Gels in Medicine and Surgery: Current Trends and Future Perspectives

Gel is a two-phase elastic colloidal material, consisting of a dispersed liquid incorporated in the solid phase [...].

• Additional antiseptics such as chlorhexidine and quaternary ammonium derivatives; • Sporicidal such as hydrogen peroxides which eliminate bacterial spores that may be present in the ingredients; • Emollients and gelling agents (such as glycerol) to reduce skin dryness and irritation; • A small amount of sterile or distilled water; • Sometimes foaming agents, dyes or perfumes, which are generally not recommended due to the risk of allergic reactions; • Alcohol-free versions typically contain povidone iodine, benzalkonium chloride or triclosan, and are believed to be less effective than alcohol-based ones [10,11].
Hyaluronic acid gel injections are used together with collagen protein injections in surgery and cosmetic dermatology to eliminate wrinkles and prevent skin aging. In otological surgery, hyaluronic acid is used as a regenerator of perforated tympanic membranes, in ophthalmic surgery for the production of artificial tears and operations on the vitreous body of the eye, in arthrology as an anti-inflammatory lubricant and preservative of the synovial fluid of the joints [12,13]. An alternative is represented by the agarose gel. As for its composition, agarose is a gel made up of a mix of sugars and proteins. The molecule is extracted from agar-agar, a gelling agent of natural origin derived from red algae, particularly widespread in Japan. The advantage of the latter, more recent gel is due to the fact that a very limited quantity of it is used and an ultra-thin needle is used: if hyaluronic acid is injected with a one-milliliter syringe, for agarose a 0.7 is used. This gel acts as a mousse that expands under the dermis, forming a sort of 3D network capable of retaining both molecules and liquids [14].
In regenerative surgery, on the other hand, blood products gels can be used. The platelet gel, derived from the concentration of plasma, allows greater tissue regeneration and is applicable to many areas of medicine: in orthopedic, ophthalmic, in the treatment of skin ulcers and, of course, in cosmetic surgery. It falls within the scope of bio-stimulation, being the plasma extracted from the patient himself capable of activating regeneration [15,16]. This bio-stimulation produces a significant increase in fibroblasts. They, after being activated, give a higher quality to the skin. In addition, this platelet gel, when injected into the dermis, acts as a catalyst for growth factors, helping to release them later. Among them we remember: PDGF, TGF, IGF I and II, EGF and FGFB [17][18][19][20][21].
Recently, thanks to the digitalization of medicine, and the improvement of 3D printing systems, these have promoted the formulation of new methods [22,23]. The same principle of "printing" has been converted to be able to generate human tissues in the laboratory. This particular application from 3D printing in the biomedical field is called 3D bioprinting. Although still under development, it is assumed that in the future 3D bioprinting could represent the new frontier of tissue and organ transplantation. The tissues "printed" in the laboratory, could in fact be subsequently transplanted by surgery in patients who need a new tissue. A photosensitive gel has been developed that can solidify when exposed to an infrared light ray capable of crossing the body's tissues without damaging them. Thanks to the three-dimensional control of the laser, it is possible to create/print solid objects inside the body of a living organism. Gel in liquid form can be injected into the tissues of a live animal and solidified in defined structures from outside the body by exposure to a light emitted by a laser that is able to pass through the tissues without damaging them [24].
Surely in recent years the field of medicine and pharmacology are making considerable progress, gel formulations are increasingly used thanks to their properties.

Conflicts of Interest:
The authors declare no conflict of interest.