Droplet-Based Single-Cell Proteomic Sample Preparation
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Solution Overview
Problem
Current single-cell proteomic analysis methods face challenges in efficiently preparing samples for low-abundance proteins, often requiring large volumes and incompatible chemicals that lead to sample loss and reduced specificity, especially when analyzing thousands of proteins in bulk samples.
Innovation Solution
A method involving dispensing n droplets of lysis buffer onto a planar surface, lysing single cells, digesting proteins, labeling peptides with chemical tags, and merging droplets to form a single-cell proteomic sample, using dimethyl sulfoxide (DMSO) for lysis and trypsin for digestion, enabling precise and efficient protein quantification and covariation analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large volumes of buffer are used for single-cell lysis and protein digestion, then complete cell lysis and protein digestion are achieved, but sample loss increases and analysis precision decreases
Solution Approach 1:
The patent segments the bulk sample into multiple individual single-cell droplets, each containing a single cell lysed in a small volume of buffer. This segmentation allows each cell to be processed in isolation with minimal buffer volume (e.g., 1-10 nL per droplet), preventing sample loss while ensuring complete lysis and digestion through optimized reagent-to-cell ratios in each micro-compartment.
Solution Approach 2:
The patent changes the volume parameter from bulk (microliters) to single-cell droplet (nanoliters or picoliters) scale. This parameter change enables complete cell lysis and protein digestion using significantly reduced buffer volumes, thereby minimizing sample loss and improving analysis precision through concentrated sample recovery.
2Productivity
If incompatible chemicals are used in bulk sample preparation, then protein digestion is efficient, but sample loss increases and quantification accuracy decreases
Solution Approach 1:
The patent segments the sample processing into individual droplets where incompatible chemicals (e.g., detergents, chaotropic agents) can be used at optimized concentrations for efficient protein digestion without affecting quantification accuracy. Each droplet acts as an isolated reaction chamber, allowing use of digestion-optimized reagents that would be incompatible in bulk due to sample loss and background interference.
Solution Approach 2:
The patent applies local quality by optimizing chemical composition for each droplet's specific function: lysis buffer composition is optimized for cell membrane disruption, while digestion buffer composition is optimized for protein cleavage efficiency. Each droplet receives chemically optimized reagents tailored to its specific processing stage, improving both digestion efficiency and quantification accuracy.
3Loss of substance
If single-cell proteomic analysis is performed with minimal sample volume, then sample loss is reduced, but achieving complete protein digestion and analysis becomes difficult
Solution Approach 1:
The patent applies preliminary action by first lysing the single cell in a small volume to release all proteins, then adding digestion enzymes (e.g., trypsin) at optimized concentrations to ensure complete protein digestion. The droplet is incubated under controlled conditions (temperature, humidity, time) before analysis, ensuring complete digestion is achieved despite the minimal sample volume.
Solution Approach 2:
The patent changes physical parameters (temperature, humidity, incubation time) and chemical parameters (enzyme concentration, buffer composition) to optimize protein digestion in minimal volumes. By controlling these parameters, complete digestion is achieved in nanoliter-scale droplets, preventing sample loss while ensuring reliable analysis.
4Productivity
If multiple single-cell samples are processed in parallel, then throughput increases, but batch effects and variability increase
Solution Approach 1:
The patent segments multiple single-cell samples into separate droplets that can be processed in parallel on a single planar surface. Each droplet is isolated, preventing cross-contamination and batch effects between samples. After individual processing, droplets can be merged for pooled analysis or analyzed separately, maintaining sample integrity while achieving high throughput.
Solution Approach 2:
The patent enables merging of multiple processed droplets into a single pooled sample for analysis. This merging approach allows parallel processing of multiple cells while reducing batch effects by combining all samples in a single analytical run, thereby increasing throughput while maintaining reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for high-throughput, accurate quantification and identification of protein covariation across single cells, reducing sample loss and batch effects, and achieving consistent protein quantification with minimal background noise, as demonstrated by analyzing thousands of single cells and cell-cycle protein markers.
Implementation Method 1
dispensing a single cell into each of the n droplets of lysis buffer to produce n droplets, each comprising a lysed single cell
Implementation Method 2
dispensing digestion buffer into each of the n droplets to digest proteins from each lysed single cell to produce n droplets comprising peptides
Implementation Method 3
dispensing a chemical tag into each of the n droplets comprising the peptides to produce labeled peptides, wherein at least one droplet of the n droplets receives a different chemical tag from at least one other droplet
Data Source
AI summary
The disclosure provides methods of forming one or more single-cell proteomic samples, such as by: dispensing n droplets of lysis buffer onto a substantially planar solid surface, wherein n>2: dispensing a single cell into each of the n droplets of lysis buffer to produce n droplets with a lysed single cell: dispensing digestion buffer into each of the n droplets to digest proteins from each lysed single cell to produce n droplets comprising peptides: dispensing a chemical tag into at least a subset of the n droplets comprising the peptides to produce labeled peptides, thereby enabling the labeled peptides in a given droplet to be distinguishable from labeled peptides in at least one other droplet: and applying a fluid to merge at least a subset of the droplets into a combined droplet on the substantially planar surface, thereby combining the labeled peptides to form a single-cell proteomic sample.