How to measure syringeability

Syringeability refers to the ease with which a substance can be drawn into and expelled from a syringe, including the force required to administer it through a needle. It plays a vital role in ensuring the usability, comfort, and safety of injectable formulations, whether used in pharmaceuticals, biotechnology, or medical devices. By assessing syringeability, manufacturers can optimise product performance, improve patient comfort, and maintain stringent quality control.

Syringeability measurement using a Texture Analyser quantifies the force needed to draw and expel substances through a syringe, essential for ensuring consistency in dosing and application. Below are key examples:

• Pharmaceuticals: Injectable drugs, including vaccines, biologics (e.g., monoclonal antibodies), or drug suspensions, must be syringeable to ensure smooth and efficient administration through needles, catheters, or other medical devices. Formulation scientists optimise the viscosity and particle size to ensure smooth injection, even through fine-gauge needles.
• Medical devices: In surgical procedures or wound healing, materials like gels or adhesives may need to be delivered through a syringe for precision application. Examples include wound care products, surgical glues, or injectable fillers.
• Cosmetics: For products like dermal fillers and injectable beauty treatments, syringeability determines ease of application and patient comfort. Poor syringeability can lead to discomfort or uneven application.
• Dental product dispensing analysis: Measuring the force needed to dispense dental products, such as adhesives or impression materials, through a syringe tip to assess ease of use.
• Veterinary medicine: Syringeability is important in veterinary medicine, where large animal doses may require injecting higher volumes or more viscous substances. Proper syringeability ensures efficient and less stressful administration for animals.
• Biopolymer solution syringeability measurement: Evaluating biopolymer solutions used in tissue engineering by measuring the force required to draw and extrude them through a syringe for medical applications.
• Inkjet ink syringeability testing: Testing the ease with which inkjet printer ink can be drawn into and expelled from a syringe to ensure consistent performance in printing.

In these examples, a Texture Analyser measures the force required for drawing and expelling substances, providing valuable insights into syringeability characteristics. These measurements help ensure consistent dosing, product performance, and user experience across various industries.

In a typical syringeability measurement test, the sample is held in a vertical position with the lower body of the syringe held securely whilst an upper grip holding the plunger pulls the sample upwards to fill the syringe or facilitates its movement downwards to eject the syringe contents.  Syringeability is measured by assessing how much force is required to expel the material from the syringe and how smoothly the material flows through the syringe and needle.

Empty syringes can also be tested – this test would be measuring wall friction between the plunger and the syringe body.

Universal Syringe Rig

• Viscosity: High-viscosity materials are more difficult to inject, requiring more force to push them through a syringe or needle. Examples include gels or thick suspensions, which often require special techniques or larger-bore needles. Low-viscosity materials, such as thin liquids or aqueous solutions, exhibit high syringeability, allowing them to flow smoothly through the syringe.
• Rheology (Flow behaviour): Newtonian fluids, which have a constant viscosity regardless of the shear rate, tend to have predictable syringeability. Materials such as saline or water-based solutions flow easily with consistent resistance. Non-Newtonian fluids, such as gels or certain suspensions, may exhibit shear-thinning (where viscosity decreases with increased shear) or shear-thickening behaviour. Shear-thinning materials are often easier to inject because they become less viscous when force is applied, reducing the resistance through the needle.
• Temperature effects: Viscosity changes with temperature, affecting syringeability. Warmer temperatures often reduce viscosity, making materials easier to inject. Conversely, colder temperatures can increase viscosity, reducing syringeability.
• Needle geometry: The gauge (diameter) and length of the needle significantly influence how easily the contents flow through it. The gauge (diameter) and length of the needle significantly influence syringeability. Thicker (lower gauge) needles allow more viscous materials to flow more easily, while thinner (higher gauge) needles increase resistance, making it harder to inject. Shorter needles require less force for injection, while longer needles can increase resistance due to the longer flow path and can make injection more difficult.
• Clogging and foaming: Solutions prone to clogging or foaming can hinder smooth withdrawal.
• Particle size and concentration: The size and concentration of suspended particles in a solution can affect syringeability. Large or irregularly shaped particles can clog needles or impede flow, making injection difficult. Higher concentrations of particles or solutes can increase viscosity and resistance, reducing syringeability.

The Stable Micro Systems Texture Analyser excels in optimising syringeability measurements through its comprehensive approach and specialised features. It accurately quantifies multiple properties including stiction, extraction force, aspiration force, and end constraints, providing a holistic view of a product's syringeability characteristics.

Equipped with dedicated tools like the Universal Syringe Rig, it precisely measures syringeability across a wide range of products from injectable pharmaceuticals to cosmetic items. The Texture Analyser captures detailed force-time-distance profiles, enabling in-depth analysis of syringeability behaviour and accurately measuring the force required to expel material from a syringe.

Backed by Stable Micro Systems' expertise in graphical interpretation and method development, makes the Texture Analyser the ideal choice for researchers and manufacturers seeking to refine product formulations and maintain quality standards in syringeability testing across various industries.