Chapter Four · failure evidence
What siRNA & RNA Interference Knockdown got wrong, from 36 dissertations
The records evaluate various applications of siRNA and RNA interference across gene silencing, functional screening, and therapeutic delivery platforms. Practitioners frequently report challenges including incomplete target depletion, delivery vehicle entrapment, non-specific off-target effects, and transient knockdown duration. These records come from PhD theses at 17 institutions, 2021 to 2026. Each links to its thesis. They were extracted by language models reading the full text, so treat each as a lead to read, not a verdict.
Incomplete target knockdown fails to reproduce knockout phenotypes or eliminate functional proteins
Partial gene depletion frequently failed to trigger morphological or phenotypic changes that were observed in complete knockout models. Additionally, mRNA knockdown often left residual protein expression intact or introduced cell-to-cell variability that obscured experimental phenotypes.
Tried and failed
shRNA-mediated gene knockdown applied to modeling complete knockout phenotypes. Reason: partial depletion failed to trigger lineage plasticity or phenotypic switching caused by complete knockout
Integrative multi-omics dissection of cancer cell states and susceptibility · MIT
Considered and rejected
Considered and rejected: Rejected siRNA knockdowns for CRISPR screen candidate validation due to incomplete target knockdown and failure of siCDK2 to outgrow siCTRL after HU treatment.
Targeting the Cell Cycle in Oral, Head, and Neck Squamous Cell Carcinoma · ResearchWorks
Considered and rejected
Considered and rejected: Rejected using siRNA knock-downs alone due to incomplete knockdown efficiency and cell-to-cell variability, transitioning to CRISPR/Cas9 knock-out cell lines.
Organisation and dynamics of mitochondria and their RNA. · EPFL
Considered and rejected
Considered and rejected: Rejected shRNA and siRNA knockdown systems in favor of constitutive pLentiCRISPRv2 knockout because incomplete depletion of ALG3 masked the growth and ER stress phenotypes.
Tried and failed
shRNA-mediated gene knockdown applied to cultured immortalised neuroblastoma cell line. Outcome: no signal. Reason: knockdown failed to replicate the Golgi morphology phenotype observed in knockout primary neurons
Disease Mechanisms and Therapeutic Strategies in Munc18-1 Encephalopathies · Cornell
Tried and failed
siRNA knockdown confirmed by mRNA quantification applied to target protein depletion in endothelial cells. Outcome: no signal. Reason: mRNA depletion did not translate to significant protein reduction on Western blot
Disrupted iron homeostasis in the vascular endothelium: implications for health and disease · Imperial
Novel engineered delivery vehicles underperform standard transfection reagents
Formulations such as protein vesicles, extracellular vesicles, and nanoplexes failed to match standard commercial reagents like Lipofectamine RNAiMAX in silencing efficacy. Direct conjugation approaches and carrier modifications also showed inferior knockdown efficiency or completely failed to silence target genes without additives.
Lost to a baseline
Transfection of 1 nM siRNA with RNAiMAX achieved ~50% luciferase knockdown in Neuro2a cells, outperforming NHS 10,000x siRNA-barcoded EVs which achieved ~25% knockdown.
Lost to a baseline
Lipofectamine RNAiMAX achieved 68% GFP knockdown at 100 nM siRNA, whereas siRNA-loaded protein vesicles showed 0% gene silencing at 50-100 nM
Engineering Recombinant Protein Vesicles for Delivery Applications · Georgia Tech
Lost to a baseline
Lipofectamine RNAiMAX positive control achieved ~82% IL-8 gene suppression compared to ~75% by UCNP-siRNA nanoplexes.
Nanochemistry for Nanomedicine: Design, Synthesis, and Applications · DSpace at SUNY Buffalo
Considered and rejected
Considered and rejected: Covalent conjugation of endosomal escape domains (EED, GFWFG) directly to siRNA was rejected due to inferior knockdown efficiency compared to transfection reagents and risks of hydrophobic collapse and immune activation.
Multiple strategies to enhance efficacy of oligonucleotide therapeutics · Oxford
Lost to a baseline
Without CaCl2, W1R9 + siRNA (25-50 nM) caused 0% GRP78 knockdown, losing to Lipofectamine RNAiMAX which achieved 25-35% protein knockdown.
Novel Peptide Nanoparticles Designed for Tumour Cell Entry Via Glucose Regulated Protein 78 Dependent Targeting · Carleton University Institutional Repository
Seed-mediated off-target effects and non-specific toxicity confound phenotypic validation
Transfection of control or individual siRNAs within pools induced false-positive viability phenotypes and unintended changes in downstream protein expression. These non-specific effects and seed-dependent off-target silencing frequently prompted researchers to abandon RNA interference in favor of CRISPR tools.
Tried and failed
siRNA knockdown of upstream regulatory pathway targets applied to cancer cell redox metabolism pathways. Reason: Knockdown caused unexpected compensatory off-target increases in downstream protein expression
Multiscale Computational Modeling of ROS-Generating Chemotherapies in Head and Neck Squamous Cell Carcinoma · Georgia Tech
Lost to a baseline
In JL-1 cells, transfection of scrambled (SCR) siRNA caused a 32% reduction in cell count, outperforming several specific siRNAs
Potential der siRNA-Transfektion auf chemotherapieresistente NSCLC- und Pleuramesotheliomzellen - Auswirkungen auf Viabilität und Wachstumsverhalten · Publikationssystem UB Tuebingen
Considered and rejected
Considered and rejected: Rejected relying solely on siRNA screening hits for target validation due to extensive seed-mediated off-target effects and false-positive viability phenotypes.
The Role of RUVBL1/RUVBL2 and Their Potential as Therapeutic Targets in Non-Small Cell Lung Cancer · DSpace at UTSWMED
Considered and rejected
Considered and rejected: Rejected using siRNA and shRNA systems in favor of CRISPR/Cas9 due to higher off-target effects in RNAi
Histone Lysine Demethylase KDM4A as a Therapeutic Target for Small Cell Lung Cancer · DSpace at UTSWMED
Tried and failed
pooled siRNA gene knockdown validation applied to host innate immune response phenotyping. Outcome: did not generalise. Reason: Observed phenotype was caused by off-target silencing from an individual siRNA within the pool.
The Relationship Between Herpes Simplex Virus 1 and the Cellular DNA Damage Response · Harvard
Standard chemical delivery methods fail across restrictive cellular and physiological barriers
Conventional chemical and liposomal transfection suffered from low uptake and poor knockdown efficiency in primary cells, requiring alternative approaches like nucleofection electroporation. Furthermore, physical barriers such as the blood-brain barrier and laser-based substrates severely restricted siRNA delivery in specialized tissues.
Tried and failed
non-liposomal chemical transfection of siRNA applied to primary and immortalised myometrial cells. Outcome: no signal. Reason: failed to achieve reliable, effective target gene knockdown compared to electroporation
Lost to a baseline
Polymer substrate laser-based transfection achieved only up to 20% efficiency for 150 kDa dextrans and 9% for siRNA with ~60% viability, performing worse than gold nanoparticles or plasmonic pyramids.
Visualization and manipulation of repair and regeneration in biological systems using light · Leibniz Universität Hannover Repository
Considered and rejected
Considered and rejected: Rejected direct 'naked' siRNA injections due to blood-brain barrier restrictions and poor neuronal uptake in vivo.
Role of Electrical Synapses in the Rat Inferior Olive: Assessment During Postnatal Development and After Knockdown of Connexin 36 · Publikationssystem UB Tuebingen
Considered and rejected
Considered and rejected: Rejected chemical/lipofectamine siRNA transfection due to poor PKAc knockdown efficiency compared to nucleofection electroporation.
Ineffective construct design and nuclear localization prevent measurable transcript silencing
Several designed siRNA and double-stranded RNA constructs failed to produce significant target mRNA depletion across experimental replicates. In other cases, siRNA knockdown proved ineffective against nuclear transcripts, leading researchers to select antisense gapmeRs instead.
Tried and failed
dsRNA-mediated RNA interference gene knockdown applied to specific serine protease immune genes. Reason: poor gene silencing efficiency and failure to successfully generate targeted dsRNA constructs
Dissecting The Melanization Immune Response In The Malaria Vector Anopheles Gambiae · Penn
Considered and rejected
Considered and rejected: Rejected using siRNA for nuclear retrocopy silencing in favor of antisense LNA gapmeRs due to siRNA inefficiency on nuclear transcripts.
Powiązania pomiędzy retrogenami i nowotworami – kontekst ewolucyjny Relationships between retrogenes and cancer – evolutionary context · AMUR - Repozytorium Uniwersytetu im. Adama Mickiewicza w Poz
Tried and failed
siRNA knockdown of target genes applied to mammary epithelial cell lines. Outcome: no signal. Reason: failed to achieve statistically significant mRNA reduction with high replicate variability
Tried and failed
siRNA-mediated gene knockdown applied to target gene mRNA depletion in cancer cells. Outcome: no signal. Reason: Designed siRNAs failed to produce measurable target mRNA knockdown despite downstream assay signal
Transient silencing duration and slow kinetics limit experimental applicability
The rapid recovery of target expression and short duration of siRNA depletion prevented its use in long-term matrix deposition and wound healing models. In addition, the slow kinetics of protein depletion made simultaneous siRNA delivery ineffective during rapid genome editing workflows.
Considered and rejected
Considered and rejected: Rejected siRNA knockdown for generating protein-depleted CDMs because siRNA produces only transient knockdowns (2-7 days) insufficient for the 10-14 day matrix deposition period and achieves incomplete knockout.
Engineering ‘extracellular matrix factories’ to study how the extracellular microenvironment regulates gene expression · University of Nottingham Repository
Tried and failed
simultaneous siRNA co-transfection without pre-depletion applied to prime editing efficiency enhancement. Outcome: no signal. Reason: siRNA knockdown kinetics were too slow to deplete target protein before editing occurred
Advancing precision genome and transcriptome engineering · Harvard
Tried and failed
layer-by-layer polymer coating for sustained oligonucleotide delivery applied to in vivo target gene knockdown in wounds. Outcome: unstable. Reason: Transient initial knockdown was lost over extended timepoints due to inadequate sustained release or rapid target recovery
Endosomal entrapment and slow release kinetics restrict functional intracellular delivery
Engineered delivery carriers and lipid nanoparticles often trapped siRNA cargo inside endosomes without achieving efficient cytosolic escape. Suboptimal charge ratios and excessive polymer hydrophobicity further impeded intracellular cargo release, drastically reducing gene downregulation.
Tried and failed
intermediate charge ratio complexation in lipid nanoparticles applied to siRNA delivery and gene silencing. Outcome: worse than baseline. Reason: intermediate charge ratios exhibited slowest release kinetics, reducing downregulation efficacy
Lipid-based nanoparticles for drug delivery · UT Austin
Tried and failed
engineered protein vesicle delivery vehicle applied to intracellular siRNA delivery for gene silencing. Outcome: no signal. Reason: endosomal entrapment and lack of intracellular cargo release even with pH-sensitive peptides
Engineering Recombinant Protein Vesicles for Delivery Applications · Georgia Tech
Tried and failed
increasing hydrophobicity in ph-responsive cationic polymer carriers applied to sirna delivery and gene knockdown. Outcome: no signal. Reason: excessive hydrophobicity from diisopropylamino substitution hindered efficient intracellular sirna release or endosomal escape
Left open by the authors
Problems the authors named and did not get to.
Left open
Test whether E-Ras knockdown via siRNAs in ESCs or ectopic expression in MEFs regulates EV-mediated reprogramming. Blocker: Requires a wet lab with mammalian cell culture, siRNA transfection, and EV isolation capabilities
Left open
Improve MAP4 knockdown efficiency in mature mammalian cardiomyocytes using multiple targeted siRNA or CRISPR interference. Blocker: Requires a wet biology lab, cardiomyocyte cell cultures, and gene editing reagents (siRNA/CRISPRi).
Left open
Evaluate connectosomes for intracellular delivery of small interfering RNAs (siRNAs) and single-stranded nucleic acids. Blocker: Requires wet-lab experimental facilities to culture cells, generate connectosomes, and test intracellular delivery of nucleic acids.
Engineering liposomal particles for direct, intracellular delivery of therapeutic molecules · UT Austin
Left open
Synthesize siRNA-SLNs using DLin-MC3-DMA instead of DOTAP and evaluate their cytotoxicity and proinflammatory properties. Blocker: Requires wet lab chemical synthesis and biological testing assays
Lipid-based nanoparticles for drug delivery · UT Austin
Left open
Investigate how nanogel crosslinking density affects siRNA core penetration using synthesis and characterization experiments. Blocker: Requires wet lab synthesis of nanogels with varied crosslinking density and experimental assays to measure siRNA penetration
Left open
Optimize siRNA loading into ClyA-ZZ bacterial outer membrane vesicles to achieve luminal internalization rather than surface aggregation. Blocker: Requires wet-lab experimental facilities, biological materials, and vesicle formulation equipment
Left open
Evaluate an in vivo liver-targeting lipid nanoparticle delivery system containing siRNAs against SDS. Blocker: Requires wet lab facilities, animal models (in vivo), and nanoparticle formulation capabilities
DEFINING THE METABOLIC LANDSCAPE OF FIBROLAMELLAR CARCINOMA · Cornell
Left open
Perform in vivo delivery experiments of siRNA, ASO, mRNA, or CRISPR editors using functionalized wireframe DNA nanoparticles in non-cancer disease models. Blocker: Requires wet lab facilities, synthesized DNA origami nanoparticles, and animal disease models for in vivo testing
Development of a Structural Nucleic Acid Delivery Vector Technology · MIT
Left open
Perform siRNA knockdown of RNU4-1, RNU4-2, and VTRNA1-3 to assess their role in viral replication or host antiviral defense. Blocker: Requires wet lab facilities, cell lines, and siRNA reagents to conduct physical knockdown assays
Oncolytic viruses in malignant pleural mesothelioma · Imperial
Left open
Evaluate the effect of LINC01013 knockdown on SNAI1 and WNT/beta-catenin signalling pathways in cardiac fibroblasts. Blocker: Requires wet lab experiments (siRNA knockdown, cell culture, molecular assays)
The role of small open reading frames in myocardial fibrosis and genetic disease · Imperial
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