Formulations are a key to maximizing performance of crop protection actives and Starpharma’s Priostar® dendrimers have a role in developing enhanced products that perform better in the field. Starpharma has been developing the proprietary Priostar® dendrimer technology to provide formulators with an innovative tool for new and existing crop protection actives. Commercial interest in Priostar® dendrimers continues to grow globally, with Adama licencing the technology for an improved 2,4-D formulation in the US, as companies experience the benefits of this technology for themselves.
1) What are Priostar® dendrimers?
|Potential Formulation Benefits of Priostar® Dendrimers:
- Increasing the solubility of actives;
- Improve the stability of actives;
- Modifying formulation movement through a substrate;
- Enhancing rainfastness ®; and
- Improving overall efficacy.
Priostar® dendrimers are compact synthetic polymers that have a branching, tree-like structure at the molecular scale giving a spherical 3-D shape with multiple functional groups on the surface. The ability to easily alter the functional groups provides great flexibility to modify the dendrimer’s properties which translates into greater utility in providing effective solutions across a number of formulation types. Priostar® dendrimers’ unique characteristics are not possessed by conventional inert ingredients, such as surfactants.
2) Increasing the solubility of actives using Priostar® dendrimers
Priostar® dendrimers can be used to increase the solubility of crop protection actives in water by a significant amount. In one example, the solubility of the herbicide trifluralin in water (at pH7) was increased 25,000 fold (from 0.22 milligrams per litre to 5.43 grams of the active per litre) following simple addition of a Priostar® dendrimer.
Increased solubility of trifluralin using Priostar® dendrimers
Solubility enhancement = 25,000 fold
Improvements in solubility as provided by Priostar® dendrimers enables unique formulation opportunities and opens up the possibility of achieving novel formulations with actives that were once considered to have limited application or effect due to their limited solubility. Further, access to new, high loading formulations of crop protection actives provides savings across the supply chain through reduced manufacturing, transport and storage costs. The desire to provide new innovative products to the market drives a large part of formulation development and Starpharma’s Priostar® dendrimers are delivering in this area.
3) Using Priostar® dendrimers to increase the stability of actives
Improving the stability of actives in a formulation is another benefit that Starpharma has observed (see Figure 1). This effect could lead to improved shelf-life of products and greater stability in the field, leading to improved control of pests.
Using Priostar® dendrimers to increase active stability under accelerated testing at 54°C
4) How Priostar® dendrimers can change formulation movement through a substrate
Starpharma has observed that Priostar® dendrimers can alter the movement of an active though a substrate. Enhancing soil permeability through the preparation of novel formulations can make them more effective at targeting pests and diseases that current formulations cannot control due to poor soil penetration.
One such study assessed the penetration of imidacloprid into a 7.5cm column of packed sand. After three days, around four times the amount of active (~40% versus <10%) percolated into the bottom 2.5 cm of the column when the formulation contained certain Priostar® dendrimers. The imidacloprid control formulation did not show as much penetration with half of the active (50%) remaining trapped in the top 2.5cm of the column compared to around 25% for the dendrimer formulation. This proof-of-concept study confirmed the capability of Priostar® dendrimers to increase percolation through the soil.
5) Enhancing rainfastness of formulations with Priostar® dendrimers
Starpharma has demonstrated that a Priostar® formulation of glyphosate
showed improved rain-fastness in glasshouse trials, making the active more resistant to being washed away in poor weather. The Priostar® formulation demonstrated up to a 150%-250% improvement in efficacy when rain was applied four hours post application, compared to a non-dendrimer control glyphosate formulation.
Priostar dendrimer technology is highly versatile and can be used in a range of formulation types such as Emuslifiable Concentrate and Suspension Concentrate formulations, as well as granules and powders. To assist with novel formulation development, Starpharma have developed a library of Priostar® dendrimers as crop protection excipients, designed with different applications in mind. The result is that we can improve a number of aspects which can limit the development of commercial products. The studies included in this article relate to specific crop protection actives, but demonstrate how Priostar® dendrimers can enhance the formulation and performance of a broad range of actives.
6) Improving efficacy with Priostar® dendrimers
Other glasshouse studies have demonstrated the benefits of Priostar® dendrimers in improving the efficacy of an active, with one example being the improvement of the systemic control of a fungicide.
Better systemic efficacy of a fungicide using Priostar® dendrimers
Early stage glasshouse studies indicated that Starpharma’s Priostar® dendrimers could improve the efficacy of glyphosate on weeds under controlled conditions. Glyphosate is currently the worlds most used herbicide with sales over US$5.5 billion in 2014 and expected to reach around US$9.5 billion by 2023, according to the report published by Global Market Insights, Inc. To evaluate the improvement in efficacy of this herbicide that Priostar® dendrimers could provide, field trials were undertaken. The results showed an improvement of approximately 15% in control of weeds with Priostar® containing glyphosate formulations compared with market-leading formulations that did not contain Priostar® dendrimers. The field trials were conducted under the conditions required for registration of formulations by the APVMA in Australia. This ensures that the trials are of a suitable level and provides a greater level of confidence in the results. The improvement in the field is an impressive result for an active that is already considered highly efficacious and is well advanced in the market.
Enhanced Priostar® dendrimer glyphosate formulation compared to
a market leading glyphosate formulation
Starpharma has a number of partnerships with major multination Agrochemical companies. Adama, one of the leading crop protection companies has signed a licence to use Priostar® dendrimers in 2,4-D formulations. Both Starpharma and Adama are working to bring the new product to market in the near future. In addition, Starpharma has many other confidential partnerships in place which are focused on the commercialization of Priostar® dendrimer enhanced formulations.
In summary, Priostar® dendrimers represent a significant step forward in formulation technology. Starpharma research has produced Priostar® dendrimer- formulations of leading agrochemicals which demonstrate significant performance enhancements. These results serve as examples of what can be achieved across a broad range of actives. Priostar® dendrimers have been proven to boost efficacy, and deliver gains in rain-fastness and control of soil migration. Major improvements have also been seen in the solubility and stability of actives. These enhancements can support the creation of new agrochemical formulations and help to carve out new market niches or breathe new life into off-patent actives.
Note: Starpharma welcomes approaches from formulators and crop protection companies who would like to evaluate Priostar® dendrimers in their own formulations.