My Soft Matter paper, “Measuring cellular forces using bis-aliphatic hydrazone crosslinked stress-relaxing hydrogels,” was named ones of the “HOT articles for October.” It’s great to see my work recognized by the editors. Head over to http://blogs.rsc.org/sm/ to have a read.
I was briefly at UCSB in 2009 and everyone on campus involved with the Material Science Department admired Shuji Nakamura, both for his kindness and likelihood of winning a Nobel Prize for his seminal work in developing the blue LED. While green and red LEDs had been around for some time, without blue there was no hope of replacing many types of lights with these energy efficient solid-state devices. Shuji’s work enabled LED light bulbs, which I absolutely adore, televisions, and other devices in addition to generally advancing our understanding of advanced materials. While I never met the man myself, I’m happy that such an admired researcher took home the Nobel Prize in Physics.
Eric Betzig earned the Nobel Prize in Chemistry for his work in super resolution optical microscopy. He holds a special place in my heart for several reasons. First, as an HHMI Investigator, he was a member of the same tight knit club that counted my graduate school advisor, Kristi Anseth, among its ranks. HHMI is a tremendous organization and I am proud to have done my graduate research in an HHMI lab. The organization has generated a Nobel Prize in each of the last three years and I look forward to many more. Second, he gave a tremendous lecture at the University of Colorado shortly before I defended, so I had the opportunity to learn more about his research in person. And finally, I spent many hours pushing the limits of confocal microscopy in graduate school and I’m happy that innovation in the area is being rewarded.
However, all is not well with the round of Nobel Prizes. In my short-lived time at UCSB, I spent most of my time in the lab of Galen Stucky, who is best known for his pioneering work on mesoporous zeolites. I was excited to read in C&EN that Galen was on the short list for the chemistry Nobel, but I have to admit, despite my appreciation of Eric’s work, that I would have preferred to see Galen on a flight to Sweden. Notwithstanding, congratulations to all the Laureates and I will in anticipation for Galen’s prize next year. In his honor, the structure of a zeolite appears below.
After four years in grad school, it can sometimes be a little strange to exit into the real world. Grinding through a PhD taught me far more than how to direct my own basic research. I developed leadership skills mentoring high school students, undergraduates, and junior graduate students. I developed communications skills teaching and presenting at conferences. I developed business skills competing in the University of Colorado New Venture Challenge, which just kicked off. And more than anything, I learned about working smart and not hard.
So where am I taking these skills? Dearest to my heart is Agribotix. As my readers have learned, Agribotix is a drone-based remote sensing company that provides actionable intelligence to farmers. We are just wrapping up a phenomenal first growing season where we provided data on more than one billion corn plants to dozens of growers and look forward to beginning to ramp up in the Fall. Fundraising efforts are just beginning to kick off and we are seeking at $2-3M initial round. While I am no longer full time at Agribotix, I am still deeply involved and have confidence that amazing things are coming.
Second, I am in the midst of writing a guide/memoir covering getting a PhD in the hard sciences. Based on my experiences and those I read about online, the vast majority of PhD students (including me, when I started) have very little practical information about how to succeed in graduate school. This ranges from where to apply, to what department to choose, to project and advisor selection, to day-to-day research, to post-graduation plans. I will be posting chapters here periodically and would love nothing more than to give back to a current crop of graduate students. I learned so much over that I would be more than willing to share before the book comes out, so please reach out if you are currently pursuing a PhD in the hard sciences and would like a totally objective, practical viewpoint.
Finally, in mid-August I began working in the Polymer Science and Materials Chemistry Practice at Exponent, the leading scientific and engineering consulting firm. The projects that have come through since I began have been a riot and it’s been really illuminating to learn how polymer science happens in the real world. In the next few months, after I have a little bit more experience under my belt, I will put together a presentation designed for current graduate students in the polymer/materials area to share what I wished I knew before beginning to work in industry. I’m also busy studying for the Chemical Engineering Fundamentals of Engineering Exam, which will be slightly more challenging than I anticipated because my undergraduate degree is not in Chemical Engineering.
That said, this website will undergo somewhat of a pivot in the next few months from primarily being designed to share my graduate research to, ideally, becoming a source of information for current and prospective graduate students. I learned a lot from my mentors throughout my studies and would like to take this opportunity to give back. I will try to write blog posts every week or so sharing some practical polymer science tips, excerpts from my book, and general commentary on the chemical and materials industries.
In the meantime, if you are a PhD or soon-to-be PhD student in the hard sciences, I would recommend checking out Philip Guo’s free E-book, The PhD Grind. Philip is in a more unique position than most graduate students, having graduated from MIT with a Computer Science Bachelor’s Degree and from Stanford with his Doctorate, but his book provides and honest look at life as a graduate student.
And finally, I am now in beautiful Atlanta, Georgia. I will write more about this later, but the city seriously need a PR department. Prior to arriving in Atlanta, I heard nothing but bad things, but this is an amazing city. A view of where we live in Midtown from the park next door is posted below.
My final paper from the Anseth Group was just published in Soft Matter. It represents the culmination of the last few years we spent developing and characterizing bis-aliphatic hydrazone crosslinked hydrogels and demonstrates, in my opinion, a really clever application for the materials. Have a read here at http://pubs.rsc.org/en/content/articlelanding/2014/sm/c4sm01365d. See the abstract below:
Studies focused on understanding the role of matrix biophysical signals on cells, especially those when cells are encapsulated in hydrogels that are locally remodelled, are often complicated by appropriate methods to measure differences between the bulk and local material properties. From this perspective, stress-relaxing materials that allow long-term culture of embedded cells provide an opportunity to elucidate aspects of this biophysical signalling. In particular, rheological characterization of the stress relaxation properties allows one to link a bulk material measurement to local aspects of cellular functions by quantifying the corresponding cellular forces that must be applied locally. Here, embryonic stem cell-derived motor neurons were encapsulated in a well-characterized covalently adaptable bis-aliphatic hydrazone crosslinked PEG hydrogel, and neurite outgrowth was observed over time. Using fundamental physical relationships describing classical mechanics and viscoelastic materials, we calculated the forces and energies involved in neurite extension, the results of which provide insight to the role of biophysical cues on this process.
In this paper, Tobin Brown and I developed and characterized a synthetically tractable photodegradable hydrogel and demonstrated the ability to control the extension of motor axons. Check it out at http://pubs.acs.org/doi/abs/10.1021/bm500731b. The abstract appears below:
Hydrogels with photocleavable units incorporated into the cross-links have provided researchers with the ability to control mechanical properties temporally and study the role of matrix signaling on stem cell function and fate. With a growing interest in dynamically tunable cell culture systems, methods to synthesize photolabile hydrogels from simple precursors would facilitate broader accessibility. Here, a step-growth photodegradable poly(ethylene glycol) (PEG) hydrogel system cross-linked through a strain promoted alkyne–azide cycloaddition (SPAAC) reaction and degraded through the cleavage of a nitrobenzyl ether moiety integrated into the cross-links is developed from commercially available precursors in three straightforward synthetic steps with high yields (>95%). The network evolution and degradation properties are characterized in response to one- and two-photon irradiation. The PEG hydrogel is employed to encapsulate embryonic stem cell-derived motor neurons (ESMNs), and in situ degradation is exploited to gain three-dimensional control over the extension of motor axons using two-photon infrared light. Finally, ESMNs and their in vivo synaptic partners, myotubes, are coencapsulated, and the formation of user-directed neural networks is demonstrated.
My ACS Macro Letters paper where I, along with Malar Azagarsamy, characterized the gelation and degradation behavior of a PEG hydrogel containing a photodegradable coumarin moiety in the crosslinker. We found the coumarin molecule enables extremely rapid degradation at both visible and ultraviolet wavelengths behaves very nicely in accordance with established theories. Have a read at http://pubs.acs.org/doi/abs/10.1021/mz500230p. The abstract is pasted below:
The design, synthesis, and characterization of a new class of coumarin-based photodegradable hydrogels are reported. Hydrogel formation was achieved rapidly and efficiently under aqueous conditions using copper-catalyzed click chemistry, which afforded excellent control over the rate of network formation. Rapid photodegradation, to the point of reverse gelation, was observed using both 365 and 405 nm light, and micrometer-scale features were eroded using two-photon irradiation at wavelengths as long as 860 nm.
On May 2nd, I successfully defended my thesis in front of my committee consisting of Kristi Anseth, my advisor, Stephanie Bryant, Jen Cha, Curt Freed, and Joel Kaar. They were very satisfied with my doctoral work and I ended up with no revisions, although I will still be submitting two papers. A week later, I walked with my class, in which twelve Chemical Engineering PhDs were awarded. Here we all are after the ceremony.
After several hard months of work, my PhD thesis is complete and in the hands of my committee members. 222 pages of pure knowledge (that must be a lucky number)! I look forward to defending May 2 and immediately beginning work full time with Agribotix (www.agribotix.com) to ensure our first customers are satisfied this summer.
Less than a week ago I have my last talk as a graduate student to a very receptive audience at the Society for Biomaterials Spring meeting in Denver. My talk, entitled “Cytocompatible Covalently Adaptable Networks to Probe Biophysical Behavior of Encapsulated Cells” detailed the work I’ve done developing the bis-aliphatic hydrazone crosslinked gel and it’s applications in biomaterials. I look forward to submitting another paper or two on the subject and then defending my thesis and moving on to the next.
My article, written with Dylan Domaille, appears in Chemistry of Materials. Check it out here: http://pubs.acs.org/doi/abs/10.1021/cm5007789. We demonstrated predictable control of the material properties of the hydrazone crosslinked hydrogel by varying bath pH. The abstract is below:
Rheological and small molecule kinetic studies were performed to study the formation and hydrolysis of the bis-aliphatic hydrazone bond. The rate of gelation was found to correspond closely with the rate of bond formation and the rate of gel relaxation with the rate of hydrolysis, indicating that small molecule kinetic studies can play an important role in material design. Furthermore, unlike aryl or acyl hydrazone bonds, the bis-aliphatic hydrazone bond forms rapidly under physiological conditions without requiring aniline catalysis yet maintains a pH-dependent rate of hydrolysis. These results suggest the bis-aliphatic hydrazone bond should find use alongside existing bioorthogonal click chemistries for bioconjugation, biomaterial synthesis, and controlled release applications.