Week 1 HW: Final Project Ideas

Target Product: Recombinant major ampullate spidroin (MaSp1/MaSp2-derived) monofilament surgical sutures. Motivation & Importance: Traditional surgical sutures present distinct trade-offs: synthetic absorbable polymers (such as polyglycolic acid) can cause localized inflammation via acidic degradation byproducts, while non-absorbable alternatives (like braided silk or nylon) carry risks of tissue drag, bacterial colonization within braided crevices, or permanent foreign-body reactions. Recombinant spider dragline silk provides a unique combination of extreme tensile strength (comparable to steel by weight), high elasticity, biocompatibility, and slow, enzymatic biodegradation into non-toxic amino acids. Biomanufacturing these proteins enables the production of fine, monofilament, ultra-strong sutures ideal for delicate, high-tension procedures—specifically ophthalmic, neurological, and plastic/reconstructive micro-surgeries where minimizing scarring, tissue trauma, and infection is critical. 2. Living System Chassis & Process Chassis: Escherichia coli (specifically engineered strains like BL21(DE3) or Rosetta 2(DE3) to support rare tRNA translation). System Inputs: Defined minimal/rich growth media supplemented with glucose or glycerol (carbon/energy source) and ammonium salts/yeast extract (nitrogen). Chemical inducers such as Isopropyl \beta-D-1-thiogalactopyranoside (IPTG) or auto-induction formulations. Trace minerals, dissolved oxygen, and supplemental amino acids (particularly glycine, alanine, and proline). Biological Processes:

1. Biomass Generation: E. coli cells proliferate exponentially during an initial batch/fed-batch phase until reaching high optical density
2. Transcriptional Activation: Induction triggers the T7 RNA polymerase system to transcribe the synthetic, codon-optimized spidroin gene construct from an expression vector.
3. Protein Translation & Folding: Ribosomes translate the glycine/alanine-rich repetitive core flanked by non-repetitive N- and C-terminal regulatory domains. Molecular chaperones prevent premature intracellular aggregation. System Outputs: Recombinant spidroin monomers (either solubilized in cytoplasm or isolated from inclusion bodies). Spent fermentation broth, metabolic byproducts (e.g., acetate), and cellular biomass. Post-harvest processing: Cell lysis, affinity chromatography/precipitation purification, and downstream extrusion into a coagulation bath (wet spinning or microfluidic spinning) to align beta-sheet nanocrystals into continuous suture filaments. Key Assumptions: The chassis relies on high-copy plasmids with robust transcriptional control, codon optimization matching E. coli codon bias, and an engineered host capable of tolerating repetitive GC-rich mRNA secondary structures without premature termination. Automation Strategy: Prototype Phase (Liquid Handling): An Opentrons Flex / OT-2 desktop liquid-handling robot will automate strain prototyping and expression screening. Spidroin constructs vary widely in stability depending on repeat length and terminal domain configurations. The robot will execute parallel 96-well mini-cultures, automated optical density measurements, IPTG induction titrations, cell lysis, and magnetic-bead-based affinity purifications to rapidly screen which construct yields the highest intact soluble protein. Scale-Up Phase (Process Automation): A programmable microfluidic spinning platform integrated with an automated multi-bioreactor system (e.g., automated fed-batch bioreactors with online DO, pH, and nutrient feed loops). Spidroin assembly requires precise shear stress and controlled buffer exchange (pH drop from 7.5 to 5.5 and ion exchange of \text{NaCl} to potassium phosphate) to mimic a spider’s duct. Microfluidic automation ensures reproducible, continuous fiber formation, eliminating batch-to-batch structural defects. Scale and Production Timeline Target Population: High-precision ophthalmic and micro-surgeries across a regional medical network (~10,000 procedures/year). Requirements per procedure: 2 packets of sutures, each containing a 45 cm (0.45 m) filament of USP size 8-0 suture (diameter \approx 40m = 4 \times 10^{-5}m Total Length: 10000 times 2 \times 0.45 = 9000m volume approx 11.3 cubic cm masss approx 14.7g total approx 49g of spidroin per year Using a standard benchtop/pilot 30 L stirred-tank bioreactor (working volume ~20 L), the entire annual quota of raw protein can be generated in a single run. Seed train (shake flasks): 24 hours. Fed-batch production phase: 36–48 hours. Cell harvest, lysis, and chromatographic purification: 72 hours Automated microfluidic spinning (at a typical continuous rate of 10\ \text{m/min}):Total End-to-End Duration: Approximately 7 to 8 working days from inoculation to spun, sterilized, ready-to-package suture filaments for an entire annual regional supply
4. Technical Unknowns and Critical Bottlenecks
5. Repetitive Sequence Instability & Premature Termination: Spidroin genes feature high repetition and elevated GC content, frequently causing recombination, plasmid loss, or translational stalling in E. coli due to depletion of specific aminoacyl-tRNA pools (glycyl- and alanyl-tRNAs). Resolution requirement: Empirically measure full-length vs. truncated protein ratios via SDS-PAGE and Western blot under varying rare-tRNA supplementation plasmids.
6. Downstream Solvation and Assembly Shear (Dope Preparation): Spidroins aggregate irreversibly into disordered beta-sheets if concentrated improperly. Developing a non-toxic spinning “dope” that avoids harsh organic solvents (such as 1,1,1,3,3,3-hexafluoroisopropanol, or HFIP) while preserving correct secondary folding during microfluidic extrusion is a significant processing hurdle. Resolution requirement: Measure protein solubility limits in aqueous buffers and determine the shear-rate threshold that initiates physiological beta-sheet crystallization.
7. Endotoxin Clearance (Pyrogenicity): As a Gram-negative bacterium, E. coli sheds lipopolysaccharide (LPS) endotoxins that co-purify with hydrophobic spidroins. Medical-grade surgical sutures must comply with stringent endotoxin limits (typically < 20\ \text{EU/device}) to avoid severe in vivo immune reactions. Resolution requirement: Quantify endotoxin removal efficiencies using quantitative LAL (Limulus Amebocyte Lysate) assays following specialized phase-separation or affinity wash steps.

AI used: agent: Gemini prompts"I have an assignment i want to biomanafacture spider silk suture by using it recombinantly, i will give you the instructions, i will make my living system e.coli. I will give you a set of questions i want you to answer according to what i told you." “(1) What you would like to biomanufacture and why?

Describe the target product or output you would like to make. Why are you interested in making it? Your motivation might be utilitarian—for example, addressing a problem in health, sustainability, food, energy, or manufacturing—but it does not need to be. Your project might instead have a social, cultural, artistic, or personal motivation. Clearly articulate what you want to make, who or what it is for, and why you think it is interesting or important. (2) What living system would you use? Propose at least one living-system manufacturing chassis that could produce your target—for example, a microbial, mammalian, or cell-free system. At a high level, describe how the system would make your target product. What goes into the system? What biological process or processes occur? What comes out? You do not need to design the complete biological system yet. Make reasonable assumptions where necessary and identify them. (3) How would you use automation? Identify at least one automation technology that you would combine with your living system.This could include a large-scale Cloud Lab, a desktop liquid-handling robot such as an Opentrons, a programmable microfluidics platform such as Nuclera’s, or another automation technology. Describe what part of the biomanufacturing workflow you would automate and why. For example, you might automate liquid handling, culturing, assembly, screening, sampling, measurement, optimization, or another step. (4) How much would you need to make, and how long would it take? Perform a back-of-the-envelope calculation estimating what it would take to manufacture your target at a meaningful scale. (a) How much? Define a scale relevant to your project and calculate approximately how much of your target product you would need to manufacture. For example, if you are producing a medicine, you might estimate the amount required to treat 1,000 people, everyone in Massachusetts, or everyone in the world. If you are producing a building material, you might calculate the amount required for one structure or an entire neighborhood. If you are producing an art or design artifact, define an appropriate scale yourself. Clearly show your calculation, including units, assumptions, and sources for important numbers. (b) How long? Using your proposed living system and automation technology, estimate how long it would take to manufacture that amount. Consider quantities such as production rate, yield, volume, number of parallel experiments or reactors, automation throughput, or whatever parameters are most appropriate for your system. You may discover that the automation technology you would use to prototype your system is very different from what you would use to manufacture at scale. If so, describe both. Again, we are looking for a reasonable engineering estimate. Show your assumptions and calculations. 5. What don’t you know yet? After completing your analysis, identify the 2–3 biggest technical unknowns, bottlenecks, or assumptions in your proposed biomanufacturing system. What would you need to learn, measure, or experimentally determine to know whether your idea could actually work?”"

Final Project