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Institute
Monocytes and macrophages are key players in maintaining immune homeostasis. Identifying strategies to manipulate their functions via gene delivery is thus of great interest for immunological research and biomedical applications. We set out to establish conditions for mRNA transfection in hard-to-transfect primary human monocytes and monocyte-derived macrophages due to the great potential of gene expression from in vitro transcribed mRNA for modulating cell phenotypes. mRNA doses, nucleotide modifications, and different carriers were systematically explored in order to optimize high mRNA transfer rates while minimizing cell stress and immune activation. We selected three commercially available mRNA transfection reagents including liposome and polymer-based formulations, covering different application spectra. Our results demonstrate that liposomal reagents can particularly combine high gene transfer rates with only moderate immune cell activation. For the latter, use of specific nucleotide modifications proved essential. In addition to improving efficacy of gene transfer, our findings address discrete aspects of innate immune activation using cytokine and surface marker expression, as well as cell viability as key readouts to judge overall transfection efficiency. The impact of this study goes beyond optimizing transfection conditions for immune cells, by providing a framework for assessing new gene carrier systems for monocyte and macrophage, tailored to specific applications.
Stem cells are capable of sensing and processing environmental inputs, converting this information to output a specific cell lineage through signaling cascades. Despite the combinatorial nature of mechanical, thermal, and biochemical signals, these stimuli have typically been decoupled and applied independently, requiring continuous regulation by controlling units. We employ a programmable polymer actuator sheet to autonomously synchronize thermal and mechanical signals applied to mesenchymal stem cells (MSC5). Using a grid on its underside, the shape change of polymer sheet, as well as cell morphology, calcium (Ca2+) influx, and focal adhesion assembly, could be visualized and quantified. This paper gives compelling evidence that the temperature sensing and mechanosensing of MSC5 are interconnected via intracellular Ca2+. Up-regulated Ca2+ levels lead to a remarkable alteration of histone H3K9 acetylation and activation of osteogenic related genes. The interplay of physical, thermal, and biochemical signaling was utilized to accelerate the cell differentiation toward osteogenic lineage. The approach of programmable bioinstructivity provides a fundamental principle for functional biomaterials exhibiting multifaceted stimuli on differentiation programs. Technological impact is expected in the tissue engineering of periosteum for treating bone defects.
On-demand motion of highly swollen polymer systems can be triggered by changes in pH, ion concentrations, or by heat. Here, shape-programmable, architectured hydrogels are introduced, which respond to ultrasonic-cavitation-based mechanical forces (CMF) by directed macroscopic movements. The concept is the implementation and sequential coupling of multiple functions (swellability in water, sensitivity to ultrasound, shape programmability, and shape-memory) in a semi-interpenetrating polymer network (s-IPN). The semi-IPN-based hydrogels are designed to function through rhodium coordination (Rh-s-IPNH). These coordination bonds act as temporary crosslinks. The porous hydrogels with coordination bonds (degree of swelling from 300 +/- 10 to 680 +/- 60) exhibit tensile strength sigma(max) up to 250 +/- 60 kPa. Shape fixity ratios up to 90% and shape recovery ratios up to 94% are reached. Potential applications are switches or mechanosensors.
Hydrogel forming physical networks based on gelatin are an attractive approach toward multifunctional biomaterials with the option of reshaping, self-healing, and stimuli-sensitivity. However, it is challenging to design such gelatin-based hydrogels to be stable at body temperature. Here, gelatin functionalized with desaminotyrosine (DAT) or desaminotyrosyl tyrosine (DATT) side chains is crosslinked with cyclodextrin (CD) dimers under formation of inclusions complexes. The supramolecular networks displayed at room temperature decreased water uptake (200-600 wt% for DAT-based systems, 200 wt% for DATT based systems), and increased storage moduli up to 25.6 kPa determined by rheology compared to DAT(T) gelatin. The gel-sol transition temperature increased from 33 up to 42 degrees C. The presented system that is completely based on natural building blocks may form the basis for materials that may potentially respond by dissolution or changes of properties to changes in environmental conditions or to the presence of CD guest molecules.
This paper presents shape-memory foams that can be temporarily fixed in their compressed state and be expanded on demand. Highly porous, nanocomposite foams were prepared from a solution of polyetherurethane with suspended nanoparticles (mean aggregate size 90 nm) which have an iron(III) oxide core with a silica shell. The polymer solution with suspended nanoparticles was cooled down to -20 degrees C in a two-stage process, which was followed by freeze-drying. The average pore size increases with decreasing concentration of nanoparticles from 158 mu m to 230 mu m while the foam porosity remained constant. After fixation of a temporary form of the nanocomposite foams, shape recovery can be triggered either by heat or by exposure to an alternating magnetic field. Compressed foams showed a recovery rate of up to 76 +/- 4% in a thermochamber at 80 degrees C, and a slightly lower recovery rate of up to 65 +/- 4% in a magnetic field.
Many physicochemical processes depend on the diffusion of small molecules through solid materials. While crystallinity in polymers is advantageous with respect to structure performance, diffusion in such materials is difficult to predict. Here, we investigate the impact of crystal morphology and organization on the diffusion of small molecules using a lattice Monte Carlo approach. Interestingly, diffusion determined with this model does not depend on the internal morphology of the semi-crystalline regions. The obtained insight is highly valuable for developing predictive models for all processes in semi-crystalline polymers involving mass transport, like polymer degradation or drug release, and provide design criteria for the time-dependent functional behavior of multifunctional polymer systems.
The macroscale function of multicomponent polymeric materials is dependent on their phase-morphology. Here, we investigate the morphological structure of a multiblock copolymer consisting of poly(L-lactide) and poly(epsilon-caprolactone) segments (PLLA-PCL), physically cross-linked by stereocomplexation with a low molecular weight poly(D-lactide) oligomer (PDLA). The effects of blend composition and PLLA-PCL molecular structure on the morphology are elucidated by AFM, TEM and SAXS. We identify the formation of a lattice pattern, composed of PLA domains within a PCL matrix, with an average domain spacing d0 = 12 - 19 nm. The size of the PLA domains were found to be proportional to the block length of the PCL segment of the copolymer and inversely proportional to the PDLA content of the blend. Changing the PLLA-PCL / PDLA ratio caused a shift in the melt transition Tm attributed to the PLA stereocomplex crystallites, indicating partial amorphous phase dilution of the PLA and PCL components within the semicrystalline material. By elucidating the phase structure and thermal character of multifunctional PLLA-PCL / PDLA blends, we illustrate how composition affects the internal structure and thermal properties of multicomponent polymeric materials. This study should facilitate the more effective incorporation of a variety of polymeric structural units capable of stimuli responsive phase transitions, where an understanding the phase-morphology of each component will enable the production of multifunctional soft-actuators with enhanced performance.
Microbially produced polyhydroxyalkanoates (PHAs) are polyesters that are degradable by naturally occurring enzymes. Albeit PHAs degrade slowly when implanted in animal models, their disintegration is faster compared to abiotic hydrolysis under simulated physiological environments. Ultrathin Langmuir-Blodgett (LB) films are used as models for fast in vitro degradation testing, to predict enzymatically catalyzed hydrolysis of PHAs in vivo. The activity of mammalian enzymes secreted by pancreas and liver, potentially involved in biomaterials degradation, along with microbial hydrolases is tested toward LB-films of two model PHAs, poly(3-R-hydroxybutyrate) (PHB) and poly[(3-R-hydroxyoctanoate)-co-(3-R-hydroxyhexanoate)] (PHOHHx). A specific PHA depolymerase fromStreptomyces exfoliatus, used as a positive control, is shown to hydrolyze LB-films of both polymers regardless of their side-chain-length and phase morphology. From amorphous PHB and PHOHHx, approximate to 80% is eroded in few hours, while mass loss for semicrystalline PHB is 25%. Surface potential and interfacial rheology measurements show that material dissolution is consistent with a random-chain-scission mechanism. Degradation-induced crystallization of semicrystalline PHB LB-films is also observed. Meanwhile, the surface and the mechanical properties of both LB-films remain intact throughout the experiments with lipases and other microbial hydrolases, suggesting that non-enzymatic hydrolysis could be the predominant factor for acceleration of PHAs degradation in vivo.
Recruitment of mesenchymal stem cells (MSCs) to damaged tissue is a crucial step to modulate tissue regeneration. Here, the migration of human adipose-derived stem cells (hADSCs) responding to thermal and mechanical stimuli was investigated using programmable shape-memory polymer actuator (SMPA) sheets. Changing the temperature repetitively between 10 and 37 degrees C, the SMPA sheets are capable of reversibly changing between two different pre-defined shapes like an artificial muscle. Compared to non-actuating sheets, the cells cultured on the programmed actuating sheets presented a higher migration velocity (0.32 +/- 0.1 vs. 0.57 +/- 0.2 mu m/min). These results could motivate the next scientific steps, for example, to investigate the MSCs pre-loaded in organoids towards their migration potential.
Boronic ester bonds can be reversibly formed between phenylboronic acid (PBA) and triol moieties. Here, we aim at a glucose-induced shape-memory effect by implementing such bonds as temporary netpoints, which are cleavable by glucose and by minimizing the volume change upon stimulation by a porous cryogel structure. The polymer system consisted of a semi-interpenetrating network (semi-IPN) architecture, in which the triol moieties were part of the permanent network and the PBA moieties were located in the linear polymer diffused into the semi-IPN. In an alkaline medium (pH = 10), the swelling ratio was approximately 35, independent of C-glu varied between 0 and 300 mg/dL. In bending experiments, shape fixity R-f approximate to 80% and shape recovery R-r approximate to 100% from five programming/recovery cycles could be determined. R-r was a function of C-glu in the range from 0 to 300 mg/dL, which accords with the fluctuation range of C-glu in human blood. In this way, the shape-memory hydrogels could play a role in future diabetes treatment options.