Citation: Dierick W, Yoshino K, “Using Prefillable Syringes for Biopharmaceuticals – Development & Challenges”. ONdrugDelivery Magazine, Issue 55 (Feb 2015), pp 10-16.

William Dierick and Keisuke Yoshino describe the development of Terumo’s PLAJEXTM prefillable syringe system, which combines specific features of a COP syringe with the proprietary i-coatingTM technology to create a silicone oil-free system. 


The progress of genetic engineering has spurred a shift in pharmaceutical development from low-molecular drugs towards biopharmaceuticals. Looking at the top ten drug sales ranking in the world, biotherapeutics, such as Humira (adalimumab), Remicade (infliximab) and Rituxan (rituximab), have progressed substantially, in contrast to low-molecular blockbusters like Lipitor (atorvastatin calcium) or Plavix (clopidogrel), which mainly constitute the market in the last decade.1 At the same time, the patent cliff of several biotherapeutics and thus the loss of exclusivity (LOE) is propelling the development of biosimilars and biobetters.

“PLAJEX, in conjunction with the smooth i-coatingTM layer on the plunger stopper surface, has demonstrably achieved secure closure integrity…”

Many biotech drug products are lyophilised in vials due to their poor stability for parenteral administration. However, the development of liquid formulations of biotech products applying prefilled syringes has been increasing rapidly, driven also by enhanced safety in use, user convenience and ease of administration. Another important aspect is the shift from hospital treatment to home-care and patient self-injection for many chronic diseases and specific therapeutic areas.

This article addresses a technology approach to developing a prefillable syringe system as an appropriate parenteral drug container for biopharmaceuticals.


Figure 1: The components of a standard prefillable syringe.

Prefillable syringe systems have to meet various requirements and functionalities, for instance container closure integrity, heat resistance, shock resistance, plunger gliding forces, waste disposal and so on. Prefillable syringes consist of various components and materials such as glass, polymers and elastomers, which have to be selected appropriately to ensure they meet the requirements for their intended use (Figure 1).

In developing prefillable syringe systems, various optimisations are considered, such as product design, contact surface treatment and materials to satisfy quality requirements for injection. Biotherapeutics are often sensitive and not so stable thus, for example, causing aggregation and being subject to oxidation. Several publications have reported specific quality issues with biomolecules in prefillable syringe systems. Aggregation of therapeutic proteins is one of the most critical risk factors since it may impact negatively on efficacy and safety due to the protein deactivation and immune responses in patients. For example, it has been reported that inducement of neutralised antibody of epoetin-alpha makes endogenous erythropoietin less active, resulting in an increased incidence of antibody-mediated pure red cell aplasia (PRCA).2,3 The US FDA recently published a guidance for industry entitled “Immunogenicity Assessment for Therapeutic Protein Products” recommending minimising any aggregation risks.4

Quality and safety issues can be very diverse and may be material related, or related to the biomolecule itself. A non-exhaustive overview is listed in Table 1.

An important issue is silicone oil-induced aggregation. Silicone oil has been used as lubrication to achieve smooth plunger gliding functionality. However, in the context of biomolecules, silicone oil became a serious issue because it can induce protein aggregation.5-7 Furthermore, the prefillable syringe manufacturing process is considered a potential risk factor. For instance, tungsten pins are used for the glass barrel tipforming process. Protein aggregation in the presence of tungsten has been observed.11-14

Historically, prefillable syringes were developed for small-molecule drugs so that many potential quality issues appeared only when introducing therapeutic proteins into prefillable syringe systems. In taking a riskmanagement approach, on basis of the issues shown in Table 1, it is suggested that three main attributes should be considered for a prefillable syringe system for use with biopharmaceuticals:

  1. Silicone oil-free system
  2. Polymer-based syringes
  3. Concepts to prevent protein oxidation.


Silicone oil-free system

Figure 2: SEM micrographs of surface and cross-section of the plunger stoppers. (a) top surface of an uncoated plunger stopper (x300), (b) cross-section of an uncoated plunger stopper (x1000), (c) top surface of an i-coatingTM coated plunger stopper (x300), and (d) cross-section of an i-coatingTM coated plunger stopper (x1000).

Various publications are reporting on protein aggregation as discussed above as well as on sub-visible particles and the interactions thereof.15-18 Therefore, the need for the development of a silicone oil-free prefillable syringe system has been established 18-22 and such quality issues became a trigger for Terumo to develop a silicone oil-free prefillable syringe system based on a plunger stopper combined with a specific coating technology. Terumo launched MINOFIT, its first silicone oil-free polymer-based prefilled syringes system in 2005.

On that basis, Terumo continued its development towards a proprietary commercial-scale process, in 2012 resulting in a coating method to form a strong, flexible and uniform layer of silicone resin through a chemical process including polymerisation of the layer, called i-coatingTM. Scanning electron microscope (SEM) images before and after the i-coatingTM treatment are shown in Figure 2. Compared with uncoated plunger stoppers (Figure 2a and b), i-coatingTM plunger stoppers, as shown in Figure 2c and 2d, provide a uniform and smooth surface layer.

Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses demonstrate that the surface layer material of the i-coatingTM plunger stopper was identified as a silicone resin with high purity. The resulting dynamic friction force from an i-coatingTM rubber sheet was about ten times lower than the same uncoated rubber, with a value similar to polytetrafluoroethylene (PTFE) sheet (data not shown). These findings have been discussed in a published article.20

Polymer-Based Syringes

Glass containers have been used extensively and have been substantive for the development of parenteral drugs. However, with the availability of biopharmaceuticals and the emergence of biosimilars, several aspects related to glass material are still to be resolved (Table 1).

Phenomenon Causing factor Related material
Physical Aggregation by silicone oil Independent of material
Aggregation by tungsten Glass
Interaction with glue Dependent on manufacture
Excessive shaking Independent of material
Chemical Alkali elution Glass
Gas permeability Polymer
Residual radicals Dependent on sterilisation
Other Container breakage Glass
Delamination Glass
Scratching of container surface Polymer
Silicone oil droplets Independent of material

Table 1: Quality issues with biopharmaceuticals.5-16

Furthermore, considering high-value biotech products, product loss from container breakage during manufacturing and transportation becomes an issue which cannot be ignored.23

Figure 3: The components of a PLAJEXTM plastic prefillable syringe.

With a specific focus on biopharmaceuticals, Terumo has developed a polymer-based prefillable syringe (PLAJEXTM) as an alternative to glass prefillable syringes to resolve problems like protein aggregation or breakage. PLAJEXTM is made of cyclo-olefin polymer (COP), having outstanding properties such as impact resistance, superior moisture-barrier, heat resistance and excellent transparency. Moreover, to eliminate the risks of protein aggregation due to interactions with the tungsten and glue, the needle is inserted directly into the barrel by insert moulding. And combined with our proprietary i-coatingTM technology, PLAJEXTM provides for a silicone oil-free syringe system. In addition, Terumo adopted autoclave sterilisation for PLAJEXTM to avoid the risk of protein oxidation from radicals that form on the polymer barrel material from sterilisation by irradiation. PLAJEXTM therefore benefits from this integrated approach, having a high transparency, superior strength, and smooth and controllable plunger gliding properties, as well as minimising the risks of protein aggregation and protein oxidation. These features are summarized in Figure 3, and discussed further hereafter.

Mechanical Strength

Figure 4: Flange breakage force (all flange) measured by universal tensile tester at a stroke rate of 50 mm/min. The value represents the mean ± SD (n=10).

A comparison of mechanical strength of the flanges of PLAJEXTM with glass syringes, measured with a universal testing machine, is shown in Figure 4, demonstrating that the flange of PLAJEXTM is nine-times stronger than that of a typical glass syringe. This is an important aspect in the context of use with auto-injector applications, in terms of functionality as well as for the detection by the user of particles or breakage inside the auto-injector.

Plunger Gliding Properties

As discussed earlier, an important feature of PLAJEXTM with Terumo’s i-coatingTM technology is that it is a silicone oil-free system. Figure 5a shows the comparison of gliding properties between traditional silicone oil-coated systems and PLAJEXTM.

Figure 5: (a) Glide force profile of silicone oil system (SO) and silicone oil-free system (SOF) stored for 12 weeks at 40°C. The data was obtained at a stroke of 200 mm/min. Glide forces were measured with a universal tensile meter. (b) Break-loose glide force change with aging time and temperature of SO and SOF system. Break-loose glide force is the maximum glide force between 0 and 5 mm of stroke distance. Data are presented as mean ± standard deviation (n = 5).

In the case of the silicone oil systems, the silicone oil layer between barrel and plunger stopper may vary over time resulting in variations in initial gliding force (breakloose force), increasing over time by aging. Figure 5b, on the other hand, shows the silicone oil free system and no change is observed following aging and at various temperature conditions. The surface layer of the i-coatingTM-treated plunger stopper is not silicone oil but silicone resin that is bonded directly to the stopper material. The absence of break-loose peaks is very beneficial for applications with autoinjectors for consistent and trouble-free functionality.

Protein Aggregation

Figure 6: Comparison study between silicone oil system (SO) and silicone oil-free system (SOF) in terms of sub-visible particles using MFI analysis. (a) ECD ≥5μm, aspect ratio is more than 0.85, (b) ECD ≥5μm, aspect ratio is less than 0.85. Data are presented as mean ± standard deviation (n = 10 for water, n = 5 for samples). *: p<0.05, ***: p <0.001.

A comparative study on protein aggregation from silicone oil interactions has been conducted. In this study, L-asparaginase is used as a protein model because of its susceptibility to aggregation from interaction with silicone oil. After the protein solution and water for injection (WFI) were filled into both silicone oil and silicone oil-free systems, each syringe was shaken gently. Protein aggregation and sub-visible particles were analysed by Micro Flow Imaging (MFI). Figure 6a shows the quantification of circular sub-visible particles representative for silicone oil and Figure 6b shows the quantification of non-circular sub-visible particles representative to protein aggregation. In the case of WFI, the number of circular sub-visible particles increased in the silicone oil system. On the other hand, this phenomenon was not observed with the silicone oil-free system, suggesting that in the silicone oil system, silicone oil from the syringe barrel wall had migrated into the WFI and formed silicone oil droplets.

With syringes filled with protein solution, a high number of circular and non-circular sub-visible particles were detected in the silicone oil system. In contrast, this was not observed in the silicone oil-free system. On the basis of these results, it can be concluded that the silicone oil-free system (the PLAJEX™ syringe incorporating Terumo’s i-coatingTM technology) can offer a solution for minimising both protein aggregation and sub-visible particles.


Even at the stage of the prefilled syringe design development, it is of utmost importance to ensure the container closure integrity in order to prevent leakage, microbial ingress and drug product quality deterioration. PLAJEX, in conjunction with the smooth i-coatingTM layer on the plunger stopper surface, has demonstrably achieved secure closure integrity, including in high-pressure leakage testing and microbial assessment testing.20

Figure 7: Micro-organism penetration study. (a) The silicone oil-free (SOF) system showing all four investigated syringes. The inner solution remained clear without any visual change. (b) Positive control (the SOF syringes with a pinhole on the barrel) of all five investigated syringes. The inner solution became considerably turbid by the invasion and growth of micro-organisms

As an example, Figure 7 shows the results of micro-organism penetration assessment. Tryptic soy broth (TSB) culture medium was filled into PLAJEXTM syringes by aseptic manipulation and then immersed into a bacterial broth for a predetermined time. After that, the samples were incubated at 31 ±1 °C for 14 days. PLAJEXTM demonstrated no particular changes in appearance and the culture medium inside the syringes remained clear (Figure 7a). In contrast, positive control samples showed a considerable change in that the medium became turbid (see Figure 7b).


So far, we have explained on our technologies to minimize the risk of protein aggregation, minimizing sub-visible particles and other quality aspects such as container breakage. Hereafter we will address also on our applied technologies to minimize the risk of protein oxidation.


Figure 8: Profile of % oxidisation of model drug during storage at 25°C. The measurement was performed by HPLC. The value represented the mean ± SD (n=3)

Terminal steam sterilisation is applied to prefilled syringes containing small-molecule drug products. However, since biotherapeutics are subject to denaturation by heat, aseptic filling into pre-sterilised prefillable syringes is the norm. A consideration of the method of sterilisation and its potential impact on the drug product is of paramount importance. Figure 8 compares the degree of oxidisation of methionine during storage for gamma-sterilised polymer prefilled syringes with that in steam-sterilised PLAJEX products.

Polymer-based prefillable syringes that are gamma-sterilised, and steam-sterilised syringes, respectively were filled with erythropoietin (EPO) aqueous solution. As noted in Figure 8, prefillable syringes sterilised by gamma irradiation showed a higher degree of methionine oxidation over time. For PLAJEXTM prefillable syringes sterilised by autoclaving, methionine oxidation was not induced. Though more detailed mechanistic studies of this phenomenon are underway, we assume that radicals generated by gamma sterilisation remained inside a prefillable syringe, causing the oxidation of biopharmaceuticals.18, 24, 25 Further studies are ongoing and planned to be published. On the basis of these results, we believe that steam sterilisation is more appropriate for polymer-based prefillable syringes for biopharmaceuticals.


Glass syringes, having low gas permeability, are often considered as superior to polymer-based syringes with respect to the avoidance of drug product oxidisation. Generally, for sensitive protein applications, nitrogen control and nitrogen blanketing is necessary in all processes such as drug solution preparation, filling and stoppering, to eliminate any risk of dissolved oxygen entering the filled glass syringe.

Figure 9: (a) The combination of PLAJEXTM with the deoxygenated packaging system. (b) Reduction profile of dissolved oxygen in water-filled prefilled syringes. Dissolved oxygen was measured by OXY-4 (PreSens). The value represented the mean ± SD (n=3).

However, utilising the specific permeability characteristics of PLAJEXTM, it is feasible to eliminate dissolved oxygen with a more simple and innovative method. This method consists of using an oxygen absorber inside the secondary packaging along with the filled PLAJEXTM. This resulting effect is as depicted in Figure 9b.

Using oxygen absorber materials with PLAJEXTM means the concentration of dissolved oxygen decreases rapidly just after packaging and continues to decrease gradual ly. After eight weeks, the concentration of dissolved oxygen was close to zero. This result shows that the combination of PLAJEXTM, the deoxygenated package system and oxygen absorber can prevent protein oxidisation.24


This article introduced specific features and functionalities of Terumo’s polymer based prefillable syringe system, PLAJEXTM. This system was developed by combining inherent features of a COP syringe with our proprietary i-coatingTM technology to realise a silicone oil-free syringe system. Several quality issues can be addressed for applications with sensitive biopharmaceuticals. In addition, polymer-based prefillable systems offer the benefits of consistent and high dimensional reproducibility and precise processing, and allow for flexibility in design to make customised versions of design specific syringes.

The global biopharma market is still growing apace due to the increasing prevalence of chronic diseases, an aging population and thanks to advancements in biomedical science creating more effective drugs. With the development of PLAJEXTM with i-coatingTM technology, Terumo aims to ensure that biopharmaceuticals can be administered safely, reliably and uncontaminated, avoiding errors in medical practice while minimising patient trauma and discomfort.


  1. Pharmaceutical Industry Vision in 2013, PMDA
  2. Casadevall N, et al, New Engl J Med, 2002, Vol 346(7), pp 469-475.
  3. Gershon SK, et al, New Engl J Med, 2002, Vol 346(20), pp 1584-1586.
  4. Guidance for Industry: “Immunogenicity Assessment for Therapeutic Protein Products”, August 2014.
  5. Jones NS, et al, J Pharm Sci, 2005, 94(4), pp 918-927.
  6. Mahler HC, et al, J Pharm Sci, 2009, Vol 98(9), pp 2909-2934.
  7. Wang W, et al, Int J Pharm, 2010, Vol 390(2), pp 89-99.
  8. Wang W et al, “Aggregation of Therapeutic Proteins.
  9. Christiaens P, PDA Workshop 2014, “Regulatory Requirements”.
  10. Ge Jiang, et al, PDA journal, 2013, Vol 67(4), pp 323-335.
  11. Mensch C, et al, PDA J Pharm Sci Technol, 2012, Vol 66(1), pp 2-11.
  12. Seidl A, et al, Pharm Res, 2012, Vol 29(6), pp 1454-1467.
  13. Liu W et al, PDA J Pharm Sci Technol, 2010, Vol 64(1), pp 11-19.
  14. Jiang Y, J Pharm Sci, 2009, Vol 98(12), pp 4695-4710.
  15. Sing SK, et al, J Pharm Sci, 2010, Vol 99(8), pp 3302-3321.
  16. Ripple DC, et al, J Pharm Sci, 2012, Vol 101(10), pp 3568-3579.
  17. Bee JS, et al, J Pharm Sci, 2012, Vol 101(10), pp 3580-3585.
  18. Forster R, PDA Annual Meeting 2013.
  19. Majumdar S, J Pharm Sci, 2011, Vol 100(7), pp 2563-2573.
  20. Yoshino K, et al, J Pharm Sci, 2014, Vol 103(5), pp 1520-1528.
  21. Uchiyama S, et al, J Pharm Sci (in press).
  22. Depaz AR, et al, J Pharm Sci, 2014, 103(5), pp 1384-1393.
  23. Reynolds G, et al, BioProcess International, 2011, Vol 9(11), pp 52-57.
  24. Nakamura K, et al, PDA J Pharm Sci Technol (in press).
  25. Nakamura K, et al, Int J Pharm (submitted).