Targeted intracranial delivery of molecularly-specific therapies within intricate brain structures poses a formidable challenge due to the heterogeneity of neuronal phenotypes and functions. Here we report the use of an implantable, miniaturized neural drug delivery system permitting dynamic adjustment of pharmacotherapies. Specifically, we exploit the spatial accuracy afforded by this method for targeting modulation of neuronal microstructures. Kappa opioid receptors (KOR) within the dorsal medial nucleus accumbens shell (NASh) are selectively activated through micro infusions of the KOR agonist, U-50488. Remarkably, we demonstrate that micro infusions of U-50488 into the dorsal NASh induces reward-like conditioned place preferences, whereas a mere 1 mm shift ventrally results in conditioned place aversions. The striking precision afforded by this method may prove useful in other neurotherapeutic interventions.

Focal epilepsy is a difficult disease to treat as two-thirds of patients will not respond to oral anti-seizure medications (ASMs) or have severe off-target effects that lead to drug discontinuation. Current non-pharmaceutical treatment methods (resection or ablation) are underutilized due to the associated morbidities, invasive nature and inaccessibility of seizure foci. Less invasive non-ablative modalities may potentially offer an alternative. Targeting the seizure focus in this way may avoid unassociated critical brain structures to preserve function and alleviate seizure burden.Here we report use of an implantable, miniaturized neural drug delivery system [microinvasive neural implant infusion platform (MINI)] to administer ASMs directly to the seizure focus in a mouse model of temporal lobe epilepsy. We examined the effect local delivery of phenobarbital and valproate had on focal seizures, as well as adverse effects, and compared this to systemic delivery.We show that local delivery of phenobarbital and valproate using our chronic implants significantly reduced focal seizures at all doses given. Furthermore, we show that local delivery of these compounds resulted in no adverse effects to motor function, whereas systemic delivery resulted in significant motor impairment.The results of this study demonstrate the potential of ASM micro dosing to the epileptic focus as a treatment option for people with drug resistant epilepsy. This technology could also be applied to a variety of disease states, enabling a deeper understanding of focal drug delivery in the treatment of neurological disorders. Jackson et al. study the effects of local delivery of anti-seizure medications to the seizure focus in a mouse model of temporal lobe epilepsy. They show that focal seizures can be suppressed, and adverse effects can be minimized with local delivery of these drugs.

Magnetic resonance (MR) imaging is a powerful clinical tool for the detection of soft tissue morphology and pathology, which often provides actionable diagnostic information to clinicians. Its clinical use is largely limited due to size, cost, time, and space constraints. Here, we discuss the design and performance of a low-field single-sided MR sensor intended for point-of-care (POC) evaluation of skeletal muscle in vivo. The 11kg sensor has a penetration depth of > 8 mm, which allows for an accurate analysis of muscle tissue and can avoid signal from more proximal layers, including subcutaneous adipose tissue. Low operational power and minimal shielding requirements are achieved through the design of a permanent magnet array and surface transceiver coil. We present the in vitro and human in vivo performance of the device for muscle tissue evaluation. The sensor can acquire high signal-to-noise (SNR > 150) measurements in minutes, making it practical as a POC tool for many quantitative diagnostic measurements, including T2 relaxometry.

Damage that affects large volumes of skeletal muscle tissue can severely impact health, mobility, and quality-of-life. Efforts to restore muscle function by implanting tissue engineered muscle grafts at the site of damage have demonstrated limited restoration of force production. Various forms of mechanical and biochemical stimulation have been shown to have a potentially beneficial impact on graft maturation, vascularization, and innervation. However, these approaches yield unpredictable and incomplete recovery of functional mobility. Here we show that targeted actuation of implanted grafts, via non-invasive transcutaneous light stimulation of optogenetic engineered muscle, restores motor function to levels similar to healthy mice 2 weeks post-injury. Furthermore, we conduct phosphoproteomic analysis of actuated engineered muscle in vivo and in vitro to show that repeated muscle contraction alters signaling pathways that play key roles in skeletal muscle contractility, adaptation to injury, neurite growth, neuromuscular synapse formation, angiogenesis, and cytoskeletal remodeling. Our study uncovers changes in phosphorylation of several proteins previously unreported in the context of muscle contraction, revealing promising mechanisms for leveraging actuated muscle grafts to restore mobility after volumetric muscle loss.

We developed a flexible “electrode-thread” array for recording dopamine neurochemical activity from a lateral distribution of subcortical targets (up to 16) transverse to the axis of insertion. Ultrathin (∼ 10 µm diameter) carbon fiber (CF) electrode-threads (CFETs) are clustered into a tight bundle to introduce them into the brain from a single entry point. The individual CFETs splay laterally in deep brain tissue during insertion due to their innate flexibility. This spatial redistribution allows navigation of the CFETs towards deep brain targets spreading horizontally from the axis of insertion. Commercial “linear” arrays provide single entry insertion but only allow measurements along the axis of insertion. Horizontally configured neurochemical recording arrays inflict separate penetrations for each individual channel (i.e., electrode). We tested functional performance of our CFET arrays in vivo for recording dopamine neurochemical dynamics and for providing lateral spread to multiple distributed sites in the striatum of rats. Spatial spread was further characterized using agar brain phantoms to measure electrode deflection as a function of insertion depth. We also developed protocols to slice the embedded CFETs within fixed brain tissue using standard histology techniques. This method allowed extraction of the precise spatial coordinates of the implanted CFETs and their recording sites as integrated with immunohistochemical staining for surrounding anatomical, cytological, and protein expression labels. Neurochemical recording operations tested here can be integrated with already widely established capabilities of CF-based electrodes to record single neuron activity and local field potentials, to enable multi-modal recording functions. Our CFET array has the potential to unlock a wide range of applications, from uncovering the role of neuromodulators in synaptic plasticity, to addressing critical safety barriers in clinical translation towards diagnostic and adaptive treatment in Parkinson’s disease and major mood disorders.

A low-field portable MR-based sensor was fabricated for the acquisition of clinical T2 relaxometry measurements in skeletal muscle. We have previously reported methods for designing low-field permanent magnet array configurations with varying sensitive region profiles. The newly constructed array has a sensitive region 15-20mm from the surface of the magnet; field maps from the constructed magnet show good alignment with simulated fields. The exclusion of subcutaneous fat tissue in the sensitive region will improve sensitivity to fluid shifts within the skeletal muscle.

Long-term treatment outcomes for patients with high grade ovarian cancers have not changed despite innovations in therapies. There is no recommended assay for predicting patient response to second-line therapy, thus clinicians must make treatment decisions based on each individual patient. Patient-derived xenograft (PDX) tumors have been shown to predict drug sensitivity in ovarian cancer patients, but the time frame for intraperitoneal (IP) tumor generation, expansion, and drug screening is beyond that for tumor recurrence and platinum resistance to occur, thus results do not have clinical utility. We describe a drug sensitivity screening assay using a drug delivery microdevice implanted for 24 h in subcutaneous (SQ) ovarian PDX tumors to predict treatment outcomes in matched IP PDX tumors in a clinically relevant time frame. The SQ tumor response to local microdose drug exposure was found to be predictive of the growth of matched IP tumors after multi-week systemic therapy using significantly fewer animals (10 SQ vs 206 IP). Multiplexed immunofluorescence image analysis of phenotypic tumor response combined with a machine learning classifier could predict IP treatment outcomes against three second-line cytotoxic therapies with an average AUC of 0.91.

Dopamine governs key behavioral processes including motivation, learning, and habit formation. Neurochemical monitoring of dopamine is necessary to identify its role in normal and pathologic conditions and in order to identify targets for treatment and to improve diagnosis. Recent advances have made it possible to record subsecond dopamine release over extended time frames (>months), opening up the possibility to evaluate dopamine's role over behavioral adaptation, learning, neurodegeneration, and other behavioral processes that take longer than a few hours. Key innovations that we have introduced involve miniaturizing implanted probe dimensions to the size of individual neurons in order to avert inflammatory responses that can restrict chronic viability and sensitivity as well as limit the feasibility of introducing multiple probes into the brain. The purpose of this chapter is to describe methods to fabricate these sensors and to implement them in rodents for the recording of dopamine release over extended periods of time.

Micro-invasive platform performs label-free liquid biopsies of the brain, enabling in vivo tracking of proteins and peptides.

The vast majority of techniques to study the physiology of the nervous system involve inserting probes into the brain for stimulation, recording, or sampling. Research is increasingly uncovering the fine microstructure of the brain, each of its regions with dedicated functions. Accurate knowledge of the placement of probes interrogating these regions is critical. We have developed a customizable concentric marking electrode (CME) consisting of an iron core within a 125 μm-stainless steel (SS) sheath for co-localization of targeted regions in the brain. We used a dielectric layer stack of SiO2, Al2O3, SiO2 to electrically encapsulate the iron core and minimize exposure area to avoid significant increases in inflammatory response triggered by the probes. The CME can record multi-neuronal extracellular firing patterns. Appropriate electrical polarity of the iron and SS components controls the deposition of iron microdeposits on brain tissue. We show that in vivo labels by this method can be as small as 100 μm, visible via noninvasive magnetic resonance imaging (MRI) as well as post-mortem histology, and illustrate how deposit size can be tuned by varying stimulus parameters. We targeted the CA3 area of the hippocampus in adult rats and demonstrate that iron microdeposits are remarkably stable and persist up to 10 months post-deposition. Using a single probe for recording and marking avoids inaccuracies with re-insertion of separate probes and utilizes iron microdeposits as valuable fiducial markers in vivo and ex vivo.

Introduction: Harnessing the diversity of sensing platforms for applications in complex environments has been an ongoing challenge in biosensing. Most techniques exhibit limitations ranging from biocompatibility, sensitivity, and signal transduction through opaque media, to longevity under non-laboratory conditions. Through multidisciplinary advances in nanoscience and medical devices, we have developed an implant for the measurement of biomarkers using a magnetic particle assay platform1,2. Exposure to target induces a switch from a dispersed to an assembled state with a corresponding change in magnetic relaxation properties allowing for robust contrast. Current applications focus on diagnostics in chronic cardiac disease and spikes in biomarker presence frequently missed by serial sampling. We address design parameters for sensing functionality, tunability, and degradation to lay the groundwork for multi-month implantation in vivo. Materials and Methods: Particle core materials provided magnetic contrast while biological functionality was tuned by surface ligands for affinity toward multivalent targets (Figure 1a). Polyclonal antibodies were conjugated to superparamagnetic iron oxide nanoparticles (20-50 nm) by maleimide-thiol chemistry. Proton Magnetic Relaxation measurements were acquired on a custom-made, single-sided, inhomogeneous field relaxometer (0.43 Tesla, 25°C, NMR MOUSE) fitted with a programmable robotic scanning stage3. A Carr-Purcell-Meiboom-Gill pulse sequence was used: TE = 0.035 ms, 5454 echoes, 15 scans, TR = 6 s. Relaxation times were determined by single exponential fit to echo peak intensities with a custom MATLAB script. Delrin diffusion devices were filled with particle colloidal suspension and sealed with 30 nm pore polycarbonate semi-permeable membranes via double-sided, pressure-sensitive adhesive (Figure 1b). Devices were exposed to target while sensor response was read every 90-120 minutes for up to 48 hrs. Degradation was measured by quantitating loss of ligand from the surface (ELISA) and changes in sensor performance after elevated temperature storage (37°C) for up to 12 weeks. Results and Discussion: Ligand valency was tuned over an order of magnitude (4-40 Antibodies/Particle) by varying bioconjugation strategies and reagents. Conjugation stability under standard storage conditions indicated a lifetime >5 months by isolating free from bound protein by centrifugation. A maximum 1% of conjugated ligand was released, minimally decreasing valency and sensor functionality. Assay performance showed prozone agglutination behavior with quantitative exposure ranging from 50-2000 ng/mL of target and contrast in <2 hrs. Device dosimeter performance was validated for a cardiac Myoglobin model. Saturation was tuned from 4 to 12 μg/mL*hrs corresponding with 8 to >24 hrs of continuous biomarker elevation at 0-500 ng/mL. 4 hr equilibration and irreversible dosimeter signal stability post-exposure for >12 hrs was also observed (Figure 1c). Biochemical and aggregation performance degradation parameters were evaluated. Over 6.5 weeks of elevated temperature storage, 1.8% of the conjugated antibody was unbound. Sensor longitudinal performance on exposure to target over 12 weeks of incubation showed a monotonically decreasing response magnitude and rate (Figure 1d). Exponential fit to sensor response decay curve predicts a 29 week “switch” (on/off) sensor lifetime for an infarction model (500 ng/mL Myo). These results indicate our sensor can be derivatized for a cardiac biomarker with usable sensitivity and saturation dosimeter response corresponding to elevations expected in a Myocardial Infarction (MI). Device performance can be tuned by matching sensor characteristics with the physiological range of target sensitivity and saturation desired. By tuning bioconjugation strategies we enhanced the performance of the biosensor by an order of magnitude over prior studies. Sensor lifetime and nanostructure degradation studies have shown the limiting performance factor is not the loss of ligand from the surface of the particles but rather the loss of binding activity as seen in elevated temperature experiments. Conclusions: This implant has the potential to broaden diagnostics in personalized medicine by addressing the hurdles of longevity and robust sensor signal stability in complex environments. In situ diagnostics offer continuous sentineling of critical biomarkers, providing a deeper understanding of local biology in dynamic, heterogeneous systems. This monitoring provides valuable timescale data to clinicians with insight into their patients’ lab results for early intervention and data collection throughout treatment. This implant has the capacity to bridge the gap between lab and clinical grade sensors, significantly improving interventional medicine by leveraging the robust and tunable nature of magnetic relaxation particle assays. References: Daniel KD, Kim GY, Vassiliou CC, et al. Implantable diagnostic device for cancer monitoring. Biosens Bioelectron. 2009;24:3252-3257. doi:10.1016/j.bios.2009.04.010 Ling Y, Pong T, Vassiliou CC, Huang PL, Cima MJ. Implantable magnetic relaxation sensors measure cumulative exposure to cardiac biomarkers. Nat Biotechnol. 2011;29(3):273-277. doi:10.1038/nbt.1780 Blumich B, Blumler P, Eidmann G, et al. The NMR-MOUSE: Construction, Excitation, and Applications. Magn Reson Imaging. 1998;16(98):479-484. Figure 1

Low-cost non-invasive diagnostic tools for staging the progression of non-alcoholic chronic liver failure from fatty liver disease to steatohepatitis are unavailable. Here, we describe the development and performance of a portable single-sided magnetic-resonance sensor for grading liver steatosis and fibrosis using diffusion-weighted multicomponent T2 relaxometry. In a diet-induced mouse model of non-alcoholic fatty liver disease, the sensor achieved overall accuracies of 92% (Cohen’s kappa, κ = 0.89) and 86% ( κ = 0.78) in the ex vivo grading of steatosis and fibrosis, respectively. Localization of the measurements in living mice through frequency-dependent spatial encoding led to an overall accuracy of 87% ( κ = 0.81) for the grading of steatosis. In human liver samples, the sensor graded steatosis with an overall accuracy of 93% ( κ = 0.88). The use of T2 relaxometry as a sensitive measure in fully automated low-cost magnetic-resonance devices at the point of care would alleviate the accessibility and cost limits of magnetic-resonance imaging for diagnosing liver disease and assessing liver health before liver transplantation.

Treatments for neurologic diseases are often limited in efficacy due to poor spatial and temporal control over their delivery. Intracerebral delivery partially overcomes this by directly infusing therapeutics to the brain. Brain structures, however, are nonuniform and irregularly shaped, precluding complete target coverage by a single bolus without significant off-target effects and possible toxicity. Nearly complete coverage is crucial for effective modulation of these structures. We present a framework with computational mapping algorithms for neural drug delivery (COMMAND) to guide multi-bolus targeting of brain structures that maximizes coverage and minimizes off-target leakage. Custom-fabricated chronic neural implants leverage rational fluidic design to achieve multi-bolus delivery in rodents through a single infusion of radioactive tracer (Cu-64). The resulting spatial distributions replicate computed spatial coverage with 5% error in vivo, as detected by positron emission tomography. COMMAND potentially enables accurate, efficacious targeting of discrete brain regions.

Hypoxia is a poor prognostic factor in multiple tumor types. Hypoxic tumors are more resistant to radiation and chemotherapy and are more likely to develop distant metastases. Radiation resistance is of particular interest in cervical cancer, as baseline tumor hypoxia has been shown to be prognostic for local failure and survival in patients treated with primary radiotherapy.1 In vivo studies have shown that radiation resistance may be overcome by increasing the delivered radiation dose by a factor of 2-3. MR-based HDR brachytherapy is well suited for localized dose escalation in hypoxic tumor sub-volumes given the ability to modulate the dose distribution while respecting normal tissue constraints. Currently available clinical techniques for measuring hypoxia are qualitative and limited by poor sensitivity. Meaningful modulation of dose distribution will require an MRI-compatible quantitative oxygen sensor capable of repeated measurements throughout the duration of treatment.

There is widespread research and popular interest in developing micro-invasive neural interfacing modalities. An increasing variety of probes have been developed and reported in the literature. Newer, smaller probes show significant benefit over larger ones in reducing tissue damage and scarring. A different set of obstacles arise, however, as probes become smaller. These include reliable insertion and robustness. This review articulates the impact of various design parameters (material, geometry, size) on probe insertion mechanisms, chronic viability, and glial scarring. We highlight various emerging technologies utilizing novel form factors including micron-scale interfaces and bio-inspired designs for probe insertion and steering.

Enhanced understanding of neuropathologies has created a need for more advanced tools. Current neural implants result in extensive glial scarring and are not able to highly localize drug delivery due to their size. Smaller implants reduce surgical trauma and improve spatial resolution, but such a reduction requires improvements in device design to enable accurate and chronic implantation in subcortical structures. Flexible needle steering techniques offer improved control over implant placement, but often require complex closed-loop control for accurate implantation. This study reports the development of steerable microinvasive neural implants (S-MINIs) constructed from borosilicate capillaries (OD = 60 µm, ID = 20 µm) that do not require closed-loop guidance or guide tubes. S-MINIs reduce glial scarring 3.5-fold compared to prior implants. Bevel steered needles are utilized for open-loop targeting of deep-brain structures. This study demonstrates a sinusoidal relationship between implant bevel angle and the trajectory radius of curvature both in vitro and ex vivo. This relationship allows for bevel-tipped capillaries to be steered to a target with an average error of 0.23 mm ± 0.19 without closed-loop control. Polished microcapillaries present a new microinvasive tool for chronic, predictable targeting of pathophysiological structures without the need for closed-loop feedback and complex imaging.

Kidney stones and ureteral stents can cause ureteral colic and pain. By decreasing contractions in the ureter, clinically prescribed oral vasodilators may improve spontaneous stone passage rates and reduce the pain caused by ureteral stenting. We hypothesized that ureteral relaxation can be improved via the local administration of vasodilators and other smooth muscle relaxants. Here, by examining 18 candidate small molecules in an automated screening assay to determine the extent of ureteral relaxation, we show that the calcium channel blocker nifedipine and the Rho-kinase inhibitor ROCKi significantly relax human ureteral smooth muscle cells. We also show, by using ex vivo porcine ureter segments and sedated pigs that, with respect to the administration of a placebo, the local delivery of a clinically deployable formulation of the two drugs reduced ureteral contraction amplitude and frequency by 90% and 50%, respectively. Finally, we show that standard oral vasodilator therapy reduced contraction amplitude by only 50% and had a minimal effect on contraction frequency. Locally delivered ureteral relaxants therefore may improve ureter-related conditions.

Magnetic resonance imaging (MRI) is a powerful diagnostic tool, but its use is restricted to the scanner suite. Here, we demonstrate that a bedside nuclear magnetic resonance (NMR) sensor can assess fluid status changes in individuals at a fraction of the time and cost compared to MRI. Our study recruited patients with end-stage renal disease (ESRD) who were regularly receiving hemodialysis treatments with intradialytic fluid removal as a model of volume overload and healthy controls as a model of euvolemia. Quantitative T 2 measurements of the lower leg of patients with ESRD immediately before and after dialysis were compared to those of euvolemic healthy controls using both a 0.28-T bedside single-voxel NMR sensor and a 1.5-T clinical MRI scanner. In the MRI data, we found that the first sign of fluid overload was an expanded muscle extracellular fluid (ECF) space, a finding undetectable at this stage using physical exam. A decrease in muscle ECF upon fluid removal was similarly detectable with both the bedside sensor and MRI. Bioimpedance measurements performed comparably to the bedside NMR sensor but were generally worse than MRI. These findings suggest that bedside NMR may be a useful method to identify fluid overload early in patients with ESRD and potentially other hypervolemic patient populations.

Purpose Recently developed implantable microdevices can perform multi-drug response assessment of cancer drugs in-vivo, with potential to develop highly optimized personalized cancer treatment strategies. However, minimally invasive/interventional image-guided methods of in-vivo microdevice implantation, securement, and retrieval are needed for broad clinical translation. Here we demonstrate proof-of-concept of an interventional microdevice implantation and retrieval method for personalized drug response assessment, using ex-vivo phantom, ex-vivo tissue, and in-vivo murine models. Methods A method for minimally-invasive microdevice implantation and retrieval was developed, by which a custom-prototyped 6 mm retrievable microdevice can be implanted into a live tumor, deliver drugs into 10 discrete regions of adjacent tissue, and retrieved along with the adjacent drug-exposed tissue with a custom-prototyped retrieval needle device to allow in-vivo multi-drug response assessment. Computed tomography (CT) and ultrasound (US)-guided minimally invasive microdevice implantation and retrieval were tested in ex-vivo phantom and tissue models. Successful retrieval was defined as retrieval of the microdevice and adjacent core phantom/tissue sample containing at least 4/10 drug delivery sites. Subsequently, 10 implantation and retrieval trials in phantom models were performed using bi-axial and tri-axial retrieval needles; success rates were calculated and compared using a two-proportion z-test and the number of successfully retrieved drug release sites per microdevice was calculated and compared using a one-tailed independent t-test. Finally, five microdevices, each containing ten reservoirs preloaded with chemotherapy agent Doxorubicin, were implanted into mouse tumors in-vivo, secured for 24-h during drug release, and microdevice/tissue retrieval was performed under ultrasound guidance. Fluorescence microscopy of the retrieved tissue was used to confirm drug delivery and apoptosis staining assessed in-vivo tissue response; correlation of drug release and apoptosis staining were used to assess in-vivo drug efficacy. Results Image-guided microdevice implantation and retrieval were successful in ex-vivo phantom and tissue models with both US and CT guidance. Bi-axial retrieval success rate was significantly higher than triaxial retrieval in ex-vivo phantom trials (90% vs 50%, z = 1.95, P = 0.026), and had nonsignificantly higher number of retrieved drug-release sites per microdevice (8.3 vs 7.0, t = 1.37, P = 0.097). Bi-axial retrieval was successful in all five in-vivo mouse tumor models, and allowed in-vivo drug response assessment at up to ten discrete drug delivery sites per microdevice. An average of 6.8/10 discrete tumor sites containing micro-doses of delivered drug were retrieved per in-vivo attempt (min 5, max 10, std 1.93). Tissue regions of drug delivery, as assessed with fluorescent Doxorubicin drug signal, correlated with regions of apoptosis staining in all in-vivo models, indicating drug efficacy. No bleeding, microdevice migration, or other complications were noted during implantation, 24-h observation, or retrieval.Conclusions The demonstrated image-guided minimally invasive microdevice implantation and retrieval method is similar to routine outpatient biopsy procedures, obviates the need for surgery, and can be performed at varying depths under CT and/or US guidance. There is potential for this method to enable clinical translation of in-vivo personalized drug response assessment/prediction in a much larger number of patients than currently possible.