Biomedical subjects

W M Reichert

Publications and source records attributed to W M Reichert.

At least 19 recordsLinked to original sources

PubMed2000

Atomic force and total internal reflection fluorescence microscopy for the study of force transmission in endothelial cells.

This paper describes the combined use of atomic force microscopy (AFM) and total internal reflection fluorescence microscopy (TIRFM) to examine the transmission of force from the apical cell membrane to the basal cell membrane. A Bioscope AFM was mounted on an inverted microscope, the stage of which was configured for TIRFM imaging of fluorescently labeled human umbilical vein endothelial cells (HUVECs). Variable-angle TIRFM experiments were conducted to calibrate the coupling angle with the depth of penetration of the evanescent wave. A measure of cellular mechanical properties was obtained by collecting a set of force curves over the entire apical cell surface. A linear regression fit of the force-indentation curves to an elastic model yields an elastic modulus of 7.22 +/- 0. 46 kPa over the nucleus, 2.97 +/- 0.79 kPa over the cell body in proximity to the nucleus, and 1.27 +/- 0.36 kPa on the cell body near the edge. Stress transmission was investigated by imaging the response of the basal surface to localized force application over the apical surface. The focal contacts changed in position and contact area when forces of 0.3-0.5 nN were applied. There was a significant increase in focal contact area when the force was removed (p < 0.01) from the nucleus as compared to the contact area before force application. There was no significant change in focal contact coverage area before and after force application over the edge. The results suggest that cells transfer localized stress from the apical to the basal surface globally, resulting in rearrangement of contacts on the basal surface.

Biophysical Phenomena↗

PubMed1999

Role of endothelial cell-substrate contact area and fibronectin-receptor affinity in cell adhesion to HEMA/EMA copolymers.

The objective of this study was to examine the effect of substrate hydrophobicity on cell-substrate contact area and the affinity between adsorbed fibronectin (Fn) and its receptor. Homo- and copolymer films of hydrophobic ethyl methacrylate (EMA) and hydrophilic hydroxyethyl methacrylate (HEMA) were spun-cast onto glass slides. Bovine aortic endothelial cells (BAEC) were plated for 2 h in serum-free medium onto polymers preadsorbed with Fn. Cells were fixed, labeled, and examined by total internal reflection fluorescence microscopy (TIRFM) to determine the topography of the basal surface as a function of distance from the substrate. Phase contrast microscopy was used to examine the total projected area of adherent cells. The cumulative contact area was greatest on cells attached to surfaces prepared from 0% HEMA and lowest on surfaces with the highest HEMA content. An equilibrium adhesion model used these data together with the critical force for detachment and the Fn density (Burmeister et al., J Biomed Mater Res 1996;30:13-22) to determine the affinity between Fn and its receptor and the bond strength. The affinity and force per bond decreased with increasing HEMA content. These results indicate that differences in the strength of endothelial cell adhesion to polymers are influenced by the conformation of the adsorbed adhesion proteins.

Animals↗

PubMed1999

Multiple-analyte fluoroimmunoassay using an integrated optical waveguide sensor.

A silicon oxynitride integrated optical waveguide was used to evanescently excite fluorescence from a multianalyte sensor surface in a rapid, sandwich immunoassay format. Multiple analyte immunoassay (MAIA) results for two sets of three different analytes, one employing polyclonal and the other monoclonal capture antibodies, were compared with results for identical analytes performed in a single-analyte immunoassay (SAIA) format. The MAIA protocol was applied in both phosphate-buffered saline and simulated serum solutions. Point-to-point correlation values between the MAIA and SAIA results varied widely for the polyclonal antibodies (R2 = 0.42-0.98) and were acceptable for the monoclonal antibodies (R2 = 0.93-0.99). Differences in calculated receptor affinities were also evident with polyclonal antibodies, but not so with monoclonal antibodies. Polyclonal antibody capture layers tended to demonstrate departure from ideal receptor-ligand binding while monoclonal antibodies generally displayed monovalent binding. A third set of three antibodies, specific for three cardiac proteins routinely used to categorize myocardial infarction, were also evaluated with the two assay protocols. MAIA responses, over clinically significant ranges for creatin kinase MB, cardiac troponin I, and myoglobin agreed well with responses generated with SAIA protocols (R2 = 0.97-0.99).

Animals↗

PubMed1999

An equilibrium model of endothelial cell adhesion via integrin-dependent and integrin-independent ligands.

Endothelial cell adhesion can be enhanced by supplementing integrin-mediated adhesion via fibronectin with the high-affinity avidin-biotin system in which biotin is covalently linked to membrane proteins and avidin binds to biotinylated surfaces (Bhat et al. J Biomed Mater Res 1998;41:377-85). An equilibrium model was extended to explain detachment of spreading cells following exposure to flow for this two ligand system. The two different receptor-ligand systems were treated as springs in parallel in which the equilibrium dissociation constant was a function of the separation distance of the cell from the surface. Flow experiments were performed to measure the endothelial cell adhesion strength as a function of the extent of biotinylation of the endothelium. Surfaces contained adsorbed fibronectin, avidin or both ligands. The contact area between the cell membrane and substrate was measured using total internal reflection fluorescence microscopy. Estimates of the unstressed dissociation constant for fibronectin and avidin were determined from data for adhesion strength and contact area of each ligand separately. Using these unstressed equilibrium constants, the model predicted, with reasonable accuracy, the strength of endothelial cell adhesion to surfaces containing fibronectin and avidin. The results indicate that as the extent of biotinylation increases, the avidin-biotin system contributes a larger fraction of the total adhesion strength but the maximum contribution of the avidin-biotin system is less than 50%. The magnitude of the affinity constant and force per bond for the avidin-biotin system are consistent with detachment by extraction of receptors from the cell. The resulting increase in the adhesion strength on surfaces with both avidin-biotin and fibronectin is due to the increase in contact area and the larger number of bonds formed.

Animals↗

PubMed1998

Fibronectin and avidin-biotin as a heterogeneous ligand system for enhanced endothelial cell adhesion.

A preadsorbed layer of "heterogeneous" integrin-dependent and -independent protein was used to enhance initial integrin-mediated endothelial cell attachment and spreading. Glass substrates were treated with fibronectin (Fn) and avidin coupled through adsorbed biotinylated bovine serum albumin (b-BSA). The slides then were seeded with biotinylated BAEC. Control "homogeneous" surfaces were slides adsorbed with either Fn or avidin coupled to b-BSA. The cells were incubated for 0.5 h in serum-containing media and exposed to a range of shear stresses in a laminar flow variable-height flow chamber. The critical shear stress to detach 50% of the seeded cells on the heterogeneous ligand surface was significantly greater than for either of the control homogeneous ligand systems (p < 0.001). Cellular spreading during the initial period of 0-2 h also was higher (p < 0.05) on the heterogeneous ligand-treated surface than on the surface of either of the homogeneous controls. The close contact area of the cell membrane with the substrate 1 h after seeding in serum-containing media was measured using TIRFM. Cells attached onto the heterogeneous ligand-treated surfaces had a significantly (p < 0.01) higher area of close contact with the substrate, which is consistent with a greater degree of attachment and spreading. The results indicate that the combination of integrin-dependent and -independent adhesion systems using heterogeneous ligands further enhances initial endothelial cell attachment and spreading.

Animals↗

PubMed1998

Engineering the tissue which encapsulates subcutaneous implants. II. Plasma-tissue exchange properties.

This study assesses the plasma-tissue exchange characteristics of the capsular tissue that forms around implants and how they are affected by implant porosity. The number of vessels and their permeability to rhodamine were measured by intravascular injection of the fluorophore tracer into Sprague-Dawley rats that hosted for 3-4 months polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE) subcutaneous implants. Rats were implanted with four pore sizes of PVA--a nonporous PVA (PVA-skin), and 5, 60, and 700 micron mean pore sizes (PVA-5, PVA-60, and PVA-700, respectively)--and two pore sizes of PTFE: 0.50 (PTFE-0.5) and 5.0 (PTFE-5) mean micron pore sizes. Photodensitometric image analysis was used to quantify the local tracer extravasation and, hence the permeability coefficients of isolated vessels around the implants. The number of functional vessels within 100 microm of the implants highlighted by the lissamine-rhodamine tracer were counted with fluorescence microscopy and with H&E stained sections using brightfield microscopy. The permeability of vessels did not vary substantially with implant pore size but generally were lower than those measured for surrounding subcutis. Pore size, however, had a dramatic effect on the vascular density of tissue-encapsulating implants: the number of microvessels (under 10 microm in radius) within the tissue surrounding the porous implants was higher than the number around nonporous implants. Pore sizes on the order of cellular dimensions incited optimal neovascularization; the vascular density around PVA-60 implants was six times higher (p < .001) and three times higher (p < .001) than those around PVA-0 implants in the fluorescent images and in brightfield, respectively. Moreover, brightfield microscopy showed the number of vessels around PVA-60 implants was almost double those in normal subcutis. The results suggest that optimal vascular density around long-term implants, such as sensors, biofluid cell constructs, and immunoisolated cell systems, may be engineered with pore size.

Animals↗

PubMed1998

Engineering the tissue which encapsulates subcutaneous implants. III. Effective tissue response times.

The results of two previous studies have shown that implant porosity can be used to increase both the measured diffusion coefficients and the vascularity within the tissue encapsulating long-term subcutaneous implants. This study investigates the hypothesis that the analyte concentrations within the tissue surrounding porous implants will respond more quickly to changes in plasma levels than does the densely packed, avascular fibrous capsule surrounding nonporous implants. The average concentration of lissamine-rhodamine was measured in tissue within 100 microm of the following implants at four different times following injection of the tracer: PVA-skin, PVA-5, PVA-60, PVA-700 (polyvinyl alcohol nonporous, 5 microm, 60 microm, and 700 microm mean pore sizes, respectively) and PTFE-0.5 and PTFE-5 (polytetrafluoroethylene 0.5 microm and 5 microm mean pore sizes, respectively). The results were compared to those of unimplanted subcutaneous tissue (SQ). In addition, the data were analyzed with a simple two-compartment model in which a tissue response time constant (taup) was extracted. As in the case of vascular density, the cellular dimension of the PVA-60 pore sizes produced surrounding tissue with the optimum response times to changes in plasma concentrations. The concentrations of rhodamine within the tissue surrounding the PVA-60 implant were the highest at all time points and responded to the change in plasma rhodamine concentration approximately three times more quickly (taup = 764 s) than the fibrous tissue encapsulating the nonporous PVA-skin (taup = 2058 s) and more than twice as quickly as SQ (taup = 1627 s). The overall mass transfer rate between plasma and the tissue surrounding the different implants calculated from the permeability and density of vessels from the previous study correlated very well (r2 = 0.7, p < .02, slope of 0.98) with the reciprocal of the tissue response time constant (taup).

Animals↗

PubMed1998

Genetic engineering of a single-chain antibody fragment for surface immobilization in an optical biosensor.

The development of a biosensor based on a genetically engineered biomolecule offers many potential advantages to sensors that rely on natural proteins only. Here we present how protein engineering techniques can be used to introduce a functional unit for surface immobilization into a single-chain antibody fragment (scFv). A peptide known to mimic the binding properties of biotin was fused to the carboxyterminus of the phosphorylcholine-binding scFv fragment of IgA McPC603. This fusion protein could be immobilized on a streptavidin monolayer. The resulting scFv monolayer was capable of binding a fluorescently labeled phosphorylcholine analog, as detected by total internal reflection fluorescence. In contrast, an scFv monolayer formed by introducing biotin through chemical modification was not capable of binding phosphorylcholine. These results demonstrate the utility of site-specific, oriented attachment strategies in the formation of protein monolayers in optical sensors, made possible by the use of protein engineering techniques.

Adhesiveness↗

PubMed1998

Using avidin-mediated binding to enhance initial endothelial cell attachment and spreading.

Binding between the protein avidin and the vitamin biotin was used as an extrinsic, high affinity receptor-ligand system to augment the intrinsic integrin-dependent cellular adhesion mechanism. Glass substrates were coupled with avidin receptors through an adsorbed film of biotinylated bovine serum albumin (b-BSA). The avidin-treated slides then were seeded with biotinylated bovine aortic endothelial cells (BAEC). A 3:1 ratio of BSA:b-BSA provided the best results in terms of specific cellular attachment, growth, and spreading. Control surfaces consisted of bare glass or glass with adsorbed BSA. Attachment of unmodified BAEC to glass decreased in the presence of anti-beta 1 integrin antibody. Adhesion of biotinylated BAEC to avidin-treated slides was not affected by anti-beta 1 integrin antibody, consistent with integrin-independent avidin-mediated adhesion. The initial rate of cell spreading was greatest for avidin-biotin-mediated adhesion (80.0 +/- 25.6 microns2/h), followed by integrin-dependent cellular adhesion on plain glass (35.7 +/- 7.7 microns2/h) and, finally, by adhesion on BSA-coated protein surfaces (10.2 +/- 0.3 microns2/h). Biotinylated and unmodified BAEC, cultured for 1 h in serum-containing media, were subjected to laminar flow in a variable-height flow chamber that provided a range of shear stresses from 0.2 to 75 dynes/cm2. The critical shear stress required to detach 50% of the cells in serum-containing media increased from 4.6 +/- 0.8 dynes/cm2 for integrin-dependent adhesion to 12.6 +/- 1.2 dynes/cm2 for avidin-biotin-mediated adhesion. Avidin-mediated attachment for biotinylated BAEC increased initial cellular spreading rates and strength of attachment (i.e., at 1 h) by a factor of two and three, respectively. These results support the hypothesis that integrin-mediated cell attachment and spreading can be enhanced using high affinity integrin-independent binding.

Animals↗

PubMed1998

Application of total internal reflection fluorescence microscopy to study cell adhesion to biomaterials.

Cell adhesion and function depend upon the formation of adhesive contacts between the cell and substrate. Determination of the cell substrate contact area is necessary in order to understand how biomaterial properties influence cell adhesion. In this review we describe the development and application of total internal reflection fluorescence microscopy (TIRFM) to quantify the separation distance of cells from a biomaterial surface. An approximate theory is presented for the straightforward calculation of separation distances when a fluor is placed in the cell membrane. The validity of this approach is discussed. TIRFM is compared to interference reflection microscopy and related techniques that measure cell/substrate separation distances. This approach is then applied to a number of important problems in cell substrate interactions, including changes in contact area and adhesion strength on biomaterial surfaces, analysis of bond strength, and real-time measurement of cell/substrate separation distances following exposure to flow.

Animals↗

PubMed1998

Planar integrated optical methods for examining thin films and their surface adlayers.

Thin film integrated optical waveguides (IOWs) have gained acceptance as a method for characterizing ultrathin dielectrical films and adlayers bound to the film surface. Here, we present the expressions that govern IOW methods as well as describe the common experimental configurations used in attenuated total reflection, fluorescence and Raman applications. The applications of these techniques to the study of adsorbed or surface-bound proteins to polymer and glass waveguides are reviewed.

Adsorption↗

PubMed1998

Improving endothelial cell adhesion to vascular graft surfaces: clinical need and strategies.

Synthetic vascular grafts do not spontaneously endothelialize in humans and require some form of anticoagulation to maintain patency. Preseeding synthetic graft materials such as expanded polytetrafluoroethylene (ePTFE) and polyethylene terephthalate (PET) with endothelial cells (EC) has been examined in various in vitro and in vivo models. Although various studies provide encouraging results, clinical trials for EC seeding on synthetic grafts have not been equally successful. This paper provides a brief review of the various reports on EC seeding in animal and clinical studies. We discuss the inefficiencies associated with the EC seeding process and examine plasma protein treatment of the graft surfaces as a viable option for improving EC attachment, retention and spreading. As an alternative to existing therapies we present data on a heterogeneous ligand treatment of fibronectin (Fn) and avidin-biotin for enhanced human umbilical vein endothelial cell (HUVEC) adhesion to ePTFE graft surfaces. Control consisted of HUVECs seeded on Fn treated ePTFE graft surfaces. Functionality of HUVECs was assessed by measuring prostacyclin production of cells on both homogeneous and heterogeneous ligand treated surfaces. Laminar flow studies with a variable width flow chamber and scanning electron microscopy were used to measure initial cell retention and observe initial cell spreading on ePTFE surfaces, respectively. HUVEC retention on heterogeneous ligand treated graft surface was significantly (p < 0.001) higher compared to homogeneous ligand treated surfaces for shear stress in the range of 10-30 dyn cm(-2). HUVEC showed more cellular spreading on the heterogeneous ligand treated surface after seeding for 1-2 h. In vivo experimentation was performed in immune deficient (nude) rats by replacing a section of both the femoral arteries with 8 mnm long, 1 mm internal diameter denucleated ePTFE grafts treated with homogeneous and heterogeneous ligands respectively. Both grafts were seeded with similar cell density for 15 min prior to implantation. EC attachment and retention was measured by staining EC with hematoxylin and counting the cells before and after flow using light microscopy. The results indicate that a heterogeneous ligand treatment of graft surfaces using avidin-biotin and Fn-integrin attachment mechanisms increase cell seeding efficiency, initial cell retention and cellular spreading.

Adsorption↗

PubMed1997

Engineering the tissue which encapsulates subcutaneous implants. I. Diffusion properties.

This report uses normal rat subcutis as a reference point to provide a quantitative analysis of small analyte transport through the tissue which encapsulates implants. Polyvinyl alcohol (PVA) with 60- and 350-micron mean pore size (PVA-60, PVA-350), nonporous PVA (PVA-skin), and stainless-steel cage (SS) specimens were implanted in the subcutis of Sprague-Dawley rats for 4 weeks to elicit a range of capsular wound-healing tissues. Histologic examination showed that the capsular tissue which formed around PVA-skin and SS specimens was densely fibrous and avascular. That forming around PVA-60 and PVA-350 was less densely fibrous and more vascular. The fibrous content of capsular tissue and subcutis was determined from eosin-stained histologic sections. Dual-chamber diffusion measurements of sodium fluorescein (Mw 376 g/mol) through capsular tissue and normal rat subcutis were used to quantitatively compare the effective diffusion coefficients of small analytes on the order of glucose. The two most fibrous capsular tissues exhibited diffusion coefficients that were statistically (p < 0.05) less than that determined for rat subcutis by 50 and 25% for PVA-skin and SS, respectively. The diffusion coefficients of the less dense capsular tissue which formed around the porous implants were not statistically different from subcutis. The experimentally measured diffusion coefficients of the two most fibrous capsular tissues were closely predicted by a simple two-component diffusion model consisting of an aqueous interstitium with an array of impenetrable bodies equal in volume fraction to the fibrous content of the tissue. This model overestimates the diffusion coefficients measured for the least fibrous tissues. Using the diffusion coefficient measured for the PVA-skin capsular tissue, a finite difference model predicts that a 200-microns-thick capsular layer would increase from 5 to 20 min the time required for subcutaneously implanted sensor to detect 95% of the blood analyte concentration. This study suggests that the fibrous capsule forming around a subcutaneously implanted smooth-surface sensor imposes a significant diffusion barrier to small analytes such as glucose, thus increasing the lag time of the sensor by as much as threefold. A corollary observation is that a sensor with a porous surface which allows tissue ingrowth may be more responsive to blood analyte fluctuations as a result of its a more vascular and less fibrous encapsulation tissue.

Animals↗

PubMed1996

Effect of fibronectin amount and conformation on the strength of endothelial cell adhesion to HEMA/EMA copolymers.

The effect of substrate surface hydrophobicity on fibronectin (Fn) adsorption and endothelial cell adhesion strength was studied. Bovine aortic endothelial cells (BAEC) were plated for 2 h with and without preadsorbed Fn on slides coated with homopolymers and copolymers of hydrophilic polyhydroxyethylmethacrylate (polyHEMA) and hydrophobic polyethylmethacrylate (polyEMA). The polarity of the substrate was determined by Wilhelmy plate contact angle. The amount of adsorbed Fn was determined using 125I-labeled Fn. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was used to detect gross conformational changes of adsorbed Fn on polyHEMA or polyEMA. BAEC were cultured in serum-free medium for 2 h and subjected to a brief exposure of laminar flow in a variable-height flow chamber that provided a range of shear stresses of 15-185 dynes/cm2. The critical shear stress to detach 50% of the cells increased with increasing EMA content to a maximum at 20% HEMA/80% EMA copolymer irrespective of the presence of preadsorbed Fn. However, the critical force increased even though there were similar amounts of Fn adsorbed on all substrates. ATR-FTIR spectroscopy showed only minor changes in beta-sheet structure of Fn adsorbed to polyHEMA and polyEMA. These results show that the force to detach cells did not increase solely with increasing amounts of adsorbed Fn; rather, these results indicate a more complex interplay involving both the amount and conformation of adsorbed Fn.

Animals↗

PubMed1996

Femtomolar sensitivity using a channel-etched thin film waveguide fluoroimmunosensor.

A dual channel, evanescent fluoroimmunoassay format is used to detect femtomolar analyte concentrations (i.e. less than 1 part per trillion [w/w]) on an etched channel siliconoxynitride thin film integrated optical waveguide. Two assays are used to demonstrate the dose-response behaviour of the sensor: (1) a direct assay of a fluorescently-labeled protein ligand binding to an immobilized protein receptor, and (2) an indirect sandwich assay of a non-fluorescent protein ligand binding to an immobilized protein receptor, as detected by the binding of a fluorescently-labeled secondary receptor protein. A red-emitting cyanine dye (Cy-5), which minimized background fluorescence and scatter losses of the waveguide, was used in both assays. To our knowledge, this is the first report of femtomolar sensitivity in an immunosensing instrument.

Biosensing Techniques↗

PubMed1994

Analysis of protein binding to receptor-doped lipid monolayers by Monte Carlo simulation.

This paper presents a Monte Carlo simulation (MCS) method for estimating the parameters that characterize ligand-receptor binding directly from experimentally derived binding isotherms. Binding parameters are estimated by incorporating an MCS algorithm for ligand binding to a two-dimensional receptor array into a nonlinear regression program. The MCS method was tested by analyzing experimental isotherms of avidin binding to biotinylated lipid in Langmuir-Blodgett (LB) monolayers. The MCS-derived cooperativity coefficients and intrinsic association constants for avidin-biotin binding to LB films are correlated strongly (R2 > 0.93) with the binding parameters determined from the same experimental data by a thermodynamic equilibrium binding model (Zhao et al. 1993. Langmuir. 9:3166-3173). This result shows MCS to be an accurate and potentially more versatile method for characterizing biomolecular interactions at surfaces.

Algorithms↗

PubMed1994

Quantitative analysis of variable-angle total internal reflection fluorescence microscopy (VA-TIRFM) of cell/substrate contacts.

Variable-angle total internal reflection fluorescence microscopy (VA-TIRFM) allows controlled variation of the illumination depth with the potential of measuring both membrane/substrate separation distances and sizes of focal contacts. VA-TIRFM images are collected from well-spread bovine aortic endothelial cells (BAEC) stained with a membrane-bound carbocyanine dye. Quantitative determination of absolute membrane/substrate separation distances and individual focal contact area are attempted using a simplified model of TIRFM optics. For angles slightly greater than the critical angle of 64 degrees, both the dorsal and ventral membranes were illuminated, while images excited above 66 degrees illuminated only focal contacts. Above 74 degrees the fluorescence of focal contacts was dominated by back-ground noise. Direct application of the simplified optical model without accounting for background intensity was unsatisfactory. However, correction for background fluorescence and nonlinear regression of the untransformed data over the working range yielded focal contact separation distances of 24 +/- 13 nm. Focal contact areas estimated by TIRFM (1.3 +/- 0.7 micron2) agreed closely with areas observed by immunofluorescence staining of vinculin (1.5 +/- 0.3 microns2).

Animals↗

PubMed1993

Polyimides as biomaterials: preliminary biocompatibility testing.

A number of commercially available polyimide materials were evaluated in vitro using a selected battery of levels I and II testing protocols prescribed by the National Institutes of Health Guidelines for Blood-Material Interactions. These procedures consisted of electron spectroscopy for chemical analysis and contact angle characterization surface studies, and protein adsorption, cell culture cytotoxicity, clotting time and haemolysis biocompatibility testing. The polyimide surfaces were invariant from the bulk composition with 60-80% C, 10-20% O and 2-5% N, producing advancing contact angles in the hydrophobic range (80-100 degrees). Consequently, they adsorbed significant amounts of albumin (2-3 micrograms/cm2) and fibrinogen (0.5-0.8 microgram/cm2). The polyimides also displayed an insignificant level of cytotoxicity and haemolysis, and clotting times ranged from 63 to 98% of normal. These clotting times and haemolytic index values were intermediate between the values observed for Teflon and Silastic controls. These factors, along with the strong adherence of polyimides to metal oxide substrates, indicate that polyimide materials are good candidates for further testing as encapsulants for implantable biosensors.

3T3 Cells↗