Surface-Active and Stimuli-Responsive Polymer−Si(100) Hybrids from Surface-Initiated Atom Transfer Radical Polymerization for Control of Cell Adhesion

Bilayer Hydrogel Composed of Elastin-Mimetic Polypeptides as a Bio-Actuator with Bidirectional and Reversible Bending Behaviors

Biologically derived hydrogels have attracted attention as promising polymers for use in biomedical applications because of their high biocompatibility, biodegradability, and low toxicity. Elastin-mimetic polypeptides (EMPs), which contain a repeated amino acid sequence derived from the hydrophobic domain of tropoelastin, exhibit reversible phase transition behavior, and thus, represent an interesting starting point for the development of biologically derived hydrogels. In this study, we succeeded in developing functional EMP-conjugated hydrogels that displayed temperature-responsive swelling/shrinking properties. The EMP-conjugated hydrogels were prepared through the polymerization of acrylated EMP with acrylamide. The EMP hydrogel swelled and shrank in response to temperature changes, and the swelling/shrinking capacity of the EMP hydrogels could be controlled by altering either the amount of EMP or the salt concentration in the buffer. The EMP hydrogels were able to select a uniform component of EMPs with a desired and specific repeat number of the EMP sequence, which could control the swelling/shrinking property of the EMP hydrogel. Moreover, we developed a smart hydrogel actuator based on EMP crosslinked hydrogels and non-crosslinked hydrogels that exhibited bidirectional curvature behavior in response to changes in temperature. These thermally responsive EMP hydrogels have potential use as bio-actuators for a number of biomedical applications.

Tunable multi-responsive nano-gated mesoporous silica nanoparticles as drug carriers

Tunable multi-responsive mesoporous silica nanoparticles were prepared by post-condensation/surface modification of MCM-41 nanoparticles. Surface grafting of a poly(N,N-dimethylaminoethyl methacrylate)-based polymer containing disulfide bonds was achieved by a click reaction. Chemical modification, morphological characteristics, and textural properties of the nanoparticles were studied using multiple characterization techniques such as Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, small-angle X-ray scattering, and nitrogen adsorption/desorption behavior. The nanoparticles retained the meso-structural integrity of MCM41 and particle size < 100 nm after grafting with the polymer. The pH and redox-responsive behavior of the nanoparticles were also studied. The nanoparticles possess excellent drug-loading capacity owing to their large surface area and 'closed gate' mechanism of the grafted polymer chains. The release profile of doxorubicin at two different pH (7.4 and 5.5) and in the presence of dithiothreitol showed a dual response behavior. The nano drug carrier device exhibited efficient intracellular uptake in cancer cells with suitable cytotoxicity and pharmacokinetic behavior, and may therefore be considered a good candidate for cancer therapy.

Thermoresponsive interfaces obtained using poly(N-isopropylacrylamide)-based copolymer for bioseparation and tissue engineering applications

Poly(N-isopropylacrylamide) (PNIPAAm) is the most well-known and widely used stimuli-responsive polymer in the biomedical field owing to its ability to undergo temperature-dependent hydration and dehydration with temperature variations, causing hydrophilic and hydrophobic alterations. This temperature-dependent property of PNIPAAm provides functionality to interfaces containing PNIPAAm. Notably, the hydrophilic and hydrophobic alterations caused by the change in the temperature-responsive property of PNIPAAm-modified interfaces induce temperature-modulated interactions with biomolecules, proteins, and cells. This intrinsic property of PNIPAAm can be effectively used in various biomedical applications, particularly in bioseparation and tissue engineering applications, owing to the functionality of PNIPAAm-modified interfaces based on the temperature modulation of the interaction between PNIPAAm-modified interfaces and biomolecules and cells. This review focuses on PNIPAAm-modified interfaces in terms of preparation method, properties, and their applications. Advances in PNIPAAm-modified interfaces for existing and developing applications are also summarized.

Preparation and Characterization of Thermoresponsive Poly(N-Isopropylacrylamide) for Cell Culture Applications

Poly(N-isopropylacrylamide) (PNIPAAm) is a typical thermoresponsive polymer used widely and studied deeply in smart materials, which is attractive and valuable owing to its reversible and remote "on-off" behavior adjusted by temperature variation. PNIPAAm usually exhibits opposite solubility or wettability across lower critical solution temperature (LCST), and it is readily functionalized making it available in extensive applications. Cell culture is one of the most prospective and representative applications. Active attachment and spontaneous detachment of targeted cells are easily tunable by surface wettability changes and volume phase transitions of PNIPAAm modified substrates with respect to ambient temperature. The thermoresponsive culture platforms and matching thermal-liftoff method can effectively substitute for the traditional cell harvesting ways like enzymatic hydrolysis and mechanical scraping, and will improve the stable and high quality of recovered cells. Therefore, the establishment and detection on PNIPAAm based culture systems are of particular importance. This review covers the important developments and recommendations for future work of the preparation and characterization of temperature-responsive substrates based on PNIPAAm and analogues for cell culture applications.

A surface-engineered NIR light-responsive actuator for controllable modulation of collective cell migration

Mechanical signal transduction is fundamental for maintaining and regulating cellular processes and functions. Here, we proposed a novel near-infrared (NIR) light-responsive optomechanical actuator for the directional regulation of collective cell adhesion and migration. This optomechanical actuator that is made up of a thermal-responsive copolymer hydrogel and gold nanorods (AuNRs), enables non-invasive activation by NIR light stimulation. The activation of the optomechanical actuator leads to hydrogel contraction and an increase in Young's modulus, which could be used for applying contraction force to cells cultured on the surface of the hydrogel actuator. By grafting cell adhesive peptide ligands, the cells could attach onto the surface of the actuator and displayed a NIR light illumination intensity dependent migration rate along a random orientation. To achieve the controllable modulation of cell behaviors, we employed a microcontact printing strategy for patterned presentation of adhesive ligands on this actuator and achieved directional cell alignment and cell migration through optomechanical actuation. These demonstrations suggest that this robust optomechanical actuator is promising for the optical modulation of cellular events and cell functions in various bioapplications.

Hydrosilane-Modified Poly(2-Hydroxyethyl Methacrylate) Brush as a Nanoadhesive for Efficient Silicone Bonding

Leaching of chemicals from adhesion promoters is, in particular, problematic for the food, water, pharmaceutical, and MedTech industries where any chemical contamination is unacceptable. A solution to this issue is to employ covalently attached nanoscale polymer brushes as adhesive layers for plastics. One of the industrially most relevant adhesion targets in that respect is poly(dimethylsiloxane) (PDMS), being used for many high-end applications such as catheters and breast implants. In this work, we have synthesized a novel surface-immobilized poly(2-hydroxyethyl methacrylate)-based brush adhesive containing reactive hydrosilane groups that can bond directly to PDMS. Two different medical grades of addition-cured PDMS were molded on top of titanium substrates already coated with the polymer brush. Titanium plates were used for the chemical analysis, and titanium rods were used for adhesion testing. Adhesion testing revealed a high adhesive force, in which cohesive failure was observed in the bulk PDMS. The necessity of the hydrosilane group in the polymer brush adhesive layer was demonstrated in comparative studies using similar brushes lacking this functionality.

Functionalization of cotton cellulose for improved wound healing

Wound dressing research has been determined by population aging, persistence of wound infection and the increase in chronic wound cases. Thus, besides mechanical protection, wound dressings must interact with the wound and improve the healing process. To achieve this demanding goal, wound dressing research has been focussing on the development of composite wound dressings that combine the best of two or more polymeric materials. Cellulosic materials are still the most used for wound management. Their importance is reflected in the number of publications on this subject in the textile engineering field. Textile wound dressing can cause maceration to the wound and pain during removal. However, the limitations of cellulosic wound dressings can be overcome by functionalization with hydrogels, which will maintain the moisture environment and improve the drug delivery ability of cotton. Therefore, the present review summarizes the composite materials research on the functionalization of cotton cellulose with hydrogels, to be applied as a wound dressing, and the methods and techniques used to synthesize those composites.

Poly(N-isopropylacrylamide)-based thermoresponsive surfaces provide new types of biomedical applications

Thermoresponsive surfaces, prepared by grafting of poly(N-isopropylacrylamide) (PIPAAm) or its copolymers, have been investigated for biomedical applications. Thermoresponsive cell culture dishes that show controlled cell adhesion and detachment following external temperature changes, represent a promising application of thermoresponsive surfaces. These dishes can be used to fabricate cell sheets, which are currently used as effective therapies for patients. Thermoresponsive microcarriers for large-scale cell cultivation have also been developed by taking advantage of the thermally modulated cell adhesion and detachment properties of thermoresponsive surfaces. Furthermore, thermoresponsive bioseparation systems using thermoresponsive surfaces for separating and purifying pharmaceutical proteins and therapeutic cells have been developed, with the separation systems able to maintain their activity and biological potency throughout the procedure. These applications of thermoresponsive surfaces have been improved with progress in preparation techniques of thermoresponsive surfaces, such as polymerization methods, and surface modification techniques. In the present review, the various types of PIPAAm-based thermoresponsive surfaces are summarized by describing their preparation methods, properties, and successful biomedical applications.

Thermoresponsive poly(glycidyl ether) brushes on gold: Surface engineering parameters and their implication for cell sheet fabrication

Thermoresponsive polymer coatings, optimized for cell adhesion and thermally-triggered cell detachment, allow the fabrication of confluent cell sheets with intact extracellular matrix. However, rational design guidelines for such coatings are rare, since temperature-triggered cell adhesion and detachment from thermoresponsive surfaces are mechanistically not well understood. Herein, we investigated the impact of molecular weight (2, 9, 24kDa), grafting density (0.04-1.4 chains nm^-2), morphology, and roughness of well-characterized thermoresponsive poly(glycidyl ether) brushes on the cell response at 37 and 20°C. NIH 3T3 mouse fibroblasts served as a model cell line for adhesion, proliferation, and cell sheet detachment. The cell response was correlated with serum protein adsorption from cell culture medium containing 10% fetal bovine serum. Intact cell sheets could be harvested from all the studied poly(glycidyl ether) coated surfaces, irrespective of the molecular weight, provided that the morphology of the coating was homogenous and the surface was fully shielded by the hydrated brush. The degree of chain overlap was estimated by the ratio of twice the polymer's Flory radius in a theta solvent to its interchain distance, which should be located in the strongly overlapping brush regime (2 R_f/l>1.4). In contrast, dense PNIPAM (2.5kDa) control monolayers did not induce protein adsorption from cell culture medium at 37°C and, as a result, did not allow a significant cell adhesion. These structural design parameters of functional poly(glycidyl ether) coatings on gold will contribute to future engineering of these thermoresponsive coatings on more common, cell culture relevant substrates.

STATEMENT OF SIGNIFICANCE

Cell sheet engineering as a scaffold-free approach towards tissue engineering resembles a milestone in regenerative medicine. The fabrication of confluent cell sheets maintains the extracellular matrix of cells which serves as the physiological cell scaffold. Thermoresponsive poly(glycidyl ether)s are highly cell-compatible and brushes thereof promote cell adhesion and growth without modification with additional cell adhesive ligands. Thus, a direct correlation of temperature-dependent serum protein adsorption and cell response with surface design parameters such as grafting density and molecular weight became accessible. Hence, surface engineering parameters of well-defined poly(glycidyl ether) monolayers for reproducible cell sheet fabrication have been identified. These design guidelines may also prove beneficial in the development of other brush-like thermoresponsive coatings for cell sheet engineering.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

Fabrication and Characterization of a Porous Silicon Drug Delivery System with an Initiated Chemical Vapor Deposition Temperature-Responsive Coating

This paper reports on the fabrication of a pSi-based drug delivery system, functionalized with an initiated chemical vapor deposition (iCVD) polymer film, for the sustainable and temperature-dependent delivery of drugs. The devices were prepared by loading biodegradable porous silicon (pSi) with a fluorescent anticancer drug camptothecin (CPT) and coating the surface with temperature-responsive poly(N-isopropylacrylamide-co-diethylene glycol divinyl ether) (pNIPAM-co-DEGDVE) or non-stimulus-responsive poly(aminostyrene) (pAS) via iCVD. CPT released from the uncoated oxidized pSi control with a burst release fashion (∼21 nmol/(cm(2) h)), and this was almost identical at temperatures both above (37 °C) and below (25 °C) the lower critical solution temperature (LCST) of the switchable polymer used, pNIPAM-co-DEGDVE (28.5 °C). In comparison, the burst release rate from the pSi-pNIPAM-co-DEGDVE sample was substantially slower at 6.12 and 9.19 nmol/(cm(2) h) at 25 and 37 °C, respectively. The final amount of CPT released over 16 h was 10% higher at 37 °C compared to 25 °C for pSi coated with pNIPAM-co-DEGDVE (46.29% vs 35.67%), indicating that this material can be used to deliver drugs on-demand at elevated temperatures. pSi coated with pAS also displayed sustainable drug delivery profiles, but these were independent of the release temperature. These data show that sustainable and temperature-responsive delivery systems can be produced by functionalization of pSi with iCVD polymer films. Benefits of the iCVD approach include the application of the iCVD coating after drug loading without causing degradation of the drug commonly caused by exposure to factors such as solvents or high temperatures. Importantly, the iCVD process is applicable to a wide array of surfaces as the process is independent of the surface chemistry and pore size of the nanoporous matrix being coated.

Effects of Grafting Density and Film Thickness on the Adhesion of Staphylococcus epidermidis to Poly(2-hydroxy ethyl methacrylate) and Poly(poly(ethylene glycol)methacrylate) Brushes

Thin polymer films that prevent the adhesion of bacteria are of interest as coatings for the development of infection-resistant biomaterials. This study investigates the influence of grafting density and film thickness on the adhesion of Staphylococcus epidermidis to poly(poly(ethylene glycol)methacrylate) (PPEGMA) and poly(2-hydroxyethyl methacrylate) (PHEMA) brushes prepared via surface-initiated atom transfer radical polymerization (SI-ATRP). These brushes are compared with poly(ethylene glycol) (PEG) brushes, which are obtained by grafting PEG onto an epoxide-modified substrate. Except for very low grafting densities (ρ = 1%), crystal violet staining experiments show that the PHEMA and PPEGMA brushes are equally effective as the PEG-modified surfaces in preventing S. epidermis adhesion and do not reveal any significant variations as a function of film thickness or grafting density. These results indicate that brushes generated by SI-ATRP are an attractive alternative to grafted-onto PEG films for the preparation of surface coatings that resist bacterial adhesion.

Marrying mussel inspired chemistry with photoiniferters: a novel strategy for surface functionalization

We demonstrated a novel strategy of marrying mussel inspired chemistry with photoiniferters for surface functionalization.

Thermoresponsive polymers based on ring-opening metathesis polymerization

A library of thermoresponsive polymers were developed with hydrophobic polynorbornene backbones and hydrophilic N-alkyl-amide/imide side groups, whose thermoresponsive behaviour in water could be conveniently tuned in a wide temperature range.

Cucurbit[8]uril directed stimuli-responsive supramolecular polymer brushes for dynamic surface engineering

In situ modification of surfaces with thin layers of polymers is of growing interest as adjustment of surface properties can be made on demand. We present herein a supramolecular 'grafting to' polymer brush via the recognition of surface-bound cucurbit[8]uril (CB[8]) rotaxanes towards end-functionalised polyethylene glycol (PEG). This dynamic supramolecular method represents advantages over traditional approaches, which employ covalent bond formation in the 'grafting to' process. Brush properties can be easily modified post-preparation by exchanging the polymers with small molecules in a controlled, reversible manner. Including both redox- and light-responsive guests in a single rotaxane entity, the CB[8]-mediated preparation of the polymer brush offers unique opportunities to switch the brush composition efficiently. While the PEG brushes are well hydrated in a good solvent (water) and stretch away from the surface, they collapse in a poor solvent (toluene), leading to the formation of a dense layer on the surface. This collapsed conformation protects the heteroternary complexes of CB[8]-rotaxane from dissociation and maintains the attachment of polymers on the surface.

Assessment of polyaniline nanoparticles toxicity and teratogenicity in aquatic environment using Rhinella arenarum model

With the rapid growth of nanotechnology and the applications of nanoparticles, environmental exposure to these particles is increasing. However, their impact in human and environmental health is not well studied. Anurans, with life stage comprising embryos, tadpoles and adults, have an extremely permeable skin which makes them excellent indicators of environmental health. This study evaluated the acute toxicity effects of polyaniline nanoparticles (PANI-Np) in different dispersant on embryos and larvae of Rhinella arenarum. The results showed that LC50 of PANI-Np dispersed in polyvinylpyrrolidone (PVP) were 1,500 mg/L, while LC50 by PANI-Np dispersed in PVP+PNIPAM (polyN-isopropylacrilamide) showed a highest toxicity (1,170 mg/L). The embryo teratogenicity increased with increasing exposure concentration in both kinds of PANI-Np although in PANI-Np1, there is an increased teratogenic effect associated with the polymer stabilizer PVP.

Biocompatible SiO2in the Fabrication of Stimuli-Responsive Hybrid Composites and Their Application Potential

Organic/inorganic hybrid composite materials have been extensively studied as they combine the properties of inorganic material and organic polymer. Among the inorganic material biocompatible silica (SiO2) is an interesting candidate for application in biotechnology because such material is wide spread in nature as well as in medicine. During the last few decades, stimuli-responsive polymers are drawing much attention from the researchers for application versatility such as target-specific delivery of drug and corrosion inhibitors. Considering the biocompatibility and many such important properties as high cargo loading capacity, long blood circulation lifetime, enhanced permeability and retention, mechanical strength, and easy processability, combination of SiO2particles with stimuli-responsive polymers is gaining attention over the last decade. This review article will report the progress made towards the development and application of stimuli-responsive hybrid composites based on SiO2.

PNIPAM nanoparticles for targeted and enhanced nose-to-brain delivery of curcuminoids: UPLC/ESI-Q-ToF-MS/MS-based pharmacokinetics and pharmacodynamic evaluation in cerebral ischemia model

Stroke is a one of the leading causes of disease and deaths worldwide, which causes irreversible deterioration of the central nervous system. Curcuminoids are reported to have a potential role in the amelioration of cerebral ischemia but they exhibit low serum and tissue levels due to low solubility and poor absorption. Curcumin (CUR), demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC)-loaded PNIPAM nanoparticles (NPs) were prepared by free radical polymerization and characterized for particles size, entrapment efficiency, zeta potential, in vitro release and ex vivo permeation study. Optimized CUR, DMC and BDMC-loaded NPs had the mean size of 92.46 ± 2.8, 91.23 ± 4.2 and 94.28 ± 1.91 nm; zeta potential of -16.2 ± 1.42, -15.6 ± 1.33 and -16.6 ± 1.21 mV; loading capacity of 39.31 ± 3.7, 38.91 ± 3.6 and 40.61 ± 3.6% and entrapment efficiency of 84.63 ± 4.2, 84.71 ± 3.99 and 85.73 ± 4.31%, respectively. Ultra-performance liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectroscopy based bioanalytical method was developed and validated for pharmacokinetics, biodistribution, brain-targeting efficiency and brain drug-targeting potential studies post-intranasal (i.n.) administration which showed enhanced bioavailability of curcuminoids in brain as compared to intravenous administration. Improved neurobehavioural activity (locomotor and grip strength) and reduced cytokines levels (TNF-α and IL-1β) was observed in middle cerebral artery occlusion induced cerebral ischemic rats after i.n. administration of curcuminoids NPs. Finally, the toxicity study was performed which revealed safe nature of developed NPs.

Improving hemocompatibility of polypropylene via surface-initiated atom transfer radical polymerization for covalently coupling BSA

Bovine serum albumin modified polypropylene for hemocompatibility was fabricated via surface-initiated atom transfer radical polymerization.

Two-dimensional patterns of poly(N-isopropylacrylamide) microgels to spatially control fibroblast adhesion and temperature-responsive detachment

Thermoresponsive poly(N-isopropyl acrylamide) (PNIPAM) microgels were patterned on polystyrene substrates via dip coating, creating cytocompatible substrates that provided spatial control over cell adhesion. This simple dip-coating method, which exploits variable substrate withdrawal speeds forming particle suspension stripes of densely packed PNIPAM microgels, while spacings between the stripes contained sparsely distributed PNIPAM microgels. The assembly of three different PNIPAM microgel patterns, namely, patterns composed of 50 μm stripe/50 μm spacing, 50 μm stripe/100 μm spacing, and 100 μm stripe/100 μm spacing, was verified using high-resolution optical micrographs and ImageJ analysis. PNIPAM microgels existed as monolayers within stripes and spacings, as revealed by atomic force microscopy (AFM). Upon cell seeding on PNIPAM micropatterned substrates, NIH3T3 fibroblast cells preferentially adhered within spacings to form cell patterns. Three days after cell seeding, cells proliferated to form confluent cell layers. The thermoresponsiveness of the underlying PNIPAM microgels was then utilized to recover fibroblast cell sheets from substrates simply by lowering the temperature without disrupting the underlying PNIPAM microgel patterns. Harvested cell sheets similar to these have been used for multiple tissue engineering applications. Also, this simple, low-cost, template-free dip-coating technique can be utilized to micropattern multifunctional PNIPAM microgels, generating complex stimuli-responsive substrates to study cell-material interactions and allow drug delivery to cells in a spatially and temporally controlled manner.

Remote and local control of stimuli responsive materials for therapeutic applications

Materials offering the ability to change their characteristics in response to presented stimuli have demonstrated application in the biomedical arena, allowing control over drug delivery, protein adsorption and cell attachment to materials. Many of these smart systems are reversible, giving rise to finer control over material properties and biological interaction, useful for various therapeutic treatment strategies. Many smart materials intended for biological interaction are based around pH or thermo-responsive materials, although the use of magnetic materials, particularly in neural regeneration, has increased over the past decade. This review draws together a background of literature describing the design principles and mechanisms of smart materials. Discussion centres on recent literature regarding pH-, thermo-, magnetic and dual responsive materials, and their current applications for the treatment of neural tissue.

ABC triblock terpolymers exhibiting both temperature- and pH-sensitive micellar aggregation and gelation in aqueous solution

Two poly(ethylene-alt-propylene)-b-poly(ethylene oxide)-b-poly(N-isopropylacrylamide-co-acrylic acid) (PEP-PEO-P(NIPAm-co-AA)) triblock terpolymers were synthesized by a combination of anionic and RAFT polymerizations, followed by acid hydrolysis. Micellar aggregation and gelation behavior in aqueous solutions were studied by dynamic light scattering (DLS) and rheology, respectively. DLS measurements on dilute solutions revealed that the triblock terpolymers form micelles with PEP cores and PEO-P(NIPAm-co-AA) coronae at room temperature and undergo a micelle to micellar aggregate transition upon heating. Rheological measurements showed that micellar aggregation manifests itself as gelation at higher concentrations (~4 wt %). The observed thermoresponsive aggregation and gelation is due to the intermicellar association of P(NIPAm-co-AA) blocks in the coronae above the lower critical solution temperature of the P(NIPAm-co-AA) block. The critical micellar aggregation and gelation temperatures are controlled by the mole fraction and degree of acrylic acid (AA) ionization in the P(NIPAm-co-AA) block, and therefore they can be modulated as functions of both pH and AA content in the polymer.

Thermoresponsive cell culture substrates based on PNIPAM brushes functionalized with adhesion peptides: theoretical considerations of mechanism and design

Thermoresponsive tissue culture substrates based on PNIPAM brushes are used to harvest confluent cell sheets for tissue engineering. The prospect of clinical use imposes the utilization of culture medium free of bovine serum, thus suggesting conjugation with adhesion peptides containing the RGD minimal recognition sequence. The optimum position of the RGD along the chain should ensure both cell adhesion at 37 °C and cell detachment at T(L) below the lower critical solution temperature of PNIPAM. Design guidelines are formulated from considerations of brush confinement by the cells: (i) Cell adhesion at 37 °C is controlled by the RGDs accessible without brush compression. (ii) Cell detachment at T(L) is driven by a disjoining force due to confinement of the swollen brush by cells retaining integrin-RGD bonds formed at 37 °C. These suggest placing the RGDs at the grafting surface or its vicinity. Randomly placed RGDs do not enable efficient detachment because a large fraction of the integrin-RGD bonds are not sufficiently tensioned at T(L), in line with experimental observations (Ebara, M.; Yamato, M.; Aoyagi, T.; Kikuchi, A.; Sakai, K.; Okano, T. Immobilization of celladhesive peptides to temperature-responsive surfaces facilitates both serum-free cell adhesion and noninvasive cell harvest. Tissue Eng. 2004, 10, 1125-1135). The theory framework enables analysis of culture media based on polymer brushes conjugated with adhesion peptides in general.