Thermosensitive Copolymers Research Articles

Temperature/GSH Dual Responsive Fluorinated Mesoporous Silica‐Coated Au NRs for Serum‐Resistant Gene Delivery**

AbstractMesoporous silica nanoparticles (MSN) are emerging as one of the most appealing candidates for gene carriers. Nevertheless, one major obstacle for their clinical application is the lack of efficient controlled release and gene delivery. In this study, a mesoporous silica‐modified gold nanorods (Au NRs) controlled release platform was synthesized. Then a thermosensitive copolymer was grafted to the surface of release platform, to impart the switching response of carrier under the photothermal of Au NRs. Fluorination were modified on the surface of MSN through a disulfide bond to achieve glutathione (GSH) response release and improve serum‐resistant ability. This gene carrier, with notable DNA condensation ability and negligible cytotoxicity, could be easily internalized into cells, enhanced green fluorescent protein expression in the presence of serum under laser irradiation. This work inspired us to solve the problem of traditional controllable sustained release and realize the performance of intracellular switch response to gene sustained release.

Effect of Tannic Acid Concentrations on Temperature-Sensitive Sol-Gel Transition and Stability of Tannic Acid/Pluronic F127 Composite Hydrogels.

Recently, interest in polyphenol-containing composite adhesives for various biomedical applications has been growing. Tannic acid (TA) is a polyphenolic compound with advantageous properties, including antioxidant and antimicrobial properties. Additionally, TA contains multiple hydroxyl groups that exhibit biological activity by forming hydrogen bonds with proteins and biomacromolecules. Furthermore, TA-containing polymer composites exhibit excellent tissue adhesion properties. In this study, the gelation behavior and adhesion forces of TA/Pluronic F127 (TA/PluF) composite hydrogels were investigated by varying the TA and PluF concentrations. PluF (above 16 wt%) alone showed temperature-responsive gelation behavior because of the closely packed micelle aggregates. After the addition of a small amount of TA, the TA/PluF hydrogels showed thermosensitive behavior similar to that of PluF hydrogels. However, the TA/PluF hydrogels containing more than 10 wt% TA completely suppressed the thermo-responsive gelation kinetics of PluF, which may have been due to the hydrogen bonds between TA and PluF. In addition, TA/PluF hydrogels with 40 wt% TA showed excellent tissue adhesion properties and bursting pressure in porcine intestinal tissues. These results are expected to aid in understanding the use of mixtures of TA and thermosensitive block copolymers to fabricate adhesive hydrogels for versatile biomedical applications.

Chitosan-PNIPAM Thermogel Associated with Hydrogel Microspheres as a Smart Formulation for MSC Injection.

Regenerative medicine based on cell therapy has emerged as a promising approach for the treatment of various medical conditions. However, the success of cell therapy heavily relies on the development of suitable injectable hydrogels that can encapsulate cells and provide a conducive environment for their survival, proliferation, and tissue regeneration. Herein, we address the medical need for cyto- and biocompatible injectable hydrogels by reporting on the synthesis of a hydrogel-forming thermosensitive copolymer. The copolymer was synthesized by grafting poly(N-isopropylacrylamide-co-carboxymethyl acrylate) (PNIPAM-COOH) onto chitosan through amide coupling. This chemical modification resulted in the formation of hydrogels that exhibit a sol-gel transition with an onset at approximately 27 °C, making them ideal for use in injectable applications. The hydrogels supported the survival and proliferation of cells for several days, which is critical for cell encapsulation. Furthermore, the study evaluates the addition of collagen/chitosan hybrid microspheres to support the adhesion of mesenchymal stem cells within the hydrogels. Altogether, these results demonstrate the potential of the PNIPAM-chitosan thermogel for cell encapsulation and its possible applications in regenerative medicine.

Effect of the Formation of Hydrophilic and Hydrophobic-Hydrophilic Associates on the Behavior of Copolymers of N-Vinylpyrrolidone with Methyl Acrylate in Aqueous Solutions.

It has been shown that there exist conditions under which thermosensitive copolymers of N-vinylpyrrolidone with methyl acrylate form hydrophobic-hydrophilic associations, which are unstable dynamic meshes, the bonds in which are continuously broken and created again, and the nature of the formation of such meshes depends significantly on the proportion of the hydrophobic component in the copolymer. It is shown that the interaction of the above copolymers with polyacrylic acid results in the formation of not only classical interpolymer complexes, but also hydrophilic interpolymer associates, which also represent unstable networks existing in a dynamic mode. In such meshes, the molecules of the above copolymers serve as a kind of cross-agent connecting the polyacid molecules. There are also conditions under which such meshes acquire a complex structure, since unstable bonds between macromolecular tangles of both the same and different types take part in their formation. It is shown that the transition from the formation of interpolymer complexes to the formation of hydrophilic interpolymer associates can occur, among other things, due to changes in the acidity or concentration of low-molecular salt in solution.

Thermosensitive Capturer Coupled with the CD63 Aptamer for Highly Efficient Isolation of Exosomes.

Exosomes are bioactive substances secreted by various cells that play a crucial role in cell communication. Due to their nanoscale size and interference from nonexosome proteins, the rapid capture and nondestructive release of exosomes remain a technical challenge which significantly hinders their biomedical application. To overcome this obstacle, we have designed a CD63 aptamer-based thermosensitive copolymer for the effective isolation of exosomes from mesenchymal stem cells (MSCs). A thermal-responsive copolymer, poly(N-isopropylacrylamide-co-butyl methacrylate-co-N-hydroxysuccinimide methacrylate) P(NIPAM-co-BMA-co-NHSMA, PNB), was prepared, which could realize reversible hydrophilic/hydrophobic phase transition by varying temperature. Then, CD63 aptamers were further modified to the copolymer to form the PNB-aptamer, where the aptamer units, acting as a "lock and key", specifically bind exosomes. Under the low critical solution temperature (LCST) of the PNB-aptamer, it can maintain a hydrophilic state, capturing exosomes from the cell culture medium. Subsequently, exosome-carrying PNB-aptamers can endure from hydrophilic to hydrophobic phase transition by increasing the temperature above its LCST, and then they can be collected after centrifugation. By introducing the complementary sequence of the CD63 aptamer, the stronger binding affinity between the complementary sequence and the aptamers facilitates the release of exosomes from the PNB-aptamer. The yield of exosome samples captured from a MSC culture medium by the PNB-aptamer system (around 62%) is considerably higher than that obtained by the current "gold standard" ultrafiltration (UC) approach (around 42%). Thus, the PNB-aptamer capturer provides a potential strategy for highly efficient exosome isolation.

A Smart Responsive Nanotheranostic System for MRI of Tumor Response to Immunotherapy and Enhanced Synergism of Thermo‐Immunotherapy

AbstractThe challenges associated with the assessment of immune checkpoint inhibitor (ICI) therapy and low immunotherapy response observed in patients with poorly immunogenic tumors are addressed. A smart‐responsive nanoprobe MZF@Gd is synthetized based on magnetic resonance tuning (MRET). The nanoprobe is designed to be targeted and cleaved by granzyme B, a marker of cytotoxic T‐cell activation. MZF@Gd consisted of superparamagnetic Mn‐ and Zn‐doped ferrite magnetic nanoparticles (MZF‐MNPs) with a magnetocaloric effect and a paramagnetic contrast agent gadolinium‐diethylenetriamine penta‐acetic acid (Gd‐DTPA). These components are connected by the granzyme B substrate peptides. The activation of the T1WI signal through MRET, following the cleavage of the probe by granzyme B, enabled the accurate evaluation of the ICI therapeutic effect. Subsequently, an active‐targeting magnetothermally responsive nanotheranostic agent FA‐P(MZF@Gd/JQ1) is fabricated. This agent incorporated the MRET probe MZF@Gd, JQ‐1 (an inhibitor of PD‐L1), the thermosensitive copolymer PCL‐b‐P(MEO2MA‐co‐OEGMA), and folic acid on the surface. Nanotheranostic agents killed tumor cells through magnetocaloric effects, stimulated antitumor immunity, and regulated the drug release, thereby achieving a synergistic effect between hyperthermia and immunotherapy. Moreover, MZF@Gd released from the agent sensitively detected the presence of granzyme B at the tumor site, thereby enabling an effective assessment of therapeutic efficacy.

Pluronic F68 Micelles as Carriers for an Anti-Inflammatory Drug: A Rheological and Scattering Investigation.

Age-long ambition of medical scientists has always been advancement in healthcare and therapeutic medicine. Biomedical research indeed claims paramount importance in nanomedicine and drug delivery, and the development of biocompatible storage structures for delivering drugs stands at the heart of emerging scientific works. The delivery of drugs into the human body is nevertheless a nontrivial and challenging task, and it is often addressed by using amphiphilic compounds as nanosized delivery vehicles. Pluronics belong to a peculiar class of biocompatible and thermosensitive nonionic amphiphilic copolymers, and their self-assemblies are employed as drug delivery excipients because of their unique properties. We herein report on the encapsulation of diclofenac sodium within Pluronic F68 self-assemblies in water, underpinning the impact of the drug on the rheological and microstructural evolution of pluronic-based systems. The self-assembly and thermoresponsive micellization were studied through isothermal steady rheological experiments at different temperatures on samples containing 45 wt % Pluronic F68 and different amounts of diclofenac sodium. The adoption of scattering techniques, small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS), allowed for the description of the system features at the nanometer length scale, providing information about the characteristic size of each part of the micellar structures as a function of temperature and drug concentration. Diclofenac sodium is not a good fellow for Pluronic F68. The triblock copolymer aids the encapsulation of the drug, highly improving its water solubility, whereas diclofenac sodium somehow hinders Pluronic self-assembly. By using a simple empirical model and no fitting parameters, the steady viscosity can be predicted, although qualitatively, through the volume fraction of the micelles extracted through scattering techniques and compared to the rheological one. A tunable control of the viscous behavior of such biomedical systems may be achieved through the suitable choice of their composition.

4D printing of hydrogels based on poly(oxazoline) and poly(acrylamide) copolymers by stereolithography

4D printed hydrogels have been generated by DLP, using resins composed of two distinct thermosensitive copolymers (poly(oxazoline) and poly(acrylamide)) and exhibit remarkable volume morphing capabilities with temperature modulation.

Thermosensitive Triblock Copolymer for Slow-Release Lubricants under Ocular Conditions.

The ocular environment is crucial for a biological lubrication system. An unstable condition of tear film may cause a series of ocular diseases due to serious friction, such as dry eye syndrome, which has drawn extensive attention nowadays. In this study, an in vitro biocompatible superlubricity system, containing thermogelling copolymers (PCGA-PEG-PCGA) and slow-release lubricant (PEG 300/Tween 80), was constructed. First, the sol-gel transition temperature and gel strength of PCGA-PEG-PCGA were adjusted based on the ocular environment by regulating the length of PCGA blocks. Furthermore, the copolymer hydrogel exhibited a reliable slow-release property within 10 days and showed low cytotoxicity. Then, the superlubricity (coefficient of friction of approximately 0.005) was achieved with its released PEG 300/Tween 80 aqueous solution at the sliding velocity range of 1-100 mm s-1 and pressure range of 10-22 kPa. However, the lubrication behaviors varied, while PEG 300 chains and Tween 80 micelles were demonstrated to form a multilayer and a single layer adsorption structure on the sliding surface, respectively. On the whole, the composite lubrication systems, especially the one composed of Tween 80, showed excellent tribological properties owing to the stable slow-release and full hydration effects under ocular conditions, which hold great potential for improving ocular lubrication and maintaining human visual health.

Mucin-mediated mucosal retention via end-terminal modified Pluronic F127-based hydrogel to increase drug accumulation in the lungs

Noninvasive lung drug delivery is critical for treating respiratory diseases. Pluronic-based copolymers have been used as multifunctional materials for medical and biological applications. However, the Pluronic F127-based hydrogel is rapidly degraded, adversely affecting the mechanical stability for prolonged drug release. Therefore, this study designed two thermosensitive copolymers by modifying the Pluronic F127 terminal groups with carboxyl (ADF127) or amine groups (EDF127) to improve the viscosity and storage modulus of drug formulations. β-alanine and ethylenediamine were conjugated at the terminal of Pluronic F127 using a two-step acetylation process, and the final copolymers were characterized using 1H nuclear magnetic resonance (1H NMR) and Fourier-transform infrared spectra. According to the 1H NMR spectra, Pluronic F127 was functionalized to form ADF127 and EDF127 with 85 % and 71 % functionalization degrees, respectively. Rheological studies revealed that the ADF127 (15 wt%) and EDF127 (15 wt%) viscosities increased from 1480 Pa.s (Pluronic F127) to 1700 Pa.s and 1800 Pa.s, respectively. Furthermore, the elastic modulus of ADF127 and EDF127 increased, compared with that of native Pluronic F127 with the addition of 5 % mucin, particularly for ADF127, thereby signifying the stronger adhesive nature of ADF127 and EDF127 with mucin. Additionally, ADF127 and EDF127 exhibited a decreased gelation temperature, decreasing from 33 °C (Pluronic F127 at 15 wt%) to 24 °C. Notably, the in vitro ADF127 and EDF127 drug release was prolonged (95 %; 48 h) by the hydrogel encapsulation of the liposome–Bdph combined with mucin, and the intermolecular hydrogen bonding between the mucin and the hydrogel increased the retention time and stiffness of the hydrogels. Furthermore, ADF127 and EDF127 incubated with NIH-3T3 cells exhibited biocompatibility within 2 mg/mL, compared with Pluronic F127. The nasal administration method was used to examine the biodistribution of the modified hydrogel carrying liposomes or exosomes with fluorescence using the IVIS system. Drug accumulation in the lungs decreased in the following order: ADF127 > EDF127 > liposomes or exosomes alone. These results indicated that the carboxyl group-modified Pluronic F127 enabled well-distributed drug accumulation in the lungs, which is beneficial for intranasal administration routes in treating diseases such as lung fibrosis.

Multifunctional Hydrogel Eye Drops for Synergistic Treatment of Ocular Inflammatory Disease.

Uveitis is a complex ocular inflammatory disease with a multifactorial etiology that can result in blindness. Although corticosteroid eye drops are the primary treatment for anterior uveitis, their efficacy is limited by low bioavailability, adverse effects, and a narrow focus on inflammation. In this study, the multifunctional hydrogel eye drops (designated as DCFH) were developed by incorporating the anti-inflammatory agent dexamethasone (DSP) and reactive oxygen species (ROS) scavenger cerium-based metal-organic frameworks (Ce-MOFs) into thermosensitive triblock copolymer F127 for the synergistic treatment against uveitis. The resulting F127 eye drops offer a favorable alternative to ophthalmic solution due to its thermosensitivity, thixotropy, light transmittance, improved ocular bioavailability, and unexpected anti-inflammatory efficacy. Notably, the participation of nanoporous Ce-MOFs, functional drug carriers, not only reduces ROS level but also boosts the anti-inflammatory activity of DSP in vitro. Therapeutically, the multifunctional DCFH exhibits superior efficacy in treating endotoxin-induced uveitis by mitigating the ophthalmic inflammatory reaction, suppressing inflammatory cytokines (e.g., TNF-α, IL-6, and IL-17) and downregulating the expression of iNOS and NLPR3. This synergistic treatment provides a valuable and promising approach for the management of uveitis and other ocular inflammatory conditions.

Transcription-Factor-Induced Aggregation of Biomimetic Oligonucleotide-b-Protein Micelles.

Polymeric micelles and especially those based on natural diblocks are of particular interest due to their advantageous properties in terms of molecular recognition, biocompatibility, and biodegradability. We herein report a facile and straightforward synthesis of thermoresponsive elastin-like polypeptide (ELP) and oligonucleotide (ON) diblock bioconjugates, ON-b-ELP, through copper-catalyzed azide-alkyne cycloaddition. The resulting thermosensitive diblock copolymer self-assembles above its critical micelle temperature (CMT ∼30 °C) to form colloidally stable micelles of ∼50 nm diameter. The ON-b-ELP micelles hybridize with an ON complementary strand and maintain their size and stability. Next, we describe the capacity of these micelles to bind proteins, creating more complex structures using the classic biotin-streptavidin pairing and the specific recognition between a transcription factor protein and the ON strand. In both instances, the micelles are intact, form larger structures, and retain their sensitivity to temperature.

Preparation and Characterization of Thermoresponsive Polymer Scaffolds Based on Poly(N-isopropylacrylamide-co-N-tert-butylacrylamide) for Cell Culture

In the realm of scaffold-free cell therapies, there is a questto develop organotypic three-dimensional (3D) tissue surrogates in vitro, capitalizing on the inherent ability of cells to create tissues with an efficiency and sophistication that still remains unmatched by human-made devices. In this study, we explored the properties of scaffolds obtained by the electrospinning of a thermosensitive copolymer, poly(N-isopropylacrylamide-co-N-tert-butylacrylamide) (P(NIPAM-co-NtBA)), intended for use in such therapies. Two copolymers with molecular weights of 123 and 137 kDa and a content of N-tert-butylacrylamide of ca. 15 mol% were utilized to generate 3D scaffolds via electrospinning. We examined the morphology, solution viscosity, porosity, and thickness of the spun matrices as well as the mechanical properties and hydrophobic–hydrophilic characteristics of the scaffolds. Particular attention was paid to studying the influence of the thermosensitive polymer’s molecular weight and dispersity on the resultant scaffolds’ properties and the role of electroforming parameters on the morphology and mechanical characteristics of the scaffolds. The cytotoxicity of the copolymers and interaction of cells with the scaffolds were also studied. Our findings provide significant insight into approaches to optimizing scaffolds for specific cell cultures, thereby offering new opportunities for scaffold-free cell therapies.

A thermosensitive gel matrix for bioreactor-assisted in-cell NMR of nucleic acids and proteins

Introducing the flow through the bioreactor has revolutionized in-cell NMR spectroscopy by prolonging the measurement time available to acquire spectral information about biomacromolecules in metabolically active cells. Bioreactor technology relies on immobilizer matrices, which secure cells in the active volume of the NMR coil and enable uniform perfusion of the growth medium, supplying fresh nutrients to the cells while removing toxic byproducts of their metabolism. The main drawbacks of commonly used matrices include the inability to recover intact cells post-measurement for additional analyses and/or requirements for specific operating temperatures. Here, we report on the development and characterization of a set of thermosensitive and nontoxic triblock copolymers based on poly(D,L-lactide)-b-poly(ethylene glycol)-b-poly(D,L-lactide) (PLA-PEG-PLA). Here, we show for the first time that these copolymers are suitable as immobilizer matrices for the acquisition of in-cell NMR spectra of nucleic acids and proteins over a commonly used sample temperature range of 15–40 °C and, importantly, allow recovery of cells after completion of in-cell NMR spectra acquisition. We compared the performances of currently used matrices in terms of cell viability (dye exclusion assays), cellular metabolism (1D 31P NMR), and quality of in-cell NMR spectra of two model biomacromolecules (hybrid double-stranded/i-motif DNA and ubiquitin). Our results demonstrate the suitability and advantages of PLA-PEG-PLA copolymers for application in bioreactor-assisted in-cell NMR.

Thermo-responsive Diels-Alder stabilized hydrogels for ocular drug delivery of a corticosteroid and an anti-VEGF fab fragment

In the present study, a novel in situ forming thermosensitive hydrogel system was investigated as a versatile drug delivery system for ocular therapy. For this purpose, two thermosensitive ABA triblock copolymers bearing either furan or maleimide moieties were synthesized, named respectively poly(NIPAM-co-HEA/Furan)-PEG6K-P(NIPAM-co-HEA/Furan) (PNF) and poly(NIPAM-co-HEA/Maleimide)-PEG6K-P(NIPAM-co-HEA/−Maleimide) (PNM). Hydrogels were obtained upon mixing aqueous PNF and PNM solutions followed by incubation at 37 °C. The hydrogel undergoes an immediate (<1 min) sol-gel transition at 37 °C. In situ hydrogel formation at 37 °C was also observed after intravitreal injection of the formulation into an ex vivo rabbit eye. The hydrogel network formation was due to physical self-assembly of the PNIPAM blocks and a catalyst-free furan-maleimide Diels−Alder (DA) chemical crosslinking in the hydrophobic domains of the polymer network. Rheological studies demonstrated sol-gel transition at 23 °C, and DA crosslinks were formed in time within 60 min by increasing the temperature from 4 to 37 °C. When incubated at 37 °C, these hydrogels were stable for at least one year in phosphate buffer of pH 7.4. However, the gels degraded at basic pH 10 and 11 after 13 and 3 days, respectively, due to hydrolysis of ester bonds in the crosslinks of the hydrogel network. The hydrogel was loaded with an anti-VEGF antibody fragment (FAB; 48.4 kDa) or with corticosteroid dexamethasone (dex) by dissolving (FAB) or dispersing (DEX) in the hydrogel precursor solution. The FAB fragment in unmodified form was quantitatively released over 13 days after an initial burst release of 46, 45 and 28 % of the loading for the 5, 10 and 20 wt% hydrogel, respectively, due to gel dehydration during formation. The low molecular weight drug dexamethasone was almost quantitively released in 35 days. The slower release of dexamethasone compared to the FAB fragment can likely be explained by the solubilization of this hydrophobic drug in the hydrophobic domains of the gel. The thermosensitive gels showed good cytocompatibility when brought in contact with macrophage-like mural cells (RAW 264.7) and human retinal pigment epithelium-derived (ARPE-19) cells. This study demonstrates that PNF-PNM thermogel may be a suitable formulation for sustained release of bioactive agents into the eye for treating posterior segment eye diseases.

Surface grafted gold nanorods (GNRDs) using thermosensitive copolymers with various transition temperatures: Nanomaterials with potential application for photothermal therapy

A series of diblock copolymers containing a biocompatible polyethylene glycol (PEG) block and a thermoresponsive poly(N-vinyl caprolactam) (PNVCL) based block, were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The cloud point temperature (Tcp) in water of the diblocks was adjusted from 35 to 42 °C by adding N-vinyl pyrrolidone (NVP) units in the thermoresponsive block. The terminal trithiocarbonate group evolving from the RAFT agent used in the synthesis, was modified to thiol to stabilize gold nanorods (GNRDs) via a “grafting-to” approach. Stability of the PEG-b-P(NVCL-co-NVP)@GNRDs nanomaterials was monitored during 8 days; where the localized surface plasmon resonance (LSPR) absorption band did not shifted or showed any broadening. Aqueous dispersed samples were irradiated with near-infrared laser light for 10 min, observing a temperature increase from 25 to 50 °C depending on the laser optical power (between 100 and 500 mW); while no precipitation was observed. For temperatures above the cloud point temperature of the copolymers (Tcp), the formation of aggregates in sizes around 200 nm was observed without precipitation. This study demonstrates that the stabilization of gold nanorods by grafting with the title thermoresponsive block copolymers, and the observed temperature-dependent block-copolymer@GNRD aggregation, has potential uses in drug-delivery applications for photothermal therapy.

Thermo-tunable Injectable Thermosensitive Hydrogel and its Application as Protein Carriers

It is known that polymer chemistries determine mechanical and physical properties of hydrogels and thus its drug delivery performance. In order to achieve desired drug release behavior, triblock copolyester PCT-PEG-PCT with proper hydrogel formulation has to be synthesized. This research has demonstrated a way to adjust hydrogel mechanical and gelation properties by simply physically mixing amphiphilic copolymers with different composition to achieve desired protein carriers. Tri-block copolymer poly (CL-co-TOSUO)-PEG-poly (CL-co-TOSUO), briefed as (PCT-PEG-PCT) with different composition have been successfully synthesized. These copolymers are thermosensitive and can form hydrogels in aqueous solution. Copolymers with higher percentage hydrophobic PCT blocks show higher mechanical stiffness and yet lower solubility. To reduce the crystallinity of the hydrophobic block and soften the hydrogel, the copolymer with long PCT blocks was physically mixed with ones with shorter PCT blocks. The polymer mixture demonstrated a moderated mechanical stiffness and desired solubility. The polymer mixture also achieved a gelation temperature at 37°C, which is desirable for drug delivery. Macromolecular drug, bovine serum albumin (BSA) was used as model drug for its release study. This protein drug was successfully loaded into the polymer mixture, and the drug release study shows the polymer mixture is able to extend a stable drug release for over 48 hours. This result confirms physical mixing of PCT-PET-PCT thermosensitive copolymers can tune gel properties and improve drug delivery performance without redesigning and synthesizing new polymers.

Preparation of thermosensitive PNIPAm- based copolymers with tertiary amino and hydroxyl monomer for cell attachment and detachment study

Thermo-responsive microcarriers are essential for large-scale expansion of anchorage-dependent cells in a suspension culture. In this study, the authors prepared four different N-isopropylacrylamide (NIPAm)-based thermosensitive copolymers by copolymerizing with N-hydroxyethyl acrylamide (HEAA), 2-Hydroxyethyl methacrylate (HEMA), 2-(Diethylamino) ethylmethacrylate (DEAEMA), and 2-(Dimethylamino) ethylmethacylate (DMAEMA) through free radical polymerization (FRP) and used them for surface modification of Cytodex-3 microcarrier. The thermosensitive characteristic of the copolymers enabled microcarriers to attach and detach cells in response to temperature changes. Herein, NIH 3T3 cells were used as a model cell line and it was found that the cells' adhesion rate on Cytodex-3 microcarriers modified with different formulations of thermosensitive copolymers was greater than unmodified microcarriers. The microcarriers coated with 5 wt% of the copolymer showed better cell attachment than 3 wt% and 10 wt% copolymer coated microcarriers. Particularly, 5 wt% P(NIPAm-5% HEMA) copolymer coated microcarriers showed excellent cell attachment than other formulations. More importantly, as the temperature was reduced to 4 °C, the cells cultured on copolymer modified microcarriers were completely detached as a cell sheet from it withoutproteolytic enzymetreatment. Besides preserving the functionality and integrity of cellular structures, the thermal-induced detachment of cells from modified microcarriers was much higher (∼9.9 x 104 cells/mL) than cells detached from the original Cytodex-3 (∼7.5x103 cells/mL) in 1 h at 4 °C. Therefore, this study verified that microcarriers modified with thermosensitive copolymers exhibited enhanced cell attachment and detachment with temperature change, while maintaining cell functionality, thereby providing adequate number of viable cells for large scale production.

Synthesis of NVCL-NIPAM Hydrogels Using PEGDMA as a Chemical Crosslinker for Controlled Swelling Behaviours in Potential Shapeshifting Applications.

Stimuli-responsive hydrogels have recently gained interest within shapeshifting applications due to their capabilities to expand in water and their altering swelling properties when triggered by stimuli, such as pH and heat. While conventional hydrogels lose their mechanical strength during swelling, most shapeshifting applications require materials to have mechanical strength within a satisfactory range to perform specified tasks. Thus, stronger hydrogels are needed for shapeshifting applications. Poly (N-isopropylacrylamide) (PNIPAm) and poly (N-vinyl caprolactam) (PNVCL) are the most popular thermosensitive hydrogels studied. Their close-to-physiological lower critical solution temperature (LCST) makes them superior candidates in biomedicine. In this study, copolymers made of NVCL and NIPAm and chemically crosslinked using poly (ethylene glycol) dimethacrylate (PEGDMA) were fabricated. Successful polymerisation was proven via Fourier transform infrared spectroscopy (FTIR). The effects of incorporating comonomer and crosslinker on the LCST were found minimal using cloud-point measurements, ultraviolet (UV) spectroscopy, and differential scanning calorimetry (DSC). Formulations that completed three cycles of thermo-reversing pulsatile swelling are demonstrated. Lastly, rheological analysis validated the mechanical strength of PNVCL, which was improved due to the incorporation of NIPAm and PEGDMA. This study showcases potential smart thermosensitive NVCL-based copolymers that can be applied in the biomedical shapeshifting area.

Conjugation of folic acid with poly (NVCL-co-PEGMA)-grafted chitosan as a new doxorubicin delivery system

This paper aimed to investigate the synthesis of a novel drug delivery system (DDS) to target tumors and implement the controlled release of doxorubicin (DOX). Chitosan was modified with 3-mercaptopropyltrimethoxysilane and subjected to graft polymerization to implement grafting with the biocompatible thermosensitive copolymer of poly (NVCL-co-PEGMA). A folate receptor-targeting agent was obtained by attaching folic acid. The DDS loading capacity for DOX via physisorption was obtained to be 846.45 mg/g. The synthesized DDS showed temperature- and pH-sensitive drug release behavior in vitro. A temperature of 37 °C and a pH of 7.4 hindered the DOX release, whereas a temperature of 40 °C and a pH of 5.5 led to DOX release acceleration. In addition, the release of DOX was found to occur in a Fickian diffusion mechanism. The MTT assay tests indicated that the synthesized DDS was not detectably toxic to cell lines of breast cancer, while the toxicity of the DOX-loaded DDS was found to be substantial. The cell absorption enhancement of folic acid led to higher cytotoxicity of the DOX-loaded DDS than bare DOX. As a result, the proposed DDS could be a promising alternative for the targeted therapy of breast cancer through controlled drug release.