In this interview, industry experts Jennifer Prestipino and Dr. Viviana Posada discuss the unique properties of silk fibroin and chitosan, their biomedical applications, and innovative techniques enhancing biomaterials through nanoscale surface modifications and UV-Vis spectroscopy.
What makes silk fibroin stand out as a biomaterial for biomedical applications?
Jen Prestipino: Silk fibroin, a protein derived from silkworms, is incredibly versatile for biomedical applications, particularly in drug delivery. Its standout properties include high biocompatibility, low immunogenicity, and robust encapsulation capabilities. These advantages are largely due to its unique beta-sheet structure, which gives it strength, elasticity, and prolonged stability against enzymatic degradation, making it ideal for controlled and sustained drug release. Additionally, silk fibroin’s chemical and structural modifiability means it can be tailored for specific therapeutic applications, whether for targeted delivery or controlled release, ensuring optimal alignment with safety and efficacy criteria.
What about chitosan, what are the standout features that make it an important material for biomedical applications?
Viviana Posada: Chitosan offers tremendous potential for modifying surface interactions, particularly at the nanoscale. In our lab, BioANSR, we’ve explored plasma nanosynthesis to engineer nanostructured surfaces on chitosan, optimizing them for antibacterial efficacy and cell alignment. This ability to create surfaces that both resist bacterial growth and promote tissue integration is transformative, especially for implants and wound healing applications. By altering surface topography and chemistry, we can achieve better biological responses, such as minimizing inflammation and guiding cellular alignment—key elements for improving clinical outcomes.
What are the essential criteria for a successful drug delivery system?
Jen Prestipino: An effective drug delivery system should meet several core criteria to maximize therapeutic benefits while minimizing side effects. First, biocompatibility is critical; the delivery system should not cause adverse immune responses or toxicity in the body.
Another key aspect is drug loading capacity, which refers to how much of the therapeutic drug the system can carry—this ensures that an adequate dosage reaches the target site.
Then, there is the issue of targeted delivery. The drug must be released precisely where needed to improve efficacy and reduce potential harm to other areas.
Lastly, controlled release is crucial to prevent premature drug release, which could cause unwanted side effects or limit the drug’s effectiveness. These criteria guide the development of different drug delivery systems, each with strengths and limitations. We aim to modify and optimize these systems to meet these criteria as closely as possible.
What are the main types of drug delivery systems, and how do they differ?
Jen Prestipino: Drug delivery systems can be categorized into three broad types: polymeric-, inorganic-, and lipid-based. Each has unique properties that make it suitable for different applications.
Polymeric systems use synthetic or natural polymers—like proteins and polysaccharides—that are biodegradable and biocompatible, which makes them safe and effective in many therapeutic scenarios.
These systems are also highly modifiable, allowing us to adjust their properties to improve targeting or efficiency. However, polymeric systems can sometimes aggregate, which raises toxicity concerns.
Inorganic systems, on the other hand, often use metal nanoparticles like gold or silica. These particles can be tailored in terms of size, charge, and coating, giving us control over their interactions in the body. Yet, due to the heavy metal content, there is a risk of toxicity.
Lipid-based systems are perhaps the most recognized today, especially since lipid nanoparticles were used in the COVID-19 vaccines. They offer high encapsulation efficiency, meaning they can carry significant amounts of therapeutic material. However, liver uptake can reduce the amount of drug that reaches the target and raise liver toxicity risks.
Overall, each system offers distinct advantages and challenges, and careful consideration is needed to match the system to the therapeutic needs.
Why is silk fibroin considered a promising material for drug delivery, and what are its key advantages?
Jen Prestipino: Silk fibroin, a protein derived from silkworms, has been used for centuries in sutures and bandages. It is now being studied for its potential in drug delivery. One of the main reasons for its appeal is its low immunogenicity and high biocompatibility.
Silk fibroin is generally well-tolerated by the body and does not trigger strong immune responses. Additionally, silk fibroin fibers are very strong due to their beta-sheet structure, which gives them durability, stability, and elasticity. This structure not only prolongs the degradation process by natural enzymes in the body, allowing for sustained drug release, but also makes it an effective encapsulation medium.
Furthermore, silk fibroin is highly modifiable chemically and structurally, meaning it can be tailored for specific applications, whether for targeted delivery or controlled release.
These properties—strength, stability, biocompatibility, and versatility—make silk fibroin an outstanding candidate for a natural polymer-based drug delivery system that aligns well with our safety, loading capacity, targeted delivery, and controlled release criteria.
Could you explain how you tested silk fibroin’s drug encapsulation efficiency?
Jen Prestipino: To assess the encapsulation efficiency of silk fibroin, I used a protocol with acetaminophen as the model drug. First, I prepared a pre-purified 5 % silk solution and added potassium phosphate to aid in the self-assembly of silk fibers around the acetaminophen.
After combining the silk solution and acetaminophen, I stored the mixture at 4 °C for two hours, allowing the fibers to encapsulate the drug particles.
Once the particles had formed, I centrifuged the sample to separate the encapsulated particles from the supernatant. By reserving this supernatant, I could later measure the residual acetaminophen that had not been encapsulated.
I calculated the encapsulation efficiency using UV-Vis spectrophotometry by comparing the initial drug concentration to the amount left in the supernatant. This technique allowed me to determine how effectively the silk fibroin encapsulates the drug, which is crucial for assessing its suitability in drug delivery applications.
How does the NanoDrop Eight Spectrophotometer facilitate these types of measurements?
Jen Prestipino: The NanoDrop Eight is an efficient tool for UV-Vis spectrophotometry because it allows us to measure eight samples at once using only one to two microliters per sample. This is a significant improvement over traditional cuvette-based spectrophotometers, which require much larger volumes and often multiple dilutions to get readings within the instrument’s absorbance range.
The NanoDrop Eight can measure up to 200 absorbance units, allowing us to avoid dilutions and thus reduce potential sources of error. This is particularly useful when working with small or precious samples, as we do not have to waste material or risk introducing errors from dilution.
For anyone looking to perform UV-Vis measurements efficiently and accurately, the NanoDrop Eight is an excellent choice.
How does surface modification enhance biomaterials like silk fibroin and chitosan?
Viviana Posada: Surface modification, particularly at the nanoscale, is crucial for optimizing how biomaterials interact with biological environments. In my research, we focus on modifying the surface of materials like silk fibroin and chitosan through plasma nanosynthesis, which allows us to create unique nanostructures on the material’s surface.
For example, we can use argon plasma to create nanopores or nanopillars that change the material’s properties without altering its bulk composition. These modifications are especially useful in biomedical applications, as they can enhance cell attachment, inhibit bacterial growth, and improve tissue integration.
For silk fibroin, we have seen that adding nanostructures can change how cells respond to the material, potentially reducing inflammatory responses. Plasma modifications have been shown to create antibacterial and favorable surfaces for cell alignment for chitosan.
By carefully controlling these surface properties, we can develop biomaterials that meet specific clinical requirements, from drug delivery to tissue engineering.
How do macrophages interact with these modified nanostructured surfaces, and why does this matter?
Viviana Posada: Macrophages interact with nanostructured surfaces differently depending on the specific topography and chemistry. We observed that when macrophages encounter surfaces with nanopillars, their behavior varies based on the tilt and density of these nanostructures.
For instance, on silk fibroin surfaces with 45-degree nanopillars, macrophages showed increased motility and were less likely to cluster, whereas, on surfaces with 60-degree structures, they adhered more firmly and moved less.
This kind of response suggests that surface modifications can influence immune cell behavior, which is vital for applications where inflammation needs to be minimized, such as implants or wound dressings.
Understanding and controlling these interactions allow us to design materials that reduce immune reactions and improve integration with body tissues.
What did you discover about cell alignment and nanostructure orientation?
Viviana Posada: During our studies, we discovered that cells naturally align themselves along the orientation of nanostructures. As we increased the length of the nanostructures on the chitosan surface, the cells attached and aligned along the structure’s direction.
This finding was quite exciting because it shows that we can guide cell behavior by simply adjusting the physical properties of the material surface. This alignment is particularly beneficial in tissue engineering, where directional growth can improve tissue structure and function.
So, by controlling nanostructure orientation, we can potentially enhance cellular organization and improve the outcomes of regenerative treatments.
What are common sources of error in UV-Vis spectrophotometry, and how can they be minimized?
Jen Prestipino: One common source of error in UV-Vis spectrophotometry is dilution, especially in traditional cuvette-based systems, where samples must be diluted to fit within the absorbance range of the instrument. Each dilution introduces the risk of error, particularly with very high concentrations.
By using NanoDrop instruments, which have a much wider absorbance range, we can often measure samples directly without dilution, avoiding this source of error. Another potential error is improper sample handling, such as using incorrect blank solutions, which can affect the accuracy of the results.
Ensuring consistent, precise handling and choosing tools like the NanoDrop spectrophotometer that minimize sample preparation can significantly improve measurement reliability.
About Dr. Viviana Posada 
Dr. Viviana Posada is a Principal Investigator at the BioAdvanced NanoSurfaces Research Lab in the Nuclear Engineering Department at Penn State University. She earned her Ph.D. from Universidad Nacional de Colombia.
She honed her expertise in biomaterials design and characterization—using techniques such as AFM, SEM, XRD, and FTIR—along with in vitro and in vivo methods at the University of Illinois at Urbana-Champaign.
Her research is centered on nanomedicine, focusing on enhancing radiopharmaceutical delivery and tissue integration through nanochemical cues.
About Jennifer Prestipino
Jennifer Prestipino is an Applications Scientist at Thermo Fisher Scientific, specializing in the NanoDrop UV-Vis Spectrophotometer product line. She has a Master’s in Molecular Biology from Drexel University and a Bachelor’s in Microbiology, Biochemistry, and Molecular Biology from Penn State University.
With extensive experience designing and implementing molecular biology workflows, Jennifer has a strong background in nucleic acid extraction, qPCR techniques, and UV-Vis spectroscopy. She is also proficient in gene therapy testing using qPCR and droplet digital PCR methods.
About Thermo Fisher Scientific – UV-Vis Spectroscopy
UV-Vis Spectrometers overview
Scientists can count on our broad range of ultraviolet (UV) and visible (Vis) spectrophotometers to deliver reliable, accurate data. The Thermo Scientific SPECTRONIC 200, GENESYS, and Evolution product lines are designed to streamline measurements providing consistent, high-quality results, time after time. Additionally, the innovative Thermo Scientific NanoDrop microvolume family of instruments, have been helping scientists accelerate the pace of discovery for over 20 years. From classroom teaching—to routine measurements—to discovery of the next scientific breakthrough, our line of spectrophotometers is designed to fit into any modern laboratory.
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