Hydrogels in cardiac tissue engineering: application and challenges

Cardiovascular disease remains the leading cause of global mortality. Current stem cell therapy and heart transplant therapy have limited long-term stability in cardiac function. Cardiac tissue engineering may be one of the key methods for regenerating damaged myocardial tissue. As an ideal scaffold material, hydrogel has become a viable tissue engineering therapy for the heart. Hydrogel can not only provide mechanical support for infarcted myocardium but also serve as a carrier for various drugs, bioactive factors, and cells to increase myocardial contractility and improve the cell microenvironment in the infarcted area, thereby improving cardiac function. This paper reviews the applications of hydrogels and biomedical mechanisms in cardiac tissue engineering and discusses the challenge of clinical transformation of hydrogel in cardiac tissue engineering, providing new strategies for treating cardiovascular diseases.

Crafting nature's wonders: nanoarchitectonics developments in bioinspired nanocellulose-based stimuli-responsive supramolecular matrices

Stimuli-responsive supramolecular assemblies have recently gained extensive attention in the biomedical field. Research focusing mainly on bioinspired functional supramolecular materials has shown great promise for potential drug delivery applications. Such materials can be engineered into 'smart' materials by utilizing various external stimuli such as pH, heat, light, and magnetic fields. Combining stimuli-responsive properties with bioinspired and biodegradable nanocellulose as a supramolecular matrix can offer a synergistic strategy for targeted and on-demand delivery of therapeutic drugs. The limitations of traditional drug delivery techniques may be greatly mitigated using this combination. In this review, we aim to provide a comprehensive overview of the recent advances in the development of stimuli-responsive nanocellulose-based drug delivery systems. Finally, we have highlighted the current challenges and future perspectives in the field, emphasizing the need for further research to overcome existing barriers and fully realize the potential of stimuli-responsive nanocellulose in drug-releasing applications. Reviewing the state-of-the-art developments and identifying critical areas for future exploration will provide valuable insights for researchers and practitioners working in nanomedicine and drug delivery, fostering the advancement of innovative and effective drug-releasing technologies.

Current Advances in Stimuli-Responsive Hydrogels as Smart Drug Delivery Carriers

In recent years, significant advancements in the field of advanced materials and hydrogel engineering have enabled the design and fabrication of smart hydrogels and nanogels that exhibit sensitivity to specific signals or pathological conditions, leading to a wide range of applications in drug delivery and disease treatment. This comprehensive review aims to provide an in-depth analysis of the stimuli-responsive principles exhibited by smart hydrogels in response to various triggers, such as pH levels, temperature fluctuations, light exposure, redox conditions, or the presence of specific biomolecules. The functionality and performance characteristics of these hydrogels are highly influenced by both their constituent components and fabrication processes. Key design principles, their applications in disease treatments, challenges, and future prospects were also discussed. Overall, this review aims to contribute to the current understanding of gel-based drug delivery systems and stimulate further research in this rapidly evolving field.

Phase transition and potential biomedical applications of thermoresponsive compositions based on polysaccharides, proteins and DNA: A review

Smart thermoresponsive polymers have long attracted attention as materials of a great potential for biomedical applications, mainly for drug delivery, tissue engineering and wound dressing, with a special interest to injectable hydrogels. Poly-N-isopropylacrylamide (PNIPAM) is the most important synthetic thermoresponsive polymer due to its physiologically relevant transition temperature. However, the use of unmodified PNIPAM encounters such problems as low biodegradability, low drug loading capacity, slow response to thermal stimuli, and insufficient mechanical robustness. The use of natural polysaccharides and proteins in combinations with PNIPAM, in the form of grafted copolymers, IPNs, microgels and physical mixtures, is aimed at overcoming these drawbacks and creating dual-functional materials with both synthetic and natural polymers' properties. When developing such compositions, special attention should be paid to preserving their key property, thermoresponsiveness. Addition of hydrophobic and hydrophilic fragments to PNIPAM is known to affect its transition temperature. This review covers various classes of natural polymers - polysaccharides, fibrous and non-fibrous proteins, DNA - used in combination with PNIPAM for the prospective biomedical purposes, with a focus on their phase transition temperatures and its relation to the natural polymer's structure.

A 3-Dimensional In Vitro Model of Zonally Organized Extracellular Matrix

OBJECTIVE

Functional cartilage repair requires the new formation of organized hyaline cartilaginous matrix to avoid the generation of fibrous repair tissue. The potential of mesenchymal progenitors was used to assemble a 3-dimensional structure in vitro, reflecting the zonation of collagen matrix in hyaline articular cartilage.

DESIGN

The 3-dimensional architecture of collagen alignment in pellet cultures of chondroprogenitors (CPs) was assessed with Picrosirius red staining analyzed under polarized light. In parallel assays, the trilineage capability was confirmed by calcium deposition during osteogenesis by alizarin S staining and alkaline phosphatase staining. Using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), mRNA levels of ALP, RUNX2, and BGLAP were assessed after 21 days of osteoinduction. Lipid droplets were stained with oil red O and adipogenic differentiation was confirmed by RT-qPCR analysis of PPARG and LPL gene expression.

RESULTS

Under conditions promoting the chondrogenic signature in self-assembling constructs, CPs formed an aligned extracellular matrix, positive for glycosaminoglycans and collagen type II, showing developing zonation of birefringent collagen fibers along the cross section of pellets, which reflect the distribution of collagen fibers in hyaline cartilage. Induced osteogenic and adipogenic differentiation confirmed the trilineage potential of CPs.

CONCLUSION

This model promotes the differentiation and self-organization of postnatal chondroprogenitors, resulting in the formation of zonally organized engineered hyaline cartilage comparable to the 3 zones of native cartilage.

High-Drug-Loading Amorphous Solid Dispersions via In Situ Thermal Cross-Linking: Unraveling the Mechanisms of Stabilization

This article takes a step forward in understanding the mechanisms involved during the preparation and performance of cross-linked high-drug-loading (HDL) amorphous solid dispersions (ASDs). Specifically, ASDs, having 90 wt % poorly water-soluble drug indomethacin (IND), were prepared via in situ thermal cross-linking of poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA) and thoroughly evaluated in terms of physical stability and in vitro supersaturation. Results showed that HDL ASDs having excellent active pharmaceutical ingredient (API) amorphous stability and prolonged in vitro supersaturation were prepared by fine tuning the cross-linking procedure. Unraveling of the processes involved during ASD's formation shed light on the significant role of the cross-linking conditions (i.e., temperature and time), the physicochemical properties of the API, and the hydrolysis level of the cross-linker as key factors in modulating ASD's stability. In-depth analysis of the prepared systems revealed the (1) reduction of API's molecular motions within the cross-linked polymeric networks (through API's strong spatial confinement), (2) the structural changes in the prepared cross-linked matrices (induced by the high API drug loading), and (3) the tuning of the cross-linking density via utilization of low-hydrolyzed PVA as the major mechanisms responsible for ASD's exceptional performance. Complementary analysis by means of molecular dynamics simulations also highlighted the vital role of strong drug-polymer intermolecular interactions evolving among the ASD components. Overall, the impression of the complexity of in situ cross-linked ASDs has been reinforced with the excessive variation of parameters investigated in the current study, offering thus insights up to the submolecular level to lay the groundwork and foundations for the comprehensive assessment of a new emerging class of HDL amorphous API formulations.

Thermally Tunable Acoustic Beam Splitter Based on Poly(vinyl alcohol) Poly(N-isopropylacrylamide) Hydrogel

In this study, we demonstrated a thermally tunable acoustic beam splitter using a poly(vinyl alcohol) poly(N-isopropylacrylamide) hydrogel (PVA-pNIPAM). The nature of PVA-pNIPAM hydrogel offers exceptional temperature-dependent physical properties due to its phase transition around its lower critical solution temperature. The acoustic impedance of the hydrogel can be tuned below, above, or matched to that of water by changing the environmental temperature. An acoustic wave propagating in water can be split into transmitted and reflected components by the PVA-pNIPAM hydrogel slab on varying its angle of incidence. The intensity ratio between the reflected and the transmitted componence can be adjusted by tuning the temperature of the medium. The acoustic beam can be entirely reflected at a temperature corresponding to the matched impedance between hydrogel and water. The beam-splitting behavior was observed for acoustic waves from both a monochromatic wave and broadband pulse source. In addition, the phase of beam split pulses can be reversed by selecting the hydrogel’s operating temperature.

Bioscaffold-based study of glioblastoma cell behavior and drug delivery for tumor therapy

Glioblastoma multiforme (GBM) is a severe form of brain cancer with an average five-year survival rate of 6.7%. Current treatment strategies include surgical resection of the tumor area and lining the lesion site with therapeutics, which offer only a moderate impact on increasing survival rates. Drug-testing models based on the monolayer cell culture method may partially explain the lack of advancement in effective GBM treatment, because this model is limited in its ability to show heterogeneous cell-cell and cell-environment interactions as tumor cells in the in vivo state. The development of bioscaffold-based culture models is an important improvement in GBM research, preclinical trials, and targeted drug testing, through better mimicking of the heterogeneity of tumor environmental conditions. A major hurdle towards better GBM outcomes is in delivering medication across the blood-brain barrier (BBB), which normally prevents the crossing of materials into the treatment site. The delivery of therapeutics using bioscaffolds is a potential means of overcoming the BBB and could potentially facilitate long-lasting drug release. A number of natural and synthetic materials have been studied for their biodegradability, toxicity, distribution, and pharmaceutical stability, which are needed to determine the overall effectiveness and safety of glioblastoma treatment. This review summarizes advancements in the research of bioscaffold-based GBM cell growth systems and the potential of using bioscaffolds as a carrier for drug delivery.

Is Viral Vector Gene Delivery More Effective Using Biomaterials?

Gene delivery has been extensively investigated for introducing foreign genetic material into cells to promote expression of therapeutic proteins or to silence relevant genes. This approach can regulate genetic or epigenetic disorders, offering an attractive alternative to pharmacological therapy or invasive protein delivery options. However, the exciting potential of viral gene therapy has yet to be fully realized, with a number of clinical trials failing to deliver optimal therapeutic outcomes. Reasons for this include difficulty in achieving localized delivery, and subsequently lower efficacy at the target site, as well as poor or inconsistent transduction efficiency. Thus, ongoing efforts are focused on improving local viral delivery and enhancing its efficiency. Recently, biomaterials have been exploited as an option for more controlled, targeted and programmable gene delivery. There is a growing body of literature demonstrating the efficacy of biomaterials and their potential advantages over other delivery strategies. This review explores current limitations of gene delivery and the progress of biomaterial-mediated gene delivery. The combination of biomaterials and gene vectors holds the potential to surmount major challenges, including the uncontrolled release of viral vectors with random delivery duration, poorly localized viral delivery with associated off-target effects, limited viral tropism, and immune safety concerns.

Thermally Tunable Dynamic and Static Elastic Properties of Hydrogel Due to Volumetric Phase Transition

The temperature dependence of the mechanical properties of polyvinyl alcohol-based poly n-isopropyl acrylamide (PVA-PNIPAm) hydrogel was studied from the static and dynamic bulk modulus of the material. The effect of the temperature-induced volumetric phase transition on Young’s Modulus, Poisson’s ratio, and the density of PVA-PNIPAm was experimentally measured and compared with a non-thermo-responsive Alginate hydrogel as a reference. An increase in the temperature from 27.5 to 32 °C results in the conventional temperature-dependent de-swelling of the PVA-PNIPAm hydrogel volume of up to 70% at the lower critical solution temperature (LCST). However, with the increase in temperature, the PVA-PNIPAm hydrogel showed a drastic increase in Young’s Modulus and density of PVA-PNIPAm and a corresponding decrease in the Poisson’s ratio and the static bulk modulus around the LCST temperature. The dynamic bulk modulus of the PVA-PNIPAm hydrogel is highly frequency-dependent before the LCST and highly temperature-sensitive after the LCST. The dynamic elastic properties of the thermo-responsive PVA-PNIPAm hydrogel were compared and observed to be significantly different from the thermally insensitive Alginate hydrogel.

Synthesis and Evaluation of a Thermoresponsive Degradable Chitosan-Grafted PNIPAAm Hydrogel as a "Smart" Gene Delivery System

Thermoresponsive hydrogels demonstrate tremendous potential as sustained drug delivery systems. However, progress has been limited as formulation of a stable biodegradable thermosensitive hydrogel remains a significant challenge. In this study, free radical polymerization was exploited to formulate a biodegradable thermosensitive hydrogel characterized by sustained drug release. Highly deacetylated chitosan and N-isopropylacrylamide with distinctive physical properties were employed to achieve a stable, hydrogel network at body temperature. The percentage of chitosan was altered within the copolymer formulations and the subsequent physical properties were characterized using ¹H-NMR, FTIR, and TGA. Viscoelastic, swelling, and degradation properties were also interrogated. The thermoresponsive hydrogels were loaded with RALA/pEGFP-N1 nanoparticles and release was examined. There was sustained release of nanoparticles over three weeks and, more importantly, the nucleic acid cargo remained functional and this was confirmed by successful transfection of the NCTC-929 fibroblast cell line. This tailored thermoresponsive hydrogel offers an option for sustained delivery of macromolecules over a prolonged considerable period.

Poly(N-isopropylacrylamide)-Based Thermoresponsive Composite Hydrogels for Biomedical Applications

Poly(N-isopropylacrylamide) (PNIPAM)-based thermosensitive hydrogels demonstrate great potential in biomedical applications. However, they have inherent drawbacks such as low mechanical strength, limited drug loading capacity and low biodegradability. Formulating PNIPAM with other functional components to form composited hydrogels is an effective strategy to make up for these deficiencies, which can greatly benefit their practical applications. This review seeks to provide a comprehensive observation about the PNIPAM-based composite hydrogels for biomedical applications so as to guide related research. It covers the general principles from the materials choice to the hybridization strategies as well as the performance improvement by focusing on several application areas including drug delivery, tissue engineering and wound dressing. The most effective strategies include incorporation of functional inorganic nanoparticles or self-assembled structures to give composite hydrogels and linking PNIPAM with other polymer blocks of unique properties to produce copolymeric hydrogels, which can improve the properties of the hydrogels by enhancing the mechanical strength, giving higher biocompatibility and biodegradability, introducing multi-stimuli responsibility, enabling higher drug loading capacity as well as controlled release. These aspects will be of great help for promoting the development of PNIPAM-based composite materials for biomedical applications.

Fabrication of a Cartilage Patch by Fusing Hydrogel-Derived Cell Aggregates onto Electrospun Film

Irregular defects at sites of degenerative cartilage often accompany osteoarthritis (OA). The development of novel cell-/biomaterial-based cartilage tissue engineering methods to address these defects may provide a durable approach to hinder the development of OA. In this study, we fabricated a neocartilage patch by fusing cell aggregates onto a biodegradable nanofiber film for degenerative cartilage repair. Human mesenchymal stem/stromal cell (MSC) aggregates were prepared and induced for chondrogenesis in a thermosensitive hydrogel, poly (N-isopropylacrylamide-co-acrylic acid (p(NIPAAm-AA)). Cell migration mediated the formation of cell aggregates in the thermosensitive hydrogel and led to a cell-dense hollow shell structure. The chondrocytes derived from MSC aggregates in the hydrogel were evidenced by the expression of chondrogenesis-related genes and extracellular matrices. They were fused onto an electrospun film by mechanical force and spatial confinement to generate a neo-cartilage patch. The fabricated neocartilage patches may be able to integrate into the irregular defects under compressive stresses and achieve cartilage regeneration in vivo. Impact statement The formation of human mesenchymal stem/stromal cells aggregates in thermosensitive hydrogels was mechanistically examined. These in situ formed cell aggregates with enhanced chondrogenesis were bioengineered into a neocartilage patch for regeneration of superficial irregular cartilage defects.

Structural and bone marrow stem cell biocompatibility studies of hydrogel synthesized via chemo-enzymatic route

Natural biopolymers have many attractive medical applications; however, complications due to fibrosis caused a reduction in diffusion and dispersal of nutrients and waste products. Consequently, severe immunocompatibility problems and poor mechanical and degradation properties in synthetic polymers ensue. Hence, the present study investigates a novel hydrogel material synthesized from caprolactone, ethylene glycol, ethylenediamine, polyethylene glycol, ammonium persulfate, and tetramethylethylenediamine via chemo-enzymatic route. Spectroscopic analyses indicated the formation of polyurea and polyhydroxyurethane as the primary building block of the hydrogel starting material. Biocompatibility studies showed positive observation in biosafety test using direct contact cytotoxicity assay in addition to active cellular growth on the hydrogel scaffold based on fluorescence observation. The synthesized hydrogel also exhibited (self)fluorescence properties under specific wavelength excitation. Hence, synthesized hydrogel could be a potential candidate for medical imaging as well as tissue engineering applications as a tissue expander, coating material, biosensor, and drug delivery system.

Thermoresponsive polysaccharides and their thermoreversible physical hydrogel networks

Thermoresponsive polymers have been used extensively for various applications including food additives, pharmaceutical formulations, therapeutic delivery, cosmetics and environmental remediation, to mention a few. Many thermoresponsive polymers have the ability to form physical hydrogel networks in response to temperature changes, which are particularly useful for emerging biomedical applications, including cell therapies, drug delivery systems, tissue engineering, wound healing and 3D bioprinting. In particular, the use of polysaccharides with thermoresponsive properties has been of interest due to their wide availability, versatile functionality, biodegradability, and in many cases, inherent biocompatibility. Naturally thermoresponsive polysaccharides include agarose, carrageenans and gellan gum, which exhibit upper critical solution temperatures, transitioning from a solution to a gel state upon cooling. Arguably, this limits their use in biomedical applications, particularly for cell encapsulation as they require raised temperatures to maintain a solution state that may be detrimental to living systems. Conversely, significant progress has been made over recent years to develop synthetically modified polysaccharides, which tend to exhibit lower critical solution temperatures, transitioning from a solution to a gel state upon warming. Of particular interest are thermoresponsive polysaccharides with a lower critical solution temperature in between room temperature and physiological temperature, as their solutions can conveniently be manipulated at room temperature before gelling upon warming to physiological temperature, which makes them ideal candidates for many biological applications. Therefore, this review provides an introduction to the different types of thermoresponsive polysaccharides that have been developed, their resulting hydrogels and properties, and the exciting applications that have emerged as a result of these properties.

Rational Development of a Novel Hydrogel as a pH-Sensitive Controlled Release System for Nifedipine

This work depicts the rational development (in-silico design, synthesis, characterization and in-vitro evaluation) of polyvinyl alcohol hydrogels (PVAH) cross-linked with maleic acid (MA) and linked to γ-cyclodextrin molecules (γ-CDPVAHMA) as systems for the controlled and sustained release of nifedipine (NFD). Through computational studies, the structural blocks (PVA chain + dicarboxylic acid + γ-CD) of 20 different hydrogels were evaluated to test their interaction energies (ΔE) with NFD. According to the ΔE obtained, the hydrogel cross-linked with maleic acid was selected. To characterize the intermolecular interactions between NFD and γ-CDPVAHMA, molecular dynamics simulation studies were carried out. Experimentally, three hydrogel formulations with different proportions of γ-CD (2.43%, 3.61% and 4.76%) were synthesized and characterized. Both loading and release of NFD from the hydrogels were evaluated at acid and basic pH. The computational and experimental results show that γ-CDs linked to the hydrogels were able to form 1:1 inclusion complexes with NFD molecules. Finally, γ-CDPVAHMA-3 demonstrated to be the best pH-sensitive release platform for nifedipine. Its effectiveness could significantly reduce the adverse effects caused by the anticipated release of NFD in the stomach of patients.

Strengthening injectable thermo-sensitive NIPAAm-g-chitosan hydrogels using chemical cross-linking of disulfide bonds as scaffolds for tissue engineering

In the present study, we fabricated non-toxic, injectable, and thermo-sensitive NIPAAm-g-chitosan (NC) hydrogels with thiol modification for introduction of disulfide cross-linking strategy. Previously, NIPAAm and chitosan copolymer has been proven to have excellent biocompatibility, biodegradability and rapid phase transition after injection, suitable to serve as cell carriers or implanted scaffolds. However, weak mechanical properties significantly limit their potential for biomedical fields. In order to overcome this issue, we incorporated thiol side chains into chitosan by covalently conjugating N-acetyl-cysteine (NAC) with carbodiimide chemistry to strengthen mechanical properties. After oxidation of thiols into disulfide bonds, modified NC hydrogels did improve the compressive modulus over 9 folds (11.4 kPa). Oscillatory frequency sweep showed a positive correlation between storage modulus and cross-liking density as well. Additionally, there was no cytotoxicity observed to mesenchymal stem cells, fibroblasts and osteoblasts. We suggested that the thiol-modified thermo-sensitive polysaccharide hydrogels are promising to be a cell-laden biomaterial for tissue regeneration.

Guidelines for Microplate Selection in High Content Imaging

Since the inception of commercialized automated high content screening (HCS) imaging devices in the mid to late 1990s, the adoption of media vessels typically used to house and contain biological specimens for interrogation has transitioned from microscope slides and petri dishes into multi-well microtiter plates called microplates. The early 96- and 384-well microplates commonly used in other high-throughput screening (HTS) technology applications were often not designed for optical imaging. Since then, modifications and the use of next-generation materials with improved optical clarity have enhanced the quality of captured images, reduced autofocusing failures, and empowered the use of higher power magnification objectives to resolve fine detailed measurements at the subcellular pixel level. The plethora of microplates and their applications requires practitioners of high content imaging (HCI) to be especially diligent in the selection and adoption of the best plates for running longitudinal studies or larger screening campaigns. While the highest priority in experimental design is the selection of the biological model, the choice of microplate can alter the biological response and ultimately may change the experimental outcome. This chapter will provide readers with background, troubleshooting guidelines, and considerations for choosing an appropriate microplate.

Influence of alginate backbone on efficacy of thermo-responsive alginate-g-P(NIPAAm) hydrogel as a vehicle for sustained and controlled gene delivery

Alginate grafted poly(N-isopropylacrylamide) hydrogels (Alg-g-P(NIPAAm)) form three-dimensional networks in mild conditions, making them suitable for incorporation of labile macromolecules, such as DNA. The impact of P(NIPAAm) on copolymer characteristics has been well studied, however the impact of alginate backbone characteristics on copolymer properties has to-date not been investigated. Six different Alg-g-P(NIPAAm) hydrogels were synthesised with 10% alginate, which varied in terms of molecular weight (MW) and mannuronate/guluronate (M/G) monomer ratio, and with 90% NIPAAm in order to develop an injectable and thermo-responsive hydrogel formulation for localised gene delivery. Hydrogel stiffness was directly proportional to MW and the M/G ratio of the alginate backbone. Hydrogels with a high MW or low M/G ratio alginate backbone demonstrated a greater stiffness than those hydrogels comprising low MW alginates and high M/G ratio. Hydrogels with a high M/G ratio also produced a complexed and meshed hydrogel network while hydrogels with a low M/G ratio produced a simplified structure with the superposition of Alg-g-P(NIPAAm) sheets. This study was designed to produce the optimal Alg-g-P(NIPAAm) hydrogel with respect to localised delivery of DNA nanoparticles as a potential medical device for those with castrate resistant prostate cancer (CRPC). Given that CRPC typically disseminates to bone causing pain, morbidity and a plethora of skeletal related events, a copolymer based hydrogel was designed to for long term release of therapeutic DNA nanoparticles. The nanoparticles were comprised of plasmid DNA (pDNA), complexed with an amphipathic cell penetrating peptide termed RALA that is designed to enter cells with high efficiency. Alginate MW and M/G ratio affected stiffness, structure, injectability and degradation of the Alg-g-P(NIPAAm) hydrogel. Algogel 3001, had the optimal characteristics for long-term application and was loaded with RALA/pDNA NPs. From the release profiles, it was evident that RALA protected the pDNA from degradation over a 30-day period and conferred a sustained and controlled release profile from the hydrogels compared to pDNA only. Taken together, we have designed a slowly degrading hydrogel suitable for sustained delivery of nucleic acids when incorporated with the RALA delivery peptide. This now opens up several opportunities for the delivery of therapeutic pDNA from this thermo-responsive hydrogel with numerous medical applications.

Anisotropic diffusion in stretched hydrogels containing erythrocytes: evidence of cell-shape distortion recorded by PGSE NMR spectroscopy

The remarkable flexibility of human red blood cells (RBCs) allows them to assume a range of shapes in normal and disease states. Biochemical mechanisms and energetic requirements associated with changes in RBC geometry are not well understood because of a lack of experimental procedures to fix and study cells in different morphological forms. By incorporating RBCs into stretchable gelatin hydrogels, we created conditions for adjustable elongation of their normal discocytic shape in all orientations. As the RBC-containing gels were stretched or compressed, the changes in the cell morphology were studied by using ¹ H-PGSE-NMR spectroscopy. Measurements of the apparent diffusion coefficient of water along the three orthogonal directions revealed tuneable anisotropy in the environment of the hydrogel samples. Light microscopy was also used for recording the extent to which RBCs were distorted in a stretched gel that had been set around them. Having demonstrated the applicability of NMR diffusometry to detect morphological changes of immobilised cells, we have laid the groundwork for future investigations of controllably distorted RBCs. Specifically, we expect studies of metabolic and biophysical properties of the physically deformed cells, thus inferring the connection between intracellular physico-chemical processes and RBC morphology. Copyright © 2016 John Wiley & Sons, Ltd.

An investigation of chitosan and its derivatives on red blood cell agglutination

RBC agglutination was determined by the number of protonated amine groups on chitosan and its derivatives.

Photoresponsive self-healing supramolecular hydrogels for light-induced release of DNA and doxorubicin

An azobenzene-containing cyclic dipeptide PAP-DKP-Lys is a photoresponsive low-MW hydrogelator. The gelation process can be triggered with temperature, pH, light, and ionic strength. The resulting self-healing gels can encapsulate dsDNA or an anticancer drug doxorubicin, and release them in a light-dependent manner.

Effects of chain flexibility on the properties of DNA hydrogels

The effect of chain rigidity on the mechanic properties of DNA hydrogels was studied. Counterintuitively, the hydrogel formed by mainly flexible chains exhibited better stability, stretchability, and much mechanical properties than the hydrogel containing only rigid chains. Calculations showed that the crosslinking ratio in the hydrogel formed by flexible chains was about twice that of the hydrogel formed by rigid chains under the same conditions. We attributed this to the ease of conformational adjustment of flexible chains. Incorporation of 25% rigid chains further improved the performance of DNA hydrogel by shrinking the pore size and tuning its distribution.

Biodegradable, thermoresponsive PNIPAM-based hydrogel scaffolds for the sustained release of levofloxacin

The cumulative release of LVF-loaded TBHs exhibited a thermo-induced slow sustained drug release and a reduction-induced fast release.

A mechanistic study on tumour spheroid formation in thermosensitive hydrogels: experiments and mathematical modelling

Thermo-reversible microgels to culture and harvest uniform-sized tumour spheroids with a narrow size-distribution.

Influence of polymer molecular weight on the in vitro cytotoxicity of poly (N-isopropylacrylamide)

Poly (N-isopropylacrylamide) (PNIPAAm) is a thermosensitive polymer with various biomedical applications. We examined molecular weight (MW)-dependent cytotoxicity of PNIPAAm. Our results indicated that low-MW PNIPAAm (degree of polymerization (DP)=35) is inherently toxic to cells. Moderate-MW PNIPAAms with their DP between 100 and 200 are non-cytotoxic. When cells are seeded on top of a polymer-coated surface, PNIPAAm with a higher MW (DP=400) shows non/low cytotoxicity, while when monolayer cells are exposed to the polymer solution, cell viability drops drastically. This may be due to lack of nutrient and oxygen rather than intrinsic toxicity of the polymer.

Effects of strongly aggregated silica nanoparticles on interfacial behaviour of water bound to lactic acid bacteria

Suspending lactic acid bacteria with silica microparticles results in complete de-agglomeration of bacteria.