Prof. Dr. Oskar Staufer

Synthetic cells have emerged as a novel biomimetic approach for studying fundamental cellular functions and enabling new therapeutic interventions. However, the potential to program synthetic cells into self-organized 3D collectives to replicate the structure and function of tissues has remained largely untapped. Here, self-assembly properties are engineered into synthetic cells to form millimeter-sized 3D lymphatic bottom-up tissues (lymphBUTs) with mechanical adaptability, metabolic activity, and hierarchical microstructural organization. It is demonstrated that primary human immune cells spontaneously infiltrate and functionally integrate into these synthetic lymph nodes to form living tissue hybrids. Applying lymphBUTs, it is shown that structured 3D organization and mechanical support drives T cell activation and the application of lymphBUTs for ex vivo expansion of regulatory CD8+ T cells is demonstrated. The study highlights the functional integration of living and non-living matter, advancing synthetic cell engineering toward 3D tissue structures.

Hematopoietic stem cells (HSCs) receive a combination of biochemical and biomechanical signals within the bone marrow that guide their differentiation process. These include soluble factor signaling with cytokines, cellular confinement in the stem cell niche, and contact-dependent receptor–ligand interactions with stromal cells. Recreating this complex microenvironment in vitro is a principal engineering challenge for regenerative therapies and tissue engineering. While cytokines can be easily supplemented in vitro, and several systems for confined HSC culture have been developed, integrating receptor-based intercellular interactions found in stem cell niches has only been achieved with quantitatively undefined heterotypic co-cultures. We report here the development of microwell-based systems that integrate synthetic cells to mimic receptor–ligand interactions within hematopoietic niches. The synthetic cells are based on droplet-supported lipid bilayers (dsLBs) with cytomimetic stiffness and present Notch receptor ligands on a laterally mobile lipid membrane. We show the system's applicability to individually tune the three signaling axes: soluble factors, confinement, and intercellular interactions for HSC differentiation. Introducing synthetic cells as an alternative to coculture and feeder cells opens the possibility to engineer precisely defined HSC niches with adjustable biochemical and biomechanical properties.

Enterococcus faecalis is a commensal bacterium in the human gut, but it can also cause life-threatening diseases, especially serious hospital-acquired infections. Bacteria release particles called extracellular vesicles (EVs), which help them interact and communicate with other cells, including bacteria and human cells. However, it is unclear how EVs produced by E. faecalis (Ef-EVs) affect the host immune system. In this study, we investigated how Ef-EVs affect immune and endothelial cells. We found that Ef-EVs activate inflammatory responses through a receptor on the cell surface, without the need to be taken up by the cells. In addition, Ef-EVs altered the metabolism of immune cells, shifting them towards a state that supports inflammation. These findings highlight a previously underexplored mechanism by which Gram-positive bacterial EVs can shape host immunity and cellular metabolism, thereby advancing our understanding of host-pathogen interactions.

Stress granules (SGs) are biomolecular condensates that form transiently in the cytosol of mammalian cells in response to stress. Dysregulation of their assembly or disassembly is implicated in human age-related diseases. While phase separation is the key process underlying SG assembly, understanding of their function, composition and regulation in response to physiological stimuli is limited. This knowledge gap reflects the challenge of gaining comprehensive and quantitative insights into the dynamic regulation of the complex composition of SGs at the single-cell level. Here we present an emulsion-based microfluidics method to overcome this limitation. “Cytosolic extracts-in-oil droplets” (CEODs) recreate a confined active cytosolic milieu that undergoes phase separation and SG formation in response to stress under physiological conditions. This approach led to the discovery of seven previously unrecognised SG components involved in signalling pathways. CEODs provide a versatile and cost-effective screening platform for future mechanistic and therapeutic studies.

Approaches in tissue engineering, organoid culture, and organs-on-chip have propelled the development of increasingly sophisticated in vitro models of human tissues. However, as they are formed from natural cells, it is challenging to control their molecular composition and biophysical properties, increasing variability and limiting their robustness. To overcome these limitations, we introduce a self-assembly strategy for synthetic cells that enables the formation of millimeter-sized synthetic constructs based on single synthetic cells. Specifically, we functionalize the lipid membrane of synthetic cells with cholesterol-tagged single-stranded DNA aptamers, which drive programmable intercellular adhesion through sequence-specific hybridization. This allows individual synthetic cells to interconnect into higher order 3D constructs. By varying aptamer complementarity, internal architecture with spatially distinct functional zones and tuneable mechanical properties can be encoded. Most importantly, the DNA-driven self-assembly operates directly in cell culture medium, is compatible with high-throughput microwell formats enabling scalable screening workflows and is reversible by DNA displacement. To demonstrate the biological functionality of these synthetic tissues, we incorporate T cell-stimulatory antibodies into spatially segregated tissue regions. This design mimics lymph node organization and supports infiltration of natural primary human T cells, which subsequently expand within the synthetic tissue. Together, these results establish a route to tissue-scale matrices built from synthetic cell collectives and represent a critical step toward functionally integrating living and non-living matter.

Developing effective vaccines against some diseases remains a global health priority. However, targeting immunity against a specific disease-related antigen requires efficient adjuvant systems that adequately promote vaccination efficacy. Extracellular vesicles have been identified as a potential adjuvant platform technology but are still limited in their reproducibility and safety. Here, we present a synthetic extracellular vesicle mimetic (EVM) platform that enhances antigen immunogenicity by incorporating the large extracellular loop (LEL) of the tetraspanin CD9, a protein abundant on natural extracellular vesicles. Liposomes with defined lipid composition were functionalized with recombinant CD9-LEL and pathogen antigens—KMP-11 from Leishmania and the SARS-CoV-2 Spike (S) protein. BALB/c mice were immunized intraperitoneally with nanovesicles carrying CD9-LEL, the pathogen antigens alone, or both. Antigen-specific IgG responses were measured by ELISA, and vesicle uptake by immune cells was assessed via flow cytometry. CD9-LEL alone did not elicit an immune response, but its co-presentation with antigens significantly enhanced specific anti-pathogen IgG titers. Notably, KMP-11 alone failed to induce detectable antibodies, while nanovesicles carrying both CD9-LEL and KMP-11 triggered strong IgG1 and IgG2b responses. Similarly, nCD9 + S induced higher IgG titers than S alone. CD9-LEL promoted uptake of nanovesicles by peritoneal macrophages, suggesting improved antigen presentation.
Combining EVMs with classical adjuvants further modulated the immune profile: alum favored IgG1 (Th2 bias), while CpG ODNs enhanced IgG2a and IgG2b (Th1 bias), crucial for intracellular pathogen clearance. The platform demonstrated safety and adaptability. In conclusion, CD9-LEL-decorated EVMs represent a promising, scalable vaccine strategy capable of boosting antigen immunogenicity and directing immune polarization, offering a versatile tool for combating challenging or emergent infectious diseases.

Natural killer (NK) cells are critical components of the first-line immune defense, responsible for eliminating tumorigenic cells. NK cell-based adoptive immunotherapy has gained increasing attention; however, cryopreservation, a standard technique for NK cell storage, significantly impairs NK cell cytotoxicity, particularly in physiological 3D environments. Here, we demonstrate that short-term co-culture with effector T cells markedly enhances NK cell motility and killing functionality. Notably, a brief 1-day co-culture is sufficient to restore cryopreservation-impaired NK cell functionality in 3D environments. This enhancement requires direct contact between T cells and NK cells, which facilitates localized high concentrations of IL-2 at the cell contact sites. To develop a controled, donor-independent solution, we demonstrate that synthetic T cells with surface-bound IL-2 exhibit superior efficiency in revitalizing cryopreserved NK cells. These findings uncover a previously unrecognized role for physical contact-mediated local IL-2 signaling and provide an efficient, cost-effective, and tunable strategy to rescue NK cell functionality post-cryopreservation, paving the way for more scalable, potent, and clinically viable NK cell-based immunotherapies.

Bispecific T cell engagers (TcEs) link T cell receptors to tumor-associated antigens on cancer cells, forming cytotoxic immunological synapses (IS). Close membrane-to-membrane contact (≤13 nm) has been proposed as a key mechanism of TcE function. To investigate this and identify potential additional mechanisms, we compared four immunoglobulin G1-based (IgG1) TcE Formats (A–D) targeting CD3ε and Her2, designed to create varying intermembrane distances (A < B < C < D). Small-angle X-ray scattering (SAXS) and modeling of the conformational states of isolated TcEs and TcE–antigen complexes predicted close contacts (≤13 nm) for Formats A and B and far contacts (≥18 nm) for Formats C and D. In supported lipid bilayer (SLB) model interfaces, Formats A and B recruited, whereas Formats C and D repelled, CD2–CD58 interactions. Formats A and B also excluded bulky Quantum dots more effectively. SAXS also revealed that TcE–antigen complexes formed by Formats A and C were less flexible than complexes formed by Formats B and D. Functional data with Her2-expressing tumor cells showed cytotoxicity, surface marker expression, and cytokine release following the order A > B = C > D. In a minimal system for IS formation on SLBs, TcE performance followed the trend A = B = C > D. Addition of close contact requiring CD58 costimulation revealed phospholipase C-γ activation matching cytotoxicity with A > B = C > D. Our findings suggest that when adhesion is equivalent, TcE potency is determined by two parameters: contact distance and flexibility. Both the close/far-contact formation axis and the low/ high flexibility axis significantly impact TcE potency, explaining the similar potency of Format B (close contact/high flexibility) and C (far contact/low flexibility). Copyright © 2025 the Author(s).

Tissue functions rely on complex structural, biochemical, and biomechanical cues that guide cellular behavior and organization. Synthetic cells, a promising new class of biomaterials, hold significant potential for mimicking these tissue properties using simplified, nonliving building blocks. Advanced synthetic cell models have already shown utility in biotechnology and immunology, including applications in cancer targeting and antigen presentation. Recent bottom-up approaches have also enabled synthetic cells to assemble into 3D structures with controlled intercellular interactions, creating tissue-like architectures. Despite these advancements, challenges remain in replicating multicellular behaviors and dynamic mechanical environments. Here, we review recent advancements in synthetic cell-based tissue formation and introduce a three-pillar framework to streamline the development of synthetic tissues. This approach, focusing on synthetic extracellular matrix integration, synthetic cell self-organization, and adaptive biomechanics, could enable scalable synthetic tissues engineering for regenerative medicine and drug development.

Self-assembly is a fundamental property of living matter that drives the three-dimensional organization of cell collectives such as tissues and organs. Here, the co-assembly of synthetic and natural cells is leveraged to create hybrid living 3D cancer cultures. We screen a range of synthetic cell models for their ability to form augmented tumoroids with artificial but controllable micro-environments, and show that the balance of inter- and extracellular adhesion and synthetic cell surface tension are key material properties driving integrated co-assembly. We demonstrate that synthetic cells based on droplet-supported lipid bilayers can establish artificial tumor immune microenvironments (ART-TIMEs), mimicking immunogenic signals within tumoroids and eliminating the need to integrate complex living immune cells. Using the ART-TIME approach, we identify a AhR-ARNT-mediated co-signaling mechanism between PD-1 and CD2 as a driver in immune evasion of pancreatic ductal adenocarcinoma. Our study advances the field of hybrid organoid engineering, offers opportunities for the construction and modelling of artificial tumour environments, and marks a step towards the design of functional living/non-living cytomimetic materials.