Development of thermo-responsive polycaprolactone macrocarriers conjugated with Poly(N-isopropyl acrylamide) for cell culture

Emerging Trends in Biodegradable Microcarriers for Therapeutic Applications

Microcarriers (MCs) are adaptable therapeutic instruments that may be adjusted to specific therapeutic uses, making them an appealing alternative for regenerative medicine and drug delivery. MCs can be employed to expand therapeutic cells. MCs can be used as scaffolds for tissue engineering, as well as providing a 3D milieu that replicates the original extracellular matrix, facilitating cell proliferation and differentiation. Drugs, peptides, and other therapeutic compounds can be carried by MCs. The surface of the MCs can be altered, to improve medication loading and release, and to target specific tissues or cells. Allogeneic cell therapies in clinical trials require enormous volumes of stem cells, to assure adequate coverage for several recruitment locations, eliminate batch to batch variability, and reduce production costs. Commercially available microcarriers necessitate additional harvesting steps to extract cells and dissociation reagents, which reduces cell yield and quality. To circumvent such production challenges, biodegradable microcarriers have been developed. In this review, we have compiled key information relating to biodegradable MC platforms, for generating clinical-grade cells, that permit cell delivery at the target site without compromising quality or cell yields. Biodegradable MCs could also be employed as injectable scaffolds for defect filling, supplying biochemical signals for tissue repair and regeneration. Bioinks, coupled with biodegradable microcarriers with controlled rheological properties, might improve bioactive profiles, while also providing mechanical stability to 3D bioprinted tissue structures. Biodegradable materials used for microcarriers have the ability to solve in vitro disease modeling, and are advantageous to the biopharmaceutical drug industries, because they widen the spectrum of controllable biodegradation and may be employed in a variety of applications.

Towards Ready-to-Use Iron-Crosslinked Alginate Beads as Mesenchymal Stem Cell Carriers

Micro-carriers, thanks to high surface/volume ratio, are widely studied as mesenchymal stem cell (MSCs) in vitro substrate for proliferation at clinical rate. In particular, Ca-alginate-based biomaterials (sodium alginate crosslinked with CaCl₂) are commonly investigated. However, Ca-alginate shows low bioactivity and requires functionalization, increasing labor work and costs. In contrast, films of sodium alginate crosslinked with iron chloride (Fe-alginate) have shown good bioactivity with fibroblasts, but MSCs studies are lacking. We propose a first proof-of-concept study of Fe-alginate beads supporting MSCs proliferation without functionalization. Macro- and micro-carriers were prepared (extrusion and electrospray) and we report for the first time Fe-alginate electrospraying optimization. FTIR spectra, stability with various mannuronic acids/guluronic acids (M/G) ratios and size distribution were analyzed before performing cell culture. After confirming literature results on films with human MSCs, we showed that Macro-Fe-alginate beads offered a better environment for MSCs adhesion than Ca-alginate. We concluded that Fe-alginate beads showed great potential as ready-to-use carriers.

Advanced Nanotechnology Approaches as Emerging Tools in Cellular-Based Technologies

Stem cells are valuable tools in regenerative medicine because they can generate a wide variety of cell types and tissues that can be used to treat or replace damaged tissues and organs. However, challenges related to the application of stem cells in the scope of regenerative medicine have urged scientists to utilize nanomedicine as a prerequisite to circumvent some of these hurdles. Nanomedicine plays a crucial role in this process and manipulates surface biology, the fate of stem cells, and biomaterials. Many attempts have been made to modify cellular behavior and improve their regenerative ability using nano-based strategies. Notably, nanotechnology applications in regenerative medicine and cellular therapies are controversial because of ethical and legal considerations. Therefore, this review describes nanotechnology in cell-based applications and focuses on newly proposed nano-based approaches. Cutting-edge strategies to engineer biological tissues and the ethical, legal, and social considerations of nanotechnology in regenerative nanomedicine applications are also discussed.

Preparation of an Antioxidant Assembly Based on a Copolymacrolactone Structure and Erythritol following an Eco-Friendly Strategy

The study presents the achievement of a new assembly with antioxidant behaviour based on a copolymacrolactone structure that encapsulates erythritol (Eryt). Poly(ethylene brassylate-co-squaric acid) (PEBSA) was synthesised in environmentally friendly conditions, respectively, through a process in suspension in water by opening the cycle of ethylene brassylate macrolactone, followed by condensation with squaric acid. The compound synthesised in suspension was characterised by comparison with the polymer obtained by polymerisation in solution. The investigations revealed that, with the exception of the molecular masses, the compounds generated by the two synthetic procedures present similar properties, including good thermal stability, with a T_peak of 456 °C, and the capacity for network formation. In addition, the investigation by dynamic light scattering techniques evidenced a mean diameter for PEBSA particles of around 596 nm and a zeta potential of -25 mV, which attests to their stability. The bio-based copolymacrolactone was used as a matrix for erythritol encapsulation. The new PEBSA-Eryt compound presented an increased sorption/desorption process, compared with the PEBSA matrix, and a crystalline morphology confirmed by X-ray diffraction analysis. The bioactive compound was also characterised in terms of its biocompatibility and antioxidant behaviour.

Therapeutic Application of an Ag-Nanoparticle-PNIPAAm-Modified Eggshell Membrane Construct for Dermal Regeneration and Reconstruction

Current therapeutic treatments for the repair and/or replacement of damaged skin following disease or traumatic injury is severely limited. The chicken eggshell membrane (ESM) is a unique material: its innate physical and mechanical characteristics offer optimal barrier properties and, as a naturally derived extract, it demonstrates inherent biocompatibility/biodegradability. To further enhance its therapeutic and clinical potential, the ESM can be modified with the thermo-responsive polymer, poly(N-isopropylacrylAmide) (PNIPAAm) as well as the incorporation of (drug-loaded) silver nanoparticles (AgNP); essentially, by a simple change in temperature, the release and delivery of the NP can be targeted and controlled. In this study, ESM samples were isolated using a decellularization protocol, and the physical and mechanical characteristics were profiled using SEM, FT-IR, DSC and DMA. PNIPAAm was successfully grafted to the ESM via amidation reactions and confirmed using FT-IR, which demonstrated the distinctive peaks associated with Amide A (3275 cm−1), Amide B (2970 cm−1), Amide I (1630 cm−1), Amide II (1535 cm−1), CH2, CH3 groups, and Amide III (1250 cm−1) peaks. Confirmation of the incorporation of AgNP onto the stratified membrane was confirmed visually with SEM, qualitatively using FT-IR and also via changes in absorbance at 380 nm using UV-Vis spectrophotometry during a controlled release study for 72 h. The biocompatibility and cytotoxicity of the novel constructs were assessed using human dermal fibroblast (HDFa) and mouse dermal fibroblast (L929) cells and standard cell culture assays. Metabolic activity assessment (i.e., MTS assay), LDH-release profiles and Live/Dead staining demonstrated good attachment and spreading to the samples, and high cell viability following 3 days of culture. Interestingly, longer-term viability (>5 days), the ESM-PNIPAAm and ESM-PNIPAAm (AgNP) samples showed a greater and sustained cell viability profile. In summary, the modified and enhanced ESM constructs were successfully prepared and characterized in terms of their physical and mechanical profiles. AgNP were successfully loaded into the construct and demonstrated a desirable release profile dependent on temperature modulation. Fibroblasts cultured on the extracted ESM samples and ESM-PNIPAAm demonstrated high biocompatibility in terms of high cell attachment, spreading, viability and proliferation rates. As such, this work summarizes the development of an enhanced ESM-based construct which may be exploited as a clinical/therapeutic wound dressing as well as a possible application as a novel biomaterial scaffold for drug development.

Validation and scalability of homemade polycaprolactone macro-beads grafted with thermo-responsive poly (N-isopropyl acrylamide) for mesenchymal stem cell expansion and harvesting

In this study, polycaprolactone (PCL) macro-beads were prepared by an oil-in-water (o/w) emulsion solvent evaporation method with poly (vinyl alcohol) (PVA) as an emulsifier and conjugated to poly (N-isopropyl acrylamide) (PNIPAAm) to be used as cell carriers with non-invasive cell detachment properties (thermo-response). Following previous studies with PCL-PNIPAAm carriers, our objectives were to confirm the successful conjugation on homemade macro-beads and to show the advantages of homemade production over commercial beads to control morphological, biological and fluidization properties. The effects of PCL concentration on the droplet formation and of flow rate and PVA concentration on the size of the beads were demonstrated. The size of the beads, all spherical, ranged from 0.5 mm to 3.7 mm with four bead categories based on production parameters. The morphology and size of the beads were observed by scanning electron microscopy to show surface roughness enhancing cell attachment and proliferation compared to commercial beads. The functionalization steps with PNIPAAm were then characterized and confirmed by Fourier transform infrared spectroscopy (FTIR), SEM and Energy Dispersion Spectroscopy (EDS). PNIPAAm-grafted macro-beads allowed mesenchymal stem cells (MSC) to spread and grow for up to 21 days. By reducing the temperature to 25 °C, the MSCs were successfully detached from the PCL-PNIPAAm beads as observed with fluorescence microscopy. Furthermore, we validated the scalability potential of both macro-beads production and conjugation with PCL, in order to produce easily kilograms of thermo-responsive macro-carriers in a lab environment. This could help moving such approaches towards clinically and industrially relevant processes were cell expansion is needed at very large scale. This article is protected by copyright. All rights reserved.

Scaffolding Biomaterials for 3D Cultivated Meat: Prospects and Challenges

Cultivating meat from stem cells rather than by raising animals is a promising solution to concerns about the negative externalities of meat production. For cultivated meat to fully mimic conventional meat's organoleptic and nutritional properties, innovations in scaffolding technology are required. Many scaffolding technologies are already developed for use in biomedical tissue engineering. However, cultivated meat production comes with a unique set of constraints related to the scale and cost of production as well as the necessary attributes of the final product, such as texture and food safety. This review discusses the properties of vertebrate skeletal muscle that will need to be replicated in a successful product and the current state of scaffolding innovation within the cultivated meat industry, highlighting promising scaffold materials and techniques that can be applied to cultivated meat development. Recommendations are provided for future research into scaffolds capable of supporting the growth of high-quality meat while minimizing production costs. Although the development of appropriate scaffolds for cultivated meat is challenging, it is also tractable and provides novel opportunities to customize meat properties.

Fabrication of Quasi-2D Shape-Tailored Microparticles using Wettability Contrast-Based Platforms

The ability to fabricate materials with ultrathin architectures enables the breakthrough of low-dimensional structures with high surface area that showcase distinctive properties from their bulk counterparts. They are exploited in a wide range of fields, including energy harvesting, catalysis, and biomedicine. Despite such versatility, the fine tuning of the lateral dimensions and geometry of these structures remains challenging. Prepatterned platforms gain significant attention as enabling technologies to process materials with highly controlled shapes and dimensions. Herein, different nanometer-thick particles of various lateral sizes and geometries (e.g., squares, circles, triangles, hexagons) are processed with high precision and definition, taking advantage of the wettability contrast of oleophilic-oleophobic patterned surfaces. Quasi-2D polymeric microparticles with high shape- and size-fidelity can be retrieved as freestanding objects in a single step. These structures show cell-mediated pliability, and their integration in gravity-enforced human adipose-derived stem cell spheroids leads to an enhanced metabolic activity and a modulated secretion of proangiogenic factors.

Microcarrier-based stem cell bioprocessing: GMP-grade culture challenges and future trends for regenerative medicine

Recently, stem cell-based therapies have been proposed as an alternative for the treatment of many diseases. Stem cells (SCs) are well known for their capacity to preserve themselves, proliferate, and differentiate into multiple lineages. These characteristics allow stem cells to be a viable option for the treatment of diverse diseases. Traditional methodologies based on 2-dimensional culture techniques (T-flasks and Petri dishes) are simple and well standardized; however, they present disadvantages that limit the production of the cell yield required for regenerative medicine applications. Lately, microcarrier (MC)-based culture techniques have emerged as an attractive platform for expanding stem cells in suspension systems. Although the use of stem cell expansion on MCs has recently shown significant increase, their implementation for medical purposes is been hampered by bottlenecks in upstream and downstream processing. Therefore, there is an urgent need in the development of bioprocesses that simplify stem cell cultures under xeno-free conditions and detachment from MCs without diminishing their pluripotency and viability. A critical analysis of the factors that impact the up and downstream bioprocessing on MC-based stem cell cultures is presented in this review. This analysis aims to raise the awareness of the current drawbacks that limit MC-based stem cell bioprocessing in regenerative medicine and propose alternatives to overcome them.

Micro computed tomography with and without contrast enhancement for the characterization of microcarriers in dry and wet state

In the field of regenerative medicine, microcarriers are used as support matrix for the growth of adherent cells. They are increasingly recognised as promising biomaterials for large scale, cost-effective cell expansion bioreactor processes. However, their individual morphologies can be highly heterogeneous which increases bioprocesses' variability. Additionally, only limited information is available on the microcarriers' 3D morphology and how it affects cell proliferation. Most imaging modalities do not provide sufficient 3D information or have a too limited field of view to appropriately study the 3D morphology. While microfocus X-ray computed tomography (microCT) could be appropriate, many microcarriers are hydrated before in-vitro use. This wet state makes them swell, changing considerably their morphology and making them indistinguishable from the culture solution in regular microCT images due to their physical density close to water. The use of contrast-enhanced microCT (CE-CT) has been recently reported for 3D imaging of soft materials. In this study, we selected a range of commercially available microcarrier types and used a combination of microCT and CE-CT for full 3D morphological characterization of large numbers of microcarriers, both in their dry and wet state. With in-house developed image processing and analysis tools, morphometrics of individual microcarriers were collected. Also, the morphology in wet state was assessed and related to accessible attachment surface area as a function of cell size. The morphological information on all microcarriers was collected in a publicly available database. This work provides a quantitative basis for optimization and modelling of microcarrier based cell expansion processes.

Thermoresponsive surfaces designed for the proliferation and differentiation of human pluripotent stem cells

Thermoresponsive surfaces enable the detachment of cells or cell sheets by decreasing the temperature of the surface when harvesting the cells. However, human pluripotent stem cells (hPSCs), such as embryonic stem cells and induced pluripotent stem cells, cannot be directly cultured on a thermoresponsive surface; hPSCs need a specific extracellular matrix to bind to the integrin receptors on their surfaces. We prepared a thermoresponsive surface by using poly(N-isopropylacrylamide-co-butylacrylate) and recombinant vitronectin to provide an optimal coating concentration for the hPSC culture. hPSCs can be cultured on the same thermoresponsive surface for 5 passages by partial detachment of the cells from the surface by decreasing the temperature for 30 min; then, the remaining hPSCs were subsequently cultured on the same dishes following the addition of new cultivation media. The detached cells, even after continual culture for five passages, showed high pluripotency, the ability to differentiate into cells derived from the 3 germ layers and the ability to undergo cardiac differentiation.

Thermoresponsive Poly(2-propyl-2-oxazoline) Surfaces of Glass for Nonenzymatic Cell Harvesting

As one of the nonenzymatic cell-harvesting technologies, a thermal-responsive surface based on poly(2-oxazoline)s has achieved initial success in supporting the adhesion and thermal-induced detachment of animal cells. However, because of the laborious preparation procedure, this technique was only limited to research purposes. In this work, through using poly(glycidyl methacrylate) (PGMA) as the anchor layer, poly(2-propyl-2-oxazoline)s (PPOx) were grafted onto glass wafers through a facile two-step coating and annealing procedure for nonenzymatic cell harvesting. In the first step, the piranha solution-activated glass wafers were immersed into the chloroform solution of PGMA and then annealed for a given period of time to immobilize PGMA onto the glass wafers through the bonding between epoxy groups and hydroxyl groups. In the second step, the PGMA-coated glass wafers were further immersed into the chloroform solution of carboxyl-functionalized PPOx. After annealing, PPOx were immobilized onto the PGMA layer through the bonding between carboxyl groups and the residual epoxy groups. Atomic force microscopy, X-ray photoelectron spectroscopy, and ellipsometry were used to characterize the modified glass wafers. The results of cytocompatibility evaluation showed that the PPOx-coated glass wafers were almost nontoxic and were able to support the adhesion and proliferation of L929 cells well. By lowering the temperature to 8 °C, L929 and Vero cells were successfully detached from the PPOx-coated glass wafers without any enzymatic treatment. Further cultivation has demonstrated that the cooling procedure had little effect on cell viability, and the cells still retained good viability after harvesting.

Coating biopolymer nanofibers with carbon nanotubes accelerates tissue healing and bone regeneration through orchestrated cell- and tissue-regulatory responses

Tailoring the surface of biomaterial scaffolds has been a key strategy to modulate the cellular interactions that are helpful for tissue healing process. In particular, nanotopological surfaces have been demonstrated to regulate diverse behaviors of stem cells, such as initial adhesion, spreading and lineage specification. Here, we tailor the surface of biopolymer nanofibers with carbon nanotubes (CNTs) to create a unique bi-modal nanoscale topography (500 nm nanofiber with 25 nm nanotubes) and report the performance in modulating diverse in vivo responses including inflammation, angiogenesis, and bone regeneration. When administered to a rat subcutaneous site, the CNT-coated nanofiber exhibited significantly reduced inflammatory signs (down-regulated pro-inflammatory cytokines and macrophages gathering). Moreover, the CNT-coated nanofibers showed substantially promoted angiogenic responses, with enhanced neoblood vessel formation and angiogenic marker expression. Such stimulated tissue healing events by the CNT interfacing were evidenced in a calvarium bone defect model. The in vivo bone regeneration of the CNT- coated nanofibers was significantly accelerated, with higher bone mineral density and up-regulated osteogenic signs (OPN, OCN, BMP2) of in vivo bone forming cells. The in vitro studies using MSCs could demonstrate accelerated adhesion and osteogenic differentiation and mineralization, supporting the osteo-promoting mechanism behind the in vivo bone forming event. These findings highlight that the CNTs interfacing of biopolymer nanofibers is highly effective in reducing inflammation, promoting angiogenesis, and driving adhesion and osteogenesis of MSCs, which eventually orchestrate to accelerate tissue healing and bone regeneration process. STATEMENT OF SIGNIFICANCE: Here we demonstrate that the interfacing of biopolymer nanofibers with carbon nanotubes (CNTs) could modulate multiple interactions of cells and tissues that are ultimately helpful for the tissue healing and bone regeneration process. The CNT-coated scaffolds significantly reduced the pro-inflammatory signals while stimulating the angiogenic marker expressions. Furthermore, the CNT-coated scaffolds increased the bone matrix production of bone forming cells in vivo as well as accelerated the adhesion and osteogenic differentiation of MSCs in vitro. These collective findings highlight that the CNTs coated on the biopolymer nanofibers allow the creation of a promising platform for nanoscale engineering of biomaterial surface that can favor tissue healing and bone regeneration process, through a series of orchestrated events in anti-inflammation, pro-angiogenesis, and stem cell stimulation.

Microcarriers for Upscaling Cultured Meat Production

Due to the considerable environmental impact and the controversial animal welfare associated with industrial meat production, combined with the ever-increasing global population and demand for meat products, sustainable production alternatives are indispensable. In 2013, the world's first laboratory grown hamburger made from cultured muscle cells was developed. However, coming at a price of $300.000, and being produced manually, substantial effort is still required to reach sustainable large-scale production. One of the main challenges is scalability. Microcarriers (MCs), offering a large surface/volume ratio, are the most promising candidates for upscaling muscle cell culture. However, although many MCs have been developed for cell lines and stem cells typically used in the medical field, none have been specifically developed for muscle stem cells and meat production. This paper aims to discuss the MCs' design criteria for skeletal muscle cell proliferation and subsequently for meat production based on three scenarios: (1) MCs are serving only as a temporary substrate for cell attachment and proliferation and therefore they need to be separated from the cells at some stage of the bioprocess, (2) MCs serve as a temporary substrate for cell proliferation but are degraded or dissolved during the bioprocess, and (3) MCs are embedded in the final product and therefore need to be edible. The particularities of each of these three bioprocesses will be discussed from the perspective of MCs as well as the feasibility of a one-step bioprocess. Each scenario presents advantages and drawbacks, which are discussed in detail, nevertheless the third scenario appears to be the most promising one for a production process. Indeed, using an edible material can limit or completely eliminate dissociation/degradation/separation steps and even promote organoleptic qualities when embedded in the final product. Edible microcarriers could also be used as a temporary substrate similarly to scenarios 1 and 2, which would limit the risk of non-edible residues.

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.

Molecular dynamics simulation of Doxorubicin loading with N-isopropyl acrylamide carbon nanotube in a drug delivery system

BACKGROUND AND OBJECTIVE

Doxorubicin is one of the common drugs used for cancer therapy. Molecular dynamics were applied to investigate the loading of Doxorubicin with thermosensitive N-isopropyl acrylamide Carbon nanotube carrier.

METHODS

The results showed that the smaller polymer chain length has more decrease of gyration radius. A decrease of gyration radius resulted in more concentrated aggregation with stronger bonds. Therefore, the shorter the polymer chain lengths, the more stable polymer interaction and better Doxorubicin delivery. Smaller polymers also form more hydrogen bonds with the drug leading to stronger and more stable carriers.

RESULTS

A lower amount of wall shear stress was found near the inner wall of the artery, distal to the plaque region (stenosis), and in both percentages of stenosis the maximum wall shear stress will accrue in the middle of the stenosis; however it is much more in the higher rate of stenosis.

CONCLUSIONS

The results indicated that N-isopropyl acrylamide - Carbon nanotube is suitable for the delivery of Doxorubicin, and five mer N-isopropyl acrylamide is the optimum carrier for Doxorubicin loading.

Synthesis of biodegradable protein–poly(ε-caprolactone) conjugates via enzymatic ring opening polymerization

Lipase–poly(HEAA) conjugates act as initiators and catalysts simultaneously for the eROP of ε-CL, forming biodegradable conjugates with amphiphilic graft copolymers.

Polycaprolactone as biomaterial for bone scaffolds: Review of literature

Bone tissue engineering using polymer based scaffolds have been studied a lot in last decades. Considering the qualities of all the polymers desired to be used as scaffolds, Polycaprolactone (PCL) polyester apart from being biocompatible and biodegradable qualifies to an appreciable level due its easy availability, cost efficacy and suitability for modification. Its adjustable physio-chemical state, biological properties and mechanical strength renders it to withstand physical, chemical and mechanical, insults without significant loss of its properties. This review aims to critically analyse the efficacy of PCL as a biomaterial for bone scaffolds.

Impact of the type of microcarrier and agitation modes on the expansion performances of mesenchymal stem cells derived from umbilical cord

The present study proposed to compare the impact of agitation mode (static, orbital, and mechanical) on the culture of mesenchymal stem cells extracted from the Wharton's jelly of umbilical cords (WJ-MSC), in a clinical grade culture medium, using human platelet lysate and different xeno-free microcarriers. Attachment, expansion, and detachment performances were characterized by a new dedicated tool of microscopic image posttreatment, allowing an in situ cell counting without detachment step. Results showed that performances in static mode were not necessarily representative of those obtained in dynamic mode. Moreover, impacts on nutrient consumptions and metabolite productions were identified, such as a higher glutamine consumption when Cytodex-1 microcarriers were used. The detachment strategy used was relatively efficient for Star-Plus, Plastic-Plus, and Hillex II, but not sufficient for Cytodex-1. Despite Cytodex-1 presented promising attachment and expansion performances, Star-Plus and Plastic-Plus showed a better compromise, respectively, for the orbital and the mechanical agitation modes.