Clinical Applications of Poly-Methyl-Methacrylate in Neurosurgery: The In Vivo Cranial Bone Reconstruction

Background: Biomaterials and biotechnology are becoming increasingly important fields in modern medicine. For cranial bone defects of various aetiologies, artificial materials, such as poly-methyl-methacrylate, are often used. We report our clinical experience with poly-methyl-methacrylate for a novel in vivo bone defect closure and artificial bone flap development in various neurosurgical operations. Methods: The experimental study included 12 patients at a single centre in 2018. They presented with cranial bone defects after various neurosurgical procedures, including tumour, traumatic brain injury and vascular pathologies. The patients underwent an in vivo bone reconstruction from poly-methyl-methacrylate, which was performed immediately after the tumour removal in the tumour group, whereas the trauma and vascular patients required a second surgery for cranial bone reconstruction due to the bone decompression. The artificial bone flap was modelled in vivo just before the skin closure. Clinical and surgical data were reviewed. Results: All patients had significant bony destruction or unusable bone flap. The tumour group included five patients with meningiomas destruction and the trauma group comprised four patients, all with severe traumatic brain injury. In the vascular group, there were three patients. The average modelling time for the artificial flap modelling was approximately 10 min. The convenient location of the bone defect enabled a relatively straightforward and fast reconstruction procedure. No deformations of flaps or other complications were encountered, except in one patient, who suffered a postoperative infection. Conclusions: Poly-methyl-methacrylate can be used as a suitable material to deliver good cranioplasty cosmesis. It offers an optimal dural covering and brain protection and allows fast intraoperative reconstruction with excellent cosmetic effect during the one-stage procedure. The observations of our study support the use of poly-methyl-methacrylate for the ad hoc reconstruction of cranial bone defects.

Neurosurgical Approaches to Brain Tissue Harvesting for the Establishment of Cell Cultures in Neural Experimental Cell Models

In recent decades, cell biology has made rapid progress. Cell isolation and cultivation techniques, supported by modern laboratory procedures and experimental capabilities, provide a wide range of opportunities for in vitro research to study physiological and pathophysiological processes in health and disease. They can also be used very efficiently for the analysis of biomaterials. Before a new biomaterial is ready for implantation into tissues and widespread use in clinical practice, it must be extensively tested. Experimental cell models, which are a suitable testing ground and the first line of empirical exploration of new biomaterials, must contain suitable cells that form the basis of biomaterial testing. To isolate a stable and suitable cell culture, many steps are required. The first and one of the most important steps is the collection of donor tissue, usually during a surgical procedure. Thus, the collection is the foundation for the success of cell isolation. This article explains the sources and neurosurgical procedures for obtaining brain tissue samples for cell isolation techniques, which are essential for biomaterial testing procedures.

Adhesion and Proliferation of Human Dermal Fibroblasts on Collagen Matrix

The purpose of this study was to evaluate adhesion and growth of human dermal fibroblasts on a 0.150 mm-thick matrix of reconstituted collagen isolated from horse tendon. Collagen was extracted and polymerized according to the standard procedures (Opocrin, Corlo, Modena, Italy). By light microscopy, the bottom surface of the matrix appeared linear and compact, whereas the superficial one was indented and less homogeneous. By scanning electron microscopy, the collagen fibrils had different diameters and the great majority of them was oriented parallel to the surface of the gel. By transmission electron microscopy, collagen fibrils showed the typical banding. Human dermal fibroblasts were seeded on the collagen matrix, previously equilibrated in growth medium. Fibroblast proliferation stopped in the second week and was always significantly lower than that of the same cell strain seeded on plastic and cultured in parallel. By light microscopy, after six days culture, cells formed a confluent multilayer on the surface of the gel. By scanning and transmission electron microscopy, fibroblasts appeared flat and adherent to the matrix. Contacts of cells among themselves and with the collagen fibrils were observed. Fibroblasts never moved into the collagen gel. In conclusion, human dermal fibroblasts can be grown in a three-dimensional matrix made by horse tendon that, on the other hand, seems to condition their proliferation rate.

In vitro investigation of the blood response to medical grade PVC and the effect of heparin on the blood response

This paper reports the results of an investigation into the blood response of polymers in vitro, using non-anticoagulated and heparinised blood and plasma. The materials studied were regenerated cellulose, (Cuprophan), an acrylonitrile-allyl sulphonate copolymer (AN69S), and medical grade polyvinyl chloride plasticised with di-2-ethyl-hexyl-phthalate (PVC/DEHP). Blood-material or plasma-material contact was achieved using a parallel plate flow cell, and C3a generation and FXII-like activity measured. The results of the study with non-anticoagulated human blood show that PVC/DEHP is a high complement activator. C3a concentration in the blood was higher after contact with PVC/DEHP than after contact with regenerated cellulose. The introduction of heparin in the blood induced complex alterations in the blood response. C3a generation could be elevated, decreased, or remain the same, depending on the material. The FXII-like activity on the surface of the PVC/DEHP after contact with plasma was also higher than the other two polymers. The introduction of heparin could increase or decrease FXII-like activity, depending on material. The patterns of response obtained with non-anticoagulated blood in vitro for AN69S and Cuprophan bore a strong resemblance with patterns of response obtained in the clinic, whereas those obtained with heparinised blood in vitro did not.

Culture materials affect ex vivo expansion of hematopoietic progenitor cells

Ex vivo expansion of hematopoietic cells is important for applications such as cancer treatment, gene therapy, and transfusion medicine. While cell culture systems are widely used to evaluate the biocompatibility of materials for implantation, the ability of materials to support proliferation of primary human cells in cultures for reinfusion into patients has not been addressed. We screened a variety of commercially available polymer (15 types), metal (four types), and glass substrates for their ability to support expansion of hematopoietic cells when cultured under conditions that would be encountered in a clinical setting. Cultures of peripheral blood (PB) CD34+ cells and mononuclear cells (MNC) were evaluated for expansion of total cells and colony-forming unit-granulocyte monocyte (CFU-GM; progenitors committed to the granulocyte and/or monocyte lineage). Human hematopoietic cultures in serum-free medium were found to be extremely sensitive to the substrate material. The only materials tested that supported expansion at or near the levels of polystyrene were tissue culture polystyrene, Teflon perfluoroalkoxy, Teflon fluorinated ethylene propylene, cellulose acetate, titanium, new polycarbonate, and new polymethylpentene. MNC were less sensitive to the substrate materials than the primitive CD34+ progenitors, although similar trends were seen for expansion of the two cell populations on the substrates tested. CFU-GM expansion was more sensitive to substrate materials than was total cell expansion. The detrimental effects of a number of the materials on hematopoietic cultures appear to be caused by protein adsorption and/or leaching of toxins. Factors such as cleaning, sterilization, and reuse significantly affected the performance of some materials as culture substrates. We also used PB CD34+ cell cultures to examine the biocompatibility of gas-permeable cell culture and blood storage bags and several types of tubing commonly used with biomedical equipment. While many of the culture bag materials gave satisfactory results, all of the tubing materials severely inhibited total cell and CFU-GM expansion. Taken together, our results show that many materials approved for blood contact or considered biocompatible are not suitable for use with hematopoietic cells cultured in serum-free medium. As hematopoietic cultures are scaled up for a variety of clinical applications, it will be essential to carefully examine the biocompatibility of all materials involved.

The influence of biomaterials on inflammatory responses to cardiopulmonary bypass

The nature of cardiopulmonary bypass and the complexity of the inflammatory response make the detection and interpretation of a biomaterial influence difficult. However, if mediation of the inflammatory response is considered to be an appropriate clinical goal, alteration to the biomaterial influence merits further investigation.

In vitro contact phase activation with haemodialysis membranes: role of pharmaceutical agents

Contact phase activation was investigated in vitro using flat sheet type of haemodialysis membranes, Cuprophan (Akzo, Faser, Germany) and AN69S (Hospal, France), and a negatively charged polyamide Ultipor NR 14225 membrane as a control. The investigation focussed on the determination of factor XII-like activity (FXIIA) as an indicator of contact phase activation in the supernatant phase and at the membrane surface after plasma-membrane contact using an incubation test cell. The findings were compared with the observations from a plasma-free system utilizing purified unactivated factor XII. The plasma FXIIA bound to the membrane surface was significantly different between the membranes, while the supernatant phase FXIIA exhibited no significant differences. In contrast, the plasma-free system exhibited significant differences in the supernatant FXIIA and membrane-bound FXIIA for all the materials used and the magnitude of the activity was significantly greater for negatively charged materials. This finding demonstrated the strong influence of the interaction of other plasma constituents on the membrane surface and as such the binding and subsequent activation of factor XII may be altered possibly due to competitive binding and steric hindrance. On the addition of anticoagulants such as heparin, low-molecular-weight heparin, citrate and hirudin, no significant differences were observed in plasma supernatant phase FXIIA. However, each anticoagulant appears to have a distinct influence on the magnitude of plasma membrane-bound FXIIA. On the addition of aprotinin (a kallikrein inhibitor), no significant differences were observed in the plasma supernatant FXIIA. In contrast, aprotinin appears to significantly reduce membrane-bound FXIIA on Cuprophan and polyamide NR, but significantly increase the magnitude of the membrane-bound FXIIA on AN69S.

Blood-contacting biomaterials: bioengineering viewpoints

The investigation of blood-contacting biomaterials is an important challenge and is relevant for an improvement in the clinical application of biomaterials. With the purpose of improved clinical treatment, bioengineering viewpoints of blood-contacting biomaterials cover the material options and selection, the utilization of materials, the development of materials with better properties, and processing characteristics, and the design of relevant evaluation procedures. The bioengineering objective remains that of achieving an enhanced understanding of the relationship between a biomaterial and the biological response.

Biomaterials for blood-contacting applications

Consideration of biomaterials for blood-contacting applications should take into account blood-biomaterial interactions, factors influencing the blood response and evaluation procedures. Examination of blood-biomaterial interactions indicates that relevant features are protein adsorption, platelet reactions, intrinsic coagulation, fibrinolytic activity, erythrocytes, leucocytes and complement activation. Factors influencing the blood response to a biomaterial in clinical application are the biomaterial structure, the presence of an antithrombotic agent, the patient status as determined by the disease and drug therapy, and the nature of the application. Evaluation options for biomaterials are clinical, in vivo, ex vivo and in vitro, with ex vivo and in vitro procedures relevant for biomaterial development.

Biomaterials in cardiopulmonary bypass

The improved utilization of biomaterials in cardiopulmonary bypass is dependent on polymer science and technology, procedures for blood compatibility assessment, optimization of biomaterial/antithrombotic agent combinations and the interpretation of clinical data.