Allometric tissue-scale forces activate mechanoresponsive immune cells to drive pathological foreign body response to biomedical implants

For decades, it has been assumed that the foreign body response (FBR) to biomedical implants is primarily a reaction to the chemical and mechanical properties of the implant. Here, we show for the first time that a third independent variable, allometric tissue-scale forces (which increase exponentially with body size), can drive the biology of FBR in humans. We first demonstrate that pathological FBR in humans is mediated by immune cell-specific Rac2 mechanotransduction signaling, independent of implant chemistry or mechanical properties. We then show that mice, which are typically poor models of human FBR, can be made to induce a strikingly human-like pathological FBR by altering these extrinsic tissue forces. Altering these extrinsic tissue forces alone activates Rac2 signaling in a unique subpopulation of immune cells and results in a human-like pathological FBR at the molecular, cellular, and local tissue levels. Finally, we demonstrate that blocking Rac2 signaling negates the effect of increased tissue forces, dramatically reducing FBR. These findings highlight a previously unsuspected mechanism for pathological FBR and may have profound implications for the design and safety of all implantable devices in humans.

Feasibility of adenosine stress cardiovascular magnetic resonance perfusion imaging in patients with MR-conditional transvenous permanent pacemakers and defibrillators

Background The use of stress perfusion-cardiovascular magnetic resonance (CMR) imaging remains limited in patients with implantable devices. The primary goal of the study was to assess the safety, image quality, and the diagnostic value of stress perfusion-CMR in patients with MR-conditional transvenous permanent pacemakers (PPM) or implantable cardioverter-defibrillators (ICD). Methods Consecutive patients with a transvenous PPM or ICD referred for adenosine stress-CMR were enrolled in this single-center longitudinal study. The CMR protocol was performed using a 1.5 T system according to current guidelines while all devices were put in MR-mode. Quality of cine, late-gadolinium-enhancement (LGE), and stress perfusion sequences were assessed. An ischemia burden of ≥ 1.5 segments was considered significant. We assessed the safety, image quality and the occurrence of interference of the magnetic field with the implantable device. In case of ischemia, we also assessed the correlation with the presence of significant coronary lesions on coronary angiography. Results Among 3743 perfusion-CMR examinations, 66 patients had implantable devices (1.7%). Image quality proved diagnostic in 98% of cases. No device damage or malfunction was reported immediately and at 1 year. Fifty patients were continuously paced during CMR. Heart rate and systolic blood pressure remained unchanged during adenosine stress, while diastolic blood pressure decreased (p = 0.007). Six patients (9%) had an ischemia-positive stress CMR and significant coronary stenoses were confirmed by coronary angiography in all cases. Conclusion Stress perfusion-CMR is safe, allows reliable ischemia detection, and provides good diagnostic value.

Application of 3D printing and its various technologies in dentistry

Many applications for these technologies have been reported in multiple fields, including dentistry, within the last three decades. It can be used in periodontology, endodontics, orthodontics, oral implantology, maxillofacial and oral surgery, and prosthodontics. In the present literature review, we have discussed the different clinical applications of various 3D printing technologies in dentistry. Evidence indicates that 3D printing approaches are usually associated with favorable outcomes based on the continuous development and production of novel approaches, enabling clinicians to develop complex equipment in different clinical and surgical aspects. Developing work models to facilitate diagnostic and surgical settings is the commonest application of these modalities in dentistry. Besides, they can also be used to manufacture various implantable devices. Accordingly, they significantly help enhance the treatment process, reducing costs and less invasive procedures with favorable outcomes. Finally, 3D printing technologies can design complex devices in a facilitated and more accurate way than conventional methods. Therefore, 3D printing should be encouraged in clinical settings for its various advantages over conventional maneuvers.

Open thoracic surgical implantation of cardiac pacemakers in rodents

Genetic engineering and implantable bioelectronics have transformed investigations of cardiovascular physiology and disease. However, the two approaches have been difficult to combine in the same species: genetic engineering is applied primarily in rodents, and implantable devices generally require large animal models. We recently developed several miniature cardiac bioelectronic devices suitable for mice and rats to combine the advantages of molecular tools and implantable devices. Successful implementation of these device-enabled studies requires microsurgery approaches that reliably interface bioelectronics to the beating heart with minimal disruption to native physiology. This protocol describes how to perform an open thoracic surgical technique for epicardial implantation of novel wireless cardiac bioelectronic devices in adult rats and has significantly lower mortality than transvenous implantation approaches. In addition, we provide the methodology for a full biocompatibility assessment of the physiological response to the implanted device. The surgical implantation procedure takes about 40 minutes to complete for an experienced operator, and up to 8 surgeries can be completed in one day. Implanted pacemakers provide programmed electrical stimulation for over 1 month. This protocol has broad applications to enable fully conscious in vivo studies of cardiovascular physiology in transgenic rodent disease models.

Recent Advances in Nanomaterials for Therapy and Diagnosis of Cardiovascular Disease

Cardiovascular diseases (CVDs) are among the world’s widely affected disorders, including ischemia and stroke. Acute Myocardial ischemia (AMI) is a deadly disease caused by irreversible damage to the left ventricular heart tissues. The thromboembolic plaque stops the oxygen supply to the main blood vessels and ventricles. During chronic inflammation, myocardial infarction and free radicals damage stable myocardium, smooth muscles cell, and epithelial cells caused by outer membrane loss and ventricular wall smoothing and dilation. Specially constructed scaffolds made of biological and nanoparticles have been created to shield the left ventricle from further injury and recover ischemic endothelial cells. Preclinical experiments have demonstrated that scaffolds containing growth factors and cells will regenerate ischemic tissue into a stable pericardium in good working order. Various medicinal approaches that treat cardiovascular disease conditions at different stages are discussed in this review article, with biomaterials receiving special attention. This review further addresses the manipulation and manufacturing of biomedical implantable devices using nanomedicine methods and drug delivery principles. The use of graphene and exosomal nanovesicle in cardiovascular therapeutics recently progressed in research studies.

An Ultra-Low Power Implantable Medical Devices: An Engineering Perspective

Implantable Medical Devices (IMDs) reside within human bodies either temporarily or permanently, for diagnostic, monitoring, or therapeutic purposes. IMDs have a history of outstanding success in the treatment of many diseases, including heart diseases, neurological disorders, and deafness etc.,With the ever-increasing clinical need for implantable devices comes along with the continuous flow of technical challenges. Comparing with the commercial portable products, implantable devices share the same need to reduce size, weight and power. Thus, the need for device integration becomes very much imperative. There are many challenges faced when creating an implantable medical device. While this paper focuses on various techniques adapted to design a reliable device and also focus on the key electronic features of designing an ultra-low power implantable medical circuits for devices and systems.

Injectable wireless microdevices: challenges and opportunities

In the past three decades, we have witnessed unprecedented progress in wireless implantable medical devices that can monitor physiological parameters and interface with the nervous system. These devices are beginning to transform healthcare. To provide an even more stable, safe, effective, and distributed interface, a new class of implantable devices is being developed; injectable wireless microdevices. Thanks to recent advances in micro/nanofabrication techniques and powering/communication methodologies, some wireless implantable devices are now on the scale of dust (< 0.5 mm), enabling their full injection with minimal insertion damage. Here we review state-of-the-art fully injectable microdevices, discuss their injection techniques, and address the current challenges and opportunities for future developments.