CPP DesignCargo ConjugationProtein DeliveryNucleic Acid Delivery
At Creative Peptides, we provide custom cell-penetrating peptide (CPP) delivery services for research teams developing intracellular delivery strategies for proteins, peptides, oligonucleotides, PNAs, and other difficult-to-enter cargoes. Our support covers CPP sequence review, custom synthesis, cargo-ready modification, covalent conjugation, noncovalent complex design, purification, and analytical characterization. By integrating cell penetrating peptide design and synthesis services, custom conjugation service, and peptide-oligonucleotide conjugation, we help biotech, pharmaceutical, CRO, and academic teams build research-ready CPP delivery constructs for uptake studies, intracellular trafficking evaluation, and sequence-to-cargo optimization.
Many intracellular delivery projects fail for practical reasons long before the biology becomes clear. A CPP may enter cells efficiently on its own, yet behave very differently after a fluorophore, protein, or oligonucleotide is attached. Likewise, a conjugate may look correct by mass but still show poor solubility, broad chromatographic behavior, endosomal trapping, or weak functional readout in the target assay.
Our CPP delivery services are designed to address common project bottlenecks such as:
Schematic overview of CPP delivery design, including sequence selection, cargo conjugation, protein transport, oligonucleotide coupling, and endosomal escape-aware optimization for intracellular delivery studies
We offer flexible CPP delivery workflows for research and non-clinical teams that need clearly defined constructs, practical technical communication, and decision-supportive data. Projects can be configured around known CPP scaffolds, client-supplied cargoes, or new constructs built through our custom peptide synthesis and peptide modification services platforms. Support can range from a single conjugation task to a broader CPP delivery package covering design, synthesis, analytical review, and follow-on optimization.
Effective CPP delivery starts with selecting a format that fits the cargo, assay, and intended intracellular question. We review the peptide sequence, cargo class, cell model, uptake goal, and preferred readout before recommending a build strategy.
This front-end review helps reduce the risk of producing a chemically correct construct that is difficult to interpret in downstream biology.
Our team prepares custom CPPs and delivery-oriented analogs using synthesis routes selected for sequence complexity and downstream conjugation plans. We support both standard research peptides and more specialized delivery-ready formats.
We focus on generating CPP starting materials that are practical to modify, interpretable in QC, and suitable for follow-on delivery studies.
Many CPP delivery projects depend on installing the right reactive handle before cargo attachment begins. We support site-aware handle placement on the peptide, cargo, or both components to improve coupling control.
Proper handle placement is often the difference between a clean, scalable conjugation route and a difficult reaction with ambiguous products.
We build custom CPP-cargo conjugates using chemistries selected for the functional groups available, the cargo's stability profile, and the intended delivery logic. Projects may involve one defined construct or a small comparison set for linker and site screening.
Our goal is to generate conjugates that are chemically well defined and experimentally useful, not just nominally attached.
CPP-enabled protein delivery requires more than attaching a peptide to a large biomolecule. The conjugation site, linker length, protein folding state, and cargo size can all influence intracellular performance. We support research-stage protein delivery constructs designed for mechanistic and assay use.
We help teams compare delivery formats that balance construct definition with preservation of cargo function.
CPP-based nucleic acid delivery must account for both biological transport and difficult hybrid chemistry. We support defined conjugates and assembly strategies for research programs working with oligonucleotide and nucleic acid analog cargoes.
We pay particular attention to conjugate integrity, charge behavior, purification difficulty, and downstream assay interpretability.
CPP delivery constructs often need a more tailored analytical plan than standard peptides because cationic sequences, hydrophobic motifs, proteins, and oligonucleotides can each shift retention, solubility, and impurity behavior. We provide analytical review and supply support aligned to research needs.
Available support options include:
The right CPP delivery format depends on the cargo's size, charge, folding sensitivity, and assay goal. Some projects benefit from a single, well-defined covalent entity, while others are better served by electrostatic assembly or fusion-style architectures. The table below outlines common format choices and the technical logic behind them.
| CPP Delivery Format | Typical Cargo | Common Build Strategy | Main Advantage | Key Constraint |
|---|---|---|---|---|
| Free or Labeled CPP | Uptake controls, localization probes, screening intermediates | Direct peptide synthesis with fluorophore, biotin, or reactive handle installation | Useful for baseline uptake and trafficking studies before cargo coupling | Performance of the free CPP may not predict behavior after cargo attachment |
| CPP-Cargo Conjugate | Small molecules, dyes, peptides, defined research probes | Covalent coupling through amide, click, thioether, disulfide, or oxime chemistry | Produces a defined molecular entity for cleaner structure-activity comparison | Attachment site and linker design can change uptake, release, or assay signal |
| CPP-Protein Construct | Enzymes, reporter proteins, protein domains, binding fragments | Site-selective conjugation, recombinant fusion planning, or adaptor-assisted assembly | Enables intracellular protein delivery studies with controlled peptide presentation | Protein folding, active-site accessibility, and heterogeneity can complicate design |
| CPP-Oligonucleotide Conjugate | siRNA, antisense oligonucleotides, short DNA or RNA constructs | Post-synthetic conjugation or modular assembly using terminal modifiers and defined linkers | A covalent construct can simplify comparison of orientation, linker, and CPP choice | Mixed charge and polarity often make purification and analytical characterization difficult |
| CPP-PNA or PMO Conjugate | PNA, PMO-like cargoes, splice-modulating or antisense research constructs | Direct conjugation with stable or cleavable spacers selected for cargo chemistry | Useful when a neutral or less polyanionic cargo benefits from defined CPP attachment | Solubility, aggregation, and endosomal release still require careful optimization |
| CPP:Nucleic Acid Complex | Larger oligonucleotides, plasmid DNA, selected RNA assemblies, hybrid payloads | Electrostatic complexation, co-assembly, or staged hybrid formulation | More practical than one-to-one conjugation for some large or highly charged cargoes | Complex stoichiometry, stability, and reproducibility must be controlled experimentally |
CPP delivery projects become more reliable when the peptide format, linker design, and analytics are chosen around the cargo rather than around a generic platform. The table below summarizes common design questions across protein and nucleic acid delivery workflows.
| Cargo Type | Common CPP Strategy | Main Design Question | Representative QC Readouts | Frequent Technical Risk |
|---|---|---|---|---|
| Peptides and Small Proteins | Defined covalent conjugate or short fusion-style construct | Will the attachment site preserve the cargo's active or binding region? | RP-HPLC, LC-MS, intact mass shift, optional functional assay review | Steric masking or over-modification reduces biological relevance |
| Folded Proteins and Enzymes | Site-selective conjugation, domain-aware fusion, or adaptor assembly | Can CPP installation be achieved without disrupting folding or activity? | Intact mass, chromatographic integrity, gel-based review, activity-compatible checks | Heterogeneous coupling and activity loss after random modification |
| siRNA and Short RNA | Covalent CPP conjugate or controlled co-assembly | Should the project prioritize defined stoichiometry or formulation flexibility? | IP-RP or hybrid chromatographic methods, mass confirmation, UV ratio, gel mobility | Charge neutralization, broad peaks, and poor endosomal release |
| ASO, PMO, and PNA | Stable covalent construct with orientation and linker screening | Which terminus and linker preserve target recognition while maintaining uptake? | HPLC or UPLC, mass analysis where feasible, purity profiling, stability comparison | Reduced hybridization performance or difficult purification |
| Plasmid DNA and Longer RNAs | Noncovalent complexation or hybrid delivery format | Is one-to-one conjugation realistic, or is assembly-based delivery more practical? | Size distribution, gel-based analysis, charge ratio review, assembly stability studies | Unstable complexes, inconsistent stoichiometry, or poor reproducibility |
| Labeled Assay Cargoes | CPP plus fluorophore, biotin, quencher, or dual-tag design | Can labeling be introduced without distorting uptake or readout? | UV/Vis, fluorescence profile, HPLC purity, mass shift confirmation | Label-driven changes in charge, hydrophobicity, or self-quenching behavior |
Cargo-Aware Planning
We design around the actual cargo class and assay objective rather than forcing proteins and nucleic acids into the same CPP workflow.
Multiple Delivery Formats
Projects can be configured as covalent conjugates, noncovalent complexes, fusion-style constructs, or modular hybrid systems depending on technical fit.
Site-Selective Chemistry
We prioritize attachment strategies that preserve CPP behavior and reduce unnecessary disruption of protein domains or oligonucleotide function.
Hybrid Analytics
Analytical planning is adjusted for peptide-only, protein-peptide, and peptide-oligonucleotide constructs instead of relying on a single generic QC package.
Flexible Construct Scope
We support single feasibility constructs, comparative linker or orientation panels, and follow-on analog generation for iterative delivery optimization.
Research-Ready Supply
From exploratory material to broader research quantities, we provide delivery constructs with documentation tailored to practical laboratory use.
Our workflow is built to move efficiently from construct planning to delivery of well-characterized CPP materials for intracellular delivery research.
1
Project Review & Delivery Strategy
2
Peptide & Cargo Preparation
3
Conjugation or Complex Assembly
4
Purification & Characterization
5
Delivery & Follow-On Optimization
CPP delivery constructs are used across discovery and translational research workflows where intracellular access, format control, and clear analytical definition matter. Below are representative use directions for our custom CPP delivery services.
If your team needs a reliable partner for cell-penetrating peptide synthesis, cargo conjugation, protein delivery construct design, or nucleic acid delivery support, Creative Peptides can help. We work with biotech companies, pharmaceutical research groups, CRO teams, and academic laboratories on custom CPP delivery projects aligned to discovery and non-clinical research goals. Contact us today to discuss your CPP sequence, cargo type, conjugation strategy, and project scope.
CPPs can be prepared for peptides, proteins, dyes, affinity tags, siRNA, antisense oligonucleotides, PNA, PMO-like cargoes, and selected DNA or RNA constructs, depending on the required delivery format.
Covalent conjugation is useful when you need a defined molecular entity for cleaner comparison. Noncovalent complexation can be more practical for larger or highly charged cargoes that are difficult to build as one-to-one conjugates.
The preferred site depends on which termini or side chains are accessible without disrupting uptake, folding, hybridization, or assay readout. Cargo function is usually the first constraint.
They can be explored for protein delivery, but attachment strategy matters. Random coupling may reduce activity, so site-selective design and protein-aware linker planning are often important.
Shorter and chemically well-defined cargoes such as siRNA, antisense oligonucleotides, PNA, and PMO-like constructs are often more suitable for defined CPP conjugates than very large nucleic acids.
