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4D-POLYpropylene meshes as SENsitive motion SEnsors

Periodic Reporting for period 1 - 4D-POLYSENSE (4D-POLYpropylene meshes as SENsitive motion SEnsors)

Reporting period: 2018-04-01 to 2020-03-31

The 4D-POLYSENSE project aimed to create a new generation of surgical meshes, able to interact with the complex three-dimensional structure of biological tissues, as a new smart material working as self-evolving motion sensor. For it, the functionalization of the PP threads surface with plasma technique, followed by graft polymerization of a thermosensitive hydrogel, named poly(N-isopropylacrylamide) (PNIPAAm), was carried out. The presence of PNIPAAm on top of PP threads allowed the system to dynamically interact with the local environment, giving rise to the appearance of the fourth dimension (4D) response. The mesh presents a folding/unfolding behaviour under small temperature and humidity variations, without loss of dimensional stability or PNIPAAm coating detachment. Consequently, it is supposed to facilitate the mesh adaptation to the abdominal wall defect to be repaired, after the surgical implantation, and to reduce the inflammatory risks cause by problems of mesh shift inside body.
The results demonstrated that our strategy can be easily extrapolated to more complex mesh architectures and, the most important, the whole system can be sterilized by conventional and non-conventional sterilization processes applied to PP biomedical devices.
In conclusion, in this project we were able to transform a knitted mesh material into a dynamic device, thanks to the arrangement of a soft and biocompatible hydrogel around the PP threads.
The project scopes can be seen in the following webs: https://upcommons.upc.edu/handle/2117/126082 https://www.youtube.com/watch?v=zGRk2qey0PQ
Firstly, several conditions of oxygen plasma treatment for the activation of polypropylene mesh surface were tested to achieve the optimum graft yield and the strong adherence of PNIPAAm hydrogel, essential for the employment of the bilayer system as a surgical implant. The scientific results were published in Soft Matter (DOI: 10.1039/c9sm00412b) along with a detailed mechanism of NIPAAm reaction and network formation. In this period, the thermosensitive response of the bilayer smart mesh material was also approached, by using temperature gradients close to the human body temperatures and to the surgeon’s manipulation room before patient surgery.
The in vitro cell viability was also investigated with two different cell lines. A modular cell adhesion and cell detachment of the fibroblast-like cells was observed. Cell attachment is desirable to prove the biocompatibility of the new device, whereas the phenomena of de-adhesion is very appealing for the final application of the mesh, i.e. to avoid mesh adherence to other organs. Those results were published in Journal of Materials Chemistry B (DOI: 10.1039/c9tb02537e).
Finally, the study of the fourth-dimension (4D) behaviour of the bilayer system was performed by applying cycles of increase/decrease temperature and by considering two different humidity conditions. It was of outmost importance to evaluate the mesh behaviour outside human body because, in the mesh sterilization process, the synthetic implant will suffer changes from dry to wet and from wet to dry states, and must resist on flexibility and mechanical properties, before reaching the final consumer (hospitals and medical clinics). Therefore, samples were subjected to sterilization processes. In this point, the mobility of the MSCA-IF researcher, Dr. Sonia Lanzalaco, to the hosting secondment (B Braun Surgical S.A.) was of fundamental relevance for her training. The scientific results on the 4D behaviour were recently accepted for publication in Advanced Functional Materials (high impact factor journal, IF: 15.621); whereas the preliminary results from samples sterilization are under intellectual property rights protection.
Additionally to the dissemination in scientific journals, the project and its results were shared in two national and two international congresses.
The experienced researcher (ER), Dr. Lanzalaco, shared her activities in social media (youtube, facebook and twitter) for academic and non-academic publics. She also had the support of other members of UPC, for the facing Open Access week (2018), and in facebook activities for research dissemination in UPC Campus.
Altogether, the 4D-POLYSENSE project represented an outstanding research programme that helped the ER to develop her interdisciplinary career, to improve her communication and interpersonal skills, and to split her scientific knowledge and expertise with the academic and with non-academic publics.
In this ambitious project, meshes repair modified with biocompatible coatings were investigated, and a new 4D-concept was introduced to a static device. The main aim of this new material is to avoid post-surgery interventions by reducing inflammatory risks after the mesh implantation. In this context, different strategies have been proposed by other authors, from alterations of the mesh structure (pore size, shape, weight density, fibres knitting design) to its modification by means of introducing new coatings to the PP threads. The last approach has gained an increased attention because it allows to achieve protection of the implant from degradation and mitigation of the foreign body reaction. Therefore, this project represents an important contribution to the field of biocompatible coatings for mesh implants.
The main achievements can be summarized as follow:
1. Demonstration that the PNIPAAm thermosensitive hydrogel is an excellent material to be covalently grafted onto the commercial PP mesh, after its initial plasma functionalization and without affecting the properties of the fibres. The bilayer system is highly stable, in dry and wet states.
2. A new generation of PP mesh with modulating cell adhesive property, obtained through the deposition of the thermosensitive coating, was achieved. This point represents a crucial goal in the biomedical field, because it will allow to strongly reduce the risk of adhesion of the implant to organs and viscera, a basic issue causing recurrent surgery.
3. A facile approach towards transforming a bidimensional (2D) PP flexible mesh into fourth dimension (4D) dynamic system has been proved, by exploring its behaviour in a temperature range of surgery’s room and human body and with different humidity conditions.
4. Sterilization processes were performed to evaluate the stability of the thermosensitive hydrogel over the implant. Since this date, no other study or publications have been reported regarding such approaches. The novelty of such results are being evaluated to be protected.
5. The project opened new possibilities of study. Thus, new project calls will be explored to its continuity.
The socio-economic impact and the societal implications of the project are addressed to all sectors involved in the production and utilization of meshes for hernia repairs. From an economic point of view, a surgical device with innovative performances has been prepared, that could be placed on the market (after the in vivo clinical tests), causing a reduction on post-surgery interventions and, thus, causing benefits on both, the public or the private economy sectors. Reduction of the surgical recurrences would limit the costs related to the purchase of materials in the hospitals and medical centres, bringing important advantages for the healthcare sector.
Altogether constitutes a great innovation in the biomedical field of non-absorbable implants.
Converting an inactive unresponsive surgical mesh into a smart self-evolving material..