Before Your First RASTRUM Print: 10 Tips for a Stronger Start
Starting a new 3D cell culture workflow is exciting, but it usually comes with practical questions. How many cells do you need? Which matrix should you start with? Should you optimize media first, or begin with matrix selection? And how much should you try to learn from the first experiment?
For many teams, the hardest part of adopting a new workflow is not the print itself. It is knowing how to start well.
RASTRUM is designed to help researchers build reproducible, high-throughput 3D cell models, but strong early results still depend on thoughtful planning. Your first print does not need to answer every question at once. It should give you a practical starting point, help you understand how your cells behave in 3D, and show you what is worth refining next.
Whether you already know your cells well from 2D culture, have experience with other 3D systems, or are building a model from the ground up, those learnings matter. During onboarding, Inventia works with users to combine their biological expertise with our experience across cell types, matrices, media conditions, and RASTRUM workflows to help guide a more tailored starting point.
Here are 10 tips to help new RASTRUM users feel more prepared before their first print.
1. Start with one clear biological question
Before designing your plate map or preparing reagents, define the main question you want your first experiment to answer.
Are you trying to understand whether your cells remain viable in 3D? Compare matrix conditions? Assess morphology? Establish a baseline for drug response? The more focused your starting question is, the easier it becomes to design a meaningful experiment.
A strong first print is usually not about testing every variable. It is about choosing the conditions most likely to give you useful early insight and a clear next step.
2. Bring what you already know about your cells
You do not need to start from scratch when moving into a RASTRUM workflow.
Your existing knowledge of your cells is valuable, whether it comes from 2D culture, spheroids, organoids, or other 3D models. Information such as growth rate, morphology, doubling time, sensitivity to handling, clumping behavior, media requirements, matrix preferences, and assay performance can all help guide early experimental design.
This is also where collaboration matters. During onboarding, Inventia works with users to combine their cell-specific knowledge with our experience across RASTRUM workflows, matrix conditions, media considerations, and assay design. The result is a more tailored starting point rather than a generic protocol.
3. Treat your first print as a starting point, not a finished workflow
3D cell culture optimization is often iterative. Your first print may highlight promising matrix conditions, show that cell density needs adjusting, or reveal that your downstream assay timing is not yet ideal.
That is a good outcome.
Rather than expecting a fully optimized model immediately, use your first print to establish a baseline and identify the next variable worth refining. A first workflow does not need to be perfect. It needs to be informative.
4. Plan your cell numbers early
Cell numbers quickly become one of the most important practical considerations in a RASTRUM workflow.
Before you begin, think through how many conditions you want to test, how many replicates you need, whether you are including 2D controls, how many timepoints you plan to collect, and whether your downstream assays require extra wells.
Cell density should also reflect your cell type and model goals. Some cells require lower densities to avoid overcrowding, while others need higher densities to establish relevant cell-cell interactions. As a general guide, maximum total cell density is approximately 20 million cells/mL, with density and ratio selected according to cell type.
When getting started with matrix selection, it can be helpful to begin with enough cells to confidently answer the first key question: Is this matrix supporting my cells? That is a much better place to start than wondering whether the biology failed simply because too few cells were present.
RASTRUM Cloud can help here by generating custom protocols for each print design, including total cell numbers needed for the experiment.
5. Prioritize cell health before print day
Healthy cells make better starting material.
For most workflows, aim to begin with cells that are actively growing, well characterized, and as consistent as possible between passages. In general, start with cells that have high viability, ideally above 80%, and aim for a single-cell suspension or small clusters below 70 µm, since cells will be suspended in the matrix components before printing.
If your cells are prone to clumping, additional preparation steps may help. A 70 µm strainer can remove larger aggregates, and DNase I may be useful where DNA-mediated clumping is an issue. For more guidance, see our technical guide on preparing sensitive cells for printing.
The goal is not just to have enough cells. It is to have cells that are ready to respond in a 3D environment.
6. Choose your matrix with intention
Matrix selection is one of the most important early decisions in a 3D culture workflow. The matrix can influence cell morphology, viability, proliferation, invasion, differentiation, and assay performance.
When choosing matrix conditions, think about what your cells experience in vivo. Do they require a soft, compliant environment? Are they typically found in a stiffer tissue? Do they rely on specific extracellular matrix cues? Your own knowledge of the cell type, combined with Inventia’s experience across different matrix conditions, can help narrow the starting point.
For new users, it is often better to test a focused number of matrix conditions rather than a large panel. That keeps the experiment manageable while still giving you comparative insight.
Related reading: The Art and Science of Matrix Selection: 5 Expert Tips from Inventia Life Science
7. Do not overlook media optimization
A media condition that works well in 2D may not automatically perform the same way in 3D.
In 3D cultures, cells experience different gradients, spatial organization, and cell-matrix interactions. That can affect nutrient access, growth factor needs, metabolic activity, and response to treatment.
When planning your first RASTRUM workflow, consider whether your existing media formulation is the best starting point or whether it makes sense to compare alternatives. Media optimization may be especially important for sensitive cell types, cocultures, stem-like models, or long-term culture systems.
This is another place where prior experience matters. If you already know your cells are sensitive to certain supplements, serum levels, growth factors, or media exchange schedules, that information can help guide your first experimental design.
8. Include the right controls
Controls are especially valuable in early 3D workflow development.
Including 2D controls can help you understand how cells behave under familiar conditions and provide a useful benchmark for interpreting 3D results. Depending on your experiment, you may also want to include:
- matrix-only controls
- untreated controls
- assay background controls
- known positive or negative biological controls
Good controls make troubleshooting easier and help you separate biological effects from workflow variables.
9. Design around your downstream assay
Your readout should shape your experimental design from the beginning.
An imaging-based workflow may require different plate formats, culture durations, or construct spacing than an endpoint viability assay. A drug response study may require enough replicates for dose-response analysis. A transcriptomics workflow may require more cells or more wells per condition.
Before your first print, ask a simple question: What data do I need at the end, and does my design support that readout?
That question helps keep the experiment grounded and prevents avoidable redesign later.
10. Keep handling steps consistent and leave room to refine
Small handling differences can have a big impact on reproducibility.
During setup, work efficiently, maintain aseptic technique, and avoid unnecessary delays. After your first print, review the results against your original goal. Did the cells remain viable? Were there clear differences between matrix conditions? Did the assay perform as expected? Were there signs that cell density, media, or culture duration should be adjusted?
It is also worth remembering that seeing something different in 3D compared with 2D does not necessarily mean something has gone wrong. In many cases, those differences are exactly why researchers move into 3D models in the first place. Changes in morphology, growth patterns, marker expression, treatment response, or cell-matrix interactions may reveal biology that is less apparent in traditional 2D culture.
Starting your RASTRUM workflow
A strong first RASTRUM print is not about answering every question at once. It is about starting with the right one.
When teams begin with healthy cells, a focused design, and a clear downstream readout in mind, the first print becomes more than a technical milestone. It becomes the foundation for a more informative and reproducible 3D workflow.
There is more than one way to get started with RASTRUM, and the right path depends on your goals, timeline, and where you are in your 3D cell culture journey.
For many users, the first step is Discovery Mode. This is where you begin working with your own RASTRUM system, apply what you already know about your cells, and start optimizing the conditions that matter most for your model.
If you are looking for a more defined starting point, you can also explore Inventia’s Validated Solutions. These workflow paths show how RASTRUM can be applied across different model types and applications, and they can be a helpful resource when thinking about what may be possible for your own research.
For teams that want additional support, Inventia’s Discovery Services team can work more directly with you to explore feasibility, generate early data, or help accelerate model development before bringing a workflow fully in-house.
Whichever path you choose, the goal is the same: to help you build a 3D cell culture workflow that is practical, informative, and relevant to your biology.
Explore Inventia’s resources or connect with our team to discuss the best way to start your RASTRUM journey.
See how RASTRUM 3D models are already being applied across drug discovery and translational research: