Sensitive Gels Research Articles

Synthesis and rheological analyzes of temperature and light sensitive gels comprising amphiphilic azobenzene polymers, chitosan and pluronic F127

AbstractThis study investigates the reinforcement of pluronic (PF127) based temperature responsive hydrogels with photosensitive functionalities to create smart and injectable materials. For this purpose, 4‐[4‐[(4‐phenyl)azo]phenoxy] methacrylate (PAzPMA) was synthesized and further polymerized via reversible addition‐fragmentation chain transfer (RAFT) polymerization. The structures of the copolymers were characterized by several techniques such as Fourier‐transform infrared (FT‐IR), nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). The azobenzene‐functionalized copolymer was combined with P127 solid polymer in micelle form and with P127 micelles in solid form to obtain PF127‐AzoMx and PF127‐AzoPx gels, respectively. When the temperature profiles of the PF127‐AzoMx and PF127‐AzoPx systems were compared with PF127, sol–gel phase transition were shifted to lower temperatures due to stronger hydrophobic interactions. Additionally, different concentrations of N,N,N‐trimethyl chitosan (f‐chitosan) were added to the gel systems and their rheological properties were investigated by exposing them to UV light. It has been observed that the presence and concentration of f‐chitosan are important for the variation of the interactions' strength between the micelles. The study highlights the potential of multifunctional hydrogels for specific biomedical applications that combine sensitivity to both thermal and optical stimuli for controlled drug delivery and tissue engineering purposes.

A method for rheological measurements of air sensitive samples.

The rheology of air or moisture sensitive liquids, gels, and glasses requires complicated rheometer-in-glovebox laboratory setups. Here, we demonstrate the use of a heavier-than-air cover gas, sulfur hexafluoride, and the design of a cover gas container that can attach to the lower geometry plate of any rheometer to carry out rheology experiments on air-sensitive liquids and soft solids. Rheological measurements of air-reactive ionic liquid trimethylsulfonium bromide-AlCl3, moisture sensitive titanium(IV) propoxide, and glycerin demonstrate the effectiveness of the cover-gas method for loading samples on acquiring correct temperature dependent viscosity data of the sample in the absence of reaction products.

Large deformation adhesion study of polymetric hydrogel under different stimuli

Hydrogels possess excellent and interesting properties that may be harnessed for future applications, especially in soft machines. However, this is not achievable if the adhesion theory of hydrogel is not well understood. This paper aims to develop an adhesion theory of hydrogels based on the Maugis model and large deformation theory. By applying the proposed theory, we predict the mechanical behaviour during the debonding process for both polymeric networks and swollen hydrogels. Furthermore, the proposed adhesion theory is extended to temperature-sensitive hydrogels, salt concentration sensitive gels, and pH-sensitive gels. Extensive parametric studies are carried out to demonstrate the effect of several key parameters which influence the response of hydrogels subjected to different stimuli. We find that different stimuli, such as a change in the temperature, the pH, can be reflected in the debonding process. Finally, by applying a network simulation method and multi particle tracking method, simulation and experiments are conducted to verify the proposed theory. The theoretical prediction matches reasonably well with the simulation and experimental results.

Basic Properties of a New Polymer Gel for 3D-Dosimetry at High Dose-Rates Typical for FFF Irradiation Based on Dithiothreitol and Methacrylic Acid (MAGADIT): Sensitivity, Range, Reproducibility, Accuracy, Dose Rate Effect and Impact of Oxygen Scavenger.

The photon induced radical-initiated polymerization in polymer gels can be used for high-resolution tissue equivalent dosimeters in quality control of radiation therapy. The dose (D) distribution in radiation therapy can be measured as a change of the physical measurement parameter T2 using T2-weighted magnetic resonance imaging. The detection by T2 is relying on the local change of the molecular mobility due to local polymerization initiated by radicals generated by the ionizing radiation. The dosimetric signals R2 = 1/T2 of many of the current polymer gels are dose-rate dependent, which reduces the reliability of the gel for clinical use. A novel gel dosimeter, based on methacrylic acid, gelatin and the newly added dithiothreitol (MAGADIT) as an oxygen-scavenger was analyzed for basic properties, such as sensitivity, reproducibility, accuracy and dose-rate dependence. Dithiothreitol features no toxic classification with a difference to THPC and offers a stronger negative redox-potential than ascorbic acid. Polymer gels with three different concentration levels of dithiothreitol were irradiated with a preclinical research X-ray unit and MR-scanned (T2) for quantitative dosimetry after calibration. The polymer gel with the lowest concentration of the oxygen scavenger was about factor 3 more sensitive to dose as compared to the gel with the highest concentration. The dose sensitivity (α = ∆R2/∆D) of MAGADIT gels was significantly dependent on the applied dose rate (≈48% reduction between = 0.6 Gy/min and = 4 Gy/min). However, this undesirable dose-rate effect reduced between 4–8 Gy/min (≈23%) and almost disappeared in the high dose-rate range (8 ≤12 Gy/min) used in flattening-filter-free (FFF) irradiations. The dose response varied for different samples within one manufacturing batch within 3%–6% (reproducibility). The accuracy ranged between 3.5% and 7.9%. The impact of the dose rate on the spatial integrity is demonstrated in the example of a linear accelerator (LINAC) small sized 5 × 10 mm2 10 MV photon field. For MAGADIT the maximum shift in the flanks in this field is limited to about 0.8 mm at a FFF dose rate of 15 Gy/min. Dose rate sensitive polymer gels likely perform better at high dose rates; MAGADIT exhibits a slightly improved performance compared to the reference normoxic polymer gel methacrylic and ascorbic acid in gelatin initiated by copper (MAGIC) using ascorbic acid.

4D dosimetry and motion management in clinical radiotherapy

Many novel modulated radiation treatment techniques are sensitive to patient motion which may degrade the dose distribution considerably. As there may be a simultaneous movement of the tumour and treatment machine, undesired heterogeneities in the dose distribution can be resulted. Methods to estimate the dosimetric effect of motion and treatment deliveries for both photons and protons are needed. We have recently studied Hodgkin’s lymphoma, liver and left sided breast cancer cases and developed tools to be able to simulate simultaneous organ movement and treatment delivery. Furthermore, it is of great importance to validate potential simulations in a realistic quality control set-up, ideally including a complete dosimetry volume and movement/deformation (4D). Radiation sensitive deformable gels have the potential to meet this dosimetry challenge owing to the unique 3D characteristic to form both phantom and detector in one volume. Multi-array detectors together with a moving platform and a realistic object trajectory is an alternative to evaluate the clinical setting. The evaluation could then in principle be done on-line. Gel/plastic 3D dosimeters have the potential to also be irradiated during motion in a similar matter but have to be read-out post irradiation.

Synthesis and Characterization of Thermoresponsive Xylan Networks by Diels–Alder Reaction

The last several decades have witnessed notable research in natural and biodegradable polymers for applications that interact with humans or the environment. This research describes the synthesis and characterization of temperature sensitive hemicellulose-based gels. Xylan type hemicellulose was converted into a thermoplastic material via the grafting of short polycaprolactone tails to enhance the material processability. The thermoplastic xylan (xylan-grafted-poly(caprolactone) was functionalized with different amounts of furan rings and allowed to react with bismaleimide through Diels–Alder reaction. The temperature dependent bonding/debonding of the designed networks was evaluated by solubility and rheological assessments. The results indicated that the temperature at which the networks disassemble varies based on the amount of the furan moieties in the initial copolymer and can range between 108.6 and 127.6 °C. The designed networks display promising molecular and synthetic features for the production...

How to Force Polymer Gels to Show Volume Phase Transitions.

Relatively few polymer gels are known to show volume phase transition where the gels undergo an abrupt change in the degree of swelling by passing through a three-phase equilibrium. Characteristic for such transition is the existence of van der Waals (vdW) loop on the dependence of solvent chemical potential versus polymer concentration. For the χ-induced transition, the existence of vdW loop is determined by the concentration dependence of the interaction function. It is shown that expansive mechanical strains can assist in development of the vdW loop. Systems characterized by continuous change of the degree of swelling transform upon such strain into ones where the degree of swelling changes much and abruptly. Also, expansive modes of strain can make the transition wider and more robust in gels where transition is already observed under free swelling condition. The possibility to induce the volume phase transition by external stresses can be utilized for finding other stimuli sensitive gels, strengthening of gel response, and in modeling of properties of gel constructs by Finite Element Method.

Fabrication of thermal sensitive folic acid based supramolecular hybrid gels for injectable drug release gels

Thermal sensitive supramolecular hybrid gels for injectable drug release were prepared by adding different amounts of agar into folic acid (FA) gelator. The gelation temperature was modulated in order to form injectable gel with body temperature (37°C). Such kind of folic acid-agar (FAG) hybrid gel makes it possible to use supramolecular gel as injectable drug loaded gels for drug release. FT-IR and UV–vis spectra indicate that agar macromolecules involve in the self-assembly process through intermolecular H-bonding and π-π stacking interactions with FA molecules. The SEM and TEM images demonstrate that the fiber diameter of FAG hybrid gel is about 20nm, much smaller than that of FA gel (40nm). However, FAG hybrid has a denser nano-fibrous network structure than FA gels. Moreover, FAG hybrid gel is endowed with a more ordered network structure and a little better crystallization capability by adding agar. FAG hybrid gel also shows a shear-thinning behavior but the shear viscosity is about 2 times higher than that of FA gel. Compared with FA gel, the storage (G′) and loss (G″) moduli of the FAG gel are higher, which implies an enhanced gel strength. At the same time, both FA and FAG gels are facilely affected by some external factors such as acid, base and salts. In acidic or basic conditions, the strength became weak and the gelation temperature (Tg) decreased. While, within certain concentrations, the salt (NaCl) increased the gel strength and Tg. FAG gel suffered lower mass loss and owned better stability in different pH solutions compared with pure FA gel. The release behavior of the FA and injectable FAG gels was investigated by using Rhodamine B as a mimic model drug. FAG hybrid gel shows a long release profile and the release time is 3 times longer than that of FA gel, up to 30h, and the accumulative release amount reaches about 86%. So it is a potential injectable gel for sustained release drug delivery system.

Effect of polymer network inhomogeneity on the volume phase transitions of thermo- and pH-sensitive weakly charged microgels

Environmentally sensitive polymer gels exhibit pronounced swelling and deswelling upon changes in temperature and pH, which has been discussed in mean-field pictures to assess at which conditions it occurs continuously or discontinuously. However, such treatment disregards nanometer-scale inhomogeneities of the distribution of cross-links and pH-sensitive groups in the polymer gel networks. To check for the impact of such inhomogeneity, we use droplet-based microfluidics to fabricate submillimeter-sized gel particles with either homogeneous-random or inhomogeneous-arranged polymer cross-linking and/or acrylic acid (AAc) group densities. These particles are then used to study their volume phase behavior from macroscopic and microscopic perspectives. Our results show that a systematic variation of the spatial distribution of ionizable groups inside the gels notably impacts the continuity and critical temperature of their volume phase transitions. This is remarkable, because even though our samples are just weakly charged, we observe effects similar to earlier findings made for strong polyelectrolytes.

Gum acacia polysaccharide-based pH sensitive gels for targeted delivery of neridronate

The preparation of polysaccharide-based gels from a combination of natural and synthetic polymers results in polymer networks with unique physicochemical properties. Polysaccharide-based gels were prepared from a combination of gum acacia, a polysaccharide, and synthetic polymers using the free radical polymerization technique. The gels were characterized by XRD, DSC, SEM, and FTIR. The swelling abilities of the gels were performed at pH 1.2 and 7.4. Release kinetic studies of neridronate from the prepared gels were performed and the release mechanism was found to be super case transport II at pH 1.2 and pH 7.4. The gels were pH sensitive and the release profile of neridronate from the gels network was influenced by the degree of cross-linking of their network and pH. The preliminary results suggest that these gels are promising devices for targeted delivery of neridronate to the gastrointestinal region.

Electroactive, Multisensitive Nanocomposite. Electrocatalytic Activity and Attachement to Gold Electrode Surface

Microgels are chemically cross-linked polymers with a network structure that are colloidal in size and swollen in a suitable solvent.1 Environmentally sensitive gels: “smart” nanogels sensitive to external stimuli such as temperature, pH, ionic strength, presence of specific ions, solvent composition and electromagnetic radiation can react quickly to environment changes.2 However, plain smart hydrogels are generally electrically nonconductive, while conductivity is required in such applications as supercapacitors, fuel cells and sensors.3 Our aim was to fabricate a new conductive multiple stimuli-responsive hybrid nanocomposite consisting of nanogel p(NIPA-BISS), AuNP’s and polyaniline (PANI). A combination of polymeric hydrogel and PANI-Au led to the materials that exhibited the properties characteristic for both components. We obtained thermally- and pH responsive, electroactive and conductive hybrid nanocomposites with good catalytic properties. We deposited them on the gold-electrode surface. The nanocomposite consisted of a nanogel containing disulfide groups in the crosslinkers to make possible its attachment to the gold-electrode surface and polyaniline nanofibers with embedded in them gold nanoparticles. The presence of polyaniline in the composite nanoparticles led to a substantial increase in conductivity and electroactivity of the nanogels and allowed elimination of aggregation of nanocomposites in acidic solutions at increased temperature. In the first step of synthesis, p(NIPS-BISS) nanogel, based on poly(N-isopropylacrylamide) cross-linked with N,N’-bisacryloylcystine, was prepared via surfactant-free emulsion polymerization (SFEP). Next, by soaking the nanogel with a solution of an oxidizing agent (chloroauric acid, HAuCl4) and placing the soaked gel in a solution of aniline in nitrobenzene, the conducting polymer and AuNPs were formed in p(NIPA-BISS) nanogel. The structure, morphology and swelling behavior of the nanogels were investigated using SEM, TEM and DLS. To evaluate the state of PANI oxidation the Raman spectroscopy was used. The electrocatalytic oxidation of ethanol at gold electrodes covered by the nanocomposites was examined using voltammetry. This work was supported by a grant from the National Science Centre of Poland, Preludium 8, 2014/15/N/ST5/02937 1. B. R. Saunders, B. Vincent, Adv. Colloid Interface Sci., 1999, 80, 1. 2. Maćkiewicz, M.; Romański, J.; Karbarz, M. New Ampholytic Microgels Based On N-Isopropylacrylamide And Α-Amino Acid: Changes In Swelling Behavior As A Function Of Temperature, Ph And Divalent Cation Concentration. RSC Adv. 2014,4, 48905- 48911. 3. Zhai, D.; Liu, B.; Shi, Y.; Pan, L.; Wang, Y.; Li, W.; Zhang, R.; Yu, G. Highly Sensitive Glucose Sensor Based On Pt Nanoparticle/Polyaniline Hydrogel Heterostructures. ACS Nano 2013, 7, 3540-3546. Figure 1

PH sensitive smart gels of cetylpyridinium chloride in binary solvent mixtures: phase behaviour, structure and composition

Figure showing the effect of pH on CPC gel formation at 25 °C and fluorescence emission spectra of CPC solutions at pH ∼ 11.8.

Effect and Evolution of Nanostructural Complexity in Sensitive Polymer Gels

Sensitive polymer gels consist of swollen networks of crosslinked macromolecules subject to a delicate interplay with their environment, allowing them to be swollen and deswollen or crosslinked and decrosslinked upon external stimulation. Such environmental sensitivity can be realized by the use of covalently crosslinked polymer networks that exhibit critical miscibility with their swelling medium or by the use of transient and reversible, supramolecular chain crosslinking. Both classes of sensitive gels are established and used in a variety of applications. However, to make this truly useful, systematic relations between the structure, dynamics, and properties of these gels must be derived. In addition to the specific trigger of gel responsiveness, a prime factor of influence in this interplay is the nanostructural polymer‐network topology. Whereas a simplistic view of a polymer network is that of an ideal, regular array of monodisperse meshes, real polymer networks often display polydisperse mesh sizes, along with structural imperfections such as loops and dangling chains, and along with further spatial inhomogeneities of their crosslinking density on a length scale of several tens of nanometers. This article summarizes recent effort to consistently probe the impact and temporal evolution of such nanostructural complexity in both gels with critical polymer–solvent miscibility and in gels with transient supramolecular crosslinking. For this purpose, different designed model systems are introduced to control and probe the polymer‐network nanostructural heterogeneity as an experimental variable. This is done using techniques such as rheology, fluorescence recovery after photobleaching, light scattering, and neutron scattering. image

Effects of pH and thermally sensitive hybrid gels on osteogenic differentiation of mesenchymal stem cells.

Osteoblastic differentiation of mesenchymal stem cells from bone marrow is an essential step for bone formation. The osteogenesis is normally induced by chemical mediators. Recent laboratory studies have revealed that mechanical properties of an extracellular matrix, typically hydrogels with different modules, also affect the fate of stem cells. The question is how to adjust their mechanical properties inside the body in biomedical applications. In this study, we designed/used a novel extracellular matrix, namely, a hybrid gel made of billions of injectable small thermally and pH-sensitive poly(N-isopropylacrylamide-co-acrylic acid) microgels whose swelling at the body pH and temperature physically jammed them and mesenchymal stem cells together, which enabled us to in situ apply an adjustable mechanical stress on those embedded stem cells. By treating the cell layer with the microgels, we found that an earlier incorporation of the microgels significantly increases the alkaline phosphatase activity, while a later addition of the microgels after the primary calcium deposition enhances the extracellular matrix mineralization in the mesenchymal stem cells cultures accompanied by up-regulation of osteogenic marker genes expression, presumably due to the calcium fixation by the carboxyl groups inside the microgels and the physical contact between the microgels and mesenchymal stem cells layers. These microgels provide an extracellular matrix microenvironment to affect the fate and biological behavior of mesenchymal stem cells, facilitating their potential applications in regenerative therapies.

Mechanics of inhomogeneous large deformation of photo-thermal sensitive hydrogels

A polymer network can imbibe copious amounts of solvent and swell, the resulting state is known as a gel. Depending on its constituents, a gel is able to deform under the influence of various external stimuli, such as temperature, pH-value and light. In this work, we investigate the photo-thermal mechanics of deformation of temperature sensitive hydrogels impregnated with light-absorbing nano-particles. The field theory of photo-thermal sensitive gels is developed by incorporating effects of photochemical heating into the thermodynamic theory of neutral and temperature sensitive hydrogels. This is achieved by considering the equilibrium thermodynamics of a swelling gel through a variational approach. The phase transition phenomenon of these gels, and the factors affecting their deformations, are studied. To facilitate the simulation of large inhomogeneous deformations subjected to geometrical constraints, a finite element model is developed using a user-defined subroutine in ABAQUS, and by modeling the gel as a hyperelastic material. This numerical approach is validated through case studies involving gels undergoing phase coexistence and buckling when exposed to irradiation of varying intensities, and as a microvalve in microfluidic application.

Physico-chemical characteristics of gamma irradiation crosslinked poly(vinyl alcohol)/magnetite ferrogel composite

Magnetic field sensitive gels, ferrogels are new promising class of hydrogels. The coupling of hydrogels and magnetic particles has potential application in soft actuators such as artificial muscles or for hyperthermia application. Here a composite of magnetite particles (Fe3O4) and poly(vinyl alcohol) (PVA) hydrogel is developed using gamma irradiation as a crosslinking agent. PVA and Fe3O4 were chosen because of their well-established biocompatibility, radiation crosslinking potential (PVA), mild magnetic properties and the Curie point near desired heating temperature range (Fe3O4). Physico-chemical characteristics of these systems show the effect of the presence of particles in the process of radiation-induced crosslinking. Obtained PVA/Fe3O4 ferrogel composite has greater swelling capacity, activation energy of dehydration and dehydration rate compared to PVA hydrogel, crosslinked under the same conditions.

Comparison of poloxamer- and chitosan-based thermally sensitive gels for the treatment of vaginal mucositis

Context: The local treatment of vaginal mucositis requires an intimate and prolonged contact of anti-infective drugs with the mucosa. This can be achieved by means of mucoadhesive and thermally sensitive vehicles, capable of gelifying at the physiological temperature.Objective: The aim of the present work was to compare the potentiality of poloxamer 407 (PLX)/chitosan lactate (CS-L) and CS-L/glycerophosphate (GP) mixtures as mucoadhesive thermally sensitive vehicles for the treatment of vaginal mucositis.Materials and methods: PLX/CS-L and CS-L/GP mixtures were characterized for gelation and mucoadhesion properties as well as for bioactive (antimicrobial and wound healing) properties. Finally, the mixtures were loaded with amoxicillin trihydrate as model drug and characterized for drug release and washability properties.Results and discussion: The addition of CS-L to PLX causes an increase in PLX gelation temperature from 30 °C to the physiological temperature. The dilution with simulated vaginal fluid causes an increase in gelation time of PLX/CS-L mixture, while no variation of such parameter is observed for CS-L/GP mixture which is nevertheless characterized by poorer elastic properties. The stronger mucoadhesion properties of CS-L/GP mixture counterbalance the poorer elasticity of the gel and are responsible for a longer drug contact with the biological substrate. CS-L/GP mixture is moreover characterized by better bioactive properties than PLX-based mixture.Conclusion: CS-L/GP mixture represents a promising thermally sensitive vehicle.

Control of molecular gelation by chemical stimuli

Molecular gels are formed by the self-assembly of low-molecular weight compounds by weak non-covalent interactions and thus, they may be easily disassembled in response to external stimuli. Chemically sensitive gels can be prepared by introducing in the molecular design functional groups that may interact either by covalent or non-covalent forces with other molecules present in the medium. Functional molecular gels have been reported that are sensitive to acids, bases, ions, redox-active compounds, neutral species, reactive compounds and enzymes. Here we present a broad revision of the different chemical inputs that can be used to tune gel properties through some appealing application-based selected examples.

Simple Microfluidic Devices for <em>in vivo</em> Imaging of <em>C. elegans</em>, <em>Drosophila</em> and Zebrafish

Micro fabricated fluidic devices provide an accessible micro-environment for in vivo studies on small organisms. Simple fabrication processes are available for microfluidic devices using soft lithography techniques 1-3. Microfluidic devices have been used for sub-cellular imaging 4,5, in vivo laser microsurgery 2,6 and cellular imaging 4,7. In vivo imaging requires immobilization of organisms. This has been achieved using suction 5,8, tapered channels 6,7,9, deformable membranes 2-4,10, suction with additional cooling 5, anesthetic gas 11, temperature sensitive gels 12, cyanoacrylate glue 13 and anesthetics such as levamisole 14,15. Commonly used anesthetics influence synaptic transmission 16,17 and are known to have detrimental effects on sub-cellular neuronal transport 4. In this study we demonstrate a membrane based poly-dimethyl-siloxane (PDMS) device that allows anesthetic free immobilization of intact genetic model organisms such as Caenorhabditis elegans (C. elegans), Drosophila larvae and zebrafish larvae. These model organisms are suitable for in vivo studies in microfluidic devices because of their small diameters and optically transparent or translucent bodies. Body diameters range from ~10 μm to ~800 μm for early larval stages of C. elegans and zebrafish larvae and require microfluidic devices of different sizes to achieve complete immobilization for high resolution time-lapse imaging. These organisms are immobilized using pressure applied by compressed nitrogen gas through a liquid column and imaged using an inverted microscope. Animals released from the trap return to normal locomotion within 10 min. We demonstrate four applications of time-lapse imaging in C. elegans namely, imaging mitochondrial transport in neurons, pre-synaptic vesicle transport in a transport-defective mutant, glutamate receptor transport and Q neuroblast cell division. Data obtained from such movies show that microfluidic immobilization is a useful and accurate means of acquiring in vivo data of cellular and sub-cellular events when compared to anesthetized animals (Figure 1J and 3C-F 4). Device dimensions were altered to allow time-lapse imaging of different stages of C. elegans, first instar Drosophila larvae and zebrafish larvae. Transport of vesicles marked with synaptotagmin tagged with GFP (syt.eGFP) in sensory neurons shows directed motion of synaptic vesicle markers expressed in cholinergic sensory neurons in intact first instar Drosophila larvae. A similar device has been used to carry out time-lapse imaging of heartbeat in ~30 hr post fertilization (hpf) zebrafish larvae. These data show that the simple devices we have developed can be applied to a variety of model systems to study several cell biological and developmental phenomena in vivo.

Simple Microfluidic Devices for <em>in vivo</em> Imaging of <em>C. elegans</em>, <em>Drosophila</em> and Zebrafish

Micro fabricated fluidic devices provide an accessible micro-environment for in vivo studies on small organisms. Simple fabrication processes are available for microfluidic devices using soft lithography techniques. Microfluidic devices have been used for sub-cellular imaging, in vivo laser microsurgery and cellular imaging. In vivo imaging requires immobilization of organisms. This has been achieved using suction, tapered channels, deformable membranes, suction with additional cooling anesthetic gas, temperature sensitive gels, cyanoacrylate glue and anesthetics such as levamisole. Commonly used anesthetics influence synaptic transmission and are known to have detrimental effects on sub-cellular neuronal transport. In this study we demonstrate a membrane based poly-dimethyl-siloxane (PDMS) device that allows anesthetic free immobilization of intact genetic model organisms such as Caenorhabditis elegans (C. elegans), Drosophila larvae and zebrafish larvae. These model organisms are suitable for in vivo studies in microfluidic devices because of their small diameters and optically transparent or translucent bodies. Body diameters range from -10 μm to -800 μm for early larval stages of C. elegans and zebrafish larvae and require microfluidic devices of different sizes to achieve complete immobilization for high resolution time-lapse imaging. These organisms are immobilized using pressure applied by compressed nitrogen gas through a liquid column and imaged using an inverted microscope. Animals released from the trap return to normal locomotion within 10 min. We demonstrate four applications of time-lapse imaging in C. elegans namely, imaging mitochondrial transport in neurons, pre-synaptic vesicle transport in a transport-defective mutant, glutamate receptor transport and Q neuroblast cell division. Data obtained from such movies show that microfluidic immobilization is a useful and accurate means of acquiring in vivo data of cellular and sub-cellular events when compared to anesthetized animals (Figure 1J and 3C-F). Device dimensions were altered to allow time-lapse imaging of different stages of C. elegans, first instar Drosophila larvae and zebrafish larvae. Transport of vesicles marked with synaptotagmin tagged with GFP (syt.eGFP) in sensory neurons shows directed motion of synaptic vesicle markers expressed in cholinergic sensory neurons in intact first instar Drosophila larvae. A similar device has been used to carry out time-lapse imaging of heartbeat in -30 hr post fertilization (hpf) zebrafish larvae. These data show that the simple devices we have developed can be applied to a variety of model systems to study several cell biological and developmental phenomena in vivo.