Special Features of Polyester-Based Materials for Medical ...

This article presents current possibilities of using polyester-based materials in hard and soft tissue engineering, wound dressings, surgical implants, vascular reconstructive surgery, ophthalmology, and other medical applications. The review summarizes the recent literature on the key features of processing methods and potential suitable combinations of polyester-based materials with improved physicochemical and biological properties that meet the specific requirements for selected medical fields. The polyester materials used in multiresistant infection prevention, including during the COVID-19 pandemic, as well as aspects covering environmental concerns, current risks and limitations, and potential future directions are also addressed. Depending on the different features of polyester types, as well as their specific medical applications, it can be generally estimated that 25&#;50% polyesters are used in the medical field, while an increase of at least 20% has been achieved since the COVID-19 pandemic started. The remaining percentage is provided by other types of natural or synthetic polymers; i.e., 25% polyolefins in personal protection equipment (PPE).

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1. Introduction

In addition to other types of polymeric materials, polyesters have found diverse uses in biomedical applications, such as controlled drug release systems [1,2,3,4,5], time-tailored implants, screws, prostheses, and different 3D structures including scaffolds for bone reconstruction and tissue engineering [6]. Various medical products containing polyesters are commercially available, while new ones are awaiting patents for placement on the market.

Polyesters such as poly(lactic acid) (PLA), poly-L-lactide (PLLA), poly(ε-caprolactone) (PCL), poly(glycolic acid) (PGA), poly(lactic-glycolic acid) (PLGA) copolymers, or poly(hydroxyalkanoates) (PHA) are synthetic biodegradable polymers highly used in medical applications due to their wide range of custom properties, availability, tailoring capacity, cost-effectiveness, and easy processing. Since its development in by DuPont and the establishment of the first large production facility by Cargill Dow Polymers in , PLA has experienced rapid growth, with a high potential to replace conventional petrochemical-based polymers in many medical applications. Before being produced on a larger scale, PLA was mainly used in medical applications due to its relatively high cost. Although most polyesters are synthesized from carbohydrate petroleum-based sources, alternative sustainable raw materials were found, with PLA, poly(hydroxybutyrate) (PHB), and partially bio-based polyethylene terephthalate (PET) being derived from renewable sources.

The polar characteristics of a polymer are among the most important properties to be considered in medical applications such as cell regeneration and tissue engineering, as variations in hydrophobicity lead to different interactions of scaffolds with cells and proteins (targeting cell attachment, spread, and viability in biological systems) [7]. From the medical point of view, the most important ones are inert nature and biocompatibility.

Polyester materials are widely studied for the development of biological tissue that can enable the restoration and maintenance of the functions of damaged human organs or tissues. This is due to the fact that esters, of which polyester materials are composed, exist naturally in the human body; i.e., fatty acids are energy sources and membrane constituents. They have biological activities that act to influence cell and tissue metabolism, function, and responsiveness to hormonal and other signals [8].

Tissue engineering can be considered an alternative to conventional more invasive surgical procedures when it comes to replacing or restoring damaged organ or tissue. The global market for tissue engineering was estimated at USD 9.9 billion in , and is expected to register a compound annual growth rate (CAGR) of about 14.2% between and [9]. The main types of tissue engineering are cells, tissue-inducing substances, and scaffolds, which are basically cells combined with a type of matrix that can provide a physical support and allow the tissue growth. Adequate mechanical stiffness is required for polyesters such as PCL and PLA intended to be used as body tissues in order to prevent new-tissue deformation and overcome in vivo stresses [6,10].

The more conventional approaches are divided mainly into autografting and allografting. In order to introduce respective treatments, tissue is transplanted within the patient from one site to another or between two different patients. Both approaches have their drawbacks; i.e., anatomical restrictions, the risk of transferring diseases between the patients, and a possible rejection response from the patient&#;s immune system [11].

Polyesters are naturally biodegradable materials due to the fact that the ester bonds can be broken down by the means of hydrolysis or esterases, and in some cases, the degradation process can be undertaken by both of the factors. The hydrolytic degradation is one of the key features behind why these materials are of growing popularity when it comes to tissue-engineering studies, as they can be engineered to yield nontoxic products that are metabolized by the human body [12]. The ability to degrade in vivo is crucial for tissue-engineering applications, as there is need for a smooth and certain transition of functionality from the degrading polymeric scaffold to newly grown tissue. As time is very important in this process, it is possible to tailor the rate of the degradation by changing the chemical structure of the polymer or its additives [13].

There are two different mechanisms for polyester degradation that can affect the implementation of certain polymers: surface and bulk erosion. In surface erosion, the polymer maintains its bulk integrity, as the erosion is limited to the surface of the material. The device will reduce in its dimensions&#;the walls will become thinner; however, the core and its properties will remain intact. It is worth mentioning that as the degradation process is highly focused on the surface of the immersed material, the mass loss and dimensional stability is strictly proportional to the area of surface that is exposed to water. The other degradation mechanism, bulk erosion, occurs when the rate at which the water penetrates is much greater than the rate at which the polymer is being converted into water-soluble materials. The dimensions of the device may remain unaffected or even will increase with the volumetric water uptake; however, it will result in erosion throughout the material volume. This is a two-step process, as the molecular weight of the material is affected by its gradual decrease, as the properties of the material will tend to downgrade at a certain pace. After exceeding a critical value of the molecular weight with water penetrating, accompanied by the cleaving of the polymer chains, especially the hydrolytically unstable chemical bonds converting longer chains into water-soluble fragments, an enzyme-based attack occurs. Final mass loss is rapid, with a sudden release of degradation products, and then the material disintegrates completely [14].

In the case of surgical implant applications, polyesters are in the first generation of commercially available implants, therefore not many scientists have published new polyester blends and composites for such applications since . Most of the literature available on the subject refers to clinical cases that compare those commercial products in a group of patients.

Wound-dressing materials should have important requirements related to their biocompatibility [15], wound healing [16], wound adhesion [17,18], maintenance of wound moisture [19,20], inhibition of the growth of bacteria [15,21,22], removal of excess exudates, and reductions in the dressing frequency [23,24].

Multiresistant infections, especially during the recent COVID-19 pandemic, have affected all of humanity from a variety of perspectives, including health issues, the socioeconomic crisis, and environmental concerns. Despite the economic shock that has affected many industries, the demand for polyester materials has shown great resilience. The use of PLA or PET for the manufacture of personal protective equipment (PPE) has received great consideration [25,26,27], with the polyester market being relieved of its worst consequences. The active integration of nanostructures into polyesters that self-sterilize against pathogens may provide a way to lower the transmission of viral infections. Given the recent growth in various infectious threats, the development of effective vaccination technologies containing novel vaccine delivery vehicles based on polyesters to immunize against various strains of viruses is in high demand. Sanitization is also highly necessary to prevent infection.

The general features of polyester-based materials used for orthopedic, tissue-engineering, wound-healing, vascular, and ophthalmology applications, as well as prevention of multiresistant infections, including during the COVID-19 pandemic, are shown in .

Neat polyesters can be combined with natural or synthetic materials to increase their bioactivities and obtain the desired properties for each medical application. The main recently designed formulations or composites containing polyesters, their manufacturing methods, and special features for the above-mentioned applications are summarized in this review.

When looking for packaging bags, we often see the word mylar bag on various websites. But yet we still don't know its meaning or are still confused about what it is exactly. Many people regard the mylar bag as a product or a packaging style, but they are wrong. Mylar is just a trademark of a specific company.

What is a mylar bag?

Mylar is a trademarked term produced by DuPont company for polyethylene terephthalate in plastic flexible packaging materials. It has several layers of laminated plastic. That have excellent oxygen absorbers&#;allowing your product to be stored in the best possible condition.

Making it suitable for food and beverage packaging. In this article, it's safe to say that mylar bags is a plastic packaging bag, just like when people say band-aids, they mean bandages.

Keep on reading to know more about what you should consider when customizing mylar bags:

1. How to choose the correct thickness

Choose the right thickness according to your packaging size. Small sizes, in general, is 3.5-4.5 mil (I personally do not recommend the 3.5 mil bags) because the chances of it tearing are high. While in large sizes, you can choose from 4.5- 6.5 mil. If your product is looking for long-term food storage, I recommend a thicker mylar bag. The reason for this is because the thicker bags provide better insulation to protect them from outside elements that can affect your product.

Mylar bags below 4.5 mils of thickness do not have barrier properties and is not suited for long-term storage since they provide less protection and insulation.

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If you're looking for a more budget-friendly, you can go for the 3.5 mil mylar bag. However, it would be best to be extra careful when handling and storing to avoid any tearing.

Contact us to discuss your requirements of Metalized Polyester Film Custom. Our experienced sales team can help you identify the options that best suit your needs.

Additional reading:
BOPP Film vs. PET Film: Which is Best for Lamination?

Also, another piece of advice is that the rule of the thumb, use the thickest mylar bag that will work for you and your products. Ensure that we can store products in their packaging regardless of weight. Opt for sturdy packaging to prevent any product damage and to the bag as well.

2. The barrier of a mylar bag is determined by the thickness and the different kinds of aluminum foil used for bag production.

Mylar bags are designed using different materials based on their features and advantages to suit their intended use. Once the material to be used has been decided, they are laminated together. To create a pouch that is sturdy and convenient to use. In most cases, the materials utilized to generate mylar bags are aluminum foil and a PET/ VMPET/ PE mix.

2.1 Let's talk about the difference s of aluminum foil and aluminum plating.

Many wholesalers of mylar bags think that the sunlight will damage the products inside the packaging. Due to the thickness of the bag being very thin. They are not entirely wrong; packaging with thin thickness can affect the entirety of the packaging's barrier properties. Outside factors like sunlight, oxygen, and moisture can pass through the packaging and affect product quality.

Aluminum foil is a thin sheet of metal used for packaging products in flexible packaging. Another thing to know is that aluminum foil is not heat-sealable, so it needs to be compounded with other materials like PE. For the aluminum plating, its barrier property is much lower than the aluminum foil. Also the packaging cost of electroplated film is much lower compared to aluminum foil packaging

2.2 How to distinguish these two materials:

• The brightness of the aluminum foil is not as bright as aluminum plating. Also, the reflective performance of the aluminum coating outshines the aluminum foil. Another thing to look for is the transparency of the matte film in both aluminum foil and aluminum plating. If you try to shine a light through the inside of the packaging in the aluminum foil, it will not pass through because it's opaque. At the same time, the light-transmitting one is the aluminum plating.
• The aluminum foil has a thick feel and is heavier in weight. In comparison, the aluminum plating feels lighter and softer compared to the aluminum foil.
• The aluminum foil is easy to fold out dead folds and dead marks. Unlike aluminum plating, it can not hold the folds; therefore, it would rebound quickly.

3. Can a Mylar bag be used in cooking?

I know a lot of consumers who heat their food in the oven while still in the packaging. We need to remember that before doing this, we must confirm whether the material specification of your packaging contains RCPP instead of LDPE. This is because if LDPE is put in a heated environment, it will release a strong plastic smell that can harm food elements.

Therefore we must use a unique RCPP material for the mylar bag to be used in the cooking environment. A friendly reminder for consumers before purchasing is to make sure that you understand the purpose of your packaging.

4. The materials you need to know if you want to vacuum your packaging

Some customers prefer to pack their food in a mylar bag and remove all the air inside to extend its shelf life. For vacuum processing, we must add nylon material in the bag production process.

By adding nylon, we can increase the toughness and the stretching force of the bag, especially if the food is sharp, it will not pierce the packaging. So before you customize your packaging, you should explain the features you want to your manufacturer.

5. How to confirm if your mylar bag BPA free or FDA food-grade

For mylar bags, it is usually laminated by several layers of film, and because of this. We have to make sure that in the final contact of food, LDPE or RCPP material is used. You must declare to your manufacturers that they can only use 100% raw material for blowing the film.

Also, they must provide a BPA and food-grade testing pass report from the FDA to prove that it is safe to use for food products. To ensure that your mylar bag meets the test standards required. You can always ask your manufacturers to send you samples of the same batch containing the inner layers, which is LDPE or RCPP. Then you can send the samples yourself to your local SGS laboratory, or if you're based in America, you may send it to the FDA for testing.

If you want to learn more, please visit our website Metalized PET Plastic Film Manufacturer.