Design and development of a hybrid bioartificial shape memory polymeric material as integral component of a new means for the anastomosis of human hollow organs

Numerous types of pathologies require the resection of the bowel and an anastomoses to rejoin the two remaining stumps to regain lumen patency. A wide variety of suture materials (i.e. naturally absorbing or non absorbing like polymeric monofilament or braided materials) have been used to secure a hand-sewn anastomoses. Other anastomotic means include non absorbable (Murphy compression buttons) and absorbable (Valtrac) compression rings. Some of the most significant complications associated with intestinal anastomosis are: inflammation, dehiscence and leakage. The aim of this thesis is to study, design and develop a novel hybrid bioarfticial polymer to be used as fastener, able to guarantee the retention of the two hollow organ stumps, in a liquid tight anastomosis, in order to address at least some of the problem listed above. To reduce possible local inflammation, acetylsalicylic acid (ASA) and nanoparticles loaded with ASA were incorporate during the hydrogel preparation providing target drug delivery. The nanoparticles have been loaded with four different drug concentrations using the HPLC method, to compare their drug loading and drug release capabilities. Moreover, the mechanical properties of the bioartificial material have been tested by using a DMA 8000, validating that the storage modulus is a function of the number of freezing-thawing cycles. Biocompatibility test and cell culture experiments have been conducted to test the cytocompatibility and fibroblasts cell adhesion, growth and proliferation. Finally, a wireless sensor has been added to monitor tissue variations at the anastomotic site during the healing process. The sensors measure impedance and conductivity of tissue to quantify compressed tissue changes result of its transitions from healthy to necrosed tissue

Collection and recording of brain signals in chicken embryos

Sleep is an important function of the human brain. Sleep and sleep cycles are fundamental for sensory system development in the whole life cycle of an individual, including embryonic life, to preserve brain activity, to create long-term memory, and for learning. The measurement of brain signals is useful to quantify different brain states, such as sleep and wake states. The origin of cycles of sleep and wake in higher vertebrate animals (birds and mammals) are currently unknown, thus it is of particular interest to combine information that reflects different aspects of brain function. Our research has been focused on the study of neurological signals during embryonic life. In this thesis, chicken embryos have been chosen as animal models for many practical reasons: the ease of access to chicken embryos, the fact that early stages of development and sleep in chicken are similar to those of humans. The developed system consists of a transmitter placed outside the eggshell and of a receiver located outside the incubator. The transmitter and the eggshell are kept inside the incubator in order to guarantee the survival of the embryo. The communication between the transmitter and the receiver is implemented via infrared signals. Subsequently, to improve the insertion and adhesion at the brain-electrode interface, new flexible polyimide electrodes have been developed instead of the metal wires, which are commonly used to detect neurological signals. Specifically, two different types of electrodes have been developed: passive and active. The passive electrode is based on a conducting polymer (PEDOT:PSS) deposited on a flexible polyimide substrate, where gold has been used to define the conducting line and the pad contact area. The active electrode is based on the fabrication of an organic electrochemical transistor (OECT), for which source and drain electrodes have been made with gold, the channel has been made with a conducting polymer (PEDOT:PSS) and the gate has been made with metal. The deposition of PEDOT:PSS has been performed using the inkjet printing technology. Different types of ink, based on a PEDOT:PSS aqueous solution, have been tested and electrically characterized. Finally, in-vivo tests on chicken embryos, using standard metal electrodes, have been completed to check the performance of the developed EEG system

Flexible polyimide electrodes for ECoG in chicken embryos

Electrocorticography (ECoG) is a valuable tool used to investigate brain activity with a better spatial resolution compared to the EEG system. We describe the fabrication of new polyimide electrodes for EcoG recording, used to research the development of wake-sleep cycles in chicken embryos. The microelectrodes are connected to a dedicated system for data acquisition. Current ECoG recordings in birds are usually made with metallic wire electrodes placed on the dura surface though a hole on the skull. This approach is not reliable for long term acquisitions (a few days) as the electrodes may generate signal artefacts and cause bleeding. Recently, flexible polymer electrodes have been proposed to avoid the stiffness of the metal wire and to improve compliance with brain surface. The electrodes are fabricated on a 75µm thick polyimide film substrate. Gold lines are used as conductive wires to read the brain potentials and transfer them to the acquisition system. To protect and isolate gold tracks, a protective spinnable polyimide layer (Hitachi PI2610) is subsequently deposited. Then, an aluminium hard mask is deposited and patterned by a lithographic step, to protect and to open a window by oxygen plasma etch in the protective layers, so that the gold pads are exposed. Finally, the electrodes are ready and are detached from the carrier tape. Preliminary insertion tests have showed the feasibility of flexible electrodes insertion in the chicken brain

Design and development of a wireless infrared EEG recorder for chicken embryos

A major unanswered question in the field of sleep studies concerns the developmental emergence of cycles of sleep and waking during embryonic life. One means for gaining valuable information about the development of this aspect of global brain function is to relate brain electrical activity recorded with electroencephalography (EEG) signals to brain metabolic activity, collected by means of Positron Emission Tomography (PET). A telemetric system for recording chicken embryo EEG signals that is electromagnetically compatible with a PET scanner has been developed for this purpose. An infrared data link has been used in order to avoid electromagnetic interference. The system is composed of a small, low-power IR transmitter which sends sampled data to a receiver that is connected to a PC for signal processing and data storage. The transmitter collects EEG/EMG data from six channels, with a sampling frequency of 200 Hz and an accuracy of 12 bits. The transmission range is up to approximately 30 cm, compatible with the required application. The total size of the transmitter is 21 mm × 16 mm, excluding the battery

Design of flexible polyimide electrodes for a Wireless Infrared EEG Recorder for chicken embryos

The study of the emergence of sleep and waking during embryonic life forms a fundamental part of understanding sleep physiology. Electroencephalography (EEG) is one of the most basic tools used to investigate sleep. We describe the preliminary design of a telemetry system composed of conductive polymer electrodes connected to a transmitter and a receiver. As an additional benefit, the system is electromagnetically compatible with Positron Emission Tomography (PET) scanners, permitting the simultaneous acquisition of PET images and EEG data. The system was developed for recording chicken embryo EEG signals. Electromagnetic interference is avoided using an infrared data link for communication. The system makes use of six conductive polymer electrodes, with dimensions on a micrometer scale, connected via a ZIF (Zero Insertion Force) connector to a small, low power IR transmitter. This transmitter is optically coupled to a receiver, that it is connected to a PC for signal processing and data storage