Microfabricated reciprocating micropump for intracochlear drug delivery with integrated drug/fluid storage and electronically controlled dosing

Outer hair cells stir cochlear fluids

Recent observations regarding the non-selective action of outer hair cells contradict frequency-selective cochlear amplification. We hypothesized that active outer hair cells drive cochlear fluid circulation. The hypothesis was tested by delivering a neurotoxin, kainic acid, to the round window of young gerbil cochleae while monitoring auditory responses in the cochlear nucleus. Sounds presented at a modest level significantly expedited kainic acid delivery. When outer-hair-cell motility was suppressed by salicylate, the facilitation effect was compromised. A low-frequency tone was more effective than broadband noise, especially for drug delivery to apical locations. Computational model simulations provided the physical basis for our observation, which incorporated solute diffusion, fluid advection, fluid-structure interaction, and outer-hair-cell motility. Active outer hair cells deformed the organ of Corti like a peristaltic tube to generate apically streaming flows along the tunnel of Corti and basally streaming flows along the scala tympani. Our measurements and simulations coherently indicate that broadband outer-hair-cell action is for cochlear fluid circulation.

Meniere's disease: Pathogenesis, treatments, and emerging approaches for an idiopathic bioenvironmental disorder

Meniere's disease (MD) is a severe inner ear condition known by debilitating symptoms, including spontaneous vertigo, fluctuating and progressive hearing loss, tinnitus, and aural fullness or pressure within the affected ear. Prosper Meniere first described the origins of MD in the 1860s, but its underlying mechanisms remain largely elusive today. Nevertheless, researchers have identified a key histopathological feature called Endolymphatic Hydrops (ELH), which refers to the excessive buildup of endolymph fluid in the membranous labyrinth of the inner ear. The exact root of ELH is not fully understood. Still, it is believed to involve several biological and bioenvironmental etiological factors such as genetics, autoimmunity, infection, trauma, allergy, and new theories, such as saccular otoconia blocking the endolymphatic duct and sac. Regarding treatment, there are no reliable and definitive cures for MD. Most therapies focus on managing symptoms and improving the overall quality of patients' life. To make significant advancements in addressing MD, it is crucial to gain a fundamental understanding of the disease process, laying the groundwork for more effective therapeutic approaches. This paper provides a comprehensive review of the pathophysiology of MD with a focus on old and recent theories. Current treatment strategies and future translational approaches (with low-level evidence but promising results) related to MD are also discussed, including patents, drug delivery, and nanotechnology, that may provide future benefits to patients suffering from MD.

Intrinsic mechanism and pharmacologic treatments of noise-induced hearing loss

Noise accounts for one-third of hearing loss worldwide. Regretfully, noise-induced hearing loss (NIHL) is deemed to be irreversible due to the elusive pathogenic mechanisms that have not been fully elucidated. The complex interaction between genetic and environmental factors, which influences numerous downstream molecular and cellular events, contributes to the NIHL. In clinical settings, there are no effective therapeutic drugs other than steroids, which are the only treatment option for patients with NIHL. Therefore, the need for treatment of NIHL that is currently unmet, along with recent progress in our understanding of the underlying regulatory mechanisms, has led to a lot of new literatures focusing on this therapeutic field. The emergence of novel technologies that modify local drug delivery to the inner ear has led to the development of promising therapeutic approaches, which are currently under clinical investigation. In this comprehensive review, we focus on outlining and analyzing the basics and potential therapeutics of NIHL, as well as the application of biomaterials and nanomedicines in inner ear drug delivery. The objective of this review is to provide an incentive for NIHL's fundamental research and future clinical translation.

Electronically powered drug delivery devices: considerations and challenges

INTRODUCTION

Electronically powered drug delivery devices enable a controlled drug release route for a more convenient and painless way with reduced side effects. The current advances in microfabrication and microelectronics have facilitated miniaturization and intelligence with the integration of sensors and wireless communication modules. These devices have become an essential component of commercialized on-demand drug delivery.

AREAS COVERED

This review aims to provide a concise overview of current progress in electronically powered drug devices, focusing on delivery strategies, manufacturing techniques, and control circuit design with specific examples.

EXPERT OPINION

The application of electronically powered drug delivery systems is now considered a feasible therapeutic approach with improved drug release efficiency and increased patient comfort. It is anticipated that these technologies will gradually fulfill clinical needs and resolve commercialization challenges in the future. This review discusses the current advances in electronic drug delivery devices, especially focusing on designing strategies to achieve an effective drug release, as well as the perspectives and challenges for future applications in clinical therapy.

The Modular µSiM Reconfigured: Integration of Microfluidic Capabilities to Study In Vitro Barrier Tissue Models under Flow

Microfluidic tissue barrier models have emerged to address the lack of physiological fluid flow in conventional "open-well" Transwell-like devices. However, microfluidic techniques have not achieved widespread usage in bioscience laboratories because they are not fully compatible with traditional experimental protocols. To advance barrier tissue research, there is a need for a platform that combines the key advantages of both conventional open-well and microfluidic systems. Here, a plug-and-play flow module is developed to introduce on-demand microfluidic flow capabilities to an open-well device that features a nanoporous membrane and live-cell imaging capabilities. The magnetic latching assembly of this design enables bi-directional reconfiguration and allows users to conduct an experiment in an open-well format with established protocols and then add or remove microfluidic capabilities as desired. This work also provides an experimentally-validated flow model to select flow conditions based on the experimental needs. As a proof-of-concept, flow-induced alignment of endothelial cells and the expression of shear-sensitive gene targets are demonstrated, and the different phases of neutrophil transmigration across a chemically stimulated endothelial monolayer under flow conditions are visualized. With these experimental capabilities, it is anticipated that both engineering and bioscience laboratories will adopt this reconfigurable design due to the compatibility with standard open-well protocols.

Prospection of Microfluidics for Local Drug Delivery

Significant endeavors can be made to develop effective drug delivery systems. Nowadays, many of these novel systems have gained attention as they focus primarily on increasing the bioavailability and bioaccessibility of several drugs to finally minimize the side effects, thus improving the treatment's efficacy. Microfluidics systems are unquestionably a superior technology, which is currently revolutionizing the current chemical and biological studies, providing diminutive chip-scale devices that offer precise dosage, target-precise delivery, and controlled release. Microfluidic systems have emerged as a promising delivery vehicle owing to their potential for defined handling and transporting of small liquid quantities. The latest microfabrication developments have been made for application to several biological systems. Here, we review the fundamentals of microfluidics and their application for local drug delivery.

Working Mechanisms and Experimental Research of Piezoelectric Pump with a Cardiac Valve-like Structure

In this study, based on the working principle of the cardiac valve structure that prevents blood from flowing back, a piezoelectric pump with a cardiac valve-like structure (PPCVLS) is designed. The operating principles of cardiac-valve-like structures (CVLSs) are introduced. Furthermore, the closure conditions of the CVLSs on both sides of the flow channel are explored. The principle behind the working-state conversion between "valve-based" and "valve-less" of PPCVLS is also analyzed. A high-speed dynamic microscopic image-analysis system was utilized to observe and verify the working-state conversion between "valve-based" and "valve-less" PPCVLSs. The resonant frequency of the piezoelectric pump was measured by Doppler laser vibrometer, and the optimal working frequency of the piezoelectric vibrator was determined as 22.35 Hz. The prototype piezoelectric pump was fabricated by the 3D printing technique, and the output performance of the piezoelectric pump was also evaluated. The experimental results show that the piezoelectric pump is valve-based when the driving voltage is greater than 140V, and the piezoelectric pump is valve-less when the driving voltage is less than 140 V. Furthermore, the maximum output pressure of the piezoelectric pump was 199 mm H₂O when driven by the applied voltage of 220 V at 7 Hz, while the maximum flow rate of the piezoelectric pump was 44.5 mL/min when driven by the applied voltage of 220 V at 11 Hz.

Local Delivery of Therapeutics to the Cochlea Using Nanoparticles and Other Biomaterials

Hearing loss negatively impacts the well-being of millions of people worldwide. Systemic delivery of ototherapeutics has limited efficacy due to severe systemic side effects and the presence of the blood-labyrinth barrier that selectively limits or enables transfer of molecules between plasma and inner ear tissues and fluids. Local drug delivery into the middle and inner ear would be preferable for many newly emerging classes of drugs. Although the cochlea is a challenging target for drug delivery, recent technologies could provide a safe and efficacious delivery of ototherapeutics. Local drug delivery routes include topical delivery via the external auditory meatus, retroauricular, transtympanic, and intracochlear delivery. Many new drug delivery systems specifically for the inner ear are under development or undergoing clinical studies. Future studies into these systems may provide a means for extended delivery of drugs to preserve or restore hearing in patients with hearing disorders. This review outlines the anatomy of the (inner) ear, describes the various local delivery systems and routes, and various quantification methodologies to determine the pharmacokinetics of the drugs in the inner ear.

Recent Advances in Intelligent Wearable Medical Devices Integrating Biosensing and Drug Delivery

The primary roles of precision medicine are to perform real-time examination, administer on-demand medication, and apply instruments continuously. However, most current therapeutic systems implement these processes separately, leading to treatment interruption and limited recovery in patients. Personalized healthcare and smart medical treatment have greatly promoted research on and development of biosensing and drug-delivery integrated systems, with intelligent wearable medical devices (IWMDs) as typical systems, which have received increasing attention because of their non-invasive and customizable nature. Here, the latest progress in research on IWMDs is reviewed, including their mechanisms of integrating biosensing and on-demand drug delivery. The current challenges and future development directions of IWMDs are also discussed.

Inner Ear Drug Delivery for Sensorineural Hearing Loss: Current Challenges and Opportunities

Most therapies for treating sensorineural hearing loss are challenged by the delivery across multiple tissue barriers to the hard-to-access anatomical location of the inner ear. In this review, we will provide a recent update on various pharmacotherapy, gene therapy, and cell therapy approaches used in clinical and preclinical studies for the treatment of sensorineural hearing loss and approaches taken to overcome the drug delivery barriers in the ear. Small-molecule drugs for pharmacotherapy can be delivered via systemic or local delivery, where the blood-labyrinth barrier hinders the former and tissue barriers including the tympanic membrane, the round window membrane, and/or the oval window hinder the latter. Meanwhile, gene and cell therapies often require targeted delivery to the cochlea, which is currently achieved via intra-cochlear or intra-labyrinthine injection. To improve the stability of the biomacromolecules during treatment, e.g., RNAs, DNAs, proteins, additional packing vehicles are often required. To address the diverse range of biological barriers involved in inner ear drug delivery, each class of therapy and the intended therapeutic cargoes will be discussed in this review, in the context of delivery routes commonly used, delivery vehicles if required (e.g., viral and non-viral nanocarriers), and other strategies to improve drug permeation and sustained release (e.g., hydrogel, nanocarriers, permeation enhancers, and microfluidic systems). Overall, this review aims to capture the important advancements and key steps in the development of inner ear therapies and delivery strategies over the past two decades for the treatment and prophylaxis of sensorineural hearing loss.

The microfluidic artificial lung: Mimicking nature's blood path design to solve the biocompatibility paradox

The increasing prevalence of chronic lung disease worldwide, combined with the emergence of multiple pandemics arising from respiratory viruses over the past century, highlights the need for safer and efficacious means for providing artificial lung support. Mechanical ventilation is currently used for the vast majority of patients suffering from acute and chronic lung failure, but risks further injury or infection to the patient's already compromised lung function. Extracorporeal membrane oxygenation (ECMO) has emerged as a means of providing direct gas exchange with the blood, but limited access to the technology and the complexity of the blood circuit have prevented the broader expansion of its use. A promising avenue toward simplifying and minimizing complications arising from the blood circuit, microfluidics-based artificial organ support, has emerged over the past decade as an opportunity to overcome many of the fundamental limitations of the current standard for ECMO cartridges, hollow fiber membrane oxygenators. The power of microfluidics technology for this application stems from its ability to recapitulate key aspects of physiological microcirculation, including the small dimensions of blood vessel structures and gas transfer membranes. An even greater advantage of microfluidics, the ability to configure blood flow patterns that mimic the smooth, branching nature of vascular networks, holds the potential to reduce the incidence of clotting and bleeding and to minimize reliance on anticoagulants. Here, we summarize recent progress and address future directions and goals for this potentially transformative approach to artificial lung support.

Studying metabolism with multi-organ chips: new tools for disease modelling, pharmacokinetics and pharmacodynamics

Non-clinical models to study metabolism including animal models and cell assays are often limited in terms of species translatability and predictability of human biology. This field urgently requires a push towards more physiologically accurate recapitulations of drug interactions and disease progression in the body. Organ-on-chip systems, specifically multi-organ chips (MOCs), are an emerging technology that is well suited to providing a species-specific platform to study the various types of metabolism (glucose, lipid, protein and drug) by recreating organ-level function. This review provides a resource for scientists aiming to study human metabolism by providing an overview of MOCs recapitulating aspects of metabolism, by addressing the technical aspects of MOC development and by providing guidelines for correlation with in silico models. The current state and challenges are presented for two application areas: (i) disease modelling and (ii) pharmacokinetics/pharmacodynamics. Additionally, the guidelines to integrate the MOC data into in silico models could strengthen the predictive power of the technology. Finally, the translational aspects of metabolizing MOCs are addressed, including adoption for personalized medicine and prospects for the clinic. Predictive MOCs could enable a significantly reduced dependence on animal models and open doors towards economical non-clinical testing and understanding of disease mechanisms.

Microimaging of a novel intracochlear drug delivery device in combination with cochlear implants in the human inner ear

The effective delivery of drugs to the inner ear is still an unmet medical need. Local controlled drug delivery to this sensory organ is challenging due to its location in the petrous bone, small volume, tight barriers, and high vulnerability. Local intracochlear delivery of drugs would overcome the limitations of intratympanic (extracochlear) and systemic drug application. The requirements for such a delivery system include small size, appropriate flexibility, and biodegradability. We have developed biodegradable PLGA-based implants for controlled intracochlear drug release that can also be used in combination with cochlear implants (CIs), which are implantable neurosensory prosthesis for hearing rehabilitation. The drug carrier system was tested for implantation in the human inner ear in 11 human temporal bones. In five of the temporal bones, CI arrays from different manufacturers were implanted before insertion of the biodegradable PLGA implants. The drug carrier system and CI arrays were implanted into the scala tympani through the round window. Implanted temporal bones were evaluated by ultra-high-resolution computed tomography (µ-CT) to illustrate the position of implanted electrode carriers and the drug carrier system. The µ-CT measurements revealed the feasibility of implanting the PLGA implants into the scala tympani of the human inner ear and co-administration of the biodegradable PLGA implant with a CI array.

Fused deposition modelling 3D printing proof-of-concept study for personalised inner ear therapy

OBJECTIVES

There is a requirement within ear therapeutics for a delivery system capable of safely delivering controlled doses to the inner ear. However, the anatomy and sensitivity of the inner ear make current delivery systems problematic and often ineffective. Therefore, a new delivery system is required to overcome these issues and provide a more efficacious system in the treatment of inner ear disease. This study assesses the potential of 3D printing (3DP) as a fabrication method for an implantable drug delivery system (DDS) to the inner ear.

KEY FINDINGS

Three implantable designs of varying geometry were produced with fused deposition modelling (FDM) 3DP, each loaded with 0.25%, 0.5% and 1% levofloxacin; filaments prepared by hot-melt extrusion. Each implant was effective in providing sustained, therapeutic release of levofloxacin for at least 4 days and as such would be effective in therapeutic treatment of many common inner ear diseases, such as otitis media or Ménière's disease.

CONCLUSIONS

This proof-of-concept research was successful in utilising FDM as a fabrication method for a DDS capable of providing prolonged release directly to the inner ear and highlights the viability of 3DP in the fabrication of an inner ear DDS.

Peristaltic on-chip pump for tunable media circulation and whole blood perfusion in PDMS-free organ-on-chip and Organ-Disc systems

Organ-on-chip (OoC) systems have become a promising tool for personalized medicine and drug development with advantages over conventional animal models and cell assays. However, the utility of OoCs in industrial settings is still limited, as external pumps and tubing for on-chip fluid transport are dependent on error-prone, manual handling. Here, we present an on-chip pump for OoC and Organ-Disc systems, to perfuse media without external pumps or tubing. Peristaltic pumping is implemented through periodic compression of a flexible pump layer. The disc-shaped, microfluidic module contains four independent systems, each lined with endothelial cells cultured under defined, peristaltic perfusion. Both cell viability and functionality were maintained over several days shown by supernatant analysis and immunostaining. Integrated, on-disc perfusion was further used for cytokine-induced cell activation with physiologic cell responses and for whole blood perfusion assays, both demonstrating the versatility of our system for OoC applications.

Microtechnologies for inner ear drug delivery

PURPOSE OF REVIEW

Treatment of auditory dysfunction is dependent on inner ear drug delivery, with microtechnologies playing an increasingly important role in cochlear access and pharmacokinetic profile control. This review examines recent developments in the field for clinical and animal research environments.

RECENT FINDINGS

Micropump technologies are being developed for dynamic control of flow rates with refillable reservoirs enabling timed delivery of multiple agents for protection or regeneration therapies. These micropumps can be combined with cochlear implants with integral catheters or used independently with cochleostomy or round window membrane (RWM) delivery modalities for therapy development in animal models. Sustained release of steroids with coated cochlear implants remains an active research area with first-time-in-human demonstration of reduced electrode impedances. Advanced coatings containing neurotrophin producing cells have enhanced spiral ganglion neuron survival in animal models, and have proven safe in a human study. Microneedles have emerged for controlled microperforation of the RWM for significant enhancement in permeability, combinable with emerging matrix formulations that optimize biological interaction and drug release kinetics.

SUMMARY

Microsystem technologies are providing enhanced and more controlled access to the inner ear for advanced drug delivery approaches, alone and in conjunction with cochlear implants.

Advances in Valveless Piezoelectric Pumps

Piezoelectric pump design is regarded as a hot research topic in the microfluidic field, and has been applied in liquid cooling, precision machinery and other relevant domains. The valveless piezoelectric pump becomes an important branch of the piezoelectric pump, because it successfully avoids the problem of “pump-lagging of valve” during the valve piezoelectric pump processing. This paper summarizes the development of valveless piezoelectric pumps, and introduces some different configurations of valveless piezoelectric pumps. The structure and material of all kinds of valveless piezoelectric pumps are elaborated in detail, and also the output performance of the pump is evaluated and analyzed with the variations in flow rate and output pressure as reference. By comparing the flow of different types of valveless piezoelectric pumps, the application of valveless piezoelectric pumps is also illustrated. The development tendency of the valveless piezoelectric pump is prospected from the perspective of structure design and machining methods, which is expected to provide novel ideas and guidance for future research.

Microfluidics for Drug Development: From Synthesis to Evaluation

Drug development is a long process whose main content includes drug synthesis, drug delivery, and drug evaluation. Compared with conventional drug development procedures, microfluidics has emerged as a revolutionary technology in that it offers a miniaturized and highly controllable environment for bio(chemical) reactions to take place. It is also compatible with analytical strategies to implement integrated and high-throughput screening and evaluations. In this review, we provide a comprehensive summary of the entire microfluidics-based drug development system, from drug synthesis to drug evaluation. The challenges in the current status and the prospects for future development are also discussed. We believe that this review will promote communications throughout diversified scientific and engineering communities that will continue contributing to this burgeoning field.

A Wirelessly Controlled Scalable 3D-Printed Microsystem for Drug Delivery

Here we present a 3D-printed, wirelessly controlled microsystem for drug delivery, comprising a refillable microreservoir and a phase-change peristaltic micropump. The micropump structure was inkjet-printed on the back of a printed circuit board around a catheter microtubing. The enclosure of the microsystem was fabricated using stereolithography 3D printing, with an embedded microreservoir structure and integrated micropump. In one configuration, the microsystem was optimized for murine inner ear drug delivery with an overall size of 19 × 13 × 3 mm3. Benchtop results confirmed the performance of the device for reliable drug delivery. The suitability of the device for long-term subcutaneous implantation was confirmed with favorable results of implantation of a microsystem in a mouse for six months. The drug delivery was evaluated in vivo by implanting four different microsystems in four mice, while the outlet microtubing was implanted into the round window membrane niche for infusion of a known ototoxic compound (sodium salicylate) at 50 nL/min for 20 min. Real-time shifts in distortion product otoacoustic emission thresholds and amplitudes were measured during the infusion, demonstrating similar results with syringe pump infusion. Although demonstrated for one application, this low-cost design and fabrication methodology is scalable for use in larger animals and humans for different clinical applications/delivery sites.

High-throughput organ-on-chip platform with integrated programmable fluid flow and real-time sensing for complex tissue models in drug development workflows

Drug development suffers from a lack of predictive and human-relevant in vitro models. Organ-on-chip (OOC) technology provides advanced culture capabilities to generate physiologically appropriate, human-based tissue in vitro, therefore providing a route to a predictive in vitro model. However, OOC technologies are often created at the expense of throughput, industry-standard form factors, and compatibility with state-of-the-art data collection tools. Here we present an OOC platform with advanced culture capabilities supporting a variety of human tissue models including liver, vascular, gastrointestinal, and kidney. The platform has 96 devices per industry standard plate and compatibility with contemporary high-throughput data collection tools. Specifically, we demonstrate programmable flow control over two physiologically relevant flow regimes: perfusion flow that enhances hepatic tissue function and high-shear stress flow that aligns endothelial monolayers. In addition, we integrate electrical sensors, demonstrating quantification of barrier function of primary gut colon tissue in real-time. We utilize optical access to the tissues to directly quantify renal active transport and oxygen consumption via integrated oxygen sensors. Finally, we leverage the compatibility and throughput of the platform to screen all 96 devices using high content screening (HCS) and evaluate gene expression using RNA sequencing (RNA-seq). By combining these capabilities in one platform, physiologically-relevant tissues can be generated and measured, accelerating optimization of an in vitro model, and ultimately increasing predictive accuracy of in vitro drug screening.

Prospects and Opportunities for Microsystems and Microfluidic Devices in the Field of Otorhinolaryngology

Microfluidic systems can be used to control picoliter to microliter volumes in ways not possible with other methods of fluid handling. In recent years, the field of microfluidics has grown rapidly, with microfluidic devices offering possibilities to impact biology and medicine. Microfluidic devices populated with human cells have the potential to mimic the physiological functions of tissues and organs in a three-dimensional microenvironment and enable the study of mechanisms of human diseases, drug discovery and the practice of personalized medicine. In the field of otorhinolaryngology, various types of microfluidic systems have already been introduced to study organ physiology, diagnose diseases, and evaluate therapeutic efficacy. Therefore, microfluidic technologies can be implemented at all levels of otorhinolaryngology. This review is intended to promote understanding of microfluidic properties and introduce the recent literature on application of microfluidic-related devices in the field of otorhinolaryngology.

Deep Volumetric Segmentation of Murine Cochlear Compartments from Micro-Computed Tomography Images

Local drug delivery to the inner ear via micropump implants has the potential to be much more effective than oral drug delivery for treating patients with sensorineural hearing loss and to protect hearing from ototoxic insult due to noise exposure or cancer treatments. Designing micropumps to deliver appropriate concentrations of drugs to the necessary cochlear compartments is of paramount importance; however, directly measuring local drug concentrations over time throughout the cochlea is not possible. Recent approaches for indirectly quantifying local drug concentrations in animal models capture a series of magnetic resonance (MR) or micro computed tomography (µCT) images before and after infusion of a contrast agent into the cochlea. These approaches require accurately segmenting important cochlear components (scala tympani (ST), scala media (SM) and scala vestibuli (SV)) in each scan and ensuring that they are registered longitudinally across scans. In this paper, we focus on segmenting cochlear compartments from µCT volumes using V-Net, a convolutional neural network (CNN) architecture for 3-D segmentation. We show that by modifying the V-Net architecture to decrease the numbers of encoder and decoder blocks and to use dilated convolutions enables extracting local estimates of drug concentration that are comparable to those extracted using atlas-based segmentation (3.37%, 4.81%, and 19.65% average relative error in ST, SM, and SV), but in a fraction of the time. We also test the feasibility of training our network on a larger MRI dataset, and then using transfer learning to perform segmentation on a smaller number of µCT volumes, which would enable this technique to be used in the future to characterize drug delivery in the cochlea of larger mammals.

Advances in passively driven microfluidics and lab-on-chip devices: a comprehensive literature review and patent analysis

The development of passively driven microfluidic labs on chips has been increasing over the years. In the passive approach, the microfluids are usually driven and operated without any external actuators, fields, or power sources. Passive microfluidic techniques adopt osmosis, capillary action, surface tension, pressure, gravity-driven flow, hydrostatic flow, and vacuums to achieve fluid flow. There is a great need to explore labs on chips that are rapid, compact, portable, and easy to use. The evolution of these techniques is essential to meet current needs. Researchers have highlighted the vast potential in the field that needs to be explored to develop rapid passive labs on chips to suit market/researcher demands. A comprehensive review, along with patent analysis, is presented here, listing the latest advances in passive microfluidic techniques, along with the related mechanisms and applications.

State-of-the-art methods in clinical intracochlear drug delivery

PURPOSE OF REVIEW

Increasing awareness and prevalence of disorders in hearing and balance have placed emphasis on treatment strategies. With the rapid evolution in molecular, gene, and nanotechnology, alternate delivery methods have advanced intracochlear drug delivery. This review aims to raise awareness of recent developments in technologies to augment current clinical practices.

RECENT FINDINGS

Intracochlear drug delivery research has expanded with the familiarity and accessibility to cochlear implantation. Various therapeutics are closely studied for both safety and efficacy as well as biologic effect. Agents including neurotrophins, antiapoptotics, cell therapy, gene therapy, and anti-inflammatory drugs are on the forefront of preclinical research. Cochlear implant electrode modification and drug administration at the time of implantation is a major focus of research. Improvements in study design have focused on overcoming barriers including elucidating the role of the blood-perilymph barrier.

SUMMARY

Inner ear drug delivery methods include systemic, intratympanic, and intracochlear administration. Therapeutic technologies aim to overcome delivery barriers and to improve overall biologic effect while minimizing toxicity. Precision of drug application through intratympanic and intracochlear administration with minimal trauma is the future of inner ear drug development.

A 3D Microscaffold Cochlear Electrode Array for Steroid Elution

In cochlear implants, the electrode insertion trauma during surgery can cause damage residual hearing. Preserving the residual hearing is an important challenge and the localized administration of drugs, such as steroids, is one of the most promising ways, but remains a challenge. Here, a microscaffold cochlear electrode array (MiSCEA) consisting of a microfabricated flexible electrode array and a 3D microscaffold for steroid reservoir is reported. The MiSCEA without loaded drug is tested by measuring the electrically evoked auditory brainstem response of the cochlea in guinea pigs (n = 4). The scaffold is then coated with steroid (dexamethasone) encapsulated in polylactic-co-glycolic acid and the continuous release of the steroid into artificial perilymph during six weeks is monitored. The steroid-containing scaffolds are then implanted into guinea pigs (n = 4) and threshold shifts are analyzed for four weeks by measuring the acoustically evoked auditory brainstem response. The threshold shifts tend to be lower in the group implanted with the steroid-containing MiSCEAs. The feasibility of 3D MiSCEA opens up the development of potential next-generation cochlear electrode with improved steroid release dynamics into cochlea.

The future of otology

BACKGROUND

The field of otology is increasingly at the forefront of innovation in science and medicine. The inner ear, one of the most challenging systems to study, has been rendered much more open to inquiry by recent developments in research methodology. Promising advances of potential clinical impact have occurred in recent years in biological fields such as auditory genetics, ototoxic chemoprevention and organ of Corti regeneration. The interface of the ear with digital technology to remediate hearing loss, or as a consumer device within an intelligent ecosystem of connected devices, is receiving enormous creative energy. Automation and artificial intelligence can enhance otological medical and surgical practice. Otology is poised to enter a new renaissance period, in which many previously untreatable ear diseases will yield to newly introduced therapies.

OBJECTIVE

This paper speculates on the direction otology will take in the coming decades.

CONCLUSION

Making predictions about the future of otology is a risky endeavour. If the predictions are found wanting, it will likely be because of unforeseen revolutionary methods.

Inner Ear Therapeutics: An Overview of Middle Ear Delivery

There are a variety of methods to access the inner ear and many of these methods depend on utilizing the middle ear as a portal. In this approach the middle ear can be used as a passive receptacle, as part of an active drug delivery system, or simply as the most convenient way to access the inner ear directly in human subjects. The purpose of this volume is to examine some of the more cutting-edge approaches to treating the middle ear. Before considering these therapies, this manuscript provides an overview of some therapies that have been delivered through the middle ear both in the past and at the current time. This manuscript also serves as a review of many of the methods for accessing the inner ear that directly utilize or pass though the middle ear. This manuscript provides the reader a basis for understanding middle ear delivery, the basis of delivery of medicines via cochlear implants, and examines the novel approach of using hypothermia as a method of altering the responses of the inner ear to damage.

Performance analysis of valveless piezoelectric pump with dome composite structures

Valveless piezoelectric pumps are used in the field of drug delivery. However, the output performances are limited by severe reflux. This article is aimed at reducing the reflux and improving the output performances. We use different pressure loss coefficients in the forward and reverse directions and design dome composite structures within the chamber of the valveless pump. The structures and working principles are described. Then, we use the fluid simulation software CFX to simulate the flow state inside the chamber under different parameters such as the dome length, 2 mm, 4 mm, 6 mm, and 8 mm; the trapezoidal one-sided angle, 1°, 3°, 5°, 7°, and 9°; and the rounded corner, from 0 to 6 mm. Finally, we also make the prototypes and test the output performances. The results show that the output flow rate can reach a maximum of 220.6 ml/min; the measured variance is 80.7 in the three experiment tests for the optimal flow rate at the dome length of 8 mm, angle of 5°, and rounded corner of 6 mm under the driving voltage of 190 V at a frequency of 45 Hz; the highest output pressure is 670.0 Pa under the voltage of 190 V at a frequency of 130 Hz. Moreover, the precision is 5.85% of the highest tested pressure compared to the simulated pressure. The output flow rate has a great improvement, and the effectiveness of the structures is proved.

A nanoliter resolution implantable micropump for murine inner ear drug delivery

Advances in protective and restorative biotherapies have created new opportunities to use site-directed, programmable drug delivery systems to treat auditory and vestibular disorders. Successful therapy development that leverages the transgenic, knock-in, and knock-out variants of mouse models of human disease requires advanced microsystems specifically designed to function with nanoliter precision and with system volumes suitable for implantation. Here we present results for a novel biocompatible, implantable, scalable, and wirelessly controlled peristaltic micropump. The micropump configuration included commercially available catheter microtubing (250 μm OD, 125 μm ID) that provided a biocompatible leak-free flow path while avoiding complicated microfluidic interconnects. Peristaltic pumping was achieved by sequentially compressing the microtubing via expansion and contraction of a thermal phase-change material located in three chambers integrated adjacent to the microtubing. Direct-write micro-scale printing technology was used to build the mechanical components of the micropump around the microtubing directly on the back of a printed circuit board assembly (PCBA). The custom PCBA was fabricated using standard commercial processes providing microprocessor control of actuation and Bluetooth wireless communication through an Android application. The results of in vitro characterization indicated that nanoliter resolution control over the desired flow rates of 10-100 nL/min was obtained by changing the actuation frequency. Applying 10× greater than physiological backpressures and ± 3 °C ambient temperature variation did not significantly affect flow rates. Three different micropumps were tested on six mice for in vivo implantation of the catheter microtubing into the round window membrane niche for infusion of a known ototoxic compound (sodium salicylate) at 50 nL/min for 20 min. Real-time shifts in distortion product otoacoustic emission thresholds and amplitudes were measured during the infusion. There were systematic increases in distortion product threshold shifts during the 20-min perfusions; the mean shift was 15 dB for the most basal region. A biocompatibility study was performed to evaluate material suitability for chronic subcutaneous implantation and clinical translational development. The results indicated that the micropump components successfully passed key biocompatibility tests. A micropump prototype was implanted for one month without development of inflammation or infection. Although tested here on the small murine cochlea, this low-cost design and fabrication methodology is scalable for use in larger animals and for clinical applications in children and adults by appropriate scaling of the microtubing diameter and actuator volume.

Intracochlear drug delivery: Fluorescent tracer evaluation for quantification of distribution in the cochlear partition

Measurement of drug distribution in the inner ear has important roles in the design of local delivery methods, such as direct, intracochlear delivery, and in assessment of emerging drug candidates in preclinical animal models. Sampling methods have been used in the past to measure drug concentrations in the cochlear fluids, but these methods provide no direct information about drug distribution in the cochlear tissues. In this work, we evaluated four fluorescent markers that simulate drug distribution in the organ of Corti after intracochlear delivery to the cochlea's scala tympani compartment. Our hypothesis is that ultimately, a cocktail comprising several fluorescent drug surrogates or fluorescently-tagged drugs, each with differing distribution, spreading, and clearance behavior, can be used to evaluate both transient and cumulative drug distributions associated with different delivery techniques. In this study, FITC-dextran, Qtracker™ 655, gentamicin Texas-Red, and FM 1-43 FX were each evaluated as candidate markers by direct intracochlear infusion into guinea-pig cochleae. Distribution of the markers was measured using fluorescence confocal microscopy imaging of cochlear whole mount dissections from animals sacrificed 3 h after the tracer-infusion. For all four tracers, strong fluorescence was observed in the tissue sections near the base, but only Qtracker™-655, gentamicin Texas-Red (GTTR) and FM 1-43 FX exhibited any specificity in labelling of the sensory hair cells. Therefore, these substances represent leading candidates for the quantification drug distribution achieved by different delivery approaches to the scala tympani.

Animal model studies yield translational solutions for cochlear drug delivery

The field of hearing and deafness research is about to enter an era where new cochlear drug delivery methodologies will become more innovative and plentiful. The present report provides a representative review of previous studies where efficacious results have been obtained with animal models, primarily rodents, for protection against acute hearing loss such as acoustic trauma due to noise overexposure, antibiotic use and cancer chemotherapies. These approaches were initiated using systemic injections or oral administrations of otoprotectants. Now, exciting new options for local drug delivery, which opens up the possibilities for utilization of novel otoprotective drugs or compounds that might not be suitable for systemic use, or might interfere with the efficacious actions of chemotherapeutic agents or antibiotics, are being developed. These include interesting use of nanoparticles (with or without magnetic field supplementation), hydrogels, cochlear micropumps, and new transtympanic injectable compounds, sometimes in combination with cochlear implants.

Wearables in Medicine

Wearables as medical technologies are becoming an integral part of personal analytics, measuring physical status, recording physiological parameters, or informing schedule for medication. These continuously evolving technology platforms do not only promise to help people pursue a healthier life style, but also provide continuous medical data for actively tracking metabolic status, diagnosis, and treatment. Advances in the miniaturization of flexible electronics, electrochemical biosensors, microfluidics, and artificial intelligence algorithms have led to wearable devices that can generate real-time medical data within the Internet of things. These flexible devices can be configured to make conformal contact with epidermal, ocular, intracochlear, and dental interfaces to collect biochemical or electrophysiological signals. This article discusses consumer trends in wearable electronics, commercial and emerging devices, and fabrication methods. It also reviews real-time monitoring of vital signs using biosensors, stimuli-responsive materials for drug delivery, and closed-loop theranostic systems. It covers future challenges in augmented, virtual, and mixed reality, communication modes, energy management, displays, conformity, and data safety. The development of patient-oriented wearable technologies and their incorporation in randomized clinical trials will facilitate the design of safe and effective approaches.

Photopatternable Magnetic Hollowbots by Nd-Fe-B Nanocomposite for Potential Targeted Drug Delivery Applications

In contrast to traditional drug administration, targeted drug delivery can prolong, localize, target and have a protected drug interaction with the diseased tissue. Drug delivery carriers, such as polymeric micelles, liposomes, dendrimers, nanotubes, and so on, are hard to scale-up, costly, and have short shelf life. Here we show the novel fabrication and characterization of photopatternable magnetic hollow microrobots that can potentially be utilized in microfluidics and drug delivery applications. These magnetic hollowbots can be fabricated using standard ultraviolet (UV) lithography with low cost and easily accessible equipment, which results in them being easy to scale up, and inexpensive to fabricate. Contact-free actuation of freestanding magnetic hollowbots were demonstrated by using an applied 900 G external magnetic field to achieve the movement control in an aqueous environment. According to the movement clip, the average speed of the magnetic hollowbots was estimated to be 1.9 mm/s.

A fluorescence-based imaging approach to pharmacokinetic analysis of intracochlear drug delivery

Advances in microelectromechanical systems (MEMS) technologies are enhancing the development of intracochlear delivery devices for the treatment of hearing loss with emerging pharmacological therapies. Direct intracochlear delivery addresses the limitations of systemic and intratympanic delivery. However, optimization of delivery parameters for these devices requires pharmacokinetic assessment of the spatiotemporal drug distribution inside the cochlea. Robust methods of measuring drug concentration in the perilymph have been developed, but lack spatial resolution along the tonotopic axis or require complex physiological measurements. Here we describe an approach for quantifying distribution of fluorescent drug-surrogate probe along the cochlea's sensory epithelium with high spatial resolution enabled by confocal fluorescence imaging. Fluorescence from FM 1-43 FX, a fixable endocytosis marker, was quantified using confocal fluorescence imaging of whole mount sections of the organ of Corti from cochleae resected and fixed at several time points after intracochlear delivery. Intracochlear delivery of FM 1-43 FX near the base of the cochlea produces a base-apex gradient of fluorescence in the row of inner hair cells after 1 h post-delivery that is consistent with diffusion-limited transport along the scala tympani. By 3 h post-delivery there is approximately an order of magnitude decrease in peak average fluorescence intensity, suggesting FM 1-43 FX clearance from both the perilymph and inner hair cells. The increase in fluorescence intensity at 72 h post-delivery compared to 3 h post-delivery may implicate a potential radial transport pathway into the scala media.

Closed-loop feedback control for microfluidic systems through automated capacitive fluid height sensing

Precise fluid height sensing in open-channel microfluidics has long been a desirable feature for a wide range of applications. However, performing accurate measurements of the fluid level in small-scale reservoirs (<1 mL) has proven to be an elusive goal, especially if direct fluid-sensor contact needs to be avoided. In particular, gravity-driven systems used in several microfluidic applications to establish pressure gradients and impose flow remain open-loop and largely unmonitored due to these sensing limitations. Here we present an optimized self-shielded coplanar capacitive sensor design and automated control system to provide submillimeter fluid-height resolution (∼250 μm) and control of small-scale open reservoirs without the need for direct fluid contact. Results from testing and validation of our optimized sensor and system also suggest that accurate fluid height information can be used to robustly characterize, calibrate and dynamically control a range of microfluidic systems with complex pumping mechanisms, even in cell culture conditions. Capacitive sensing technology provides a scalable and cost-effective way to enable continuous monitoring and closed-loop feedback control of fluid volumes in small-scale gravity-dominated wells in a variety of microfluidic applications.

A portable and reconfigurable multi-organ platform for drug development with onboard microfluidic flow control

The drug development pipeline is severely limited by a lack of reliable tools for prediction of human clinical safety and efficacy profiles for compounds at the pre-clinical stage. Here we present the design and implementation of a platform technology comprising multiple human cell-based tissue models in a portable and reconfigurable format that supports individual organ function and crosstalk for periods of up to several weeks. Organ perfusion and crosstalk are enabled by a precision flow control technology based on electromagnetic actuators embedded in an arrayed format on a microfluidic platform. We demonstrate two parallel circuits of connected airway and liver modules on a platform containing 62 electromagnetic microactuators, with precise and controlled flow rates as well as functional biological metrics over a two week time course. Technical advancements enabled by this platform include the use of non-sorptive construction materials, enhanced scalability, portability, flow control, and usability relative to conventional flow control modes (such as capillary action, pressure heads, or pneumatic air lines), and a reconfigurable and modular organ model format with common fluidic port architecture. We demonstrate stable biological function for multiple pairs of airway-liver models for periods of 2 weeks in the platform, with precise control over fluid levels, temperature, flow rate and oxygenation in order to support relevant use cases involving drug toxicity, efficacy testing, and organ-organ interaction.