Soft nanotechnology

Ever since humans imagined the ability to deliberately manipulate matter on the atomic scale, they have glimpsed the boundless possibilities of the science of nanotechnology. And for almost as long, they have disputed whether molecular machines should be built using a “hard” (physical engineering) or “soft” (biology-based) approach. On his blog, Richard Jones, author of the book Soft Machines, discusses some of the more intricate details and debates in molecular nanotechnology.

In a recent post, Jones delves into the issue of what lessons nanotechnology should take away from biological systems: should we view cell biology as the penultimate achievement in nanotechnology, or can we improve upon the slap-dash, trial-and-error approach of evolution by making rational choices in materials? In his words:

The engineers’ view, if I can put it that way, is that nature shows what can be achieved with random design methods and a palette of unsuitable materials allocated by the accidents of history. If you take this point of view, it seems obvious that it should be fairly straightforward to make nanoscale machines whose performance vastly exceeds that of biology, by making rational choices of materials, rather than making do with what the accidents of evolution have provided, and by using the design principles we’ve learnt in macroscopic engineering.

The opposite view stresses that evolution is an extremely effective way of searching parameter space, and that in consequence is that we should assume that biological design solutions are likely to be close to optimal for the environment for which they’ve evolved. Where these design solutions seem odd from our point of view, their unfamiliarity is to be ascribed to the different ways in which physics works at the nanoscale. At its most extreme, this view regards biological nanotechnology, not just as the existence proof for nanotechnology, but as an upper limit on its capabilities.

Ultimately, argues Jones, nanotechnology has a lot to learn from biological systems — but that doesn’t preclude the possibility of improving upon it, either. He cites the emerging science of synthetic biology as a field that is using a sensible engineering approach to the development of biological nanodevices such as molecular motors, and wonders if this approach may ultimately lead to a biomemetic nanotechnology.

The right lessons for nanotechnology to learn from biology might not always be the obvious ones, but there’s no doubting their importance. Can the traffic ever go the other way – will there be lessons for biology to learn from nanotechnology? It seems inevitable that the enterprise of doing engineering with nanoscale biological components must lead to a deeper understanding of molecular biophysics. I wonder, though, whether there might not be some deeper consequences. What separates the two extreme positions on the relevance of biology to nanotechnology is a difference in opinion on the issue of the degree to which our biology is optimal, and whether there could be other, fundamentally different kinds of biology, possibly optimised for a different set of environmental parameters. It may well be a vain expectation to imagine that a wholly synthetic nanotechnology could ever match the performance of cell biology, but even considering the possibility represents a valuable broadening of our horizons.

In a more recent post, Jones announces the upcoming Soft Nanotechnology meeting in London next year.

A forthcoming conference in London will be discussing the “soft” approach to nanotechnology. The meeting – Faraday Discussion 143 – Soft Nanotechnology – is organised by the UK’s Royal Society of Chemistry, and follows a rather unusual format. Selected participants in the meeting submit a full research paper, which is peer reviewed and circulated, before the meeting, to all the attendees. The meeting itself concentrates on a detailed discussion of the papers, rather than a simple presentation of the results.

Radical life extension and information-theoretic death

Immortality as a zero probability of information-theoretic death may not be possible or realistic. A more practical (and less controversial) objective of radical life extension would be to minimize the chance of information-theoretic death. In analogy with Aubrey de Grey’s objective to cure human aging by engineering negligible senescence (SENS), the objective of radical life extension should be to achieve a negligible chance of information-theoretic death. Although curing aging will be necessary, it will be far from sufficient to achieve greatly extended lifespans. Even if aging can be completely abolished by advanced molecular technologies, humans will still be vulnerable to major accidents and homicide. Of course, such events may not necessarily produce acute information-theoretic death, but it can be argued that when humanity becomes more robust and advanced, the nature of accidents (space travel) and murder (“information-theoretic murder”) may become more destructive as well. This raises the question of whether our ability to eliminate “traditional” risk factors can outpace the number and nature of new risks.

Perhaps the most logical proposal to achieve a negligible chance of information-theoretic death is to duplicate a person. If enough duplicates are made, the chance that all of them will die can be made very small. But this raises the issue of whether such duplicates are the same individual. Some people would argue that this strategy does not produce atomistic non-serial immortality. It is also not clear how the question of whether a copy of an individual is the same individual can ever be resolved by empirical observation or logical deduction.

Perhaps the most realistic proposal to reduce the probability of information-theoretic death would be to separate the neurological basis of the person from its body in such a fashion that the risk of complete destruction of the person would become negligible. One such proposal is briefly discussed by Robert Ettinger in his book “Man into Superman.” In Chapter 4 on “Cyborgs, Saucer Men, and Extended Bodies,” Ettinger notes that “the brain need not necessarily be mobile; in fact, it might be better protected and served if fixed at home base. The sensors and effectors–eyes, hands, etc.–could be far away, and even widely scattered, with communication by appropriate signals (not necessarily radio).” Because such an “extended body” would not rely on controversial technologies such as duplication and mind-uploading, the traditional concept of identity can be reconciled with reduced vulnerability. Clearly, this idea could benefit from detailed elaboration and specific proposals.

The prospect of such extended bodies raises an important question about resuscitation of cryonics patients. When should they be revived? Naturally, a necessary condition is the ability to reverse any damaged incurred during the cryopreservation process itself and being able to cure the patient’s terminal disease. Most people who have made cryonics arrangements will add that the general ability to rejuvenate a person should be a necessary condition as well. Because all these conditions require availability of similar technologies, it is doubtful that the choice between these scenarios has practical relevance. A more stringent condition, however, would be a request to only attempt resuscitation if the chance of information-theoretic death is smaller after resuscitation than in long term low temperature care. This option raises an uncomfortable question — are patients in low temperature care safer from information-theoretic death than a person alive today? Answering this questions involves a lot of complicated issues such as the technical feasibility of cryonics, the nature of long term care of cryonics patients, and, ultimately, how one weighs the certainty of being alive today against the probability of a (vastly) longer lifespan in the future.

Warm biostasis through nanotechnology

One concern about chemical fixation as a low cost alternative to cryonics is that current fixatives may not be able to permanently fix all biomolecules that are important to preserve the identity of the person. A related concern is that postmortem delays may not permit adequate perfusion of the brain, resulting in pockets of decomposed tissue. On this issue, biostasis at cryogenic temperatures (cryonics) has a distinct advantage because extreme cold will also preserve tissues that were not, or were poorly, penetrated by the cryoprotectant agent.

But even if cryoprotectant toxicity will be overcome to enable reversible vitrification of humans, the procedures of cryoprotectant perfusion, cryogenic cooldown, long term care, rewarming, and resuscitation may often involve (unintended) imperfections that will require advanced cell repair technologies for successful resuscitation.

Perhaps those same advanced technologies could produce a form of biostasis that avoids the crude consequences of contemporary chemical fixation by making precise modifications within and between cells to arrest metabolism and decomposition.

Looking for discussion of this idea, Brian Wowk pointed this writer to Eric Drexler who envisioned such a form of warm biostasis in Engines of Creation. In chapter 7 (section 5) Drexler calls this form of warm biostasis “anesthesia plus:”

To see how one approach would work, imagine that the blood stream carries simple molecular devices to tissues, where they enter the cells. There they block the molecular machinery of metabolism – in the brain and elsewhere – and tie structures together with stabilizing cross-links. Other molecular devices then move in, displacing water and packing themselves solidly around the molecules of the cell. These steps stop metabolism and preserve cell structures.

This procedure would produce a state in which the person will appear to be dead (and warm) for all practical purposes:

If a patient in this condition were turned over to a present-day physician ignorant of the capabilities of cell repair machines, the consequences would likely be grim. Seeing no signs of life, the physician would likely conclude that the patient was dead, and then would make this judgment a reality by “prescribing” an autopsy, followed by burial or burning.

Such a form of warm biostasis would not only produce a true molecular alternative to cryonics, it would also enable long-duration space travel and could be employed as a means to provide trauma care in emergency situations. These kind of applications of molecular nanotechnology are extremely advanced and, as a result, literature, either fiction or non-fiction, about them is virtually non-existent. It seems that the first rigorous treatment of cellular and whole-body warm biostasis will be published in Robert Freitas’ Nanomedicine Volume IIB and Nanomedicine Volume III (personal correspondence).

Perhaps the future of biostasis will be an advanced form of chemical fixation after all.

Biostasis through chemopreservation

Twenty years ago, Charles B. Olson published an article called “A Possible Cure for Death” in the journal Medical Hypotheses. In it, he favorably compares methods of chemical preservation to cryogenic preservation. Unfortunately, this article provoked no wide discussion or attempts at implementation. As the author notes on his website, other than requests for reprints, “nothing more came of it.” And yet the arguments in it are still sound and just as persuasive today as they were then. Why the reluctance?

Freezing has a certain subjective appeal. We freeze foods and rewarm them to eat. We read stories about children who have fallen into ice cold water and survived for hours without breathing. We know that human sperm, eggs, and even embryos can be frozen and thawed without harm. Freezing seems intuitively reversible and complete. Perhaps this is why cryonics quickly attained, and has kept, its singular appeal for life extensionists.

By contrast, we tend to associate chemical preservation with processes that are particularly irreversible and inadequate. Corpses are embalmed to prevent decay for only a short time. Taxidermists make deceased animals look alive, although most of their body parts are missing or transformed. “Plastinated” cadavers are used to demonstrate surface anatomy in schools and museums. No wonder, then, that cryonicists routinely dismiss chemopreservation as a truly bad idea. Although from time to time chemopreservation is raised as a possible alternative to cryonics (Perry, page 21-24), to this day it has not been given the full consideration it deserves

Part of the confusion around chemopreservation concerns the quality of preservation that is possible with this method. Chemical methods of preservation such as fixation are not only adequate, they have long been the gold standard for biologists studying the structure of cells and the brain. As Olson notes,

The technological advances in the preparation of tissue for microscopy have directly improved the prospects of brain preservation for reanimation. This is not a coincidence: the goals of microscopy and brain preservation for reanimation are fundamentally similar. In both cases, a maximal amount of structural detail is preserved such that information can be extracted.

When fixed immediately and properly embedded in a solid medium, tissue can preserve physical structure indefinitely. The entire brain can begin to be fixed by arterial perfusion within minutes after pronouncement of death. Fixation can be done by hospital pathologists or funeral home specialists. The brain can then be impregnated with a solid-setting polymer so that it becomes fully inert.

But what of reversibility? Olson dismisses the need for reversibility. The information in the brain can be retrieved and run on a different substrate — a new organic or machine brain. However, K. Eric Drexler’s proposal in Engines of Creation, nanoscale mechanical repair, could also apply to chemopreserved brains just as to cryopreserved brains. The damage caused by fixation and embedding might be able to be reversed just as the damage caused by freezing or vitrification, if, in both cases, identity-critical information preserved in the brain has not been lost.

If personal identity is preserved in the brain in physical structures such as synaptic circuits, then we know that chemopreservation can preserve these structures just as well as cryopreservation. In fact, chemopreservation entirely avoids the danger of ice formation and fracturing, which in theory could destroy physical structures in the brain and cause irretrievable identity-critical information loss. While fixatives cause molecular changes in the brain, by crosslinking and denaturing proteins, cryoprotectants also cause chemical damage which must later be repaired. While it is not certain that chemopreservation can preserve all identity-critical information, it is also not certain that cryonics stabilization, cryoprotection, and vitrification preserve all identity-critical information.

For those who accept the method of resuscitation by scanning the brain and running it its processes on a different substrate (“mind uploading“), chemopreservation might present additional benefits. The chemopreserved brain, unlike the cryopreserved brain, is ideally suited to microscopic extraction of information:

The molecules in a chemopreserved brain have been extensively crosslinked and can be embedded in a plastic which was designed for electron microscopy. Consequently they will be resistant to the heat and damage generated by whatever beam of particles (or other investigative device) is used to determine the details of the internal structure. In contrast, a frozen brain is not particularly prepared to resist damage, and is acutely sensitive to any heat generated.

But even for those who prefer mechanical repair of the brain, chemopreservation presents benefits that cryopreservation does not.

First, it is potentially cheaper, because it does away with the need for expensive long-term care. Chemopreserved patients would not require labor to keep them in the same condition, other than storage in a secure, designated area, unlike cryopreserved patients who are in continual danger of thawing. Cryopreserved patients require continual monitoring of liquid nitrogen levels and topping off with more liquid nitrogen, as well as special, expensive containers that can hold liquid nitrogen, and these containers need regular maintenance, repair, and replacement. Liquid nitrogen also presents hazards that require continual air monitoring and alarms.

The basic techniques for chemopreserving a brain — fixation and polymer impregnation — would also not require the services of specially trained volunteers or professionals; they are routine techniques used in hospital pathology labs and departments of anatomy around the world. As Olson notes, “the cost of brain chemopreservation could be less than that of a typical funeral.”

People are routinely turned away from cryonics providers because they cannot afford cryopreservation. So what are we waiting for?