**2. To develop non-biological implants and study the soft tissue response to it**

Such capabilities are possessed by hydrogels - spatially crosslinked hydrophilic polymers that have been successfully used for several decades as materials for tissue engineering and plastic surgery, means for targeted transport of drugs, optical and analytical sensors, matrices for biological research [5], etc. Abnormally high compared with solid polymers, the biocompatibility of gels with high equilibrium water content, primarily due to the similarity of their 3D structure with the extracellular matrix [6]. Achieving a significant improvement in the physicochemical and operational parameters of gels seems to be possible by obtaining a hybrid hydrogel material based on polyvinyl alcohol and acrylic hydrogel, which was the subject of one of the studies performed by the authors [7].

**Material and methods.** Gels based on acrylic acid (AAc) were obtained by radical polymerization of an aqueous solution of monomers (AAc and N, N′-methylenebisacrylamide (MBA)) at a temperature of 70°С. Matrices based on polyvinylformal (PVF) were obtained by treating polyvinyl alcohol (PVA) with formaldehyde in the presence of a strong acid.

Experimental studies were conducted on the basis of the vivarium of the State Institution "The Filatov Institute of Eye Diseases and Tissue Therapy of the NAMS of Ukraine". Experimental studies were performed on rabbits of the Chinchilla breed, weighing 2–3 kg, aged 5–6 months, which during the study were in the same living conditions. All experimental studies were conducted in compliance with ethical standards provided by the international principles of the European Convention on the Protection of Vertebrate Animals Used for Experimental and Other Scientific Purposes (Strasbourg, 1986) and the norms of biomedical ethics approved by the First National Congress of Bioethics of Ukraine), as well as the law of Ukraine №3447-IV "On protection of animals from cruel treatment" (Kyiv, 2006).

To study the reaction of the soft tissues of the orbit and auricle, we used an implant hybrid hydrogel developed at the Ovcharenko Institute of Biocolloid Chemistry of the National Academy of Sciences of Ukraine in Kyiv. We implanted a hybrid hydrogel in a scleral sac; orbital tissue and in the ear tissue of rabbits.

We implanted a hybrid hydrogel implant into the scleral sac, parabulbar tissue of the eyeball and auricle of a rabbit/.

Surgical interventions were performed under general anesthesia (at the rate of 1 ml of 0.1% sodium thiopental solution per 1 kg of rabbit body weight intramuscularly). Evaluation of the response of soft tissues and bone structures to implant materials was carried out on the basis of analysis of changes in clinical and pathomorphological parameters was performed after 10, 30 and 60 days. Evaluation of the studied clinical signs (swelling of the tissues of the orbit, cheeks, auricle, the condition of the sutures, the presence of secretions) was performed on the 2nd, 5th, 10th and then every five days. Pathohistological evaluation of oculoorbital tissues, orbit and auricle tissue was performed after 10, 30 and 60 days.

**Results and discussion.** Analysis of scanning electron micrographs of the hybrid hydrogel material showed that its structure is characterized by a well-developed system of connected pores smaller than 1 mm, as well as the presence of pores with a diameter of several hundred micrometers. It should also be noted that the pore walls have a porous structure with an approximate pore diameter of 10 μm and a wall thickness of several micrometers. Thus, due to partial squeezing of the gelforming composition from the pore space of the spongy polymer matrix based on the PVF, it was possible to prevent clogging of open and combined transport pores,

**Figure 1.** *Appearance of a hybrid hydrogel implant.*

which allowed to ensure high permeability of hybrid material to gases, liquids and biological tissues (**Figure 1**).

In general modification of the PVF with acrylic hydrogel decreased the size of pores inside the walls for all hydrogel systems and also fill the larger pores with diameters approx. 500 μm. The synthesized polymer systems belong to porous materials with pore diameters from a few micrometers to a few hundred micrometers. Nanopores have not been found in synthesized systems [8].

Experimental studies in rabbits showed that in the first 5 days after implantation of the hybrid hydrogel in the scleral sac, orbit and auricle, all animals had swelling of the postoperative suture and adjacent conjunctiva, as well as a slight serous-secretion from the conjunctival cavity. After five days, there was a decrease in edema and discharge from the conjunctival cavity and lasted for 8–10 days. It is important to note that when examining the postoperative wound of the skin and conjunctiva in the first days and in the following days with the implantation of a hybrid hydrogel, wound healing was the primary tension.

The obtained satisfactory result of clinical evaluation of soft tissues of the orbit and auricle to the implantation of a hybrid hydrogel, we found it appropriate to assess the response of cellular structures to the implant, the presence of germination of surrounding tissues in its structure and propensity to resorption.

Pathohistological studies showed that on the 10th day after the implantation of the hybrid hydrogel into the scleral sac, inflammatory infiltration of the sclera was noted in the site of the implant location. However, no inflammation was noted in the scleral portions distant from the implant.

In the infiltrate, in addition to lymphocytes, there is a fairly large number of eosinophilic leukocytes (**Figure 2a**).

An important requirement for the implant material is the ability to germinate the surrounding tissue structure of the implant, as well as its tendency to resorption. Therefore, it was expedient for us to study the influence of the surrounding biological tissues on the mesh-like structure of the implant (**Figure 2b**).

In **Figure 2b** it can be noted that the structure of the implant is preserved, and along the crossbars there is the formation of delicate bundles of collagen fibers, which are slightly infiltrated by lymphocytes. The composition of "cellular" structures is absent, possibly as a result of histological processing. We did not observe any changes on the side of the orbit walls.

In clinical practice, there is a need to fill the soft tissues after removal of tumors of the orbit, eyelids and oculoorbital area. In this regard, we found it appropriate to study the relationship of the implant - a hybrid hydrogel with soft tissues and cartilaginous structures. Pathohistological studies have shown that when the implant is placed in the tissues of the auricle after 10 days, a delicate fibrous tissue is formed around it, which is infiltrated by inflammatory cells. At the same time the

**215**

small quantities.

*Improving the Antitumor Effect of Doxorubicin in the Treatment of Eyeball and Orbital Tumors*

*A and b. the tenth day after implantation of the hybrid hydrogel in the scleral sac; a - (1-implant; 2- inflammatory scleral infiltration) (hematoxylin–eosin; x 120), b - (1-implant; 2- fibrous capsule)* 

weak basophilic maintenance of "cellular" structures remains, and on partitions the

Thus, the assessment of clinical signs and the results of histopathological examinations after implant placement - a hybrid hydrogel in the scleral sac and tissues of the rabbit auricle allowed to draw preliminary conclusions, which were that within 8–10 days there was an inflammatory reaction from the tissues of the orbit and auricle, especially the first 5 days. It is important to note that in no case did we notice the implant being exposed and the wound healing was the primary tension. Pathohistological studies showed that around the implant, both in the scleral sac and in the tissues of the auricle there are all signs of inflammation (lymphoid and leukocyte infiltration, etc.), the presence of signs of germination surrounding the tissue structure of the implant and its tendency to resorption. Having obtained preliminary data, it was expedient for us to study the nature of the interaction of the implant - a hybrid hydrogel with the surrounding tissues in the longer term. Therefore, we

decided to assess the nature of histopathological changes after 30 days.

When placing the implant in the scleral sac after 30 days, inflammatory phenomena around it is absent, but there was the formation of a fibrous capsule with the spread of fibrous tissue on the partitions of "cellular" structures. The fibrous layers are quite rough and do not contain inflammatory elements (**Figure 3**). Up to 30 days, the content of "cellular" structures was determined by the wall and in

initial phenomena of fibrotization are noted.

*Thirty days after implantation of the hybrid hydrogel in the scleral sac.*

*DOI: http://dx.doi.org/10.5772/intechopen.95080*

**Figure 2.**

**Figure 3.**

*(hematoxylin–eosin; x 70).*

*Improving the Antitumor Effect of Doxorubicin in the Treatment of Eyeball and Orbital Tumors DOI: http://dx.doi.org/10.5772/intechopen.95080*

#### **Figure 2.**

*A and b. the tenth day after implantation of the hybrid hydrogel in the scleral sac; a - (1-implant; 2- inflammatory scleral infiltration) (hematoxylin–eosin; x 120), b - (1-implant; 2- fibrous capsule) (hematoxylin–eosin; x 70).*

#### **Figure 3.** *Thirty days after implantation of the hybrid hydrogel in the scleral sac.*

weak basophilic maintenance of "cellular" structures remains, and on partitions the initial phenomena of fibrotization are noted.

Thus, the assessment of clinical signs and the results of histopathological examinations after implant placement - a hybrid hydrogel in the scleral sac and tissues of the rabbit auricle allowed to draw preliminary conclusions, which were that within 8–10 days there was an inflammatory reaction from the tissues of the orbit and auricle, especially the first 5 days. It is important to note that in no case did we notice the implant being exposed and the wound healing was the primary tension. Pathohistological studies showed that around the implant, both in the scleral sac and in the tissues of the auricle there are all signs of inflammation (lymphoid and leukocyte infiltration, etc.), the presence of signs of germination surrounding the tissue structure of the implant and its tendency to resorption. Having obtained preliminary data, it was expedient for us to study the nature of the interaction of the implant - a hybrid hydrogel with the surrounding tissues in the longer term. Therefore, we decided to assess the nature of histopathological changes after 30 days.

When placing the implant in the scleral sac after 30 days, inflammatory phenomena around it is absent, but there was the formation of a fibrous capsule with the spread of fibrous tissue on the partitions of "cellular" structures. The fibrous layers are quite rough and do not contain inflammatory elements (**Figure 3**). Up to 30 days, the content of "cellular" structures was determined by the wall and in small quantities.

Formation of a fibrous capsule and massive growth of fibrous tissue along the partitions of "cellular" structures (1-implant; 2- growth of fibrous tissue along the partitions of "cellular" structures) (Hematoxylin–eosin; x 180).

A similar pathohistological picture was observed after 30 days of the implantation of a hybrid hydrogel in the tissues of the auricle, which consisted in fibrotization of the walls of the "honeycomb" structures of the implant without signs of inflammation. It should be noted that after 60 days we did not notice signs of inflammation around the implant except for the formation of a fibrous capsule.

The obtained experimental studies, which study the nature of the reaction of soft tissue bone structures of rabbits to the implantation of a hybrid hydrogel in the scleral sac and auricle tissue, allowed to answer a number of questions that arise in the development of implant materials.

The first and most important requirement for implants is their biocompatibility. As our studies showed, in all experimental rabbits there was a moderate inflammatory reaction, which disappeared by 8–10 days. It is important to note that in all groups of animals studied wound healing was the primary tension, and therefore in no case was the exposure of the implant, which indicates a very important positive indicator for implants. Pathohistological studies showed that up to 10 days there are final inflammatory phenomena close to the implant in the form of lymphoid and leukocyte infiltration, while in more remote areas relative to the implant, they were absent. The second important indicator we noted is the germination of the surrounding tissues in the implant structure and the formation of a delicate fibrous capsule by the tenth day after its implantation (**Figure 2b**), and by the 30th day the formation of a massive fibrous capsule (**Figure 3**). The third important advantage of the implant is the lack of its tendency to resorption, which is very important to obtain a stable clinical result. It is also important to note that we did not observe changes in the bone structures of the orbit and in the cartilaginous plate of the rabbit auricle when placing the implant in the soft structures of the orbit and auricle.

Our in vivo experimental studies demonstrated that the high biocompatibility of the hybrid highly porous material based on polyvinylform developed by them, the lack of resorption and the ability to germinate the surrounding biological tissues. This indicates the high prospects of the developed material and provides grounds for further research aimed at improving its performance.
