Delivery System Based on Polymeric Microspheres

Polymer-based drug delivery system provides a robust technology platform to enable sustained, spatio-temporally controlled drug release. Biodegradable polymer microspheres with drug release profiles and predetermined degradation have been a major research focus for the development of effective drug delivery systems with a variety of applications, such as vaccine development, cancer and cardiovascular diseases. Besides the expertise in antibody design and engineering, Creative Biolabs is also dedicated to targeted drug delivery system design by using different kinds of targeting modules. With years of experience in drug delivery, the science team at Creative Biolabs can provide customers with comprehensive delivery systems based on polymeric microspheres.

Polymeric Microspheres

Microspheres are defined as spherical microscopic particles that range in size from 1 µm to 1,000 µm. The use of polymers for synthesizing microspheres enables the production of uniformly shaped and well-defined spheres in a wide range of sizes. Polymeric microspheres can be synthesized using a variety of different methods. Microsphere synthesis can be roughly divided into two different strategies. The spheres can be formed during the polymerization process, starting from a monomer solution, or can be produced from linear pre-existing polymer chains. The loading of microspheres can be divided into two basic strategies. The drug can be added during the synthesis of microspheres or can be soaked in after production.

Schemes of different synthetic polymeric microsphere synthesis routes.¹

Improving Microsphere-based Therapies by Controlled Local Drug Delivery

When microspheres are applied as fillers or bulking agents, the release of factors that influence the growth and differentiation of cells at specific locations may be considered. Polymeric microspheres are suitable as a drug delivery system for the sustained systemic delivery of diagnostic or therapeutic components. It allows the sustained release of a drug over a long period of time and has thus been proposed as a carrier for local drug delivery.

Among a great variety of polymers that have been utilized for drug delivery, poly(lactide-co-glycolide) (PLGA), copolymers of lactic acid and glycolic acid, have received a considerable amount of medical and pharmaceutical attention due to its biodegradability, biocompatibility, and convenient processability. Besides, PLGA has been approved by FDA for clinical use and PLGA microspheres constitute a versatile class of drug delivery vehicles. The release of an encapsulated agent from PLGA microspheres is controlled by both polymer degradation and diffusion. The drug release kinetics can be also tailored by varying the molecular weight (MW), copolymer composition, and microsphere size. For instance, the use of PLGA with higher MW resulted in slower drug release and lower MW PLGA leads to faster drug release that is mostly determined by diffusion. When smaller microspheres are used for drug delivery, the lower surface to volume ratio should be taken into account. The more surface area is present, the faster the initial release will be.

Fig.2 Scheme of preparation method of hydrogel microspher.²

Delivery System Based on Polymeric Microspheres

• Scientists used a modified solid in-oil-in-water (S/O/W) emulsion-solvent evaporation technique to prepare bevacizumab-dextran loaded sustained release PLGA/PCADK (poly(cyclohexane-1,4-diyl acetone dimethylene ketal)) microspheres after demonstrating the better biocompatibility of bevacizumab with PCADK monomers. These results suggested that bevacizumab-loaded PLGA/PCADK microspheres prepared according to the modified S/O/W method represent a useful approach to intravitreal therapy for ocular diseases.


• In fibrotic tissues, the platelet-derived growth factor receptor beta (PDGFβR) is highly upregulated, which provides a target for site-specific delivery of drugs. Scientists developed an injectable sustained release formulation for the subcutaneous delivery of the PDGFβR-targeted drug carrier protein pPB-HSA, which is composed of multiple PDGFβR-recognizing moieties (pPB) attached to human serum albumin (HSA). They finally demonstrate that subcutaneously administered polymeric microspheres present a suitable sustained release drug delivery system for the controlled systemic delivery for proteins such as pPB-HAS. Similar results have been reported in other literature as shown in Figure 3.

Fig.3 A diagram of PLGA-based biodegradable microspheres in drug delivery.³

Synthetic polymeric microspheres are frequently used in clinical practice, and the number of applications is steadily increasing. It has become clear that microspheres have advantages that make them well suited for clinical application.

• Microspheres are easy and relatively cheap to produce.
• The polymers used for the synthesis of commercial spheres are proven to be biocompatible and safe.

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Polymeric microspheres are nowadays an important part of the targeted drug delivery, making the treatment of patients easier and safer. If you are interested in our controlled release delivery system based on polymeric microspheres, please don’t hesitate to contact us for more information.

References

1. Saralidze, Ketie, Leo H. Koole, and Menno LW Knetsch. "Polymeric microspheres for medical applications." Materials 3.6 (2010): 3537-3564.
2. Chi, Honggang, et al. "Preparation strategy of hydrogel microsphere and its application in skin repair." Frontiers in Bioengineering and Biotechnology 11 (2023).
3. Su, Yue, et al. "PLGA-based biodegradable microspheres in drug delivery: recent advances in research and application." Drug delivery 28.1 (2021): 1397-1418.

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