Showing papers by "Mark S. Humayun published in 2012"

Systems and methods for in vitro and in vivo imaging of cells on a substrate

Abstract: Disclosed herein are generally to methods and systems that facilitate imaging of cells on a substrate and more particularly to pre-implantation (in vitro) and post-implantation (in vivo) imaging of cell-seeded substrates implanted in target tissues in the context of stem cell therapy.

Frequency and amplitude modulation have different effects on the percepts elicited by retinal stimulation.

Abstract: PURPOSE. In an effort to restore functional form vision, epiretinal prostheses that elicit percepts by directly stimulating remaining retinal circuitry were implanted in human subjects with advanced retinitis pigmentosa RP). In this study, manipulating pulse train frequency and amplitude had different effects on the size and brightness of phosphene appearance. METHODS. Experiments were performed on a single subject with severe RP (implanted with a 16-channel epiretinal prosthesis in 2004) on nine individual electrodes. Psychophysical techniques were used to measure both the brightness and size of phosphenes when the biphasic pulse train was varied by either modulating the current amplitude (with constant frequency) or the stimulating frequency (with constant current amplitude). RESULTS. Increasing stimulation frequency always increased brightness, while having a smaller effect on the size of elicited phosphenes. In contrast, increasing stimulation amplitude generally increased both the size and brightness of phosphenes. These experimental findings can be explained by using a simple computational model based on previous psychophysical work and the expected spatial spread of current from a disc electrode. CONCLUSIONS. Given that amplitude and frequency have separable effects on percept size, these findings suggest that frequency modulation improves the encoding of a wide range of brightness levels without a loss of spatial resolution. Future retinal prosthesis designs could benefit from having the flexibility to manipulate pulse train amplitude and frequency independently (clinicaltrials.gov number, NCT00279500). (Invest Ophthalmol Vis Sci. 2012;53:205‐214) DOI:10.1167/iovs.118401

Mesh-supported submicron parylene-C membranes for culturing retinal pigment epithelial cells

Abstract: In this work, a mesh-supported submicron parylene-C membrane (MSPM) is proposed as an artificial Bruch's membrane for the therapy of age-related macular degeneration (AMD). Any artificial Bruch's membrane must first satisfy two important requirements. First, it should be as permeable as healthy human Bruch's membrane to support nutrients transportation. Secondly, it should be able to support the adherence and proliferation of retinal pigment epithelial (RPE) cells with in vivo-like morphologies and functions. Although parylene-C is widely used as a barrier layer in many biomedical applications, it is found that parylene-C membranes with submicron thickness are semipermeable to macromolecules. We first measure the permeability of submicron parylene-C and find that 0.15-0.30 μm parylene-C has similar permeability to healthy human Bruch's membranes. Blind-well perfusion cell viability experiments further demonstrate that nutrients and macromolecules can diffuse across 0.30 μm parylene-C to nourish the cells. A mesh-supported submicron parylene-C membrane (MSPM) structure is design to enhance the mechanical strength of the substrate. In vitro cells culture on the MSPM (with 0.30 μm ultrathin parylene-C) shows that H9-RPE cells are able to adhere, proliferate, form epithelial monolayer with tight intracellular junctions, and become well-polarized with microvilli, which exhibit similar characteristics to RPE cells in vivo. These studies have demonstrated the potential of the MSPM as an artificial Bruch's membrane for RPE cell transplantation.

A novel approach for subretinal implantation of ultrathin substrates containing stem cell-derived retinal pigment epithelium monolayer.

Abstract: Objective: To evaluate the feasibility of a new technique for the implantation of ultrathin substrates containing stem cell-derived retinal pigment epithelium (RPE) cells into the subretinal space of retina-degenerate Royal College of Surgeon (RCS) rats. Methods: A platform device was used for the implantation of 4-µm-thick parylene substrates containing a monolayer of human embryonic stem cell-derived RPE (hESC-RPE). Normal Copenhagen rats (n = 6) and RCS rats (n = 5) were used for the study. Spectral-domain optical coherence tomography (SD-OCT) scanning and histological examinations were performed to confirm placement location of the implant. hESC-RPE cells attached to the substrate before and after implantation were evaluated using standard cell counting techniques. Results: SD-OCT scanning and histological examination revealed that the substrates were precisely placed in the rat's subretinal space. The hESC-RPE cell monolayer that covered the surface of the substrate was found to be intact after implantation. Cell counting data showed that less than 2% of cells were lost from the substrate due to the implantation procedure (preimplantation count 2,792 ± 74.09 cells versus postimplantation count 2,741 ± 62.08 cells). Detailed microscopic examination suggested that the cell loss occurred mostly along the edges of the implant. Conclusion: With the help of this platform device, it is possible to implant ultrathin substrates containing an RPE monolayer into the rat's subretinal space. This technique can be a useful approach for stem cell-based tissue bioengineering techniques in retinal transplantation research.

Accommodating intraocular lens

Abstract: Systems, devices, and methods are presented for a prosthetic injectable intraocular lens. The lenses can be made from silicone, fluorosilicone, and phenyl substituted silicone and be semipermeable to air. One or more silicone elastomeric patches located outside the optical path on the anterior side but away from the equator can be accessed by surgical needles in order to fill or adjust optically clear fluid within the lens. The fluid can be adjusted in order to set a base dioptric power of the lens and otherwise adjust a lens after its initial insertion. The elastomeric patches are sized so that they self-seal after a needle is withdrawn. A straight or stepped slit in the patch can allow a blunt needle to more easily access the interior of the lens.

Scanning Endoscopic Imaging Probes and Related Methods

Abstract: An imaging probe may utilize a suitably shaped lens structure to deflect light off-axis, allowing for the acquisition of B-scans by rotary or reciprocating motion of the lens. In some embodiments, imaging probes are integrated into various medical-treatment devices.

Implantable drug pumps and refill devices therefor

Abstract: Implanted drug pump devices can be refilled with a refill needle inserted through a fill port in the drug reservoir of the drug pump device. Proper needle insertion may be verified visually or using electrical, magnetic, optical, acoustic, or other suitable sensing mechanisms.

Accurate flow control in drug pump devices

Abstract: The accuracy of drug delivery with drug pump devices may be improved by a combination of pump operation at high flow resistances and pump pressures, pressure-relief mechanisms, and sensor-based feedback for pump control.

Implantable intraocular pressure drain

Abstract: An implanted parylene tube shunt relieves intra-ocular pressure. The device is implanted with an open end in the anterior chamber of the eye, allowing excess fluid to be drained through the tube out of the eye. In one embodiment, only a first end of the tube implanted into the anterior chamber of the eye is open. Intra-ocular pressure (IOP) is then monitored, for example utilizing an implanted sensor. When IOP exceeds a critical valve, a practitioner intervenes, puncturing with a laser a thinned region of the tube lying outside the eye, thereby initiating drainage of fluid and relieving pressure. In accordance with alternative embodiments, the both ends of the tube are open, and the tube includes a one-way valve configured to permit drainage where IOP exceeds the critical value. The tube may include projecting barbs to anchor the tube in the eye without the need for sutures.

Filling and implanting accommodative intraocular lenses

Abstract: Advances in filling apparatus, handheld tools, surgical techniques and intraoperative biometry for implanting and adjusting an accommodative liquid lens are disclosed. The lens may be attached to or retained within a handheld surgical tool, which can be fluidly connectable to a filling console to fill the lens with a liquid. In various embodiments, a filling console facilitates aspirating liquid out of the lens in order to ensure the absence of residual bubbles and filling of the lens with fluid during surgery, as well as during post-operative adjustments to the lens. Actuated by the surgeon, the filling console can aspirate fluid from the lens and inject fluid into the lens following insertion thereof.

Ocular lens cutting device

Abstract: Ocular lens cutting devices and methods for cutting and removing tissue such as lens fragments from an eye of a patient are disclosed In one embodiment, an ocular lens cutting device includes an outer member and an inner member positioned within the outer member The outer member and the inner member can each include at least one cutting edge The at least one cutting edge of the outer member and the at least one cutting edge of the inner member can cooperate to form a cutting structure as the inner member moves with respect to the outer member The ocular lens cutting device can also be connected to a vacuum source which can allow the ocular lens cutting device to grasp the tissue to be cut and remove the cut fragments from the surgical area

Feeling the Pressure: A Parylene-Based Intraocular Pressure Sensor

Abstract: Intraocular pressure (IOP) is important for the prevention and treatment of certain human eye diseases. For example, glaucoma is the second leading cause of blindness in the world according to the World Health Organization [1]. The majority of glaucoma patients have an IOP >; 20 mmHg (compared with a normal IOP of 10 mmHg), which could damage patients optic nerves in the backside of the eye and cause irreversible blindness. Currently, there is no cure for glaucoma, but with early diagnosis and proper treatment, the visual loss can be slowed or eliminated. Due to the lack of other symptoms or pain, and the eye's ability to compensate for loss of peripheral vision, many glaucoma patients are unaware of the disease's development until it is severe. In fact, only half of the patients in the United States are aware of having glaucoma. Therefore, early diagnosis and treatment are important to prevent blindness. Thus, a device to diagnose early-stage glaucoma is in demand.

Method of cryopreservation of stem cell-derived retinal pigment epithelial cells on polymeric substrate

Abstract: Disclosed herein are methods and compositions for the cryopreservation of stem cells, such as stem-cell derived retinal pigment epithelial cells, that have been seeded onto and cultured on a substrate, such as a polymeric substrate. Such cryopreserved stem cells are useful for cell therapies, such as treatment of ocular damage or disease.

Instruments and methods for the implantation of cell-seeded substrates

Abstract: Disclosed herein are instruments and methods for delivery of substrates, including cell-seeded substrates, to target tissues requiring treatment for various diseases that induce cell death, damage or loss of function. The substrates are configured to provide cells, including stem cells, with a structural support that allows interconnection with and transmission of biological signals between the cells and the target tissue.

Acute variations in retinal vascular oxygen content in a rabbit model of retinal venous occlusion.

Abstract: Purpose: To study the variation in intravascular oxygen saturation (oximetry) during an acute retinal vein occlusion (RVO) using hyperspectral computed tomographic spectroscopy based oximetry measurements. Methods: Thirty rabbits were dilated and anesthetized for experiments. Baseline oximetry measurements were made using a custom-made hyperspectral computed tomographic imaging spectrometer coupled to a fundus camera. RVO were induced using argon green laser following an intravenous injection of Rose Bengal. RVO induction was confirmed by fluorescein angiography. Retinal oximetry measurements were repeated in arterial and venous branches one hour after RVO induction and up to 4 weeks afterwards. Comparison of retinal oximetry before and after vein occlusion was made using the Student T-test. Results: One hour after RVO induction, we observed statistically significant reductions in the intravascular oxygen saturation in temporal retinal arteries (85.166.1% vs. 80.666.6%; p,0.0001) and veins (71.465.5% vs. 64.064.7%; p,0.0001). This decrease was reversible in animals that spontaneously recannulated the vein occlusion. There were no statistically significant differences in oxygen saturation in the nasal control arteries and veins before and after temporal vein RVO induction. Conclusions: We demonstrate, for the first time, acute changes in the intravascular oxygen content of retinal vessels 1 hour after RVO. These changes are reversible upon spontaneous recannulation of retinal vessels. This study demonstrates that hyperspectral computer tomographic spectroscopy based oximetry can detect physiological variations in intravascular retinal oxygen saturation. The study also provides the first qualitative and quantitative evidence of the variation in retinal vascular oxygen content directly attributable to an acute retinal vein occlusion.

Flexible circuit electrode array for improved layer adhesion

Abstract: The present invention is a flexible circuit electrode array for improved layer adhesions where the metal conductors overlap the polymer insulator. The steps to build the flexible circuit are as follows. Deposit a base polymer layer. Deposit a conductive trace over the base polymer layer. Deposit a top polymer layer over the trace and prepare a void in the top polymer layer smaller than the surface of the trace. Deposit an electrode on the trace through the void with a periphery larger than, and overlapping the void.

Ocular ultrasound probe

Abstract: Devices, systems and methods for ocular ultrasound are provided having therapeutic and/or diagnostic applications. In one aspect, an ocular probe is disclosed that is uniquely configured for use in the eye on the basis of shape and frequency. The ocular probe may be multi-functional, providing sensor, optical or other functionality in additional to ultrasound energy.

Surgical implantation instrument

Abstract: Surgical introducers aid surgeons in the implantation of medical devices. The introducer provides support and an even distribution of force for ease of insertion and prevention of damage to the medical device while protecting the tissue into which the device is implanted. A representative embodiment includes or consists of a locking device, a pair of forceps, a specially configured and/or angled head with a seat for the device to be implanted, and a gripping area.

Fluorescein angiography, optical coherence tomography, and histopathologic findings in a VEGF(165) animal model of retinal angiogenesis.

Abstract: To establish an animal model of retinal neovascularization using vascular endothelial growth factor (VEGF165) and analyze the model using optical coherence tomography (OCT), fluorescein angiography (FA), and histopathologic evaluation. Twelve rabbits were divided into groups as follows: group 1 (n = 3), sham intravitreous injections of 0.1 ml of balanced saline; group 2 (n = 6), one 10-μg intravitreal injection of VEGF165 on day 0; and group 3 (n = 3), two 10-μg intravitreal injections of VEGF165, one on day 0 and one on day 7. Follow-up evaluations (days 0, 3, 7, 14, 21, 28) included obtaining fundus color photographs and FA, OCT, and histopathologic examinations. Eyes were enucleated and stained with hematoxylin and eosin (HE severe capillary nonperfusion was seen during week 4. At the end of the follow-up period, OCT and histopathologic examination of group 3 showed peripapillary tractional retinal detachments. By day 7, the differences between the retinal thickness seen on OCT in groups 2 and 3 and the group 1 control group were significant (p < 0.001). The histologic findings showed increased vessel size in groups 2 and 3 by days 14 and 28 compared with the controls. FA, OCT, and histopathologic findings showed that this retinal neovascularization model is efficient, sustainable, and reliable. One injection of VEGF165 created neovascularization that peaked after 1 week; two injections created more intense neovascularization that evolved to retinal detachments after 4 weeks.

A 3D parylene scaffold cage for culturing retinal pigment epithelial cells

Abstract: This work reports a 3D parylene scaffold cage for culturing stem-cell-differentiated retinal pigment epithelial (RPE) cells for the therapy of age-related macular degeneration, which is caused by degenerated permeability of the Bruch's membrane first and then the loss of RPE cells This reported cage can support sufficient nutrient permeation to nourish the RPE cells inside with in vivo like morphology Compared to previous single layer scaffold substrates, this cage can effectively prevent the undesirable cell migration away from the scaffold

Instrument and methods for filling an implanted drug pump

Abstract: A tool for refilling an implantable pump (100) having at least one reservoir (104). The tool includes a plurality of independent fluid channels (212, 214, 216); a fluid reservoir in fluid communication with a first one of the fluid channels; at least one pump fluidly coupled to the fluid channels, the at least one pump and the independent fluid channels differing from each other in number, wherein (i) a pump is configured to apply positive pressure to the first fluid channel so as to drive fluid from the fluid reservoir therethrough, and (ii) a pump is configured to apply negative pressure to the second fluid channel; and a connector (210) for removably connecting the fluid channels to the at least one reservoir.

Out of Darkness: Helping the Blind See with Artificial Vision

Abstract: Visual impairment is a major disability faced by millions around the world. People use sight to obtain information needed for mobility, reading, and motor skills, and thus loss of sight can severely restrict one's professional advancement and social interactions.

Evaluation of Ultrasound-Assisted Thrombolysis Using Custom Liposomes in a Model of Retinal Vein Occlusion

Abstract: Purpose. To study the potential efficacy of ultrasound (US) assisted by custom liposome (CLP) destruction as an innovative thrombolytic tool for the treatment of retinal vein occlusion (RVO).

High-resolution OCT: an innovative tool for posterior segment imaging.

Abstract: Optimal management of posterior segment disorders requires a high-resolution and preferably noninvasive imaging tool for better definition of diseases. High-resolution optical coherence tomography can provide noninvasive, high-definition imaging of the posterior segment, allowing earlier diagnosis, better follow-up of chronic cases, and more accurate and timely monitoring of the effect of therapeutic agents. Recent findings suggest an individualized approach to vitreoretinal and choroidal diseases is possible based not only on traditional ophthalmic investigations, but also on high-resolution optical coherence tomography. This innovative tool has the combined advantages of high speed, high resolution, and safe use.

Polymer scaffolds and their use in the treatment of vision loss

Abstract: The present invention provides for scaffolds for growing RPE cells, comprising two or more biodegradable polymers. The present invention also provides for methods for creating a scaffold for growing RPE cells. Additionally, the present invention provides for RGD peptide linked polymer scaffolds for supporting the growth of RPE cells. The present invention provides methods of culturing RPE cells using the scaffolds produced herein. The present invention also provides methods of treating vision loss through the administration of RPE cell attached RGD peptide linked polymer scaffolds produced herein. The present invention further provides kits for treating vision loss.