Biocompatibility and 3 promising apps for chitin and chitosan

Shrimps saving lives!

If you have never thought about how a shrimp can save your live, now it’s the time to do it! After giving chitin some perspective in this other post, what we have here are some of the odd applications scientific community have developed from this material and it’s derivatives. But first, a little side note: chitosan it’s nothing but the product of the artificial N-deacetylation  of chitin by chemical treatment. Nothing very exotic here. The image below explains everything by itself.

n-deacetilation.png

 So, applications of a particular material are very related to what it can offer, obviously obvious! This is: Which are its properties? And then, what can we do with this material considering these properties? Chitin and chitosan have both very good biocompatibility; so the medical and clinical applications fields are both very significant for this products. Biocompatibility refers to the ability of this substance to be use in contact with body tissues, and don’t elicit any huge immune system reaction, for example.

Now, if you’re thinking about complex prosthetic clinical situations, then well…wigs

I’m not joking!. Considering chitin tend to form fibers, the dull shine of those, and the other physical characteristics that give them a natural look, one of the applications of chitin would be artificial hair. And also surgical thread.

But yes, ok, there are also very fancy and promising health applications, and quite complicated too. I’ll talk about tissue engineering in the near future, but for now all I want to say is: growing your very own tissue over a burned or damage part of your body using a chitosan scaffold…damn, that sounds futuristic.

But for now, let me introduce you the chitin nanogels! Or CNGs. It’s a very cool name indeed, I’ve to admit. Maybe I shouldn’t explain this so it don’t lose the glamour. Mmmh.

Anyway, according to IUPAC definition, a gel is a “nonfluid colloidal network or polymer network that is expanded throughout its whole volume by a fluid”. Thus, in CNGs, what you have is an aqueos-polimeric porous network of chitin with very small but numerous “holes” (high external surface in fact) for putting anything in. So CNGs work like sophisticated vehicles that you can first load with drugs and then inject/dispose in the specific organ to treat.

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CNGs preparation and drug loading process. Image credit: M. Vishnu Priya et al. [2]

CNGs are not only biocompatible, they’re biodegradable. So the human body can slowly eliminate this gel while it release the content it was loaded with. A few of the countless possibilities:

Anti-fungal CNG (Fluconazole loaded gel)

Anti-bacterial CNG (nickel loaded gel)

Cancer treatment CNG (Doxorubicin loaded gel)

Proteins transport CNG (insert protein here)

Example! In eye drops treatment, Fluconazole loaded CNGs has shown deeper tissue penetration in experiments on porcine cornea, while it maintains a slow but constant release of the drug; very important for anti-fungal treatments. Nice!

CNGs are a promising field of investigation, but they need investment so they can be applied to specific situations and show their potential. Meanwhile, we can found more mundane applications, but not less promising. Maybe more, in fact.

There’re a bunch of properties still in the chitin and chitosan magazine. Antifungal and bactericidal features, for example, better than those from alginate or silver sulfadiazine, used for burned skin treatments. And they are also permeable to oxygen. All this plus the adhesive nature of this substances due to its porosity equals: wound dressing!

Even more, chitosan has proven to promote granulation (creation of new connective tissue and blood vessels) and organization in open bounds, while chitin also promotes macrophage (inmune system) migration and fibroblast proliferation (a type of cell that synthesizes collagen).

Wound_healing_phases.png
Wound healing process time scale. Note that tissue formation by granulation starts around 12 hours after the trauma, and macrophages are predominant over neutrophils a little later.

And, even if all this seems quite enough, chitosan has shown high antihemorrhagic (hemostatic) properties, so you can stop the bleeding from a severe wound a 55% faster using a proper chitosan bandage. This hemostatic properties of chitosan seem to be related to its high hydration capacity. What did I said? Shrimps saving lives!!

To hell with chitin if this is not a fast, cheap, and useful application! Excuse my intensity, but I really see the promise in this one.

In fact, there are wound dressings based on chitosan already at the market. One example are the HemCon bandages, that use this new technology.

And, as a final note of contrast, an app out of the materials field. Chitin has been also assayed as mold control agent in fruit. Acting as an elicitor of the peroxidase and polyphenol oxidase, wich are both part of the self-defense system of the fruit, chitin can thus inhibit the blue mold (Penicillium expansum) growth in pearfruit, for example.

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But, the funny thing is: it seems that is the fruit itself who is in fact doing all the work, and chitin is only eliciting (bringing on) the fruit natural defenses against these agents. Elicitors like chitin would be a very good alternative to the nowadays not very acclaimed fungicides with which the fruit are treated for its storing. Would you eat chitin treated fruit better than that sold today with fungicides? Which one do you think is the best and most promising application of chitin and chitosan? Please, let me know what you think in the box below. See you in the next post.

References:

[1] Majeti N.V. Ravi Kumar. A review of chitin and chitosan applications. Reactive & Functional Polymers. 2000; 46: 1–27

[2] M. Vishnu Priya, M. Sabitha, R. Jayakumar. Colloidal chitin nanogels: A plethora of applications under one shell. Carbohydrate Polymers. 2016; 136: 609-617

[3] Mohammed, N. et. al (2013). Fluconazole loaded chitin nanogels as a topical oculardrug delivery agent for corneal fungal infections. J. of Biomedical Nanotechnology, 9, 1521–1531

[4] M. Burkatovskaya et al. Use of chitin bandage to prevent fatal infections developing from highly contaminated wounds in mice. Biomaterials. 2006; 27: 4157-4164

[5] R. Jaakumar et al. Biomaterials based on chitin and chitosan in wound dressing applications. Biotechnology Advances. 2011; 29: 322-337.

[6] R. A. A. Muzzarelli. Chitins and chitosans for the repair of wounded skin, nerve, cartilage and bone. Carbohydrate Polymers. 2009; 76: 167-182.

[7] Shuai Wu et al. The efficient hemostatic effect of antartic krill chitosan is related to its hydration property. 2015; 132: 295-303.

[8] D. Fu, H. Xiang, C. Yu, X. Zheng, T. Yu. Colloidal chitin reduces disease incidence of wounded pear fruit inoculated by Penicilium expansum. 2016; 111: 1-5

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