Design and characterization of microspheres for a 3D mesenchymal stem cell culture

Formation and culture of cell spheroids by using magnetic nanostructures resembling a crown of thorns

In contrast to traditional two-dimensional cell-culture conditions, three-dimensional (3D) cell-culture models closely mimic complexin vivoconditions. However, constructing 3D cell culture models still faces challenges. In this paper, by using micro/nano fabrication method, including lithography, deposition, etching, and lift-off, we designed magnetic nanostructures resembling a crown of thorns. This magnetic crown of thorns (MCT) nanostructure enables the isolation of cells that have endocytosed magnetic particles. To assess the utility of this nanostructure, we used high-flux acquisition of Jurkat cells, an acute-leukemia cell line exhibiting the native phenotype, as an example. The novel structure enabled Jurkat cells to form spheroids within just 30 min by leveraging mild magnetic forces to bring together endocytosed magnetic particles. The size, volume, and arrangement of these spheroids were precisely regulated by the dimensions of the MCT nanostructure and the array configuration. The resulting magnetic cell clusters were uniform in size and reached saturation after 1400 s. Notably, these cell clusters could be easily separated from the MCT nanostructure through enzymatic digestion while maintaining their integrity. These clusters displayed a strong proliferation rate and survival capabilities, lasting for an impressive 96 h. Compared with existing 3D cell-culture models, the approach presented in this study offers the advantage of rapid formation of uniform spheroids that can mimicin vivomicroenvironments. These findings underscore the high potential of the MCT in cell-culture models and magnetic tissue enginerring.

Mapping the microcarrier design pathway to modernise clinical mesenchymal stromal cell expansion

Microcarrier expansion systems show exciting potential to revolutionise mesenchymal stromal cell (MSC)-based clinical therapies by providing an opportunity for economical large-scale expansion of donor- and patient-derived cells. The poor reproducibility and efficiency of cell expansion on commercial polystyrene microcarriers have driven the development of novel microcarriers with tuneable physical, mechanical, and cell-instructive properties. These new microcarriers show innovation toward improving cell expansion outcomes, although their limited biological characterisation and compatibility with dynamic culture systems suggest the need to realign the microcarrier design pathway. Clear headway has been made toward developing infrastructure necessary for scaling up these technologies; however, key challenges remain in characterising the wholistic effects of microcarrier properties on the biological fate and function of expanded MSCs.

Droplet Microfluidics Powered Hydrogel Microparticles for Stem Cell-Mediated Biomedical Applications

Stem cell-related therapeutic technologies have garnered significant attention of the research community for their multi-faceted applications. To promote the therapeutic effects of stem cells, the strategies for cell microencapsulation in hydrogel microparticles have been widely explored, as the hydrogel microparticles have the potential to facilitate oxygen diffusion and nutrient transport alongside their ability to promote crucial cell-cell and cell-matrix interactions. Despite their significant promise, there is an acute shortage of automated, standardized, and reproducible platforms to further stem cell-related research. Microfluidics offers an intriguing platform to produce stem cell-laden hydrogel microparticles (SCHMs) owing to its ability to manipulate the fluids at the micrometer scale as well as precisely control the structure and composition of microparticles. In this review, the typical biomaterials and crosslinking methods for microfluidic encapsulation of stem cells as well as the progress in droplet-based microfluidics for the fabrication of SCHMs are outlined. Moreover, the important biomedical applications of SCHMs are highlighted, including regenerative medicine, tissue engineering, scale-up production of stem cells, and microenvironmental simulation for fundamental cell studies. Overall, microfluidics holds tremendous potential for enabling the production of diverse hydrogel microparticles and is worthy for various stem cell-related biomedical applications.

Hydrogel Microparticles for Bone Regeneration

Hydrogel microparticles (HMPs) stand out as promising entities in the realm of bone tissue regeneration, primarily due to their versatile capabilities in delivering cells and bioactive molecules/drugs. Their significance is underscored by distinct attributes such as injectability, biodegradability, high porosity, and mechanical tunability. These characteristics play a pivotal role in fostering vasculature formation, facilitating mineral deposition, and contributing to the overall regeneration of bone tissue. Fabricated through diverse techniques (batch emulsion, microfluidics, lithography, and electrohydrodynamic spraying), HMPs exhibit multifunctionality, serving as vehicles for drug and cell delivery, providing structural scaffolding, and functioning as bioinks for advanced 3D-printing applications. Distinguishing themselves from other scaffolds like bulk hydrogels, cryogels, foams, meshes, and fibers, HMPs provide a higher surface-area-to-volume ratio, promoting improved interactions with the surrounding tissues and facilitating the efficient delivery of cells and bioactive molecules. Notably, their minimally invasive injectability and modular properties, offering various designs and configurations, contribute to their attractiveness for biomedical applications. This comprehensive review aims to delve into the progressive advancements in HMPs, specifically for bone regeneration. The exploration encompasses synthesis and functionalization techniques, providing an understanding of their diverse applications, as documented in the existing literature. The overarching goal is to shed light on the advantages and potential of HMPs within the field of engineering bone tissue.

Biomimicking nanofibrous gelatin microspheres recreating the stem cell niche for their ex-vivo expansion and in-vivo like differentiation for injectable stem cell transplantation

Stem cells based novel treatment modality for degenerative and immune dysfunction diseases created a huge demand of suitable carriers to support ex-vivo production of quality stem cells, and effective in-vivo transplantation of stem cells and their fate. In spite of promising candidature of nanofibrous microspheres (NFM) to recreate native stem cell niches to be used for possible scaling-up for ex-vivo stem cells expansion, it remains fairly unexplored. A systematic study on the stem cell-NFM interaction comparative with commercial microspheres (CM) has been performed for the first time. Gelatin NFM with variable physicochemical properties such as size, surface properties, surface chemistry, and variable degradability were prepared using microemulsion coupled with thermally induced phase separation (TIPS) method. Effect of physicochemical properties of NFM and their cellular interaction such as binding, morphology, metabolic activity and proliferation studies were performed using human bone marrow-derived mesenchymal stem cells (hBMSCs), human dental follicle stem cells (hDFSCs) and human gingival fibroblast (HGF) cells and compared with the commercial and solid microspheres. Gelatin NFM supports excellent cell binding, proliferation, metabolic activities and chemical cues specific differentiation. All out-turns indicate that NFM stand to be an outstanding candidate for ex-vivo cells' expansion and injectable carriers for stem cell transplantation.

In Vitro Cell Behavior and Antibiotic Activity under Sustained Release of Doxycycline-Loaded Poly(lactic-co-glycolic acid) Microspheres

The state-of-the-art sustained drug delivery systems are related to features to improve pharmacological transport through a controlled ratio between drug release and the desired therapeutic effect. Microspheres of biodegradable polymers, such as poly(lactic-co-glycolic acid) (PLGA), play an important role in these approaches, directing the release in a specific region of interest. In this way, the encapsulation of doxycycline (DOX) as a microbial agent turns the PLGA microspheres into a potential device for the treatment of topic oral diseases. Thus, this work aimed to produce DOX-loaded PLGA microspheres and see how they interfered with mesenchymal stem cell viability and in the sustained release in antimicrobial assays. Scanning electron microscopy showed the spherical microstructured pattern, revealing assorted sized distribution, with major diameters ranging 1–3 µm. The encapsulation efficiency presented a mean of 80% in both methods to obtain the microspheres (sonication and magnetic rotation). The DOX release test revealed a gradual and continuous profile of 30–40% between 120 and 168 h. Mesenchymal stem cells cultured in PLGA with or without DOX at several concentrations revealed no effect on the cell metabolic activity. Striking morphology changes were observed by confocal microscopy after 1 to 3 days under culture. The live/dead assay indicated that when microsphere densities were increased (from 10 to 100 µg/mL) cultured cells presented an internalized pattern of microspheres in both groups of PLGA containing DOX or not, while slight cell death signals were identified nearby microsphere clusters. Microbiological assays performed by the agar diffusion test pointed out that an inhibition zone was identified in Staphylococcus aureus (S. aureus) cultures at earlier times of DOX release. Despite the well-known use of PLGA as a drug delivery vehicle, when synthesized with DOX, it presents both characteristics of the desired treatment to prevent healthy tissue damage while avoiding bacterial growth in a microenvironment with anatomical features, such as grooves, projections, and other tough conditions that favor the development of oral diseases.

Biomimetic 3D Environment Based on Microgels as a Model for the Generation of Drug Resistance in Multiple Myeloma

The development of three-dimensional environments to mimic the in vivo cellular response is a problem in the building of disease models. This study aimed to synthesize and validate three-dimensional support for culturing monoclonal plasma cells (mPCs) as a disease model for multiple myeloma. The three-dimensional environment is a biomimetic microgel formed by alginate microspheres and produced on a microfluidic device whose surface has been functionalized by a layer-by-layer process with components of the bone marrow’s extracellular matrix, which will interact with mPC. As a proof of concept, RPMI 8226 cell line cells were cultured in our 3D culture platform. We proved that hyaluronic acid significantly increased cell proliferation and corroborated its role in inducing resistance to dexamethasone. Despite collagen type I having no effect on proliferation, it generated significant resistance to dexamethasone. Additionally, it was evidenced that both biomolecules were unable to induce resistance to bortezomib. These results validate the functionalized microgels as a 3D culture system that emulates the interaction between tumoral cells and the bone marrow extracellular matrix. This 3D environment could be a valuable culture system to test antitumoral drugs efficiency in multiple myeloma.

Ursolic Acid Loaded-Mesoporous Hydroxylapatite/ Chitosan Therapeutic Scaffolds Regulate Bone Regeneration Ability by Promoting the M2-Type Polarization of Macrophages

PURPOSE

Mesoporous hydroxylapatite (MHAP) might be important for bone regeneration, and ursolic acid (UA) has anti-inflammatory effects. Accordingly, we developed, for the first time, ursolic acid-loaded MHAP-chitosan (MHAP-CS-UA) scaffolds to treat bone defects.

METHODS

In vitro, we synthesize biomaterial scaffolds. By SEM, XRD, EDS and FTIR, we test the performance of the hybrid scaffolds. By drug release, flow cytometry, immunofluorescence, alizarin red staining, and Western blotting, we test the anti-inflammatory and osteo-inductive properties of scaffolds. In vivo, we verify osseointegration ability and bone regeneration.

RESULTS

The MHAP is a rod-shaped structure with a length of 100~300nm and a diameter of 40~60nm. The critical structure gives the micro-scaffold a property of control release due to the pore sizes of 1.6~4.3 nm in hydroxyapatite and the hydrogen bonding between the scaffolds and UA drugs. The released UA drugs could notably inhibit the polarization of macrophages to pro-inflammatory macrophages (M1 type) and promote the expression of osteogenic-related genes (COL1, ALP and OPG) and osteogenic-related proteins (BMP-2, RUNX2 and COL1).

CONCLUSION

The MHAP-CS-UA scaffolds have good anti-inflammatory, osseointegration, osteo-inductivity and bone regeneration. And they will be the novel and promising candidates to cure the bone disease.

Preparation of thermosensitive PNIPAm-based copolymer coated cytodex 3 microcarriers for efficient nonenzymatic cell harvesting during 3D culturing

Enzymatic detachment of cells might damage important features and functions of cells and could affect subsequent cell-based applications. Therefore, nonenzymatic cell detachment using thermosensitive polymer matrix is necessary for maintaining cell quality after harvesting. In this study, we prepared thermosensitive PNIPAm-co-AAc-b-PS and PNIPAm-co-AAm-b-PS copolymers and low critical solution temperature (LCST) was tuned near to body temperature. Then, spin coated polymer films were prepared for cell adhesion and thermal-induced cell detachment. The alpha-step analysis and scanning electron microscope image of the films suggested that the thickness of the films depends on the molecular weight and concentration which ranged from 206 to 1330 nm for PNIPAm-co-AAc-b-PS and 97.5-497 nm for PNIPAm-co-AAm-b-PS. The contact angles of the films verified that the polymer surface was moderately hydrophilic at 37°C. Importantly, RAW264.7 cells were convincingly proliferated on the films to a confluent of >80% within 48 h and abled to detach by reducing the temperature. However, relatively more cells were grown on PNIPAm-co-AAm-b-PS (5%w/v) films and thermal-induced cell detachment was more abundant in this formulation. As a result, PNIPAm-co-AAm-b-PS (5%w/v) was further used to coat commercial cytodex 3 microcarriers for 3D cell culturing and interestingly enhanced cell detachment with preserved potential of recovery was observed at a temperature of below LCST. Thus, surface modification of microcarriers with thermosensitive PNIPAm-co-AAm-b-PS could be vital strategy for nonenzymatic cell detachment and to achieve adequate number of cells with maximum cell viability and functionality.

HEMA and alginate-based chondrogenic semi-interpenetrated hydrogels: synthesis and biological characterization

Cartilage tissue engineering (CTE) has the general objective of restoring and improving damaged cartilage. A very interesting strategy of CTE is to combine different polymers to obtain a viscoelastic material. In this study, we have evaluated the applicability of poly(2-hydroxyethyl methacrylate) networks semi-interpenetrated with sodium alginate for CTE. Alginate-containing hydrogels show an increase in scaffold porosity and swelling capacity, when compared with nonporous poly(2-hydroxyethyl methacrylate) scaffolds. Primary chondrocytes from young rats were cultured on the hydrogels, and an increase in chondrocyte proliferation and chondrocytic markers was observed in alginate-containing hydrogels. Chondrocytic phenotype was preserved on hydrogels containing the lowest amount of crosslinker and initiator (SEMI 3 and SEMI 4). In addition, nitric oxide production by RAW264.7 macrophages grown on hydrogels was tested, and none of the hydrogels showed high levels of this inflammatory marker after 2 days. These results indicate that our alginate-containing hydrogels could be useful for CTE.