates of dissolving. This would allow the cells to interact while keeping some structure in place to hold the tissue in place for a longer period of time.
Choosing Your Polymer Type
With Bio-Spun™ scaffolds having a better structure to grow cells onto than current membranes, the next step is to select one you should choose for your experiments. This is no one “one size fits all” approach. Each experiment has its own nuances so this advice is for guidance. Table 1 provides some general properties for each Bio-Spun™ scaffold type.
Members of the BioSurfaces team would be glad to assist in the selection process.