Yes, I know what you are thinking: Jell-O? Why would Jell-O be used in a materials lab for growing cells? Well, it isn’t the taste of this childhood snack that makes it perfect for tissue engineering; it is its composition. The most abundant protein in our body is a compound called collagen, which makes up most of the extracellular matrix that cells live in. If you take collagen and break it up into smaller pieces, you get gelatin, the material that makes up Jell-O. Tissue engineers, who work to maintain, improve, and/or restore biological tissues in our bodies, can use gelatin to simulate an in vivo environment, meaning the natural environment of a living organism. 这不仅在组织培养中打开了应用，而且在注射治疗中也有无数的应用, which are injectable solutions that can regrow or enhance existing tissue. While the field of tissue engineering is in its infancy, 利用明胶等支架进行组织培养的治疗方法已经应用于受伤患者的合成皮肤和器官.
Injuries and degenerative diseases, such as Alzheimer’s and multiple sclerosis, can lead to long recoveries and/or irreversible damage. To alleviate these effects, one could inject specific stem cells into the damaged area to grow themselves, trigger new growth within your body, and limit inflammation. However, 将细胞直接注射到体内会导致细胞在全身的低活力和显著的分散, moving them away from where they are needed most. Here is where our “scientific Jell-O” comes in. Gelatin, which is a hydrated complex of polymers, can be used to surround encapsulated cells, thereby increasing viability and stabilizing cell location following their injection. My research in Dr. Kyung Jae Jeong’s lab at the University of New Hampshire, 它是由研究经验和学徒计划(REAP)通过哈默尔本科研究中心资助的, 研究了改变明胶制成的水凝胶的方法，使它们在注射治疗中更有效.
Figure 1. A microscope image of Jeong lab's novel 10% gelatin microgels.
Microporous Hydrogel Methodology and Characterization
传统的水凝胶是聚合物链的复合体，与它们的质量相比，它能容纳大量的水. However, these hydrogels lack porosity, mitigating cell growth and penetration of host biology. To address this, my faculty mentor, Dr. Jeong, and my graduate mentor, Dr. Seth Edwards, 使用由明胶制成的新型可注射微孔水凝胶，促进细胞扩散和增殖. 传统的水凝胶可能更容易想象成一个固体的果冻块，里面粘着细胞, 而微凝胶结构是由许多小的果冻珠和细胞在空间中生长组成的ween. My summer research focused on the alteration of microgel diameter. 控制微凝胶的直径可以影响水凝胶的性质，如营养转移和有效表面积, and cellular responses such as cell morphology, spreading, and differentiation. 这些变量有助于描述细胞行为的可预测性和体内治疗的安全性.
Figure 2. A microscope image of 5% gelatin microgels with a TWEEN 20 emulsifier developed by the author.
I formed the microgels by dissolving gelatin in water and dropping the solution into an oil bath, creating an emulsion. 明胶溶液在油中分解成小液滴，这些液滴可以被收集起来并一起固化. The small spheres of gelatin are connected by microbial transglutaminase (mTG), a bacterial enzyme that connects the glutamine and lysine substituents of gelatin. After curing, a bulk hydrogel is left with space for cells to grow in between the microspheres. (Figure 1)
I tried lower concentrations of gelatin during the emulsion process, varying the mixing speeds and microgel curing times. Each variable had its own effect, some greater than others. 我还加入了不同浓度的乳化剂(TWEEN 20)，以减少水合明胶表面的极性. 通过在水凝胶乳化方案中加入乳化剂并将明胶浓度从原来的10%降至5%, the diameter of the microgels were reduced to an eighth of their original size (around 40 µm). (Figure 2)
通过这种微凝胶的新操作，我进一步研究了细胞毒性(环境对细胞的毒性)。. To do this, 我培养了3T3细胞(小鼠成纤维细胞的一种快速生长的细胞系)，形成了小直径和对照直径的微凝胶. After three days of culture, 我比较了纯明胶微凝胶与低明胶浓度的TWEEN 20的对照.
Figure 3. 在微孔水凝胶结构中生长的活细胞(绿色)和死细胞(红色)的共聚焦显微镜堆叠图像(左)和切片图像(右).
I measured viability by performing a live/dead assay with confocal imaging. 这需要使用高清显微镜，并添加染料将活细胞染成绿色，将死细胞染成红色. I detected no difference in cell viability between the two hydrogels. (Figure 3)
为了进一步分析，我用更小的微凝胶对大块水凝胶进行了流变学测试，以测量和表征其弹性. 这表明，在固化过程的各个点上，较小的水凝胶形成的体积水凝胶比较大的对照微凝胶形成的体积水凝胶更硬. Rheology was performed only once, making the results less reliable. However, the stiffness is most likely caused by a larger surface area, which makes more interactions through mTG cross-links/bonds.
Results and Avenues for Application within Tissue Engineering
In the end I was able to decrease the diameter of the gelatin microgels, but I have yet to show their relation to cell growth. In theory, 不同浓度的明胶和乳化剂在我创造的微凝胶中应该会诱导不同的细胞增殖和分化. 通过常规的无孔水凝胶研究表明，硬度确实会改变细胞的分化趋势. However, it is unclear if the cells are affected by the stiffness change in the porous environment. While the bulk hydrogel may have more mTG cross-linking, and thus be stiffer, 还有一个很大的内部网络可以限制细胞的整体刚度. If that is the case, then a variation in hydrogel stiffness is important for different applications within the body. Depending on the biological environment this technology is applied to, less stiff hydrogel that degrades more quickly may be required, while others require the opposite. For example, neurons might like a less rigid structure with a smaller microgel for increased surface area, 而骨细胞可能喜欢更硬的凝胶和更大的微凝胶，以便更好地渗透宿主生物.
Having control over all variables in the hydrogel leads to greater specificity and customization, depending on the intended use. As of now, conventional hydrogels are nonporous, and therefore restrict cell growth, penetration of host biology, nutrient transfer, and cell viability. The novel microporous hydrogels fix these problems but are not fully understood. 每个细胞位置和细胞类型都需要不同的条件才能有效地使用注射疗法. These conditions can theoretically be accommodated with this technology, but these possibilities must be researched. If my research could be extrapolated, 对微凝胶交联和直径的充分了解可能会导致注射治疗的新领域. Personally, 我希望把这项技术应用到红细胞培养上，继续在郑某实验室工作。. And to think, all of this possibility was sitting right in front of our faces in Jell-O’s composition.
I would like to acknowledge my faculty research mentor Dr. 京宰正，谢谢你不仅让我成为第一年的研究员，还加速了我的学习，为我营造了一个充满机会的环境. Further, I am grateful to Dr. Seth Edwards, my graduate mentor, 感谢你在我人生道路上的每一步都陪伴着我，永远在我身边——在我的人生历程中，你是真正的指导者. None of this would be possible without the amazing staff and donors (Mr. Dana Hamel, Dr. George Wildman, Mr. Nicholas Bencivenga) at the Hamel Center for Undergraduate Research at UNH; without the Research, Experience, and Apprenticeship Program, I would not be writing today. I owe my future to the work and charity of these people, and I am forever grateful to the numerous efforts that have been made to benefit me.
Author and Mentor Bios
Originally from Concord, New Hampshire, Jack Fenway Reynolds will graduate in May 2026 with a bachelor of science degree in bioengineering. 他通过哈默尔大学本科生研究中心资助的研究经验和学徒计划(REAP)进行了他对微凝胶的研究. Jack was looking for a project involving neurons and therapeutics, specifically in neurodegenerative diseases due to his mother's diagnosis with multiple sclerosis. 他对神经元有限的再生能力和克服这一限制的方法非常感兴趣. In talking with Dr. Jeong about possible topics relating to Jack’s interests, Dr. Joeng proposed the microgels his lab had been working on. Jack was pleasantly surprised at how accessible research was. As a new researcher, Jack describes having a steep learning curve, but he was mostly independent and was involved in scientific conversation with Ph.D. students and professors within a few weeks. He decided to submit to Inquiry because he is passionate about the public understanding of science. While using gelatin in this project, he wanted to convey the simplicity of this technology to excite people about the future, highlight the possibilities, and maybe inspire someone else. Jack would like to pursue a Ph.D. in a related scientific field and work in pharmaceutical/therapeutic development. While the research was very enlightening for the content and methodology, writing for Inquiry has shown him where science meets the public. 杰克现在想站在科学的最前沿，向公众宣传科学发展.
Dr. Kyung Jae Jeong 是澳门葡京网赌游戏化学工程和生物工程副教授, beginning in 2013. His research interests revolve around biomaterials, drug delivery systems, medical devices, and tissue engineering. He mentored author, Jack Reynolds, for a Research Experience Apprenticeship Program (REAP) during the summer of 2023. Dr. Jeong has been interested in creating functional injectable hydrogels for medicine. However, the injectable hydrogels were nonporous and not optimal for cell delivery. 他的实验室在2018年致力于开发利用酶促反应组装明胶微凝胶的方法，并于去年将该方法应用于神经干细胞的封装. Dr. Jeong has mentored Inquiry author, Ryan Boudreau previously. He describes Jack as “pleasant to work with” as well as being “highly motivated to learn new things, intellectually bright, and hard-working.”
Copyright 2024, Jack Reynolds
