Charge-based strategy improves controlled delivery of therapeutic peptides from gelatin-based materials

Engineers at Rice University have devised a novel method to enhance the controlled release of therapeutic peptides from gelatin-based materials, potentially improving their application in tissue engineering and drug delivery systems. This breakthrough, detailed in a recent study published in Cell Biomaterials, involves manipulating the electrical charge of both the peptides and the gelatin carriers to prolong the release duration of these bioactive molecules. The research, led by Antonios Mikos, the Louis Calder Professor of Bioengineering and Chemical and Biomolecular Engineering at Rice University, was conducted in collaboration with scientists from Kyoto University. The team focused on osteogenic growth peptide (OGP), a small molecule known for promoting bone formation. By altering the charge of this peptide and the gelatin microparticles used to encapsulate it, the researchers aimed to address the issue of rapid diffusion typically observed with small molecules in hydrogel environments. Using confocal microscopy, the researchers visualized the distribution of the peptide-loaded gelatin microparticles, highlighting the effectiveness of the charge-based approach. Gelatin was chosen as the carrier due to its biocompatibility and widespread use in regenerative medicine. Its inherent ability to carry an electrical charge, which can be adjusted through processing methods, made it ideal for studying the impact of charge interactions on peptide retention and release. The study involved modifying the OGP peptide with different charged amino acid sequences, resulting in positively charged, negatively charged, and neutral variants. These modified peptides were then incorporated into gelatin microparticles. In addition, some gelatin particles were directly modified with charged sequences to assess the influence of localized charge sites on peptide behavior. Results indicated that the electrical charge of the therapeutic peptide itself was the primary factor influencing its retention within the gelatin matrix. Positively charged modifications enhanced the peptide’s interaction with the gelatin, reducing the initial burst release commonly seen in hydrogel-based systems. While the charge of the gelatin carrier also impacted the release dynamics, direct modification of the gelatin with additional charged sequences had a more limited effect and did not significantly alter the particles’ swelling or degradation rates. One variant of the positively charged OGP was released gradually over 14 to 21 days under conditions simulating a healing tissue environment. This represents a substantial improvement over previous hydrogel-based methods, which often required chemical bonding to achieve similar extended release periods for small, soluble peptides. Mikos emphasized the significance of the findings, stating that therapeutic peptides offer unique advantages due to their specificity and ease of manufacturing. However, their small size has posed challenges in maintaining their presence at the target site for sufficient durations. By fine-tuning the charge properties, the researchers demonstrated a practical solution to this longstanding issue. The study underscores the potential of electrostatic interactions in tailoring the release profiles of therapeutic agents. This approach could lead to more effective drug delivery systems, particularly in applications requiring sustained release over extended periods. The versatility of gelatin as a carrier, combined with the simplicity of charge modifications, opens up new possibilities for designing biomaterials with precisely controlled release characteristics. Further research will focus on translating these findings into clinical applications. Researchers plan to explore the effects of charge modifications on other types of peptides and evaluate their performance in vivo. The ultimate goal is to develop advanced biomaterials capable of delivering therapeutics in a manner that aligns with the physiological demands of tissue regeneration and repair.